|
Exocrine System
Exocrine glands are glands that secrete substances onto an epithelial surface by way of a duct. Examples of exocrine glands include sweat, salivary, mammary, ceruminous, lacrimal, sebaceous, prostate and mucous. Exocrine glands are one of two types of glands in the human body, the other being endocrine glands, which secrete their products directly into the bloodstream. The liver and pancreas are both exocrine and endocrine glands; they are exocrine glands because they secrete products—bile and pancreatic juice—into the gastrointestinal tract through a series of ducts, and endocrine because they secrete other substances directly into the bloodstream. Exocrine sweat glands are part of the integumentary system; they have eccrine and apocrine types. Classification Structure Exocrine glands contain a glandular portion and a duct portion, the structures of which can be used to classify the gland. * The duct portion may be branched (called compound) or unbranched (called sim ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Acinus
An acinus (; : acini; adjective, acinar or acinous) refers to any cluster of cells that resembles a many-lobed "berry", such as a raspberry ('' acinus'' is Latin for "berry"). 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. Exocrine glands 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 (Cowper's) glands The thyroid follicles can also 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 usually stain pale, while serous acini usually stain dark. Lungs The end of the terminal bronchioles in the lungs The lungs are the primary organs of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bile
Bile (from Latin ''bilis''), also known as gall, is a yellow-green/misty green fluid produced by the liver of most vertebrates that aids the digestion of lipids in the small intestine. In humans, bile is primarily composed of water, is produced continuously by the liver, and is stored and concentrated in the gallbladder. After a human eats, this stored bile is discharged into the first section of the small intestine, known as the duodenum. Composition In the human liver, bile is composed of 97–98% water, 0.7% bile salts, 0.2% bilirubin, 0.51% fats ( cholesterol, fatty acids, and lecithin), and 200 meq/L inorganic salts. The two main pigments of bile are bilirubin, which is orange-yellow, and its oxidised form biliverdin, which is green. When mixed, they are responsible for the brown color of feces. About of bile is produced per day in adult human beings. Function Bile or gall acts to some extent as a surfactant, helping to emulsify the lipids in food. B ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Intestinal Gland
In histology, an intestinal gland (also Crypt (anatomy), crypt of Johann Nathanael Lieberkühn, Lieberkühn and intestinal crypt) is a gland found in between Intestinal villus, villi in the intestinal epithelium, intestinal epithelial lining of the small intestine and large intestine (or colon). The glands and intestinal villi are covered by epithelium, which contains multiple types of Cell (biology), cells: enterocytes (absorbing water and electrolytes), goblet cells (secreting mucus), enteroendocrine cells (secreting hormones), cup cells, myofibroblast, tuft cells, and at the base of the gland, Paneth cells (secreting anti-microbial peptides) and stem cells. Structure Intestinal glands are found in the epithelia of the small intestine, namely the duodenum, jejunum, and ileum, and in the large intestine (colon), where they are sometimes called ''colonic crypts''. Intestinal glands of the small intestine contain a base of replicating stem cells, Paneth cells of the innate immune sy ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Goblet Cell
Goblet cells are simple columnar epithelial cells that secrete gel-forming mucins, like mucin 2 in the lower gastrointestinal tract, and mucin 5AC in the respiratory tract. The goblet cells mainly use the merocrine method of secretion, secreting vesicles into a duct, but may use apocrine methods, budding off their secretions, when under stress. The term '' goblet'' refers to the cell's goblet-like shape. The apical portion is shaped like a cup, as it is distended by abundant mucus laden granules; its basal portion lacks these granules and is shaped like a stem. The goblet cell is highly polarized with the nucleus and other organelles concentrated at the base of the cell and secretory granules containing mucin, at the apical surface. The apical plasma membrane projects short microvilli to give an increased surface area for secretion. Goblet cells are typically found in the respiratory, reproductive and lower gastrointestinal tract and are surrounded by other columnar cell ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Salivary Gland
The salivary glands in many vertebrates including mammals are exocrine glands that produce saliva through a system of ducts. Humans have three paired major salivary glands ( parotid, submandibular, and sublingual), as well as hundreds of minor salivary glands. Salivary glands can be classified as serous, mucous, or seromucous (mixed). In serous secretions, the main type of protein secreted is alpha-amylase, an enzyme that breaks down starch into maltose and glucose, whereas in mucous secretions, the main protein secreted is mucin, which acts as a lubricant. In humans, 1200 to 1500 ml of saliva are produced every day. The secretion of saliva (salivation) is mediated by parasympathetic stimulation; acetylcholine is the active neurotransmitter and binds to muscarinic receptors in the glands, leading to increased salivation. A proposed fourth pair of salivary glands, the tubarial glands, were first identified in 2020. They are named for their location, being positione ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Eccrine Sweat Gland
