1.
Pileipellis
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The pileipellis is the uppermost layer of hyphae in the pileus of a fungal fruit body. It covers the trama, the tissue of the fruit body. Pileipellis type is an important character in the identification of fungi, pileipellis types include the cutis, trichoderm, epithelium, and hymeniderm types. A cutis is a type of pileipellis characterized by hyphae that are repent, that is, in an ixocutis, the hyphae are gelatinous. In a trichoderm, the outermost hyphae emerge roughly parallel, like hairs, the prefix tricho- comes from a Greek word for hair. In an ixotrichodermium, the outermost hyphae are gelatinous, an epithelium is a pileipellis consisting of rounded cells in multiple layers, often connected in chains, and sometimes breaking off. Also called hymeniform, or palisade at times, when viewed from above, a hymeniderm or cellular cuticle appears to be paved with roughly circular polygonal elements. The elements may be globular cells or may be the tips of hyphae extending deeper into the surface
2.
Terminologia Histologica
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The Terminologia Histologica is a controlled vocabulary for use in cytology and histology. In April 2011, Terminologia Histologica was published online by the Federative International Programme on Anatomical Terminologies and it was intended to replace Nomina Histologica. The Nomina Histologica was introduced in 1977, with the edition of Nomina Anatomica. It was developed by the Federative International Committee on Anatomical Terminology
3.
Epithelium
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Epithelial is one of the four basic types of animal tissue, along with connective tissue, muscle tissue and nervous tissue. Epithelial tissues line the cavities and surfaces of blood vessels and organs throughout the body, there are three principal shapes of epithelial cell, squamous, columnar, and cuboidal. All glands are made up of epithelial cells, functions of epithelial cells include secretion, selective absorption, protection, transcellular transport, and sensing. Epithelial layers contain no blood vessels, so they must receive nourishment via diffusion of substances from the connective tissue. Cell junctions are well-employed in epithelial tissues, in general, epithelial tissues are classified by the number of their layers and by the shape and function of the cells. The three principal shapes associated with epithelial cells are—squamous, cuboidal and columnar, squamous epithelium has cells that are wider than their height. Cuboidal epithelium has cells whose height and width are approximately the same, columnar epithelium has cells taller than they are wide. However, when taller simple columnar epithelial cells are viewed in cross section showing several nuclei appearing at different heights and this kind of epithelium is therefore described as pseudostratified columnar epithelium. Transitional epithelium has cells that can change from squamous to cuboidal, Simple epithelium is a single layer of cells with every cell in direct contact with the basement membrane that separates it from the underlying connective tissue. In general, it is found where absorption and filtration occur, the thinness of the epithelial barrier facilitates these processes. In general, simple epithelial tissues are classified by the shape of their cells, the four major classes of simple epithelium are, simple squamous, simple cuboidal, simple columnar, pseudostratified. Simple squamous, which is found lining areas where passive diffusion of gases occur, E. g. skin, walls of capillaries, linings of the pericardial, pleural, and peritoneal cavities, as well as the linings of the alveoli of the lungs. Simple cuboidal, these cells may have secretory, absorptive, or excretory functions, examples include small collecting ducts of kidney, pancreas and salivary gland. Simple columnar, cells can be secretory, absorptive, or excretory, Simple columnar epithelium can be ciliated or non-ciliated, ciliated columnar is found in the reproductive tract. Non-ciliated epithelium can also possess microvilli, pseudostratified columnar epithelium, can be ciliated or non-ciliated. The ciliated type is called respiratory epithelium as it is almost exclusively confined to the larger respiratory airways of the nasal cavity, trachea. Stratified epithelium differs from simple epithelium in that it is multilayered and it is therefore found where body linings have to withstand mechanical or chemical insult such that layers can be abraded and lost without exposing subepithelial layers. Cells flatten as the layers become more apical, though in their most basal layers the cells can be squamous, stratified epithelia can have the following specializations, The basic cell types are squamous, cuboidal, and columnar classed by their shape
4.
Simple squamous epithelium
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A simple squamous epithelium is a single layer of flat cells in contact with the basal lamina of the epithelium. This type of epithelium is often permeable and occurs where small molecules pass quickly through membranes via filtration or diffusion, simple squamous epithelia are found in capillaries, alveoli, glomeruli, and other tissues where rapid diffusion is required. Cells are flat with flattened/rounded nucleus and it is also called pavement epithelium due to its tile-like appearance. This epithelium is associated with filtration and diffusion. This tissue is extremely thin, and forms a delicate lining
5.
Stratified squamous epithelium
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A stratified squamous epithelium consists of squamous epithelial cells arranged in layers upon a basal membrane. Only one layer is in contact with the basement membrane, the other layers adhere to one another to maintain structural integrity. Although this epithelium is referred to as squamous, many cells within the layers may not be flattened, in the deeper layers, the cells may be columnar or cuboidal. It forms the outermost layer of the skin and the lining of the mouth, esophagus. Non-keratinized surfaces must be kept moist by bodily secretions to prevent them drying out. Examples of non-keratinized stratified squamous epithelium include cornea, lining mucosa of oral cavity, esophagus, anal canal, foreskin, keratinized surfaces are protected from abrasion by keratin and kept hydrated and protected from dehydration by glycolipids produced in the stratum granulosum. Examples of keratinized stratified squamous epithelium include epidermis of the palm of the hand and sole of the foot, and the masticatory mucosa
6.
Simple columnar epithelium
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A simple columnar epithelium is a columnar epithelium that is uni-layered. In humans, a columnar epithelium lines most organs of the digestive tract including the stomach, small intestine. Simple columnar epithelia line the uterus, Simple columnar epithelium is further divided into two categories, ciliated and non-ciliated. Non-ciliated types are found in the digestive tract, ciliated types are found within bronchioles of the respiratory tract and in the oviduct of the female reproductive tract. These viruses may kill the cells or stop the cilia beating. In either case, mucus builds up and forms a site for secondary bacterial infections. A ciliated columnar epithelium lines the lumen of the uterine tube and this is found lining sections of the gastrointestinal tract and may be brush bordered. Histology at KUMC epithel-epith05 Gall bladder - Simple columnar epithelium UIUC Histology Subject 1061 - Uterine tube lumen
7.
Stratified columnar epithelium
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Stratified columnar epithelium is a rare type of epithelial tissue composed of column shaped cells arranged in multiple layers. Stratified columnar epithelia are found in the conjunctiva of the eye, in parts of the pharynx, anus, the uterus, and it is also found in the lobar ducts in salivary glands. The cells function in secretion and protection, in simple terms, the upper and lowermost layer of cells are columnar in shape. The middle layer contains cuboidal cells and it forms the lining of the respiratory tract, ureter and oviduct among other locations. Stratified columnar epithelium at cytochemistry. net Anatomy Atlases - Microscopic Anatomy, plate 02.23 - Stratified Columnar Epithelium
8.
Pseudostratified columnar epithelium
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A pseudostratified epithelium is a type of epithelium that, though comprising only a single layer of cells, has its cell nuclei positioned in a manner suggestive of stratified epithelia. As it rarely occurs as squamous or cuboidal epithelia, it is considered synonymous with the term pseudostratified columnar epithelium. The nuclei of cells, however, are disposed at different levels. Not all ciliated cells extend to the surface, such cells are capable of cell division providing replacements for cells lost or damaged. Pseudostratified epithelia function in secretion or absorption, if a specimen looks stratified but has cilia, then it is a pseudostratified ciliated epithelium, since stratified epithelia do not have cilia. Ciliated pseudostratified columnar epithelia are found in the linings of the trachea as well as the respiratory tract. Non-ciliated pseudostratified columnar epithelia are located in the part of male vas deferens. Pseudostratified columnar epithelia with stereocilia are located in the epididymis, stereocilia of the epididymis are not cilia because their cytoskeleton is composed of actin filaments, not microtubules. They are structurally and molecularly more similar to microvilli than to true cilia, pseudostratified columnar epithelia are found forming the straight, tubular glands of the endometrium in females
9.
