An acinus refers to any cluster of cells that resembles a many-lobed "berry", such as a raspberry. The berry-shaped termination of an exocrine gland, where the secretion is produced, is acinar in form, as is the alveolar sac containing multiple alveoli in the lungs. Acinar exocrine glands are found in many organs, including: the stomach the sebaceous gland of the scalp the salivary glands of the tongue the liver the lacrimal glands the mammary glands the pancreas the bulbourethral glandsThe thyroid follicles can be considered of acinar formation but in this case the follicles, being part of an endocrine gland, act as a hormonal deposit rather than to facilitate secretion. Mucous acini stain pale, while serous acini stain dark; the term "acinus" is considered synonymous with alveolus by some sources, but not all. The respiratory bronchioles in the lungs terminate in acini, many-lobed sacs containing groupings of alveoli. Alveolar gland Intercalated duct
Skin is the soft outer tissue covering of vertebrates with three main functions: protection and sensation. Other animal coverings, such as the arthropod exoskeleton, have different developmental origin and chemical composition; the adjective cutaneous means "of the skin". In mammals, the skin is an organ of the integumentary system made up of multiple layers of ectodermal tissue, guards the underlying muscles, bones and internal organs. Skin of a different nature exists in amphibians and birds. All mammals have some hair on their skin marine mammals like whales and porpoises which appear to be hairless; the skin 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 and the production of vitamin D folates. Damaged skin may heal by forming scar tissue; this is sometimes depigmented. The thickness of skin varies from location to location on an organism.
In humans for example, the skin located under the eyes and around the eyelids is the thinnest skin in the body at 0.5 mm thick, is one of the first areas to show signs of aging such as "crows feet" and wrinkles. The skin on the palms and the soles of the feet is the thickest skin on the body; the speed and quality of wound healing in skin is promoted by the reception of estrogen. Fur is dense hair. 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, can be processed to create leather. Reptiles and fish have hard protective scales on their skin for protection, birds have hard feathers, all made of tough β-keratins. Amphibian skin is not a strong barrier regarding the passage of chemicals via skin and is subject to osmosis and diffusive forces. For example, a frog sitting in an anesthetic solution would be sedated as the chemical diffuses through its skin. Amphibian skin plays key roles in everyday survival and their ability to exploit a wide range of habitats and ecological conditions.
Mammalian skin is composed of two primary layers: the epidermis, which provides waterproofing and serves as a barrier to infection. It forms a protective barrier over the body's surface, responsible for keeping water in the body and preventing pathogens from entering, is a stratified squamous epithelium, composed of proliferating basal and differentiated suprabasal keratinocytes. Keratinocytes are the major cells, constituting 95% of the epidermis, while Merkel cells and Langerhans cells are present; the epidermis can be further subdivided into the following strata or layers: Stratum corneum Stratum lucidum Stratum granulosum Stratum spinosum Stratum germinativum Keratinocytes in the stratum basale proliferate through mitosis and the daughter cells move up the strata changing shape and composition as they undergo multiple stages of cell differentiation to become anucleated. During that process, keratinocytes will become organized, forming cellular junctions between each other and secreting keratin proteins and lipids which contribute to the formation of an extracellular matrix and provide mechanical strength to the skin.
Keratinocytes from the stratum corneum are shed from the surface. The epidermis contains no blood vessels, 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 thin sheet of fibers called the basement membrane, made through the action of both tissues. The basement membrane controls the traffic of the cells and molecules between the dermis and epidermis but serves, through the binding of a variety of cytokines and growth factors, as a reservoir for their controlled release during physiological remodeling or repair processes; the dermis is the layer of skin beneath the epidermis that consists of connective tissue and cushions the body from stress and strain. The dermis provides tensile strength and elasticity to the skin through an extracellular matrix composed of collagen fibrils and elastic fibers, embedded in hyaluronan and proteoglycans. Skin proteoglycans are varied and have specific locations.
