Small intestineThe small intestine or small bowel is an organ in the gastrointestinal tract where most of the absorption of nutrients from food takes place. It lies between the stomach and large intestine, and receives bile and pancreatic juice through the pancreatic duct to aid in digestion. The small intestine is about 6.5 metres (21 feet) long and folds many times to fit in the abdomen.
DigestionDigestion is the breakdown of large insoluble food compounds into small water-soluble components so that they can be absorbed into the blood plasma. In certain organisms, these smaller substances are absorbed through the small intestine into the blood stream. Digestion is a form of catabolism that is often divided into two processes based on how food is broken down: mechanical and chemical digestion.
Brush borderA brush border (striated border or brush border membrane) is the microvillus-covered surface of simple cuboidal and simple columnar epithelium found in different parts of the body. Microvilli are approximately 100 nanometers in diameter and their length varies from approximately 100 to 2,000 nanometers.NutrientA nutrient is a substance used by an organism to survive, grow and reproduce. The requirement for dietary nutrient intake applies to animals, plants, fungi and protists. Nutrients can be incorporated into cells for metabolic purposes or excreted by cells to create non-cellular structures such as hair, scales, feathers, or exoskeletons.
EpitheliumEpithelium or epithelial tissue is a thin, continuous, protective layer of cells with little extracellular matrix. An example is the epidermis, the outermost layer of the skin. Epithelial (mesothelial) tissues line the outer surfaces of many internal organs, the corresponding inner surfaces of body cavities, and the inner surfaces of blood vessels. Epithelial tissue is one of the four basic types of animaltissue, along with connective tissue, muscle tissue and nervous tissue.
Lumen (anatomy)In biology, a lumen (pl.: lumina) is the inside space of a tubular structure, such as an artery or intestine. It comes from Latin lumen'an opening'.
EnterocyteEnterocytes, or intestinal absorptive cells, are simple columnarepithelial 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.
EnzymeLarge biological molecule that acts as a catalystThe enzyme glucosidase converts the sugar maltose into two glucose sugars. Active site residues in red, maltose substrate in black, and NADcofactor in yellow. (PDB: 1OBB)An enzyme is a biological macromolecule, usually a protein, that acts as a biological catalyst, accelerating chemical reactions without being consumed in the process.
Amino acidOrganic compounds containing amine and carboxylic groupsStructure of a typical L-alpha-amino acid in the "neutral" formAmino acids are organic compounds that contain both amino and carboxylic acidfunctional groups. Although over 500 amino acids exist in nature, by far the most important are the 22 α-amino acids incorporated into proteins. Only these 22 appear in the genetic code of life.
MicrovillusMicrovilli (sing.: microvillus) are microscopic cellular membrane protrusions that increase the surface area for diffusion and minimize any increase in volume, and are involved in a wide variety of functions, including absorption, secretion, cellular adhesion, and mechanotransduction.
Circular foldsThe circular folds (also known as valves of Kerckring, valves of Kerchkring, plicae circulares, plicae circulae, and valvulae conniventes) are large valvular flaps projecting into the lumen of the small intestine.
Goblet cellGoblet 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.*As an Amazon Associate I earn from qualifying purchases.