Simple cuboidal epithelium
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Simple cuboidal epithelium is a type of epithelium that consists of a single layer of cuboidal cells. These cuboidal cells have large, spherical and central nuclei, simple cuboidal epithelia are found on the surface of ovaries, the lining of nephrons, the walls of the renal tubules, and parts of the eye and thyroid. On these surfaces, the cells perform secretion and absorption, simple cuboidal cells are also found in kidney tubules, glandular ducts, ovaries, and the thyroid gland. Simple cuboidal cells are found in rows with their spherical nuclei in the center of the cells and are directly attached to the basal surface. Simple ciliated cuboidal cells are present in the respiratory bronchioles. These cells provide protection and may be active or passive, depending on the location, simple cuboidal epithelium commonly differentiates to form the secretory and duct portions of glands. They also constitute the germinal epithelium which covers the ovary and the walls of the seminiferous tubules in the male testes. These cells offer some protection and function in absorption and secretion, histology at KUMC epithel-epith03 Thyroid gland
10.
Stratified cuboidal epithelium
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Stratified cuboidal epithelium is a type of epithelial tissue composed of multiple layers of cube-shaped cells. Only the most superficial layer is made up of cells. This type of tissue can be observed in sweat glands, mammary glands, circumanal glands and they protect areas such as the ducts of sweat glands, mammary glands, and salivary glands. Overview at umdnj. edu Histology at KUMC epithel-epith17 Sweat Duct Histology image, 43_03 at the University of Oklahoma Health Sciences Center - Skin
11.
Respiratory epithelium
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Respiratory epithelium is a type of epithelium found lining the respiratory tract, where it serves to moisten and protect the airways. It also functions as a barrier to pathogens and foreign particles, preventing infection. The respiratory epithelium lining the upper respiratory airways is classified as ciliated pseudostratified columnar epithelium and this designation is due to the arrangement of the multiple cell types composing the respiratory epithelium. While all cells make contact with the basement membrane and are, therefore, a layer of cells. Hence, it appears as though several layers of cells are present, the majority of cells composing the ciliated pseudostratified columnar epithelium are of three types, a) ciliated cells, b) goblet cells, and c) basal cells. The ciliated cells are epithelial cells with specialized ciliary modifications. And determines how well mucociliary clearance works, the basal cells are small, nearly cuboidal cells thought to have some ability to differentiate into other cells types found within the epithelium. Certain parts of the tract, such as the oropharynx, are also subject to the abrasive swallowing of food. To prevent the destruction of the epithelium in these areas, it changes to stratified squamous epithelium. The squamous layer of the oropharynx is continuous with the esophagus, Histology image, 13903loa – Histology Learning System at Boston University Histology of The Respiratory System
12.
Intestinal epithelium
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The intestinal epithelium is the layer of cells that forms the luminal surface or lining of both the small and large intestine of the gastrointestinal tract. It is composed of columnar epithelium. It has two important functions, absorbing helpful substances and providing a barrier against harmful substances, some diseases and conditions are caused by dysfunction in the intestinal epithelium, and some diseases and conditions cause problems with these cells, which then leads to further complications. The epithelium is part of the mucosa layer. The epithelium is composed of a layer of cells. The other two layers of the mucosa, the lamina propria and the muscularis mucosae, support and articulate the epithelium layer. To securely contain of the contents of the lumen, the cells of the epithelial layer are joined together by tight junctions thus forming a contiguous. Epithelial cells are renewed every 4–5 days through a process of renewal. Renewal relies on cells that reside at the crypt base of the intestinal glands. After being formed at the base, the new cells migrate upwards, eventually, they undergo apoptosis and are shed off into the intestinal lumen. In this way, the number of cells making up the intestinal epithelium remains constant. In the small intestine, the layer is specially adapted to provide a large surface area in order to maximize the absorption of nutrients. Villi and intestinal glands serve to increase the surface area tenfold. Microvilli covering the surface of the enterocytes increase the absorptive surface twentyfold. These numerous microscopic finger-like projections form an undulated brush border, the brush border on the apical surface of the epithelial cells is covered with glycocalyx, which is composed of oligosaccharides attached to membrane glycoproteins and glycolipids. Six different cell types are produced by the cells that reside at the base of the crypts. Each type matures according to its specific differentiation program as it migrates up, many of genes necessary for differentiation into the different epithelial cell types have been identified and characterized. The cell types produced are, enterocytes, Goblet cells, enteroendocrine cells, Paneth cells, microfold cells, cup cells and their functions are listed here, Enterocytes are the most numerous and function primarily for nutrient absorption
13.
Transitional epithelium
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Transitional epithelium is a type of tissue consisting of multiple layers of epithelial cells which can contract and expand. It is so named because of this function in the transition of degree of distension and this tissue structure type is found in urothelium, including that of the renal pelvis, urinary bladder, the ureters, the superior urethra, and the prostatic and ejaculatory ducts of the prostate. The appearance of transitional epithelium depends on the layers in which it resides, cells of the basal layer are cuboidal, or cube-shaped, and columnar, or column-shaped, while the cells of the superficial layer vary in appearance depending on the degree of distension. These cells appear to be cuboidal with an apex when the organ or the tube in which they reside is not stretched. When the organ or tube is stretched, the tissue compresses, when this happens, the cells flatten, and they appear to be squamous and irregular. The transitional epithelium cells stretch readily in order to accommodate fluctuation of volume of the liquid in an organ, Transitional epithelium also functions as barrier between the lumen, or inside hollow space, of the tract that it lines and the bloodstream. To help achieve this, the cells of transitional epithelium are connected by tight junctions and this barrier prevents reabsorption of toxic wastes and pathogens by the bloodstream. Transitional epithelium is made up of three types of layers, basal, intermediate, and superficial. The basal layer fosters the epithelial cells in order to provide constant renewal of the epithelium. These cells cytoplasm is rich in tonofilaments and mitochondria, however, the tonofilaments play a role in the attachment of the basal layer to the basement membrane via desmosomes. The intermediate cell layer is highly proliferative and, therefore, provides for rapid cell regeneration in response to injury or infection of the organ or tube in which it resides and these cells contain a prominent Golgi apparatus and an array of membrane-bound vesicles. These function in the packaging and transport of proteins, such as keratin, the superficial cell layer, that which lines the lumen, is the only fully differentiated layer of the epithelium. It provides a barrier between the lumen and the bloodstream, so as not to allow the bloodstream to reabsorb harmful wastes or pathogens. All transitional epithelial cells are covered in microvilli and a fibrillar mucous coat, the epithelium contains many intimate and delicate connections to neural and connective tissue. These connections allow for communication to tell the cells to expand or contract, the superficial layer of transitional epithelium is connected to the basal layer via cellular projections, such as intermediate filaments protruding from the cellular membrane. These structural elements cause the epithelium to allow distension, however, all cells touch the basement membrane. This impermeability is due to a highly keratinized cellular membrane synthesized in the Golgi apparatus, the membrane is made up of a hexagonal lattice put together in the Golgi apparatus and implanted into the surface of the cell by reverse pinocytosis, a type of exocytosis. The cells in the layer of the transitional epithelium are highly differentiated
14.
Animal
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Animals are multicellular, eukaryotic organisms of the kingdom Animalia. The animal kingdom emerged as a clade within Apoikozoa as the group to the choanoflagellates. Animals are motile, meaning they can move spontaneously and independently at some point in their lives and their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later in their lives. All animals are heterotrophs, they must ingest other organisms or their products for sustenance, most known animal phyla appeared in the fossil record as marine species during the Cambrian explosion, about 542 million years ago. Animals can be divided broadly into vertebrates and invertebrates, vertebrates have a backbone or spine, and amount to less than five percent of all described animal species. They include fish, amphibians, reptiles, birds and mammals, the remaining animals are the invertebrates, which lack a backbone. These include molluscs, arthropods, annelids, nematodes, flatworms, cnidarians, ctenophores, the study of animals is called zoology. The word animal comes from the Latin animalis, meaning having breath, the biological definition of the word refers to all members of the kingdom Animalia, encompassing creatures as diverse as sponges, jellyfish, insects, and humans. Aristotle divided the world between animals and plants, and this was followed by Carl Linnaeus, in the first hierarchical classification. In Linnaeuss original scheme, the animals were one of three kingdoms, divided into the classes of Vermes, Insecta, Pisces, Amphibia, Aves, and Mammalia. Since then the last four have all been subsumed into a single phylum, in 1874, Ernst Haeckel divided the animal kingdom into two subkingdoms, Metazoa and Protozoa. The protozoa were later moved to the kingdom Protista, leaving only the metazoa, thus Metazoa is now considered a synonym of Animalia. Animals have several characteristics that set apart from other living things. Animals are eukaryotic and multicellular, which separates them from bacteria and they are heterotrophic, generally digesting food in an internal chamber, which separates them from plants and algae. They are also distinguished from plants, algae, and fungi by lacking cell walls. All animals are motile, if only at life stages. In most animals, embryos pass through a stage, which is a characteristic exclusive to animals. With a few exceptions, most notably the sponges and Placozoa and these include muscles, which are able to contract and control locomotion, and nerve tissues, which send and process signals
15.
