Intestinal villi (SG: villus) are small, finger-like projections that extend into the lumen of the small intestine. Each villus is approximately 0.5–1.6 mm in length (in humans), and has many microvilli projecting from the enterocytes of its epithelium which collectively form the striated or brush border. Each of these microvilli are about 1 µm in length, around 1000 times shorter than a single villus. The intestinal villi are much smaller than any of the circular folds in the intestine.
Villi increase the internal surface area of the intestinal walls making available a greater surface area for absorption. An increased absorptive area is useful because digested nutrients (including monosaccharide and amino acids) pass into the semipermeable villi through diffusion, which is effective only at short distances. In other words, increased surface area (in contact with the fluid in the lumen) decreases the average distance travelled by nutrient molecules, so effectiveness of diffusion increases. The villi are connected to the blood vessels so the circulating blood then carries these nutrients away.
Cross-section histology of small intestinal villi of the human terminal ileum.
MicroCT-based volume projection of the jejunal mucosa of a chicken. Virtual volume block with vertically truncated villi in oblique view. Scalebar = 0.2 mm.
MicroCT-based volume projection of the jejunal mucosa of a chicken. Virtual horizontal cut through villi. Scalebar = 0.2 mm.
There, the villi and the microvilli increase intestinal absorptive surface area approximately 40-fold and 600-fold, respectively, providing exceptionally efficient absorption of nutrients in the lumen.[2]
There are also enzymes (enterocyte digestive enzyme) on the surface for digestion. Villus capillaries collect amino acids and simple sugars taken up by the villi into the blood stream. Villus lacteals (lymph capillaries) collect absorbed chylomicrons, which are lipoproteins composed of triglycerides, cholesterol and amphipathic proteins, and are taken to the rest of the body through the lymph fluid.
Villi are specialized for absorption in the small intestine as they have a thin wall, one cell thick, which enables a shorter diffusion path. They have a large surface area so there will be more efficient absorption of fatty acids and glycerol into the blood stream. They have a rich blood supply to keep a concentration gradient.[3]
Structure of a villus (see reference quoted in text)
Clinical significanceedit
Villous atrophyedit
Different stages of coeliac disease
In diseases of the small intestine the villi can become flattened due to the effects of inflammation, and the villi can sometimes disappear. This deterioration is known as villous atrophy, and is often a feature of coeliac disease.[4]
Additional imagesedit
Microvilli (shaggy hair) show electron dense plaques (open arrow) at their apices.
C. W. Chan, Y. K. Leung and K. W. Chan (2014). "Microscopic anatomy of the vasculature of the human intestinal villus - a study with review". European Journal of Anatomy, 18 (4): 291–301.
February 16, 2024
intestinal, villus, intestinal, villi, villus, small, finger, like, projections, that, extend, into, lumen, small, intestine, each, villus, approximately, length, humans, many, microvilli, projecting, from, enterocytes, epithelium, which, collectively, form, s. Intestinal villi SG villus are small finger like projections that extend into the lumen of the small intestine Each villus is approximately 0 5 1 6 mm in length in humans and has many microvilli projecting from the enterocytes of its epithelium which collectively form the striated or brush border Each of these microvilli are about 1 µm in length around 1000 times shorter than a single villus The intestinal villi are much smaller than any of the circular folds in the intestine Intestinal villusMicrograph of the small intestine mucosa showing villi top half of image H amp E stainSection of duodenum of a cat X 60 DetailsPart ofWall of small intestineSystemDigestive systemIdentifiersLatinsmall intestinalesTA98A05 6 01 011TA22941FMA15072 76464 15072Anatomical terminology edit on Wikidata Villi increase the internal surface area of the intestinal walls making available a greater surface area for absorption An increased absorptive area is useful because digested nutrients including monosaccharide and amino acids pass into the semipermeable villi through diffusion which is effective only at short distances In other words increased surface area in contact with the fluid in the lumen decreases the average distance travelled by nutrient molecules so effectiveness of diffusion increases The villi are connected to the blood vessels so the circulating blood then carries these nutrients away Contents 1 Structure 1 1 Microanatomy 2 Function 3 Clinical significance 3 1 Villous atrophy 4 Additional images 5 References 6 Further readingStructure editMicroanatomy edit nbsp Vertical section of a villus from the dog s small intestine X 80 Simple columnar epithelium labeled at right third from top nbsp Transverse section of a villus from the human intestine X 350 a Basement membrane here somewhat shrunken away from the epithelium b Lacteal c Columnar epithelium d Its striated border e Goblet cells f Leucocytes in epithelium f Leucocytes below epbithelium g Blood vessels h Muscle cells cut across nbsp Cross section histology of small intestinal villi of the human terminal ileum nbsp MicroCT based volume projection of the jejunal mucosa of a chicken Virtual volume block with vertically truncated villi in oblique view Scalebar 0 2 mm nbsp MicroCT based volume projection of the jejunal mucosa of a chicken Virtual horizontal cut through villi Scalebar 0 2 mm Enterocytes along with goblet cells represent the principal cell types of the epithelium of the villi in the small intestine 1 Function editThere the villi and the microvilli increase intestinal absorptive surface area approximately 40 fold and 600 fold respectively providing exceptionally efficient absorption of nutrients in the lumen 2 There are also enzymes enterocyte digestive enzyme on the surface for digestion Villus capillaries collect amino acids and simple sugars taken up by the villi into the blood stream Villus lacteals lymph capillaries collect absorbed chylomicrons which are lipoproteins composed of triglycerides cholesterol and amphipathic proteins and are taken to the rest of the body through the lymph fluid Villi are specialized for absorption in the small intestine as they have a thin wall one cell thick which enables a shorter diffusion path They have a large surface area so there will be more efficient absorption of fatty acids and glycerol into the blood stream They have a rich blood supply to keep a concentration gradient 3 nbsp Structure of a villus see reference quoted in text Clinical significance editVillous atrophy edit nbsp Different stages of coeliac diseaseIn diseases of the small intestine the villi can become flattened due to the effects of inflammation and the villi can sometimes disappear This deterioration is known as villous atrophy and is often a feature of coeliac disease 4 Additional images edit nbsp Microvilli shaggy hair show electron dense plaques open arrow at their apices References edit Paneth cells Cytokines amp Cells Encyclopedia COPE Andreas Bernkop Schnurch 2009 Bernkop Schnurch Andreas ed Oral Delivery of Macromolecular Drugs Barriers Springer doi 10 1007 978 1 4419 0200 9 ISBN 978 1 4419 0199 6 Digestion Digestive System Enzymes Absorption in the Small Intestine Archived from the original on 2016 11 18 Retrieved 2014 12 30 Causes Coeliac UK Retrieved 12 July 2020 Further reading editC W Chan Y K Leung and K W Chan 2014 Microscopic anatomy of the vasculature of the human intestinal villus a study with review European Journal of Anatomy 18 4 291 301 Retrieved from https en wikipedia org w index php title Intestinal villus amp oldid 1191631543, wikipedia, wiki, book, books, library,
