Peptide and amino acid uptake. Peptidases in the glycocalyx cleave proteins to amino acids or small peptides.
Enteropeptidase (also known as enterokinase) is responsible for activating
pancreatictrypsinogen into
trypsin, which activates other pancreatic
zymogens. They are involved in the
Krebs and the
Cori Cycles and can be synthesized with
lipase.
Resorption of unconjugated bile salts. Bile that was released and not used in emulsification of lipids are reabsorbed in the
ileum. Also known as the
enterohepatic circulation.
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. The receptor component confers additional stability to the molecule.
Lactose intolerance is the most common problem of carbohydrate digestion and occurs when the human body doesn't produce a sufficient amount of
lactase enzyme to break down the sugar lactose found in dairy. As a result of this deficiency, undigested lactose is not absorbed and is instead passed on to the colon. There bacteria metabolize the lactose and in doing so release gas and metabolic products that enhance colonic motility. This causes gas and other uncomfortable symptoms.
Rotavirus selectively invades and kills mature enterocytes in the small intestine.[3]
Stem cell aging
Intestinal stem cell aging has been studied in Drosophila as a model for understanding the biology of stem cell/niche aging.[4] Using knockdown mutants defective in various genes that function in the
DNA damage response in enterocytes, it was shown that deficiency in the DNA damage response accelerates intestinal stem cell aging, thus providing a better understanding of the molecular mechanisms of this aging process.[4]
^Robbins and Cotran Pathologic Basis of Disease, Chapter 17, 749-819
^
abPark JS, Jeon HJ, Pyo JH, Kim YS, Yoo MA. Deficiency in DNA damage response of enterocytes accelerates intestinal stem cell aging in Drosophila. Aging (Albany NY). 2018 Mar 7;10(3):322-338. doi: 10.18632/aging.101390. PMID: 29514136; PMCID: PMC5892683
External links
Histology image: 11706loa – Histology Learning System at Boston University - "Digestive System: Alimentary Canal — jejunum, goblet cells and enterocytes"