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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] |
Micrograph
A micrograph is an image, captured photographically or digitally, taken through a microscope or similar device to show a magnify, magnified image of an object. This is opposed to a macrograph or photomacrograph, an image which is also taken on a microscope but is only slightly magnified, usually less than 10 times. Micrography is the practice or art of using microscopes to make photographs. A photographic micrograph is a photomicrograph, and one taken with an electron microscope is an electron micrograph. A micrograph contains extensive details of microstructure. A wealth of information can be obtained from a simple micrograph like behavior of the material under different conditions, the phases found in the system, failure analysis, grain size estimation, elemental analysis and so on. Micrographs are widely used in all fields of microscopy. Types Photomicrograph A light micrograph or photomicrograph is a micrograph prepared using an optical microscope, a process referred to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tuft Cell
Tuft cells are chemosensory cells in the epithelial lining of the intestines. Similar tufted cells are found in the respiratory epithelium where they are known as brush cells. The name "tuft" refers to the brush-like microvilli projecting from the cells. Ordinarily there are very few tuft cells present but they have been shown to greatly increase at times of a parasitic infection. Several studies have proposed a role for tuft cells in defense against parasitic infection. In the intestine, tuft cells are the sole source of secreted interleukin 25 (IL-25). ATOH1 is required for tuft cell specification but not for maintenance of a mature differentiated state, and knockdown of Notch results in increased numbers of tuft cells. Human tuft cells The human gastrointestinal (GI) tract is full of tuft cells for its entire length. These cells were located between the crypts and villi. On the basal pole of all cells was expressed DCLK1. They did not have the same morphology as was ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sucrase
Sucrases are digestive enzymes that catalyze the hydrolysis of sucrose to its component monosaccharides, fructose and glucose. One form, sucrase-isomaltase, is secreted in the small intestine on the brush border. The enzyme invertase, which occurs more commonly in plants, fungi and bacteria, also hydrolyzes sucrose (and other fructosides) but by a different mechanism: it is a fructosidase, whereas sucrase is a glucosidase. Types * is sucrase-isomaltase * is sucrose alpha-glucosidase Physiology Sucrose intolerance (also known as congenital sucrase-isomaltase deficiency (CSID), genetic sucrase-isomaltase deficiency (GSID), or sucrase-isomaltase deficiency) occurs when sucrase is not being secreted in the small intestine. With sucrose intolerance, the result of consuming sucrose is excess gas production and often diarrhea and malabsorption. Lactose intolerance is a similar condition that reflects an individual's inability to hydrolyze the disaccharide lactose. Sucrase is secret ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Peptidase
A protease (also called a peptidase, proteinase, or proteolytic enzyme) is an enzyme that catalyzes proteolysis, breaking down proteins into smaller polypeptides or single amino acids, and spurring the formation of new protein products. They do this by cleaving the peptide bonds within proteins by hydrolysis, a reaction where water breaks bonds. Proteases are involved in numerous biological pathways, including digestion of ingested proteins, protein catabolism (breakdown of old proteins), and cell signaling. In the absence of functional accelerants, proteolysis would be very slow, taking hundreds of years. Proteases can be found in all forms of life and viruses. They have independently evolved multiple times, and different classes of protease can perform the same reaction by completely different catalytic mechanisms. Classification Based on catalytic residue Proteases can be classified into seven broad groups: * Serine proteases - using a serine alcohol * Cysteine protea ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Digestive Enzyme
Digestive enzymes take part in the chemical process of digestion, which follows the mechanical process of digestion. Food consists of macromolecules of proteins, carbohydrates, and fats that need to be broken down chemically by digestive enzymes in the mouth, stomach, pancreas, and duodenum, before being able to be absorbed into the bloodstream. Initial breakdown is achieved by chewing (mastication) and the use of digestive enzymes of saliva. Once in the stomach further mechanical churning takes place mixing the food with secreted gastric acid. Digestive gastric enzymes take part in some of the chemical process needed for absorption. Most of the enzymatic activity, and hence absorption takes place in the duodenum. Digestive enzymes are found in the digestive tracts of animals (including humans) and in the tracts of carnivorous plants, where they aid in the digestion of food, as well as inside cells, especially in their lysosomes, where they function to maintain cellular surv ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Enterocyte
