Epithelium
Epithelium is one of the four basic types of animal tissue, along with connective tissue, muscle tissue and nervous tissue. Epithelial tissues line the outer surfaces of organs and blood vessels throughout the body, as well as the inner surfaces of cavities in many internal organs. An example is the outermost layer of the skin. There are three principal shapes of epithelial cell: squamous and cuboidal; these can be arranged in a single layer of cells as simple epithelium, either squamous, columnar, or cuboidal, or in layers of two or more cells deep as stratified, either squamous, columnar or cuboidal. In some tissues, a layer of columnar cells may appear to be stratified due to the placement of the nuclei; this sort of tissue is called pseudostratified. All glands are made up of epithelial cells. Functions of epithelial cells include secretion, selective absorption, transcellular transport, sensing. Epithelial layers contain no blood vessels, so they must receive nourishment via diffusion of substances from the underlying connective tissue, through the basement membrane.
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 and columnar. Squamous epithelium has cells; this is found as the lining of the mouth, the blood vessels and in the alveoli of the lungs. Cuboidal epithelium has cells whose height and width are the same. Columnar epithelium has cells taller. By layer, epithelium is classed as either simple epithelium, only one cell thick or stratified epithelium having two or more cells in thickness or multi-layered – as stratified squamous epithelium, stratified cuboidal epithelium, stratified columnar epithelium, both types of layering can be made up of any of the cell shapes. However, when taller simple columnar epithelial cells are viewed in cross section showing several nuclei appearing at different heights, they can be confused with stratified epithelia; this kind of epithelium is therefore described as pseudostratified columnar epithelium.
Transitional epithelium has cells that can change from squamous to cuboidal, depending on the amount of tension on the epithelium. 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 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 squamous. Simple cuboidal: these cells may have secretory, absorptive, or excretory functions. Examples include small collecting ducts of kidney and salivary gland. Simple columnar. Non-ciliated epithelium can possess microvilli; some tissues are referred to as simple glandular columnar epithelium. These secrete mucus and are found in stomach and rectum. Pseudostratified columnar epithelium; the ciliated type is called respiratory epithelium as it is exclusively confined to the larger respiratory airways of the nasal cavity and bronchi.
Stratified epithelium differs from simple epithelium. 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, cuboidal or columnar. Stratified epithelia can have the following specializations: The basic cell types are squamous and columnar classed by their shape. Cells of epithelial tissue are scutoid shaped packed and form a continuous sheet, they have no intercellular spaces. All epithelia is separated from underlying tissues by an extracellular fibrous basement membrane; the lining of the mouth, lung alveoli and kidney tubules are all made of epithelial tissue. The lining of the blood and lymphatic vessels are of a specialised form of epithelium called endothelium. Epithelium lines both the outside and the inside cavities and lumina of bodies; the outermost layer of human skin is composed of dead stratified squamous, keratinized epithelial cells.
Tissues that line the inside of the mouth, the esophagus, the vagina, part of the rectum are composed of nonkeratinized stratified squamous epithelium. Other surfaces that separate body cavities from the outside environment are lined by simple squamous, columnar, or pseudostratified epithelial cells. Other epithelial cells line the insides of the lungs, the gastrointestinal tract, the reproductive and urinary tracts, make up the exocrine and endocrine glands; the outer surface of the cornea is covered with fast-growing regenerated epithelial cells. A specialised form of epithelium – endothelium forms the inner lining of blood vessels and the heart, is known as vascular endotheliu
Mammal
Mammals are vertebrate animals constituting the class Mammalia, characterized by the presence of mammary glands which in females produce milk for feeding their young, a neocortex, fur or hair, three middle ear bones. These characteristics distinguish them from reptiles and birds, from which they diverged in the late Triassic, 201–227 million years ago. There are around 5,450 species of mammals; the largest orders are the rodents and Soricomorpha. The next three are the Primates, the Cetartiodactyla, the Carnivora. In cladistics, which reflect evolution, mammals are classified as endothermic amniotes, they are the only living Synapsida. The early synapsid mammalian ancestors were sphenacodont pelycosaurs, a group that produced the non-mammalian Dimetrodon. At the end of the Carboniferous period around 300 million years ago, this group diverged from the sauropsid line that led to today's reptiles and birds; the line following the stem group Sphenacodontia split off several diverse groups of non-mammalian synapsids—sometimes referred to as mammal-like reptiles—before giving rise to the proto-mammals in the early Mesozoic era.