Eccrine sweat glands (; from Greek '' ek(s)+krinein'' 'out(wards)/external+ secrete') are the major sweat glands of the human body. Eccrine sweat glands are found in virtually all skin, with the highest density in the palms of the hands, and soles of the feet, and on the head, but much less on the torso and the extremities. In other mammals, they are relatively sparse, being found mainly on hairless areas such as foot pads. They reach their peak of development in humans, where they may number 200–400/cm2 of skin surface.Bolognia, J., Jorizzo, J., & Schaffer, J. (2012). Dermatology (3rd ed., pp. 539-544). hiladelphia Elsevier Saunders. They produce sweat, a merocrine secretion which is clear, odorless substance, consisting primarily of water. These are present from birth. Their secretory part is present deep inside the dermis. Eccrine glands are composed of an intraepidermal spiral duct, the "acrosyringium"; a dermal duct, consisting of a straight and coiled portion; and a se ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Exocytosis
Exocytosis is a term for the active transport process that transports large molecules from cell to the extracellular area. Hormones, proteins and neurotransmitters are examples of large molecules that can be transported out of the cell. Exocytosis is a crucial transport mechanism that enables polar molecules to flow through the cell membranes’ hydrophobic lipid bilayer. The transport process is essential to hormone secretion, immune response and neurotransmission. Both prokaryotes and eukaryotes undergo exocytosis. Prokaryotes secrete molecules and cellular waste through translocons that are localized to the cell membrane. In addition, they secrete molecules to other cells through specialized organs. Eukaryotes rely on multiple cellular processes to perform the exocytosis process. Eukaryotes have several organelles and a nucleus in the cytoplasm that are connected through multiple transport routes, that is formally known as the secretory pathway. This is a complex pathway with ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Merocrine
Merocrine (or eccrine) is a term used to classify exocrine glands and their secretions in the study of histology. A cell is classified as merocrine if the secretions of that cell are excreted via exocytosis from secretory cells into an epithelial-walled duct or ducts and then onto a bodily surface or into the lumen. Merocrine is the most common manner of secretion. The gland releases its product and no part of the gland is lost or damaged (compare holocrine and apocrine). The term eccrine is specifically used to designate merocrine secretions from sweat glands ( eccrine sweat glands), although the term merocrine is often used interchangeably. Examples * * * Paneth cells of the intestine * Certain sweat gland Sweat glands, also known as sudoriferous or sudoriparous glands, , are small tubular structures of the skin that produce sweat. Sweat glands are a type of exocrine gland, which are glands that produce and secrete substances onto an epithelial s ...s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Holocrine
Holocrine (from Ancient Greek ὅλος; ''hólos'', “whole, entire” + κρῑ́νω; ''krī́nō'', “to separate”) is a term used to classify the mode of secretion in exocrine glands in the study of histology. Holocrine secretions are produced in the cytoplasm of the cell and released by the rupture of the plasma membrane, which destroys the cell and results in the secretion of the product into the Lumen (anatomy), lumen. Holocrine gland secretion is the most damaging (to the cell itself and not to the host which begot the cell) type of secretion, with merocrine secretion being the least damaging and apocrine secretion falling in between. Examples of holocrine glands include the sebaceous glands of the skin and the meibomian glands of the eyelid. The sebaceous gland is an example of a holocrine gland because its product of secretion (sebum) is released with remnants of dead cells. References External links Diagram at uwa.edu.au {{Glands Exocrine system ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Apocrine
Apocrine () is a term used to classify the mode of secretion of exocrine glands. In apocrine secretion, secretory cells accumulate material at their apical ends, often forming blebs or "snouts", and this material then buds off from the cells, forming extracellular vesicles. The secretory cells therefore lose part of their cytoplasm in the process of secretion. An example of true apocrine glands is the mammary glands, responsible for secreting breast milk. Apocrine glands are also found in the anogenital region and axilla The axilla (: axillae or axillas; also known as the armpit, underarm or oxter) is the area on the human body directly under the shoulder joint. It includes the axillary space, an anatomical space within the shoulder girdle between the arm a ...e. Apocrine secretion is less damaging to the gland than holocrine secretion (which destroys a cell) but more damaging than merocrine secretion ( exocytosis). File:405 Modes of Secretion by Glands Apocrine.p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Merocrine
Merocrine (or eccrine) is a term used to classify exocrine glands and their secretions in the study of histology. A cell is classified as merocrine if the secretions of that cell are excreted via exocytosis from secretory cells into an epithelial-walled duct or ducts and then onto a bodily surface or into the lumen. Merocrine is the most common manner of secretion. The gland releases its product and no part of the gland is lost or damaged (compare holocrine and apocrine). The term eccrine is specifically used to designate merocrine secretions from sweat glands ( eccrine sweat glands), although the term merocrine is often used interchangeably. Examples * * * Paneth cells of the intestine * Certain sweat gland Sweat glands, also known as sudoriferous or sudoriparous glands, , are small tubular structures of the skin that produce sweat. Sweat glands are a type of exocrine gland, which are glands that produce and secrete substances onto an epithelial s ...s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Acinar Gland
An acinus (; : acini; adjective, acinar or acinous) refers to any cluster of cells that resembles a many-lobed "berry", such as a raspberry (''acinus'' is Latin for "berry"). 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. Exocrine glands 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 (Cowper's) glands The thyroid follicles can also 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 usually stain pale, while serous acini usually stain dark. Lungs The end of the terminal bronchioles in the lungs mark the beginning of a pulmonary acinus ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
