The jejunum is the moment share of the small intestine in humans and most higher vertebrates, including mammals, reptiles, and birds. Its line is specialised for the concentration by enterocytes of little alimentary 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 muscleman of the duodenum, a location called the duodenojejunal fold. [ 4 ] The division between the jejunum and ileum is not anatomically discrete. [ 5 ] In adult humans, the little intestine is normally 6–7 molarity ( 20–23 foot ) long ( position mortem ), about two-fifths of which ( about 2.5 m ( 8.2 foot ) ) is the jejunum. [ 4 ]
structure [edit ]
The inner surface of the jejunum—which is exposed to ingested food—is covered in finger–like projections of mucous membrane, called villus, which increase the surface sphere of tissue available to absorb nutrients from absorb foodstuffs. The epithelial cells which line these villi have microvilli. The ecstasy of nutrients across epithelial cells through the jejunum and ileum includes the passive transportation of sugar fructose and the active transport of amino acids, small peptides, vitamins, and most glucose. The villus in the jejunum are much longer than in the duodenum or ileum.
The ph in the jejunum is normally between 7 and 8 ( achromatic or slightly alkaline ). The jejunum and the ileum are suspended by mesentery which gives the intestine great mobility within the abdomen. It besides contains round and longitudinal polish muscle which helps to move food along by a process known as peristalsis .
histology [edit ]
The jejunum contains very few Brunner ‘s glands ( found in the duodenum ) or Peyer ‘s patches ( found in the ileum ). however, there are a few jejunal lymph nodes suspended in its mesentery. The jejunum has many large circular folds in its submucosa called fold circulares that which increase the surface area for food assimilation. The fold circulares are best developed in the jejunum. There is no trace of limit between the jejunum and the ileum. however, there are insidious histological differences :
- The jejunum has less fat inside its mesentery than the ileum.
- The jejunum is typically of larger diameter than the ileum.
- The villi of the jejunum look like long, finger-like projections, and are a histologically identifiable structure.
- While the length of the entire intestinal tract contains lymphoid tissue, only the ileum has abundant Peyer’s patches, which are unencapsulated lymphoid nodules that contain large numbers of lymphocytes and immune cells, like microfold cells.
- Transmission electron microscope ( TEM ) trope of human jejunum
- TEM image of mouse jejunum ( 14,000-fold exaggeration )
- Dog jejunum ( exaggerated 100-fold )
function [edit ]
The lining of the jejunum is specialized for the absorption by enterocytes of belittled food particles which have been previously digested by enzymes in the duodenum. once absorbed, nutrients ( with the exception of fatten, which goes to the lymph ) pass from the enterocytes into the enterohepatic circulation and enter the liver via the hepatic portal vein vein, where the lineage is processed. [ 6 ]
early animals [edit ]
In fish, the divisions of the minor intestine are not as clear and the terms middle intestine or mid-gut may be used rather of jejunum. [ 7 ]
history [edit ]
etymology [edit ]
Jejunum is derived from the Latin password jējūnus, meaning “ fast. ” It was so called because this part of the small intestine was frequently found to be invalidate of food following death, [ 8 ] due to its intensive peristaltic action relative to the duodenum and ileum. The early Modern English adjective jejune is derived from the same root. [ 9 ]