The modern mammalian orders arose in the Paleogene and Neogene periods of the Cenozoic era, after the extinction of non-avian dinosaurs, have been among the dominant terrestrial animal groups from 66 million years ago to the present. The basic body type is quadruped, most mammals use their four extremities for terrestrial locomotion. Mammals range in size from the 30–40 mm bumblebee bat to the 30-meter blue whale—the largest animal on the planet. Maximum lifespan varies from two years for the shrew to 211 years for the bowhead whale. All modern mammals give birth to live young, except the five species of monotremes, which are egg-laying mammals; the most species-rich group of mammals, the cohort called placentals, have a placenta, which enables the feeding of the fetus during gestation. Most mammals are intelligent, with some possessing large brains, self-awareness, tool use. Mammals can communicate and vocalize in several different ways, including the production of ultrasound, scent-marking, alarm signals and echolocation.
Mammals can organize themselves into fission-fusion societies and hierarchies—but can be solitary and territorial. Most mammals are polygynous. Domestication of many types of mammals by humans played a major role in the Neolithic revolution, resulted in farming replacing hunting and gathering as the primary source of food for humans; this led to a major restructuring of human societies from nomadic to sedentary, with more co-operation among larger and larger groups, the development of the first civilizations. Domesticated mammals provided, continue to provide, power for transport and agriculture, as well as food and leather. Mammals are hunted and raced for sport, are used as model organisms in science. Mammals have been depicted in art since Palaeolithic times, appear in literature, film and religion. Decline in numbers and extinction of many mammals is driven by human poaching and habitat destruction deforestation. Mammal classification has been through several iterations since Carl Linnaeus defined the class.
No classification system is universally accepted. George Gaylord Simpson's "Principles of Classification and a Classification of Mammals" provides systematics of mammal origins and relationships that were universally taught until the end of the 20th century. Since Simpson's classification, the paleontological record has been recalibrated, the intervening years have seen much debate and progress concerning the theoretical underpinnings of systematization itself through the new concept of cladistics. Though field work made Simpson's classification outdated, it remains the closest thing to an official classification of mammals. Most mammals, including the six most species-rich orders, belong to the placental group; the three largest orders in numbers of species are Rodentia: mice, porcupines, beavers and other gnawing mammals. The next three biggest orders, depending on the biological classification scheme used, are the Primates including the apes and lemurs. According to Mammal Species of the World, 5,416 species were identified in 2006.
These were grouped into 153 families and 29 orders. In 2008, the International Union for Conservation of Nature completed a five-year Global Mammal Assessment for its IUCN Red List, which counted 5,488 species. According to a research published in the Journal of Mammalogy in 2018, the number of recognized mammal species is 6,495 species included 96 extinct; the word "mammal" is modern, from the scientific name Mammalia coined by Carl Linnaeus in 1758, derived from the Latin mamma. In an influential 1988 paper, Timothy Rowe defined Mammalia phylogenetically as the crown group of mammals, the clade consisting of the most recent common ancestor of living monotremes and therian m
Superior mesenteric vein
The superior mesenteric vein is a blood vessel that drains blood from the small intestine. At its termination behind the neck of the pancreas, the SMV combines with the splenic vein to form the hepatic portal vein; the SMV lies to the right of the named artery, the superior mesenteric artery, which originates from the abdominal aorta. Tributaries of the superior mesenteric vein drain the small intestine, large intestine, stomach and appendix and include: Right gastro-omental vein inferior pancreaticoduodenal veins veins from jejunum veins from ileum middle colic vein - drains the transverse colon right colic vein - drains the ascending colon ileocolic vein Thrombosis of the superior mesenteric vein is quite rare, but a significant cause of mesenteric ischemia and can be fatal, it is estimated. ^ Tessier DJ, Williams RA, Mesenteric ischemic thrombosis, eMedicine, URL: http://www.emedicine.com/med/topic2753.htm, Accessed July 30, 2005. "Mesenteric vein superior". Medcyclopaedia. GE. Archived from the original on 2008-06-06.
Anatomy photo:39:02-0102 at the SUNY Downstate Medical Center - "Intestines and Pancreas: The Superior Mesenteric Vessels" Anatomy image:8696 at the SUNY Downstate Medical Center
Circular folds
The circular folds are large valvular flaps projecting into the lumen of the small intestine. The entire small intestine has circular folds of mucous membrane called the valves of Kerckring and plicae circulares; the majority extend transversely around the cylinder of the small intestine for about one-half or two-thirds of its circumference, but some form complete circles, others have a spiral direction. The larger folds are about 1 cm. in depth at their broadest part. The larger and smaller folds alternate with each other, they are not found at the commencement of the duodenum, but begin to appear about 2.5 or 5 cm beyond the pylorus. In the lower part of the descending portion, below the point where the bile and pancreatic ducts enter the small intestine, they are large and approximated. In the horizontal and ascending portions of the duodenum and upper half of the jejunum they are large and numerous, but from this point, down to the middle of the ileum, they diminish in size. In the lower part of the ileum they entirely disappear.