Tissue (biology)
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In biology, tissue is a cellular organizational level intermediate between cells and a complete organ. A tissue is an ensemble of similar cells from the origin that together carry out a specific function. Organs are then formed by the grouping together of multiple tissues. The study of tissue is known as histology or, in connection with disease, the classical tools for studying tissues are the paraffin block in which tissue is embedded and then sectioned, the histological stain, and the optical microscope. In the last couple of decades, developments in microscopy, immunofluorescence. With these tools, the appearances of tissues can be examined in health and disease. Animal tissues are grouped into four types, connective, muscle, nervous. Collections of tissues joined in structural units to serve a common function compose organs, while all animals can generally be considered to contain the four tissue types, the manifestation of these tissues can differ depending on the type of organism. For example, the origin of the cells comprising a particular type may differ developmentally for different classifications of animals. By contrast, a true epithelial tissue is present only in a layer of cells held together via occluding junctions called tight junctions. This tissue covers all surfaces that come in contact with the external environment such as the skin, the airways. It serves functions of protection, secretion, and absorption, and is separated from other tissues below by a basal lamina and they are made up of cells separated by non-living material, which is called an extracellular matrix. This matrix can be liquid or rigid, for example, blood contains plasma as its matrix and bones matrix is rigid. Connective tissue gives shape to organs and holds them in place, blood, bone, tendon, ligament, adipose and areolar tissues are examples of connective tissues. One method of classifying tissues is to divide them into three types, fibrous connective tissue, skeletal connective tissue, and fluid connective tissue. Muscle cells form the active contractile tissue of the known as muscle tissue or muscular tissue. Muscle tissue functions to force and cause motion, either locomotion or movement within internal organs. Cells comprising the nervous system and peripheral nervous system are classified as nervous tissue
16.
Connective tissue
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Connective tissue is one of the four types of biological tissue that supports, connects or separates different types of tissues and organs in the body. The other three types are epithelial, muscle, and nervous tissue, Connective tissue is found in between other tissues everywhere in the body, including the nervous system. In the central system, the three outer membranes that envelop the brain and spinal cord are composed of connective tissue. All connective tissue consists of three components, fibers, ground substance and cells. Blood and lymph lack the fiber component, all are immersed in the body water. The cells of connective tissue include fibroblasts, adipocytes, macrophages, mast cells, Connective tissue can be broadly subdivided into connective tissue proper, and special connective tissue. Connective tissue proper consists of connective tissue and dense connective tissue Special connective tissue consists of reticular connective tissue, adipose tissue, cartilage, bone. Other kinds of connective tissues include fibrous, elastic, and lymphoid connective tissues, new vascularised connective tissue that forms in the process of wound healing is termed granulation tissue. Fibroblasts are the responsible for the production of some CT. Type I collagen, is present in forms of connective tissue. Characteristics of CT, Cells are spread through an extracellular fluid, ground substance - A clear, colorless, and viscous fluid containing glycosaminoglycans and proteoglycans to fix the body water and the collagen fibers in the intercellular spaces. Ground substance slows the spread of pathogens, not all types of CT are fibrous. Examples of non-fibrous CT include adipose tissue and blood, adipose tissue gives mechanical cushioning to the body, among other functions. Although there is no dense collagen network in adipose tissue, groups of cells are kept together by collagen fibers. The matrix of blood is plasma, both the ground substance and proteins create the matrix for CT. Types of fibers, Connective tissue has a variety of functions that depend on the types of cells. They also allow organs to resist stretching and tearing forces, elastic fibers, made from elastin and fibrillin, also provide resistance to stretch forces. They are found in the walls of blood vessels and in certain ligaments
17.
Muscle tissue
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Muscle tissue is a soft tissue that composes muscles in animal bodies, and gives rise to muscles ability to contract. This is opposed to other components or tissues in muscle such as tendons or perimysium and it is formed during embryonic development through a process known as myogenesis. Muscle tissue varies with function and location in the body, in mammals the three types are, skeletal or striated muscle, smooth or non-striated muscle, and cardiac muscle, which is sometimes known as semi-striated. Smooth and cardiac muscle contracts involuntarily, without conscious intervention and these muscle types may be activated both through interaction of the central nervous system as well as by receiving innervation from peripheral plexus or endocrine activation. Striated or skeletal muscle only contracts voluntarily, upon influence of the nervous system. Sub-categorization of muscle tissue is also possible, depending on other things the content of myoglobin, mitochondria. Muscle are elongated cells ranging from several millimetres to about 10 centimetres in length, striated muscle is further classified as either skeletal or cardiac muscle. Striated muscle is typically subject to control, while smooth muscle is not. An average adult male is made up of 42% of skeletal muscle and it also has striations unlike smooth muscle. In vertebrates, there is a third muscle tissue recognized, Cardiac muscle, found only in the heart, is a striated muscle similar in structure to skeletal muscle but not subject to voluntary control. Cardiac and skeletal muscles are striated in that they contain sarcomeres and are packed into highly regular arrangements of bundles, while skeletal muscles are arranged in regular, parallel bundles, cardiac muscle connects at branching, irregular angles. Striated muscle contracts and relaxes in short, intense bursts, whereas smooth muscle sustains longer or even near-permanent contractions and it can carry more oxygen and sustain aerobic activity. Type I muscle fiber are sometimes broken down into Type I and Type Ic categories, Type IIx, which is less dense in mitochondria and myoglobin. This is the fastest muscle type in humans and it can contract more quickly and with a greater amount of force than oxidative muscle, but can sustain only short, anaerobic bursts of activity before muscle contraction becomes painful. N. B. in some books and articles this muscle in humans was, confusingly, Type IIb, which is anaerobic, glycolytic, white muscle that is even less dense in mitochondria and myoglobin. In small animals like rodents this is the major fast muscle type, smooth muscle is an involuntary non-striated muscle. It is divided into two subgroups, the single-unit and multiunit smooth muscle, within single-unit cells, the whole bundle or sheet contracts as a syncytium. Multiunit smooth muscle tissues innervate individual cells, as such, they allow for control and gradual responses
18.
Nervous tissue
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Nervous tissue is responsible for sending signals to the brain about suicidal thoughts. Nervous tissue is made up of different types of cells, all of which have an axon. Bundles of axons make up the nerves, functions of the nervous system are sensory input, integration, control of muscles and glands, homeostasis, and mental activity. Nervous tissue is composed of neurons, also called nerve cells, typically, nervous tissue is categorized into four types of tissue. In the central system, the tissue types found are grey matter. In the peripheral nervous system, the types are nerves. The tissue is categorized by its neuronal and neuroglial components, neurons are cells with specialized features that allow them to receive and facilitate nerve impulses, or action potentials, across their membrane to the next neuron. They possess a cell body, with cell projections called dendrites. Dendrites are thin, branching projections that receive electrochemical signaling to create a change in voltage in the cell, axons are long projections that carry the action potential away from the cell body toward the next neuron. The bulb-like end of the axon, called the terminal, is separated from the dendrite of the following neuron by a small gap called a synaptic cleft. When the action potential travels to the terminal, neurotransmitters are released across the synapse and bind to the post-synaptic receptors. Neurons are classified both functionally and structurally and they are the major neuron type in the CNS and include interneurons and motor neurons. These are found in the layer of the cerebellum. Neuroglia encompasses the non-neural cells in tissue that provide various crucial supportive functions for neurons. They are smaller than neurons, and vary in structure according to their function, neuroglial cells are classified as follows, Microglial cells, Microglia are macrophage cells that make up the primary immune system for the CNS. They are the smallest neuroglial cell, astrocytes, Star-shaped macroglial cells with many processes found in the CNS. They are the most abundant cell type in the brain, and are intrinsic to a healthy CNS, oligodendrocytes, CNS cells with very few processes. They form myelin sheaths on the axons of a neuron, which are lipid-based insulation that increases the speed at which the action potential, can travel down the axon
19.
