In histology, an intestinal gland (also crypt of Lieberkühn and intestinal crypt) is a gland found in the epithelial lining of the small intestine and colon. The glands and intestinal villi are covered by epithelium which contains multiple types of cells: enterocytes (absorbing water and electrolytes), goblet cells (secreting mucus), enteroendocrine cells (secreting hormones), tuft cells and, at the base of the gland, Paneth cells (secreting anti-microbial peptides) and stem cells.
Intestinal crypts are found in the epithelia of the small intestine, namely the duodenum, jejunum and ileum. Intestinal crypts contain a base of replicating stem cells, Paneth cells of the innate immune system, and goblet cells, which produce mucous. :282 In the colon, crypts do not have Paneth cells.
The enterocytes in the mucosa contain digestive enzymes that digest specific food while they are being absorbed through the epithelium. These enzymes include peptidases, sucrase, maltase, lactase and intestinal lipase. This is in contrast to the stomach where chief cells secrete pepsinogen, in the intestine the aforementioned digestive enzymes are not secreted by the cells of the intestine.
Also, new epithelium is formed here, which is important because the cells at this site are continuously worn away by the passing food. The basal (further from the intestinal lumen) portion of the crypt contains multipotent stem cells. During each mitosis, one of the two daughter cells remains in the crypt as a stem cell, while the other differentiates and migrates up the side of the crypt and eventually into the villus. Goblet cells are among the cells produced in this fashion. Many genes have been shown to be important for the differentiation of intestinal stem cells.[clarification needed]
Loss of proliferation control in the crypts is thought to lead to colorectal cancer.
Intestinal juice refers to the clear to pale yellow watery secretions from the glands lining the small intestine walls. The Brunner´s glands secrete large amounts of alkaline mucus in response to (1) tactile or irritating stimuli on the duodenal mucosa; (2) vagal stimulation, which causes increased Brunner’s glands secretion concurrently with increase in stomach secretion; and (3) gastrointestinal hormones, especially secretin.
Its function is to complete the process begun by pancreatic juice; the enzyme trypsin exists in pancreatic juice in the inactive form trypsinogen, it is activated by the intestinal enterokinase in intestinal juice. Trypsin can then activate other protease enzymes and catalyze the reaction pro-colipase → colipase. Colipase is necessary, along with Bile Salts, to enable Lipase function.
Intestinal juice also contains hormones, digestive enzymes, mucus, substances to neutralize hydrochloric acid coming from the stomach and erepsin which further digests polypeptides into amino acids, completing protein digestion.
Pathologic processes that lead to crohn's, i.e. on-going, intestinal crypt destruction are associated with branching of the crypts.
Causes of crypt branching include:
- inflammatory bowel disease (e.g. ulcerative colitis, Crohn's disease),
- persistent infectious colitides, and
- ischemic colitis.
The eponymous term (crypts of Lieberkühn) is named after the 18th-century German anatomist Johann Nathanael Lieberkühn.
- Deakin, Barbara Young ... [et al.] ; drawings by Philip J. (2006). Wheater's functional histology : a text and colour atlas (5th ed. ed.). [Edinburgh?]: Churchill Livingstone/Elsevier. ISBN 978-0-4430-6-8508.
- Gonçalves, Carlos; Bairos, Vasco (2010). Histologia, Texto e Imagens (in Portuguese) (3 ed.). Imprensa da Universidade de Coimbra. p. 261. ISBN 9789892600703.
- Guyton and Hall Textbook of Medical Physiology, 11th edition, p. 805
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- synd/2651 at Who Named It?
- intestinal+glands at eMedicine Dictionary