Unlike the gastric folds in the stomach, they are permanent, are not obliterated when the intestine is distended. The spaces between circular folds are smaller than the haustra of the colon, and, in contrast to haustra, circular folds reach around the whole circumference of the intestine; these differences can assist in distinguishing the small intestine from the colon on an abdominal x-ray. The circular folds slow the passage of the digested food along the intestines, afford an increased surface for absorption, they are covered with small finger-like projections called villi. Each villus, in turn, is covered with microvilli; the microvilli absorb nutrients from the chyme. This article incorporates text in the public domain from page 1173 of the 20th edition of Gray's Anatomy Anatomy photo:39:12-0302 at the SUNY Downstate Medical Center - "Intestines and Pancreas: The Jejunum and the Ileum"
Anatomical terminology
Anatomical terminology is a form of scientific terminology used by anatomists and health professionals such as doctors. Anatomical terminology uses many unique terms and prefixes deriving from Ancient Greek and Latin; these terms can be confusing to those unfamiliar with them, but can be more precise, reducing ambiguity and errors. Since these anatomical terms are not used in everyday conversation, their meanings are less to change, less to be misinterpreted. To illustrate how inexact day-to-day language can be: a scar "above the wrist" could be located on the forearm two or three inches away from the hand or at the base of the hand. By using precise anatomical terminology such ambiguity is eliminated. An international standard for anatomical terminology, Terminologia Anatomica has been created. Anatomical terminology has quite regular morphology, the same prefixes and suffixes are used to add meanings to different roots; the root of a term refers to an organ or tissue. For example, the Latin names of structures such as musculus biceps brachii can be split up and refer to, musculus for muscle, biceps for "two-headed", brachii as in the brachial region of the arm.
The first word describes what is being spoken about, the second describes it, the third points to location. When describing the position of anatomical structures, structures may be described according to the anatomical landmark they are near; these landmarks may include structures, such as the umbilicus or sternum, or anatomical lines, such as the midclavicular line from the centre of the clavicle. The cephalon or cephalic region refers to the head; this area is further differentiated into the cranium, frons, auris, nasus and mentum. The neck area is called cervical region. Examples of structures named according to this include the frontalis muscle, submental lymph nodes, buccal membrane and orbicularis oculi muscle. Sometimes, unique terminology is used to reduce confusion in different parts of the body. For example, different terms are used when it comes to the skull in compliance with its embryonic origin and its tilted position compared to in other animals. Here, Rostral refers to proximity to the front of the nose, is used when describing the skull.
Different terminology is used in the arms, in part to reduce ambiguity as to what the "front", "back", "inner" and "outer" surfaces are. For this reason, the terms below are used: Radial referring to the radius bone, seen laterally in the standard anatomical position. Ulnar referring to the ulna bone, medially positioned when in the standard anatomical position. Other terms are used to describe the movement and actions of the hands and feet, other structures such as the eye. International morphological terminology is used by the colleges of medicine and dentistry and other areas of the health sciences, it facilitates communication and exchanges between scientists from different countries of the world and it is used daily in the fields of research and medical care. The international morphological terminology refers to morphological sciences as a biological sciences' branch. In this field, the form and structure are examined as well as the changes or developments in the organism, it is functional.
It covers the gross anatomy and the microscopic of living beings. It involves the anatomy of the adult, it includes comparative anatomy between different species. The vocabulary is extensive and complex, requires a systematic presentation. Within the international field, a group of experts reviews and discusses the morphological terms of the structures of the human body, forming today's Terminology Committee from the International Federation of Associations of Anatomists, it deals with the anatomical and embryologic terminology. In the Latin American field, there are meetings called Iberian Latin American Symposium Terminology, where a group of experts of the Pan American Association of Anatomy that speak Spanish and Portuguese and studies the international morphological terminology; the current international standard for human anatomical terminology is based on the Terminologia Anatomica. It was developed by the Federative Committee on Anatomical Terminology and the International Federation of Associations of Anatomists and was released in 1998.