Organ (anatomy)
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In biology, an organ or viscus is a collection of tissues joined in a structural unit to serve a common function. In anatomy, a viscus is an organ, and viscera is the plural form. Organs are composed of main tissue, parenchyma, and sporadic tissues, the main tissue is that which is unique for the specific organ, such as the myocardium, the main tissue of the heart, while sporadic tissues include the nerves, blood vessels, and connective tissues. The main tissues that make up an organ tend to have common embryologic origins, functionally related organs often cooperate to form whole organ systems. Organs exist in all biological organisms, in particular they are not restricted to animals. In single-cell organisms like bacteria, the analogue of an organ is called organelle. A hollow organ is an organ that forms a hollow tube or pouch, such as the stomach or intestine, or that includes a cavity. Two or more organs working together in the execution of a specific body function form an organ system, the functions of organ systems often share significant overlap. For instance, the nervous and endocrine system both operate via an organ, the hypothalamus. For this reason, the two systems are combined and studied as the neuroendocrine system, the same is true for the musculoskeletal system because of the relationship between the muscular and skeletal systems. Mammals such as humans have a variety of organ systems and these specific systems are also widely studied in human anatomy. Cardiovascular system, pumping and channeling blood to and from the body and lungs with heart, digestive system, digestion and processing food with salivary glands, esophagus, stomach, liver, gallbladder, pancreas, intestines, colon, rectum and anus. Excretory system, kidneys, ureters, bladder and urethra involved in balance, electrolyte balance. Integumentary system, skin, hair and nails, nervous system, collecting, transferring and processing information with brain, spinal cord and nerves. Reproductive system, the sex organs, such as ovaries, fallopian tubes, uterus, vulva, vagina, testes, vas deferens, seminal vesicles, prostate, respiratory system, the organs used for breathing, the pharynx, larynx, trachea, bronchi, lungs and diaphragm. Skeletal system, structural support and protection with bones, cartilage, ligaments, the organ level of organisation in animals can be first detected in flatworms and the more advanced phyla. The less-advanced taxa do not show consolidation of their tissues into organs, the study of plant organs is referred to as plant morphology, rather than anatomy, as in animal systems. Organs of plants can be divided into vegetative and reproductive, vegetative plant organs are roots, stems, and leaves
20.
Blood vessel
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The blood vessels are the part of the circulatory system that transports blood throughout the human body. The word vascular, meaning relating to the vessels, is derived from the Latin vas. A few structures do not contain blood vessels and are labeled, tunica media, circularly arranged elastic fiber, connective tissue, polysaccharide substances, the second and third layer are separated by another thick elastic band called external elastic lamina. The tunica media may be rich in smooth muscle, which controls the caliber of the vessel. Veins dont have the external elastic lamina, but only an internal one, tunica adventitia, entirely made of connective tissue. It also contains nerves that supply the vessel as well as nutrient capillaries in the blood vessels. Capillaries consist of more than a layer of endothelium and occasional connective tissue. When blood vessels connect to form a region of diffuse vascular supply it is called an anastomosis, anastomoses provide critical alternative routes for blood to flow in case of blockages. There is a layer of muscle surrounding the arteries and the veins which help contract and this creates enough pressure for blood to be pumped around the body. Blood vessels are part of the system, together with the heart. They are roughly grouped as arterial and venous, determined by whether the blood in it is flowing away from or toward the heart. The term arterial blood is used to indicate blood high in oxygen. This is because they are carrying the blood to and from the lungs, respectively, blood vessels do not actively engage in the transport of blood, but arteries—and veins to a degree—can regulate their inner diameter by contraction of the muscular layer. This changes the flow to downstream organs, and is determined by the autonomic nervous system. Vasodilation and vasoconstriction are also used antagonistically as methods of thermoregulation, oxygen is the most critical nutrient carried by the blood. In all arteries apart from the artery, hemoglobin is highly saturated with oxygen. In all veins apart from the vein, the hemoglobin is desaturated at about 75%. The blood pressure in blood vessels is traditionally expressed in millimetres of mercury, in the arterial system, this is usually around 120 mmHg systolic and 80 mmHg diastolic
21.
Body cavity
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A body cavity is any fluid-filled space in a multicellular organism other than those of vessels. The human body cavity normally refers to the body cavity. A coelom is a cavity lined by a derived from mesoderm. Organs formed inside a coelom can freely move, grow, and develop independently of the wall while fluid cushions. Arthropods and most mollusks have a coelom, usually the pericardial cavity. Their principal body cavity is the hemocoel or haeomocoel of a circulatory system. Mammalian embryos develop two cavities, the coelom and the extraembryonic coelom. The intraembryonic coelom is lined by somatic and splanchnic lateral plate mesoderm, the intraembryonic coelom is the only cavity that persists in the mammal at term, which is why its name is often contracted to simply coelomic cavity. Subdividing the coelomic cavity into compartments, for example, the pericardial cavity / pericardium, organisms can be also classified according to the type of body cavity they possess. Anatomical structures are described in terms of the cavity in which they reside. The body maintains its internal organization by means of membranes, sheaths, the dorsal cavity and the ventral cavity are the largest body compartments. These cavities contain and protect delicate internal organs, and the cavity allows for significant changes in the size. The lungs, heart, stomach, and intestines, for example, can expand, the ventral cavity includes the thoracic and abdominopelvic cavities and their subdivisions. The dorsal cavity includes the cranial and spinal cavities, the cranial cavity is a large, bean-shaped cavity filling most of the upper skull where the brain is located. The vertebral cavity is a narrow, thread-like cavity running from the cranial cavity down the entire length of the spinal cord. Together the cranial cavity and vertebral cavity can be referred to as the body cavity. In the posterior cavity, the cranial cavity houses the brain, just as the brain and spinal cord make up a continuous, uninterrupted structure, the cranial and spinal cavities that house them are also continuous. The thoracic cavity consists of three cavities that fill the area of the chest
22.
