Enterocytes, or intestinal absorptive cells, are simple columnar epithelial cells found in the small intestines and colon. A simple columnar epithelium is a Columnar epithelium that is uni-layered In biology and medicine epithelium is a tissue composed of cells that line the cavities and surfaces of structures throughout the body In Biology the small Intestine is the part of the Gastrointestinal tract (gut between the Stomach and the Large intestine, and comprises A glycocalyx surface coat contains digestive enzymes. Glycocalyx is a general term referring to extracellular Polymeric material produced by some Bacteria, Epithelia and other cells Microvilli on the apical surface increase surface area for the digestion and transport of molecules from the intestinal lumen. Microvilli (singular microvillus) are microscopic cellular membrane protrusions that increase the surface area of cells and are involved in a wide variety of functions including The cells also have a secretory role.
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Functions
The major functions of enterocytes include[1]:
- Ion uptake, including sodium, calcium, magnesium, and iron. This typically occurs through active transport. Active transport is the mediated process of moving particles across Biological membrane against the concentration gradient
- Water uptake. This follows the osmotic gradient established by Na+/K+ ATPase on the basolateral surface. This can occur transcellularly or paracellularly. Diffusion is the net movement of particles (typically molecules from an area of high concentration to an area of low concentration by uncoordinated random movement Paracellular transport refers to the transfer of substances between cells of an Epithelium.
- Sugar uptake. Polysaccharidases and disaccharidases in the glycocalyx break down large sugar molecules, which are then absorbed. Glucose crosses the apical membrane of the enterocyte using the Na+ dependent glucose transporter. Glucose (Glc a Monosaccharide (or simple Sugar) also known as grape sugar, is an important Carbohydrate in Biology. Glucose transporters (GLUT or SLC2A family are a family of Membrane proteins found in most mammalian cells Function Glucose is an essential It moves through the cytosol (cytoplasm) and exits the enterocyte via the basolateral membrane (into the blood capillary) using GLUT-2 (SLC2A2). The cytosol or intracellular fluid (or cytoplasmic matrix) is the liquid found inside cells. Capillaries are the smallest of a body's Blood vessels measuring 5-10 μm in diameter which connect Arterioles and Venules and enable the interchange Galactose uses the same transport system. Galactose (Gal (also called brain sugar) is a type of Sugar which is less sweet than Glucose. Fructose, on the other hand, crosses the apical membrane of the enterocyte, using GLUT-5 (SLC2A5). Fructose (also levulose or laevulose) is a simple reducing Sugar ( Monosaccharide) found in many foods and is one of the three It is thought to cross into the blood capillary using one of the other GLUT transporters.
- Peptide and amino acid uptake. Peptidases in the glycocalyx cleave proteins to amino acids or small peptides. Enteropeptidase is responsible for activating pancreatic trypsinogen into trypsin, which activates other pancreatic zymogens. Enteropeptidase (also called enterokinase) is an Enzyme involved in human Digestion. The pancreas is a Gland organ in the digestive and Endocrine system of Vertebrates. Trypsinogen (EC 342318/20/21/23/24/26 is the Precursor form of the Pancreatic Enzyme Trypsin or a Zymogen. Trypsin ( is a Serine protease found in the Digestive system, where it breaks down Proteins Trypsin predominantly cleaves peptide chains at the carboxyl A zymogen (or proenzyme) is an inactive Enzyme precursor. A zymogen requires a biochemical change (such as a Hydrolysis reaction revealing the
- Lipid uptake. Lipids are broken down by pancreatic lipase and bile, and then diffuse into the enterocytes. The pancreas is a Gland organ in the digestive and Endocrine system of Vertebrates. A lipase is a Water-soluble Enzyme that Catalyzes the Hydrolysis of Ester bonds in water–insoluble Lipid Bile or gall is a bitter yellow or green Alkaline fluid secreted by Hepatocytes from the Liver of most Vertebrates In many species Smaller lipids are transported into intestinal capillaries, while larger lipids are processed by the Golgi and smooth endoplasmic reticulum into lipoprotein chylomicra and exocytozed into lacteals. The endoplasmic reticulum (Greek endo = "within" (prefix plásma = "formed entity" Latin reticulum = "little net" or ER, is an Organelle Chylomicrons are large lipoprotein particles that transport dietary lipids from the intestines to other locations in the body Exocytosis (ek-soh-sy-TOH-sis Greek: Έξω - external and κύτος - cell is the durable process by which a cell directs secretory vesicles out of the Cell A lacteal is a lymphatic capillary that absorbs dietary fats in the villi of the Small intestine.
- Vitamin uptake. Receptors bind to the vitamin B12-gastric intrinsic factor complex and are taken into the cell. Intrinsic factor is a Glycoprotein produced by the Parietal cells of the Stomach.
- Resorption of unconjugated bile salts. Bile that was released and not used in emulsification of lipids are reabsorbed in the ileum. In Anatomy of the Digestive system, the ileum is the final section of the Small intestine. Also known as the enterohepatic circulation. Enterohepatic circulation refers to the circulation of Bile from the Liver, where it is produced to the Small intestine, where it aids in Digestion
- Secretion of immunoglobulins. IgA from plasma cells in the mucosa are absorbed through receptor mediated endocytosis on the basolateral surface and released as a receptor-IgA complex into the intestinal lumen. Immunoglobulin A ( IgA) is an Antibody playing a critical role in mucosal immunity Plasma cells (also called plasma B cells or plasmocytes) are cells of the Immune system that secrete large amounts of antibodies. The mucous membranes (or mucosae; singular mucosa) are linings of mostly endodermal origin covered in Epithelium, which are involved in Endocytosis is a process where cells absorb material ( Molecules such as proteins from the outside by engulfing it with their Cell membrane. The receptor component confers additional stability to the molecule.
Pathology
Dietary fructose intolerance occurs when there is a deficiency in the amount of fructose carrier. Fructose malabsorption or Dietary Fructose Intolerance is a digestive disorder of the Small intestine in which the Fructose carrier in Enterocytes GLUT5 is a Fructose transporter Fructose malabsorption or Dietary Fructose Intolerance is a dietary disability of the Small intestine, where the amount
Lactose intolerance is the most common problem of carbohydrate digestion and is created by an insufficient amount of lactase (a disaccharidase) enzyme, which is used to break down the sugar. Lactose intolerance is the inability to metabolize Lactose, a sugar found in Milk and other Dairy products because the required enzyme Lactase (LCT a part of the β-galactosidase family of Enzymes is a Glycoside hydrolase involved in the Hydrolysis As a result of this deficiency, undigested lactose cannot be absorbed and is instead passed on to the colonic bacteria, which metabolize the lactose. The bacteria release gas and metabolic products that enhance colonic motility.
Problems with the gastric intrinsic factor or its receptor can result in pernicious anemia. Pernicious anemia (also known as Biermer's anemia, Addison's anemia, or Addison-Biermer anemia) is a form of Megaloblastic anemia due to
References
- ^ Ross, M. H. & Pawlina, W. 2003. Histology: A Text and Atlas, 4th Edition. Lippincott Williams & Wilkins, Philadelphia.
External links
- Histology at BU 11706loa - "Digestive System: Alimentary Canal - jejunum, goblet cells and enterocytes"
- MeSH Enterocytes
Dictionary
enterocyte
-noun
- A cell found in the lining of the intestines and colon, participating in absorption of nutrients and secretion of digestive enzymes.
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