It supersedes Nomina Anatomica. Terminologia Anatomica contains terminology for about 7500 human gross anatomical structures. For microanatomy, known as histology, a similar standard exists in Terminologia Histologica, for embryology, the study of development, a standard exists in Terminologia Embryologica; these standards specify accepted names that can be used to refer to histological and embryological structures in journal articles and other areas. As of September 2016, two sections of the Terminologia Anatomica, including central nervous system and peripheral nervous system, were merged to form the Terminologia Neuroanatomica; the Terminologia Anatomica has been perceived with a considerable criticism regarding its content including coverage and spelling mistakes and errors. Anatomical terminology is chosen to highlight the relative location of body structures. For instance, an anatomist might describe one band of tissue as "inferior to" another or a physician might describe a tumor as "superficial to" a deeper body structure.
Anatomical terms used to describe location
Alpha defensin
Alpha defensins are a family of mammalian defensin peptides. Defensins are 2-6 kDa, microbicidal peptides active against many Gram-negative and Gram-positive bacteria and enveloped viruses, containing three pairs of intramolecular disulfide bonds. On the basis of their size and pattern of disulfide bonding, mammalian defensins are classified into alpha and theta categories. Alpha-defensins, which have been identified in humans and several rodent species, are abundant in neutrophils, certain macrophage populations and Paneth cells of the small intestine. Defensins are produced constitutively and/or in response to microbial products or proinflammatory cytokines; some defensins are called corticostatins because they inhibit corticotropin-stimulated corticosteroid production. The mechanism by which microorganisms are killed and/or inactivated by defensins is not understood completely. However, it is believed that killing is a consequence of disruption of the microbial membrane; the polar topology of defensins, with spatially separated charged and hydrophobic regions, allows them to insert themselves into the phospholipid membranes so that their hydrophobic regions are buried within the lipid membrane interior and their charged regions interact with anionic phospholipid head groups and water.
Subsequently, some defensins can aggregate to form'channel-like' pores. The net outcome is the disruption of membrane integrity and function, which leads to the lysis of microorganisms; some defensins are synthesized as propeptides. Alpha defensins of the mouse bowel were called cryptdins when first discovered. Human alpha defensin peptides were isolated from the neutrophils and are thus called human neutrophil peptides. Human neutrophil peptides are known as α-defensins. Sequences of major human α-defensins: HNP-1, HNP-2 and HNP-3 are encoded by two genes DEFA1 and DEFA3 localized at chromosome 8, location 8p23.1. DEFA1 and DEFA3 encode identical peptides except the conversion of the first amino acid from alanine in HNP-1 to aspartic acid in HNP-3. Human neutrophil peptides are found in human atherosclerotic arteries, inhibit LDL metabolism and fibrinolysis and promote Lp binding. Human neutrophil-derived alpha-defensins are capable of enhancing phagocytosis by mouse macrophages. HNP1-3 have been reported to increase the production of tumor necrosis factor and IL-1, while decreasing the production of IL-10 by monocytes.
Increased levels of proinflammatory factors and suppressed levels of IL-10 at the site of microbial infection are to amplify local inflammatory responses. This might be further reinforced by the capacity of some human and rabbit alpha-defensins to inhibit the production of immunosuppressive glucocorticoids by competing for the binding of adrenocorticotropic hormone to its receptor. Moreover, human alpha-defensins can enhance or suppress the activation of the classical pathway of complement in vitro by binding to solid-phase or fluid-phase complement C1q, respectively; the capacity of defensins to enhance phagocytosis, promote neutrophil recruitment, enhance the production of proinflammatory cytokines, suppress anti-inflammatory mediators and regulate complement activation argues that defensins upregulate innate host inflammatory defenses against microbial invasion. Human Neutrophil Defensin-1, -3, -4 Are Elevated in Nasal Aspirates from Children with Naturally Occurring Adenovirus Infection.