Epidermis
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The epidermis is the outer of the two layers that make up the skin, the inner layer being the dermis. It provides a barrier to infection from pathogens and regulates the amount of water released from the body into the atmosphere through transepidermal water loss. The outermost part of the epidermis is composed of stratified layers of flattened cells, the epidermis has no blood supply and is nourished almost exclusively by diffused oxygen from the surrounding air. It is 95% keratinocytes but also contains melanocytes, Langerhans cells, Merkel cells, rete ridges are epidermal thickenings that extend downward between dermal papillae. Blood capillaries are found beneath the epidermis, and are linked to an arteriole, the epidermis is composed of 4 or 5 layers depending on the region of skin being considered. Those layers in descending order are, cornified layer Composed of 10 to 30 layers of polyhedral, anucleated corneocytes, with the palms, most of the barrier functions of the epidermis localize to this layer. Clear/translucent layer The skin found in the palms and soles is known as thick skin because it has 5 epidermal layers instead of 4, granular layer Keratinocytes lose their nuclei and their cytoplasm appears granular. Lipids, contained into those keratinocytes within lamellar bodies, are released into the space through exocytosis to form a lipid barrier. Those polar lipids are then converted into non-polar lipids and arranged parallel to the cell surface, for example glycosphingolipids become ceramides and phospholipids become free fatty acids. Langerhans cells, immunologically active cells, are located in the middle of this layer, Composed mainly of proliferating and non-proliferating keratinocytes, attached to the basement membrane by hemidesmosomes. Melanocytes are present, connected to numerous keratinocytes in this and other strata through dendrites, Merkel cells are also found in the stratum basale with large numbers in touch-sensitive sites such as the fingertips and lips. They are closely associated with cutaneous nerves and seem to be involved in light touch sensation, the term Malpighian layer is usually defined as both the stratum basale and stratum spinosum. The epidermis is separated from the dermis, its underlying tissue, the stratified squamous epithelium is maintained by cell division within the stratum basale. Differentiated keratinocytes secrete keratin proteins which contribute to the formation of a matrix and is an integral part of the skin barrier function. The entire epidermis is replaced by new growth over a period of about 48 days. Calcium concentration in the stratum corneum is very low in part because those relatively dry cells are not able to dissolve the ions and this calcium gradient parallels keratinocyte differentiation and as such is considered a key regulator in the formation of the epidermal layers. Elevation of extracellular calcium concentrations induces an increase in intracellular free calcium concentrations, moreover, it has been suggested that an extracellular calcium-sensing receptor also contributes to the rise in intracellular calcium concentration. Epidermal organogenesis, the formation of the epidermis, begins in the covering the embryo after neurulation
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Skin
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Skin is the soft outer tissue covering vertebrates. Other animal coverings, such as the arthropod exoskeleton have different developmental origin, structure, the adjective cutaneous means of the skin. In mammals, the skin is an organ of the system made up of multiple layers of ectodermal tissue. Skin of a different nature exists in amphibians, reptiles, all mammals have some hair on their skin, even marine mammals like whales, dolphins, and porpoises which appear to be hairless. The skin interfaces with the environment and is the first line of defense from external factors, for example, the skin plays a key role in protecting the body against pathogens and excessive water loss. Its other functions are insulation, temperature regulation, sensation, severely damaged skin may heal by forming scar tissue. This is sometimes discoloured and depigmented, the thickness of skin also varies from location to location on an organism. The skin on the palms and the soles of the feet is 4 mm thick, the speed and quality of wound healing in skin is promoted by the reception of estrogen. Primarily, fur augments the insulation the skin provides but can serve as a secondary sexual characteristic or as camouflage. On some animals, the skin is hard and thick. Reptiles and fish have hard scales on their skin for protection. Amphibian skin is not a barrier, especially regarding the passage of chemicals via skin and is often subject to osmosis. For example, a sitting in an anesthetic solution would be sedated quickly. Amphibian skin plays key roles in everyday survival and their ability to exploit a range of habitats. Keratinocytes are the cells, constituting 95% of the epidermis, while Merkel cells, melanocytes. Keratinocytes from the stratum corneum are eventually shed from the surface, the epidermis contains no blood vessels, and cells in the deepest layers are nourished by diffusion from blood capillaries extending to the upper layers of the dermis. The epidermis and dermis are separated by a sheet of fibers called the basement membrane. The dermis is the layer of skin beneath the epidermis consists of connective tissue and cushions the body from stress
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Gland
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A gland is an organ in an animals body that synthesizes substances for release into the bloodstream or into cavities inside the body or its outer surface. Every gland is formed by an ingrowth from an epithelial surface and this ingrowth may in the beginning possess a tubular structure, but in other instances glands may start as a solid column of cells which subsequently becomes tubulated. As growth proceeds, the column of cells may divide or give off offshoots, in many glands, the number of branches is limited, in others a very large structure is finally formed by repeated growth and sub-division. As a rule, the branches do not unite with one another, but in one instance, the liver, glands are classified according to their shape. If the gland retains its shape as a tube throughout it is termed a tubular gland, in the second main variety of gland the secretory portion is enlarged and the lumen variously increased in size. These are termed alveolar or saccular glands, glands are divided based on their function into two groups, Endocrine glands secrete substances that circulate through the blood stream. These glands that secrete their products through the basal lamina into the blood stream and these glands often secrete hormones, and play an important role in maintaining homeostasis. The pineal gland, thymus gland, pituitary gland, thyroid gland, exocrine glands secrete their products through a duct onto an outer surface of the body, such as the skin or the gastrointestinal tract. Secretion is directly onto the apical surface, the glands in this group can be divided into three groups, Apocrine glands a portion of the secreting cells body is lost during secretion. E. g. mammary gland, sweat gland of arm pit, pubic region, skin around anus, lips, holocrine glands the entire cell disintegrates to secrete its substances, meibomian and zeis glands. Merocrine glands cells secrete their substances by exocytosis, E. g. max sweat gland of humans, goblet cells, salivary gland, tear gland, intestinal glands. The type of product of exocrine glands may also be one of three categories, Serous glands secrete a watery, often protein-rich, fluid-like product, e. g. sweat glands. Mucous glands secrete a viscous product, rich in carbohydrates, e. g. goblet cells, sebaceous glands secrete a lipid product. These glands are known as oil glands, e. g. Fordyce spots. Adenosis is any disease of a gland, the diseased gland has abnormal formation or development of glandular tissue which is sometimes tumorous. This article incorporates text from a now in the public domain, Chisholm, Hugh
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Secretion
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Secretion is the movement of material from one point to another, e. g. secreted chemical substance from a cell or gland. In contrast, excretion, is the removal of certain substances or waste products from a cell or organism, the classical mechanism of cell secretion is via secretory portals at the cell plasma membrane called porosomes. Porosomes are permanent cup-shaped lipoprotein structure at the plasma membrane. Secretion in bacterial species means the transport or translocation of molecules for example, proteins. Secretion is an important mechanism in bacterial functioning and operation in their natural surrounding environment for adaptation. Eukaryotic cells, including human cells, have a highly evolved process of secretion, proteins targeted for the outside are synthesized by ribosomes docked to the rough endoplasmic reticulum. As they are synthesized, these proteins translocate into the ER lumen, where they are glycosylated, misfolded proteins are usually identified here and retrotranslocated by ER-associated degradation to the cytosol, where they are degraded by a proteasome. The vesicles containing the properly folded proteins then enter the Golgi apparatus, in the Golgi apparatus, the glycosylation of the proteins is modified and further posttranslational modifications, including cleavage and functionalization, may occur. The proteins are then moved into secretory vesicles which travel along the cytoskeleton to the edge of the cell, more modification can occur in the secretory vesicles. Eventually, there is vesicle fusion with the membrane at a structure called the porosome, in a process called exocytosis. Strict biochemical control is maintained over this sequence by usage of a pH gradient, the pH of the cytosol is 7.4, the ERs pH is 7.0, and the cis-golgi has a pH of 6.5. Secretory vesicles have pHs ranging between 5.0 and 6.0, some secretory vesicles evolve into lysosomes, which have a pH of 4.8, there are many proteins like FGF1, FGF2, interleukin-1 etc. which do not have a signal sequence. They do not use the classical ER-golgi pathway and these are secreted through various nonclassical pathways. At least four nonclassical protein secretion pathways have been described, many human cell types have the ability to be secretory cells. They have a well-developed endoplasmic reticulum and Golgi apparatus to fulfill their function, meibomian glands in the eyelid secrete sebum to lubricate and protect the eye. Secretion is not unique to eukaryotes alone, it is present in bacteria, ATP binding cassette type transporters are common to all the three domains of life. Some secreted proteins are translocated across the membrane by the Sec translocon. Others are translocated across the membrane by the twin-arginine translocation pathway