For example, hyaluronan and decorin are present throughout the dermis and epidermis extracellular matrix, whereas biglycan and perlecan are only found in the epidermis. It harbors many mechanoreceptors that provide the sense of touch and heat through nociceptors and thermoreceptors, it contains the hair follicles, sweat glands, sebaceous glands, apocrine glands, lymphatic vessels and blood vessels. The blood vessels in the dermis provide nourishment and waste removal from its own cells as well as for the epidermis; the dermis is connected to the epidermis through a basement membrane and is structurally divided into two areas: a superficial area adjacent to the epidermis, called the papillary region, a deep thicker area known as the reticular region. The papillary region is composed of loose areolar connective tissue; this is named for its fingerlike projections called papillae. The papillae provide the dermis with a "bumpy" surface that interdigitates with the epidermis, strengthening the connection between the tw
Endocrine glands are glands of the endocrine system that secrete their products, directly into the blood rather than through a duct. The major glands of the endocrine system include the pineal gland, pituitary gland, ovaries, thyroid gland, parathyroid gland and adrenal glands; the hypothalamus and pituitary gland are neuroendocrine organs. The pituitary gland hangs from the base of the brain by the pituitary stalk, is enclosed by bone, it consists of a hormone-producing glandular portion the anterior pituitary and a neural portion the posterior pituitary, an extension of the hypothalamus. The hypothalamus regulates the hormonal output of the anterior pituitary and creates two hormones that it exports to the posterior pituitary for storage and release. Four of the six anterior pituitary hormones are tropic hormones that regulate the function of other endocrine organs. Most anterior pituitary hormones exhibit a diurnal rhythm of release, subject to modification by stimuli influencing the hypothalamus.
Somatotropic hormone or growth hormone is an anabolic hormone that stimulates growth of all body tissues skeletal muscle and bone. It may act indirectly via insulin-like growth factors. GH mobilizes fats, stimulates protein synthesis, inhibits glucose uptake and metabolism. Secretion is regulated by growth hormone releasing hormone and growth hormone inhibiting hormone, or somatostatin. Hypersecretion causes gigantism in children and acromegaly in adults. Thyroid-stimulating hormone promotes normal activity of the thyroid gland. Thyrotropin-releasing hormone stimulates its release. Adrenocorticotropic hormone stimulates the adrenal cortex to release corticosteroids. ACTH release is triggered by corticotropin-releasing hormone and inhibited by rising glucocorticoid levels; the gonadotropins—follicle-stimulating hormone and luteinizing hormone regulate the functions of the gonads in both sexes. FSH stimulates sex cell production. Gonadotropin levels rise in response to gonadotropin-releasing hormone.
Negative feedback of gonadal hormones inhibits gonadotropin release. Prolactin promotes milk production in human females, its secretion is prompted by prolactin-releasing hormone and inhibited by prolactin-inhibiting hormone. The neurohypophysis stores and releases two hypothalamic hormones: Oxytocin stimulates powerful uterine contractions, which trigger labor and delivery of an infant, milk ejection in nursing women, its release is mediated reflexively by the hypothalamus and represents a positive feedback mechanism. Antidiuretic hormone stimulates the kidney tubules to reabsorb and conserve water, resulting in small volumes of concentrated urine and decreased plasma osmolarity. ADH is released in response to high solute concentrations in the blood and inhibited by low solute concentrations in the blood. Hyposecretion results in diabetes insipidus; the thyroid gland is located at the front of the neck, in front of the thyroid cartilage, is shaped like a butterfly, with two wings connected by a central isthmus.
