Intestinal gland

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Intestinal gland
Small intestine low mag.jpg
Micrograph of the small intestine mucosa showing the crypts of Lieberkühn - bottom 1/3 of image. H&E stain.
Latin glandulae intestinales
Gray's p.1174
Anatomical terminology

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.

Structure[edit]

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. [1] :282 In the colon, Intestinal crypts do not have Paneth cells.[2]

Function[edit]

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[edit]

Intestinal juice refers to the clear to pale yellow watery secretions from the glands lining the small intestine walls. Secretion is stimulated by the mechanical pressure of partly digested food in the intestine.[citation needed]

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.[citation needed]

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.[citation needed]

Clinical significance[edit]

Micrograph showing intestinal crypt branching, a histopathological finding of chronic colitides. H&E stain.

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:

Micrograph showing crypt inflammation. H&E stain.

Crypt inflammation is known as cryptitis and characterized by the presence of neutrophils between the enterocytes. A severe cryptitis may lead to a crypt abscess.

History[edit]

The eponymous term (crypts of Lieberkühn) is named after the 18th-century German anatomist Johann Nathanael Lieberkühn.

See also[edit]

Additional images[edit]

References[edit]

  1. ^ 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. 
  2. ^ Gonçalves, Carlos; Bairos, Vasco (2010). Histologia, Texto e Imagens (in Português) (3 ed.). Imprensa da Universidade de Coimbra. p. 261. ISBN 9789892600703. 

External links[edit]