Enterocytes, or intestinal absorptive cells, are simple columnar epithelial cells which line the inner surface of the small and large intestines. A glycocalyx surface coat contains digestive enzymes. Microvilli on the apical surface increase its surface area. This facilitates transport of numerous small molecules into the enterocyte from the intestinal lumen. These include broken down proteins, fats, and sugars, as well as water, electrolytes, vitamins, and bile salts. Enterocytes also have an endocrine role, secreting hormones such as leptin. Function The major functions of enterocytes include: *Ion uptake, including sodium, calcium, magnesium, iron, zinc, and copper. This typically occurs through active transport. *Water uptake. This follows the osmotic gradient established by Na+/K+ ATPase on the basolateral surface. This can occur transcellularly or paracellularly. *Sugar uptake. Polysaccharidases and disaccharidases in the glycocalyx break down large sugar molecule ... [...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] |
Innate Immune System
The innate immune system or nonspecific immune system is one of the two main immunity strategies in vertebrates (the other being the adaptive immune system). The innate immune system is an alternate defense strategy and is the dominant immune system response found in plants, fungi, prokaryotes, and invertebrates (see #Beyond vertebrates, Beyond vertebrates).. The major functions of the innate immune system are to: * recruit immune cells to infection sites by producing chemical factors, including chemical mediators called cytokines * activate the complement cascade to identify bacteria, activate cells, and promote clearance of immune complex, antibody complexes or dead cells * identify and remove foreign substances present in organs, tissues, blood and lymph, by specialized white blood cells * activate the adaptive immune system through antigen presentation * act as a physical and chemical barrier to infectious agents; via physical measures such as skin and mucus, and chemical me ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Paneth Cell
Paneth cells are cells in the small intestine epithelium, alongside goblet cells, enterocytes, and enteroendocrine cells. Some can also be found in the cecum and Vermiform appendix, appendix. They are located below the intestinal stem cells in the intestinal glands (also called crypts of Lieberkühn gland, Lieberkühn) and the large eosinophilic refractile granules that occupy most of their cytoplasm. When exposed to bacteria or bacterial antigens, Paneth cells secrete several anti-microbial compounds (notably defensins and lysozyme) that are known to be important in immunity and host-defense into the Lumen (anatomy), lumen of the intestinal gland, thereby contributing to maintenance of the gastrointestinal barrier by controlling the enteric bacteria. Therefore, Paneth cells play a role in the innate immune system. Paneth cells are named after 19th-century pathologist Joseph Paneth. Structure Paneth cells are found throughout the small intestine and the appendix at the base ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ileum
The ileum () is the final section of the small intestine in most higher vertebrates, including mammals, reptiles, and birds. In fish, the divisions of the small intestine are not as clear and the terms posterior intestine or distal intestine may be used instead of ileum. Its main function is to absorb vitamin B12, vitamin B12, bile salts, and whatever products of digestion that were not absorbed by the jejunum. The ileum follows the duodenum and jejunum and is separated from the cecum by the ileocecal valve (ICV). In humans, the ileum is about 2–4 m long, and the pH is usually between 7 and 8 (neutral or slightly base (chemistry), basic). ''Ileum'' is derived from the Greek word εἰλεός (eileós), referring to a medical condition known as ileus. Structure The ileum is the third and final part of the small intestine. It follows the jejunum and ends at the ileocecal junction, where the wikt:terminal, terminal ileum communicates with the cecum of the large intestine thro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Jejunum
The jejunum is the second part of the small intestine in humans and most higher vertebrates, including mammals, reptiles, and birds. Its lining is specialized for the absorption by enterocytes of small nutrient molecules which have been previously digested by enzymes in the duodenum. The jejunum lies between the duodenum and the ileum and is considered to start at the suspensory muscle of the duodenum, a location called the duodenojejunal flexure. The division between the jejunum and ileum is not anatomically distinct. In adult humans, the small intestine is usually long (post mortem), about two-fifths of which (about ) is the jejunum. Structure The interior surface of the jejunum—which is exposed to ingested food—is covered in finger–like projections of mucosa, called villi, which increase the surface area of tissue available to absorb nutrients from ingested foodstuffs. The epithelial cells which line these villi have microvilli. The transport of nutrien ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Duodenum
The duodenum is the first section of the small intestine in most vertebrates, including mammals, reptiles, and birds. In mammals, it may be the principal site for iron absorption. The duodenum precedes the jejunum and ileum and is the shortest part of the small intestine. In humans, the duodenum is a hollow jointed tube about long connecting the stomach to the jejunum, the middle part of the small intestine. It begins with the duodenal bulb, and ends at the duodenojejunal flexure marked by the suspensory muscle of duodenum. The duodenum can be divided into four parts: the first (superior), the second (descending), the third (transverse) and the fourth (ascending) parts. Overview The duodenum is the first section of the small intestine in most higher vertebrates, including mammals, reptiles, and birds. In fish, the divisions of the small intestine are not as clear, and the terms ''anterior intestine'' or ''proximal intestine'' may be used instead of duodenum. In mammals the d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