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Absorption (chemistry)
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In chemistry, absorption is a physical or chemical phenomenon or a process in which atoms, molecules or ions enter some bulk phase – gas, liquid or solid material. This is a different process from adsorption, since molecules undergoing absorption are taken up by the volume, a more general term is sorption, which covers absorption, adsorption, and ion exchange. Absorption is a condition in which something takes in another substance, for some examples of this effect, see liquid-liquid extraction. It is possible to extract from one phase to another a solute without a chemical reaction. Examples of such solutes are noble gases and osmium tetroxide, the process of absorption means that a substance captures and transforms energy. The absorbent distributes the material it captures throughout whole and adsorbent only distributes it through the surface and this equation is valid if concentrations are not too large and if the species x does not change its form in any of the two phases 1 or 2. In the case of gas absorption, one may calculate its concentration by using, e. g. the Ideal gas law, in alternative fashion, one may use partial pressures instead of concentrations. Absorption is a process that may be chemical or physical, chemical absorption or reactive absorption is a chemical reaction between the absorbed and the absorbing substances. Sometimes it combines with physical absorption and this type of absorption depends upon the stoichiometry of the reaction and the concentration of its reactants
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Sense
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A sense is a physiological capacity of organisms that provides data for perception. The senses and their operation, classification, and theory are overlapping topics studied by a variety of fields, most notably neuroscience, cognitive psychology, the nervous system has a specific sensory system or organ, dedicated to each sense. Humans have a multitude of senses, sight, hearing, taste, smell, and touch are the five traditionally recognized senses. However, what constitutes a sense is a matter of debate, leading to difficulties in defining what exactly a distinct sense is. Other animals also have receptors to sense the world around them, humans have a comparatively weak sense of smell and a stronger sense of sight relative to many other mammals while some animals may lack one or more of the traditional five senses. Some animals may also intake and interpret sensory stimuli in different ways. Some species of animals are able to sense the world in a way humans cannot, with some species able to sense electrical and magnetic fields. There is no agreement as to the number of senses because of differing definitions of what constitutes a sense. The senses are frequently divided into exteroceptive and interoceptive, Exteroceptive senses are senses that perceive the bodys own position, motion, external senses include the traditional five, sight, hearing, touch, smell and taste, as well as thermoception and possibly an additional weak magnetoception. Proprioceptive senses include nociception, equilibrioception, proprioception, interoceptive senses are senses that perceive sensations in internal organs. Non-human animals may possess senses that are absent in humans, such as electroreception and detection of polarized light, in Buddhist philosophy, Ayatana or sense-base includes the mind as a sense organ, in addition to the traditional five. This addition to the commonly acknowledged senses may arise from the psychological orientation involved in Buddhist thought, the mind considered by itself is seen as the principal gateway to a different spectrum of phenomena that differ from the physical sense data. This way of viewing the human sense system indicates the importance of internal sources of sensation and perception that complements our experience of the external world, there are two types of photoreceptors, rods and cones. Rods are very sensitive to light, but do not distinguish colors, cones distinguish colors, but are less sensitive to dim light. There is some disagreement as to whether this one, two or three senses. Neuroanatomists generally regard it as two senses, given that different receptors are responsible for the perception of color and brightness, the inability to see is called blindness. Blindness may result from damage to the eyeball, especially to the retina, damage to the nerve that connects each eye to the brain. Temporary or permanent blindness can be caused by poisons or medications, people with blindsight are usually not aware that they are reacting to visual sources, and instead just unconsciously adapt their behaviour to the stimulus
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Molecular diffusion
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Molecular diffusion, often simply called diffusion, is the thermal motion of all particles at temperatures above absolute zero. The rate of movement is a function of temperature, viscosity of the fluid. Diffusion explains the net flux of molecules from a region of higher concentration to one of lower concentration, the result of diffusion is a gradual mixing of material such that the distribution of molecules is uniform. Since the molecules are still in motion, but an equilibrium has been established, in a phase with uniform temperature, absent external net forces acting on the particles, the diffusion process will eventually result in complete mixing. Consider two systems, S1 and S2 at the temperature and capable of exchanging particles. If there is a change in the energy of a system, for example μ1>μ2 an energy flow will occur from S1 to S2, because nature always prefers low energy. Molecular diffusion is described mathematically using Ficks laws of diffusion. Diffusion is of importance in many disciplines of physics, chemistry. Diffusion is part of the transport phenomena, of mass transport mechanisms, molecular diffusion is known as a slower one. In cell biology, diffusion is a form of transport for necessary materials such as amino acids within cells. Diffusion of solvents, such as water, through a membrane is classified as osmosis. Metabolism and respiration rely in part upon diffusion in addition to bulk or active processes, for example, in the alveoli of mammalian lungs, due to differences in partial pressures across the alveolar-capillary membrane, oxygen diffuses into the blood and carbon dioxide diffuses out. Lungs contain a large area to facilitate this gas exchange process. Fundamentally, two types of diffusion are distinguished, Tracer diffusion and Self-diffusion, which is a mixing of molecules taking place in the absence of concentration gradient. This type of diffusion can be followed using isotopic tracers, hence the name, the tracer diffusion is usually assumed to be identical to self-diffusion. This diffusion can take place under equilibrium, an excellent method for the measurement of self-diffusion coefficients is pulsed field gradient NMR, where no isotopic tracers are needed. The self-diffusion coefficient of water has been determined with high accuracy. The self-diffusion coefficient of water is,2. 299·10−9 m²·s−1 at 25 °C and 1. 261·10−9 m²·s−1 at 4 °C
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Basement membrane
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The basement membrane is a thin, fibrous, extracellular matrix of tissue that separates the epithelium, mesothelium and endothelium from underlying connective tissue. As seen with electron microscope, the basement membrane is composed of two layers, the lamina and the underlying layer of reticular connective tissue. The underlying connective tissue attaches to the lamina with collagen VII anchoring fibrils. The two layers together are referred to as the basement membrane. The basal lamina layer can further be divided into two layers, the clear layer closer to the epithelium is called the lamina lucida, while the dense layer closer to the connective tissue is called the lamina densa. In addition to collagen, this supportive matrix contains intrinsic macromolecular components, the lamina densa, whose collagen IV fibers are coated with the heparan sulfate-rich proteoglycan perlecan, and the lamina lucida together make up the basal lamina. Integrins are not part of the lamina, they are part of desmosomes which are in the basement membrane. This is achieved by cell-matrix adhesions through substrate adhesion molecules, the basement membrane acts as a mechanical barrier, preventing malignant cells from invading the deeper tissues. Early stages of malignancy that are limited to the epithelial layer by the basement membrane are called carcinoma in situ. The basement membrane is essential for angiogenesis. Basement membrane proteins have been found to accelerate differentiation of endothelial cells, some diseases result from a poorly functioning basement membrane. The cause can be defects, injuries by the bodys own immune system. Genetic defects in the fibers of the basement membrane cause Alport syndrome. Non-collagenous domain basement membrane collagen type IV is autoantigen of autoantibodies in the autoimmune disease Goodpastures syndrome, a group of diseases stemming from improper function of basement membrane zone are united under the name epidermolysis bullosa. Intima Kefalides, Nicholas A. & Borel, Jacques P. eds, basement membranes, cell and molecular biology
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Cell junction