In one small study, a significant increase in alpha-defensin levels was detected in T cell lysates of schizophrenia patients. The Virtual Colony Count antibacterial assay was developed to measure the activity of all six human alpha defensins on the same microplate. HNPs have been extensively studied as plasma marker of a range of diseases such as atherosclerosis, rheumatic diseases, cancer and schizophrenia. Antibodies directed against processed HNP-1 seem to have low affinity for the propeptides, proHNPs. A recent study used antibodies directed against proHNPs to show that the predominant forms of alpha-defensins in plasma are in fact proHNPs. ProHNPs are synthesized by neutrophil precursors in the bone marrow and appear to be specific markers of granulopoiesis. Defensin α-defensin β-defensin θ-defensin Cryptdin
Lymph node
A lymph node or lymph gland is an ovoid or kidney-shaped organ of the lymphatic system, of the adaptive immune system, present throughout the body. They are linked by the lymphatic vessels as a part of the circulatory system. Lymph nodes are major sites of B and T lymphocytes, other white blood cells. Lymph nodes are important for the proper functioning of the immune system, acting as filters for foreign particles and cancer cells. Lymph nodes do not have a detoxification function, dealt with by the liver and kidneys. In the lymphatic system the lymph node is a secondary lymphoid organ. A lymph node is enclosed in a fibrous capsule and is made up of an outer cortex and an inner medulla. Lymph nodes have clinical significance, they become inflamed or enlarged in various diseases which may range from trivial throat infections, to life-threatening cancers. The condition of the lymph nodes is important in cancer staging, which decides the treatment to be used, determines the prognosis; when swollen, inflamed or enlarged, lymph nodes can be hard, tender.
Lymph nodes are oval shaped and range in size from a few millimeters to about 1 -- 2 cm long. Each lymph node is surrounded by a fibrous capsule, which extends inside the lymph node to form trabeculae; the substance of the lymph node is divided into the inner medulla. The cortex is continuous around the medulla except where the medulla comes into direct contact with the hilum. Thin reticular fibers of reticular connective tissue, elastin form a supporting meshwork called a reticulin inside the node. B cells are found in the outer cortex where they are clustered together as follicular B cells in lymphoid follicles and the T cells are in the paracortex; the lymph node is divided into compartments called lymph nodules each consisting of a cortical region of combined follicle B cells, a paracortical region of T cells, a basal part of the nodule in the medulla. The number and composition of follicles can change when challenged by an antigen, when they develop a germinal center. Elsewhere in the node, there are only occasional leukocytes.
As part of the reticular network there are follicular dendritic cells in the B cell follicle and fibroblastic reticular cells in the T cell cortex. The reticular network not only provides the structural support, but the surface for adhesion of the dendritic cells and lymphocytes, it allows exchange of material with blood through the high endothelial venules and provides the growth and regulatory factors necessary for activation and maturation of immune cells. Lymph enters the convex side of the lymph node through multiple afferent lymphatic vessels, flows through spaces called sinuses. A lymph sinus which includes the subcapsular sinus, is a channel within the node, lined by endothelial cells along with fibroblastic reticular cells and this allows for the smooth flow of lymph through them; the endothelium of the subcapsular sinus is continuous with that of the afferent lymph vessel and with that of the similar sinuses flanking the trabeculae and within the cortex. All of these sinuses drain the filtered lymphatic fluid into the medullary sinuses, from where the lymph flows into the efferent lymph vessels to exit the node at the hilum on the concave side.
These vessels are smaller and don't allow the passage of the macrophages so that they remain contained to function within the lymph node. In the course of the lymph, lymphocytes may be activated as part of the adaptive immune response; the lymph node capsule is composed of dense irregular connective tissue with some plain collagenous fibers, from its internal surface are given off a number of membranous processes or trabeculae. They pass inward, radiating toward the center of the node, for about one-third or one-fourth of the space between the circumference and the center of the node. In some animals they are sufficiently well-marked to divide the peripheral or cortical portion of the node into a number of compartments, but in humans this arrangement is not obvious; the larger trabeculae springing from the capsule break up into finer bands, these interlace to form a mesh-work in the central or medullary portion of the node. In these trabecular spaces formed by the interlacing trabeculae is contained the proper lymph node substance or lymphoid tissue.
The node pulp does not, however fill the spaces, but leaves, between its outer margin and the enclosing trabeculae, a channel or space of uniform width throughout. This is termed the subcapsular sinus. Running across it are a number of finer trabeculae of reticular connective tissue, the fibers of which are, for the most part, covered by ramifying cells; the subcapsular sinus is the space between the capsule and the cortex which allows the free movement of lymphatic fluid and so contains few lymphocytes. It is continuous with the similar lymph sinuses; the lymph node contains lymphoid tissue, i.e. a meshwork or fibers called reticulum with white blood cells enmeshed in it. The regions where there are few cells within the meshwork are known as lymph sinus, it is lined by reticular cells and fixed macrophages. The subcapsular sinus has clinical importance as it is the most location where the earliest manifestations of a metastatic carcinoma in a lymph node would be found; the cortex of the lymph node is the outer portion of the node, underneath the capsule and the subcapsular sinus.
It has a deeper part known as the paracortex. The subcapsular sinus drains to the trabecul sinuses, the lymph flows into the medullary sinuses; the outer cortex consists of the B c
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