Thyroid tissue consists of follicles with stored protein called colloid, containing thyroglobulin, a precursor to other thyroid hormones, which are manufactured within the colloid. The thyroid hormones increase the rate of cellular metabolism, include thyroxine and triiodothyronine. Secretion is stimulated by the hormone TSH, secreted by the anterior pituitary; when thyroid levels are high, there is negative feedback. Most T4 is converted to T3 in the target tissues. Calcitonin, produced by the parafollicular cells of the thyroid gland in response to rising blood calcium levels, depresses blood calcium levels by inhibiting bone matrix resorption and enhancing calcium deposit in bone. Excessive secretion cause deficiency cause hypothyroidism; the parathyroid glands, of which there are 4-6, are found on the back of the thyroid glands, secrete parathyroid hormone, which causes an increase in blood calcium levels by targeting bone, the intestine, the kidneys. PTH is the antagonist of calcitonin. PTH release is triggered by falling blood calcium levels and is inhibited by rising blood calcium levels.
The adrenal glands are located above the kidneys in humans and in front of the kidneys in other animals. The adrenal glands produce a variety of hormones including adrenaline and the steroids aldosterone and cortisol, it controls the behaviour during crisis and emotional situations. It stimulates its conducting tissues and metabolic processes; the pancreas, located in the abdomen and behind the stomach, is both an exocrine and an endocrine gland. The alpha and beta cells are the endocrine cells in the pancreatic islets that release insulin and glucagon and smaller amounts of other hormones into the blood. Insulin and glucagon influence blood sugar levels. Glucagon is released when blood glucose level is low, stimulates the liver to release glucose into the blood. Insulin increases the rate of glucose metabolism by most body cells. Somatostatin is released by delta acts as an inhibitor of GH, insulin and glucagon; the ovaries of the female, located in the pelvic cavity, release two main hormones.
Secretion of oestrogens by the ovarian follicles begins at puberty under the influence of FSH. Estrogens stimulate maturation of the female reproductive system and development of the secondary sexual characteristics. Progesterone is released in response to high blood levels of LH, it works wi
Pseudostratified columnar epithelium
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 occurs as squamous or cuboidal epithelia, it is considered synonymous with the term pseudostratified columnar epithelium; the term pseudostratified is derived from the appearance of this epithelium in section which conveys the erroneous impression that there is more than one layer of cells, when in fact this is a true simple epithelium since all the cells rest on the basal lamina. The nucleous of these cells, are disposed at different levels, thus creating the illusion of cellular stratification. Not all ciliated cells extend to the luminal surface. Pseudostratified epithelia function in absorption. If a specimen looks stratified but has cilia it is a pseudostratified ciliated epithelium, since stratified epithelia do not have cilia. Ciliated pseudostratified columnar epithelia is the type of respiratory epithelium found in the linings of the trachea as well as the upper respiratory tract.
Non-ciliated pseudostratified columnar epithelia are located in the membranous 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 molecularly more similar to microvilli than to true cilia. Pseudostratified columnar epithelia are found forming the straight, tubular glands of the endometrium in females, they are found in the internal part of the ear. Slide at ohio-state.edu
Simple cuboidal epithelium
Simple cuboidal epithelium is a type of epithelium that consists of a single layer of cuboidal cells. These cuboidal cells have large and central nuclei. Simple cuboidal epithelia are found on the surface of ovaries, the lining of nephrons, the walls of the renal tubules, parts of the eye and thyroid. On these surfaces, the cells perform absorption. Simple cuboidal cells are found in kidney tubules, glandular ducts and the thyroid gland. Simple cuboidal cells are found in single 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 and cellular specialization. Simple cuboidal epithelium differentiates to form the secretory and duct portions of glands, they constitute the germinal epithelium which covers the ovary and the internal walls of the seminiferous tubules in the male testes.
These cells offer some function in absorption and secretion. Histology at KUMC epithel-epith03 "Thyroid gland"
If glands are categorized by shape, tubular glands contrast with alveolar glands. Tubular glands retain their shape as a tube throughout their length whereas alveolar glands have a saclike secretory portion. Tubular glands are further classified as one of the following types: skin - glands in skin structure hair follicles - for hair growth
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