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A cell junction is a type of structure that exists within the tissue of some multicellular organisms, such as animals. Cell junctions consist of multiprotein complexes that provide contact between neighboring cells or between a cell and the extracellular matrix and they also build up the paracellular barrier of epithelia and control the paracellular transport. Cell junctions are especially abundant in epithelial tissues, cell junctions are especially important in enabling communication between neighboring cells via specialized proteins called communicating junctions. Cell junctions are important in reducing stress placed upon cells. In multicellular plants, the functions of cell junctions are instead provided for by cell walls. The analogues of communicative cell junctions in plants are called plasmodesmata, cells within tissues and organs must be anchored to one another and attached to components of the extracellular matrix. These junctions are most abundant in tissues that are subject to constant mechanical stress such as skin, desmosomes, also termed as maculae adherentes, can be visualized as rivets through the plasma membrane of adjacent cells. Intermediate filaments composed of keratin or desmin are attached to membrane-associated attachment proteins that form a dense plaque on the face of the membrane. Cadherin molecules form the actual anchor by attaching to the plaque, extending through the membrane. Hemidesmosomes form rivet-like links between cytoskeleton and extracellular matrix such as the basal laminae that underlie epithelia. Like desmosomes, they tie to intermediate filaments in the cytoplasm, adherens junctions share the characteristic of anchoring cells through their cytoplasmic actin filaments. Similarly to desmosomes and hemidesmosomes, their transmembrane anchors are composed of cadherins in those that anchor to other cells, there is considerable morphologic diversity among adherens junctions. Those that tie cells to one another are seen as isolated streaks or spots, the band-type of adherens junctions is associated with bundles of actin filaments that also encircle the cell just below the plasma membrane. Spot-like adherens junctions help cells adhere to extracellular matrix both in vivo and in vitro where they are called focal adhesions and this is possible due to six connexin proteins interacting to form a cylinder with a pore in the centre called a connexon. The connexon complexes stretches across the membrane and when two adjacent cell connexons interact, they form a complete gap junction channel. Connexon pores vary in size, polarity and therefore can be specific depending on the proteins that constitute each individual connexon. Gap junctions play vital roles in the body, including their role in the uniform contractile of the heart muscle. They are also relevant in signal transfers in the brain, retinal and skin cells are also dependent on gap junctions in cell differentiation and proliferation
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Morphology (biology)
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Morphology is a branch of biology dealing with the study of the form and structure of organisms and their specific structural features. This includes aspects of the appearance, i. e. external morphology, as well as the form and structure of the internal parts like bones and organs. This is in contrast to physiology, which deals primarily with function, Morphology is a branch of life science dealing with the study of gross structure of an organism or taxon and its component parts. The word morphology is from the Ancient Greek don, morphé, meaning form, among other important theorists of morphology are Lorenz Oken, Georges Cuvier, Étienne Geoffroy Saint-Hilaire, Richard Owen, Karl Gegenbaur and Ernst Haeckel. In English-speaking countries, the term molecular morphology has been used for time for describing the structure of compound molecules, such as polymers. Comparative Morphology is analysis of the patterns of the locus of structures within the plan of an organism. Functional Morphology is the study of the relationship between the structure and function of morphological features, experimental Morphology is the study of the effects of external factors upon the morphology of organisms under experimental conditions, such as the effect of genetic mutation. Anatomy is a branch of morphology that deals with the structure of organisms, most taxa differ morphologically from other taxa. Typically, closely related taxa differ much less than more distantly related ones, cryptic species are species which look very similar, or perhaps even outwardly identical, but are reproductively isolated. Conversely, sometimes unrelated taxa acquire a similar appearance as a result of convergent evolution or even mimicry, in addition, there can be morphological differences within a species, such as in Apoica flavissima where queens are significantly smaller than workers. A further problem with relying on morphological data is that what may appear, morphologically speaking, the significance of these differences can be examined through the use of allometric engineering in which one or both species are manipulated to phenocopy the other species. Invention and development of microscopy enable the observation of 3-D cell morphology with both spatial and temporal resolution. The dynamic processes of cell morphology which are controlled by a complex system play an important role in varied important biological process, such as immune. Comparative anatomy Insect morphology Morphometrics Neuromorphology Phenetics Phenotype Phenotypic plasticity Plant morphology
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Microvillus
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Thousands of microvilli form a structure called the brush border that is found on the apical surface of some epithelial cells, such as the small intestines. Microvilli are observed on the surface of eggs, aiding in the anchoring of sperm cells that have penetrated the extracellular coat of egg cells. Clustering of elongated microtubules around a sperm allows for it to be drawn closer and they are large objects that increase surface area for absorption. Microvilli are also of importance on the surface of white blood cells. Microvilli are covered in plasma membrane, which encloses cytoplasm and microfilaments, though these are cellular extensions, there are little or no cellular organelles present in the microvilli. Each microvillus has a bundle of cross-linked actin filaments, which serves as its structural core. 20 to 30 tightly bundled actin filaments are cross-linked by bundling proteins fimbrin, villin and espin to form the core of the microvilli. In the enterocyte microvillus, the core is attached to the plasma membrane along its length by lateral arms made of myosin 1a. Myosin 1a functions through a site for filamentous actin on one end. As mentioned, microvilli are formed as cell extensions from the membrane surface. Actin filaments, present in the cytosol, are most abundant near the cell surface and these filaments are thought to determine the shape and movement of the plasma membrane. The nucleation of actin fibers occurs as a response to external stimuli and this could account for the uniformity of the microvilli, which are observed to be of equal length and diameter. This nucleation process occurs from the end, allowing rapid growth from the plus end. Though the length and composition of microvilli is consistent within a group of homogenous cells. For example, the microvilli in the small and large intestines in mice are different in length. Microvilli function as the surface of nutrient absorption in the gastrointestinal tract. Because of this function, the microvillar membrane is packed with enzymes that aid in the breakdown of complex nutrients into simpler compounds that are more easily absorbed. For example, enzymes that digest carbohydrates called glycosidases are present at concentrations on the surface of enterocyte microvilli
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Keratin
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Keratin is one of a family of fibrous structural proteins. Keratin is the protein that protects cells from damage or stress. It is the key structural material making up the layer of human skin. Keratin monomers assemble into bundles to form filaments, which are tough and form strong unmineralized epidermal appendages found in reptiles, birds, amphibians. The only other biological matter known to approximate the toughness of keratinized tissue is chitin, keratin derives from Greek κερατίνη from Greek keras meaning horn originating from the Proto-Indo-European *ḱer- of the same meaning. It is composed of horn like, i. e. kerato, to which the chemical suffix -in is appended, the Greek keras is used in many animal names, e. g. Rhinoceros, meaning nose with a horn. Keratin filaments are abundant in keratinocytes in the layer of the epidermis. In addition, keratin filaments are present in cells in general. For example, mouse thymic epithelial cells are known to react with antibodies for keratin 5, keratin 8 and these antibodies are used as fluorescent markers to distinguish subsets of TECs in genetic studies of the thymus. The α-keratins in the hair, stratum corneum, horns, nails, claws and hooves of mammals, the harder β-keratins found in nails and in the scales and claws of reptiles, their shells, and in the feathers, beaks, claws of birds and quills of porcupines. The baleen plates of filter-feeding whales are made of keratin, keratins are polymers of type I and type II intermediate filaments, which have only been found in the genomes of chordates. Nematodes and many other animals seem to only have type VI intermediate filaments, lamins. The human genome encodes 54 functional keratin genes which are located in two clusters on chromosomes 12 and 17 and this suggests that they have originated from a series of gene duplications on these chromosomes. The first sequences of keratins were determined by Hanukoglu and Fuchs and these sequences revealed that there are two distinct but homologous keratin families which were named as Type I keratin and Type II keratins. This model has been confirmed by the determination of the structure of a helical domain of keratins. Fibrous keratin molecules supercoil to form a stable, left-handed superhelical motif to multimerise. The major force that keeps the structure is hydrophobic interactions between apolar residues along the keratins helical segments. Limited interior space is the reason why the triple helix of the protein collagen, found in skin, cartilage and bone
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Pyknosis
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Pyknosis, or karyopyknosis, is the irreversible condensation of chromatin in the nucleus of a cell undergoing necrosis or apoptosis. It is followed by karyorrhexis, or fragmentation of the nucleus, pyknosis is also observed in the maturation of erythrocytes and the neutrophil. The maturing metarubricyte will condense its nucleus before expelling it to become a reticulocyte, the maturing neutrophil will condense its nucleus into several connected lobes that stay in the cell until the end of its cell life. Pyknotic nuclei are found in the zona reticularis of the adrenal gland. They are also found in the keratinocytes of the outermost layer in parakeratinised epithelium
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Oral mucosa
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The oral mucosa is the mucous membrane lining the inside of the mouth and consists of stratified squamous epithelium termed oral epithelium and an underlying connective tissue termed lamina propria. The oral cavity has sometimes been described as a mirror that reflects the health of the individual, labial mucosa refers to the inside lining of the lips and is part of the lining mucosa. Alveolar mucosa refers to the lining between the buccal and labial mucosae and it is a brighter red, smooth and shiny with many blood vessels, and is not connected to underlying tissue by rete pegs. Oral mucosa consists of two layers, the stratified squamous epithelium and the deeper lamina propria. Depending on the region of the mouth, the epithelium may be nonkeratinized or keratinized, nonkeratinized squamous epithelium covers the soft palate, inner lips, inner cheeks, and the floor of the mouth, and ventral surface of the tongue. Keratinized squamous epithelium is present in the gingiva and hard palate as well as areas of the dorsal surface of the tongue. Keratinization is the differentiation of keratinocytes in the stratum granulosum into nonvital surface cells or squames to form the stratum corneum, the cells terminally differentiate as they migrate to the surface from the stratum basale where the progenitor cells are located to the superficial surface. Unlike keratinized epithelium, nonkeratinized epithelium normally has no superficial layers showing keratinization, nonkeratinized epithelium may, however, readily transform into a keratinizing type in response to frictional or chemical trauma, in which case it undergoes hyperkeratinization. Histologically, an amount of keratin is noted on the surface of the tissue. In patients who have such as clenching or grinding their teeth. This larger white, rough, raised lesion needs to be recorded so that changes may be made in the treatment plan regarding the patient’s parafunctional habits. Even keratinized tissue can undergo further level of hyperkeratinization, an increase in the amount of keratin is produced as a result of physical trauma to the region. Changes such as hyperkeratinization are reversible if the source of the injury is removed, hyperkeratinized tissue is also associated with the heat from smoking or hot fluids on the hard palate in the form of nicotinic stomatitis. The lamina propria is a connective tissue layer that consists of a network of type I and III collagen. The main cells of the lamina propria are the fibroblasts, which are responsible for the production of the fibers as well as the extracellular matrix, the lamina propria, like all forms of connective tissue proper, has two layers, papillary and dense. The papillary layer is the superficial layer of the lamina propria. It consists of connective tissue within the connective tissue papillae, along with blood vessels. The tissue has an amount of fibers, cells
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Urothelium
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Urothelium is an example of transitional epithelium. It is the type of epithelium that lines much of the tract including the renal pelvis, the ureters, the bladder. Urothelial tissue is highly specific to the tract, and has high elasticity. Urothelium consists of approximately 3-5 cell layers, accompanied by a layer of protective glycoprotein plaques at its luminal surface. Epithelia are sites of specific diseases, cancers that originate in epithelial cells are termed carcinomas, and they are characterized as having lost the mature, differentiated morphology and molecular patterns of the normal tissue. Infectious diseases also afflict epithelia where diverse microbes have surface structures that bind specific features of particular epithelial cells, genetic defects can also inhibit normal epithelial integrity, such as defects in intercellular adhesion molecules that result in blistering diseases. The second most common disease is urinary tract infection. UTIs afflict approximately half of all women during their lifetime, the majority of these infections are due to uropathogenic Escherichia coli bacteria. However, UTIs can also develop in healthcare settings and such infections are caused by a frequency of non-E. coli bacteria. One unusual condition which affects the urothelium is interstitial cystitis, a condition with similar to UTI. During hydrodistention of the bladder, small petechial hemorrhages are frequently found throughout the bladder, larger Hunners Ulcers, known for their characteristic waterfall bleeding effect, represent larger areas of bladder wall thinning and/or trauma. The cause of IC is currently unknown though some suggest that it could be genetic, researcher Susan Keay has found an unusual protein in the urine of IC patients which appears to interfere with healing, known as an Antiproliferative Factor. Because the bladder is in contact with urine for extended periods, for example, cigarette smoking leads to the concentration of carcinogens in the urine and is a leading cause of bladder cancer. Aristolochic acid, a found in plants of the Aristolochiaceae family, also causes DNA mutations and is a cause of liver, urothelial. Occupational exposure to chemicals is also a risk factor for bladder cancer. This can include aromatic amines, polycytic aromatic hydrocarbons, and diesel engine exhaust
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Human skin
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The human skin is the outer covering of the body. In humans, it is the largest organ of the integumentary system, the skin has up to seven layers of ectodermal tissue and guards the underlying muscles, bones, ligaments and internal organs. Human skin is similar to that of most other mammals, though nearly all human skin is covered with hair follicles, it can appear hairless. There are two types of skin, hairy and glabrous skin. The adjective cutaneous means of the skin. Because it interfaces with the environment, skin plays an important immunity role in protecting the body against pathogens and its other functions are insulation, temperature regulation, sensation, synthesis of vitamin D, and the protection of vitamin B folates. Severely damaged skin will try to heal by forming scar tissue and this is often discolored and depigmented. In humans, skin pigmentation varies among populations, and skin type can range from dry to oily, such skin variety provides a rich and diverse habitat for bacteria that number roughly 1000 species from 19 phyla, present on the human skin. Skin has mesodermal cells, pigmentation, such as provided by melanocytes. It also contains DNA repair enzymes that help reverse UV damage, one form predominantly produced by UV light, malignant melanoma, is particularly invasive, causing it to spread quickly, and can often be deadly. Human skin pigmentation varies among populations in a striking manner and this has led to the classification of people on the basis of skin color. The skin is the largest organ in the human body, for the average adult human, the skin has a surface area of between 1. 5-2.0 square meters. The thickness of the skin varies considerably over all parts of the body, an example is the skin on the forearm which is on average 1.3 mm in the male and 1.26 mm in the female. The average square inch of skin holds 650 sweat glands,20 blood vessels,60,000 melanocytes, the average human skin cell is about 30 micrometers in diameter, but there are variants. A skin cell usually ranges from 25-40 micrometers, depending on a variety of factors, skin is composed of three primary layers, the epidermis, the dermis and the hypodermis. Epidermis, epi coming from the Greek meaning over or upon, is the outermost layer of the skin. It forms the waterproof, protective wrap over the surface which also serves as a barrier to infection and is made up of stratified squamous epithelium with an underlying basal lamina. The main type of cells make up the epidermis are Merkel cells, keratinocytes, with melanocytes
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Pulmonary alveolus
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An alveolus is a hollow cavity found in the lung parenchyma, and is the basic unit of respiration. Lung alveoli are the ends of the tree, branching from either alveolar sacs or alveolar ducts. Alveoli are particular to mammalian lungs, different structures are involved in gas exchange in other vertebrates. The alveolar membrane is the gas-exchange surface, carbon dioxide rich blood is pumped from the rest of the body into the alveolar blood vessels where, through diffusion, it releases its carbon dioxide and absorbs oxygen. The alveoli are located in the zone of the lungs, at the ends of the alveolar ducts and alveolar sac. They provide total surface area of about 75 m2, a typical pair of human lungs contain about 700 million alveoli, producing 70m2 of surface area. Each alveolus is wrapped in a mesh of capillaries covering about 70% of its area. An adult alveolus has an diameter of 200 micrometres, with an increase in diameter during inhalation. The alveoli consist of a layer and an extracellular matrix surrounded by small blood vessels called capillaries. In some alveolar walls there are pores between alveoli called Pores of Kohn, the alveoli contain some collagen and elastic fibres. The elastic fibres allow the alveoli to stretch as they are filled with air during inhalation and they then spring back during exhalation in order to expel the carbon dioxide-rich air. There are three types of cell in the alveolar wall–two types of alveolar cell and a phagocyte. Surfactant is continuously released by exocytosis and it forms an underlying aqueous protein-containing hypophase and an overlying phospholipid film composed primarily of dipalmitoyl phosphatidylcholine. The phagocytes are macrophages, that destroy foreign material, such as bacteria, the wall of each alveolus, is lined by thin, flat, type I cells, contains numerous capillaries, and is the site of gas exchange, which occurs by diffusion. The relatively low solubility of oxygen necessitates the large surface area. Weaving between the capillaries and helping to support them is a fabric of elastic and collagenous fibres. The collagen fibres, being rigid, give the wall firmness. The other type II cells in the wall are granular cells, which secrete surfactant
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Endothelium
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It is a thin layer of simple squamous cells called endothelial cells. Endothelial cells in contact with blood are called vascular endothelial cells. Vascular endothelial cells line the entire system, from the heart to the smallest capillaries. These cells have unique functions in vascular biology and these functions include fluid filtration, such as in the glomerulus of the kidney, blood vessel tone, hemostasis, neutrophil recruitment, and hormone trafficking. Endothelium of the surfaces of the heart chambers is called endocardium. Both blood and lymphatic capillaries are composed of a layer of endothelial cells called a monolayer. In straight sections of a vessel, vascular endothelial cells typically align. Many considered the endothelium a specialized epithelial tissue, excessive or prolonged increases in permeability of the endothelial monolayer, as in cases of chronic inflammation, may lead to tissue edema/swelling. The most prevailing mechanism of endothelial dysfunction is an increase in reactive oxygen species, the signalling protein ERK5 is essential for maintaining normal endothelial cell function
