What specialised feature of small intestine account for
What specialised feature of small intestine account for efficientabsorption of digested food stuffs.
Parts of small intestine• 3parts• 1/duodenum• 2/ jejunum• 3/ ileum.• Duodenum leads to jejunum and then to ileum
When chyme reaches small intestine• When chyme reaches duodenum, its acidity causes release of enzymes from pancreas, liver and duodenal cells.
Absorptive function of jejunum• Jejunum is second portion of small intestine.• Its length is about 2.4 metres.• 2/5th of small intestine is jejunum.
Absorptive function of ileum• Nearly all absorption of products of digestion takes place in ileum.• The internal(inside)• surface of ileum has many folds.• These are velvety in appearance due to the presence of villi.• Villi are finger like projections/outgrowths.
villus• Each villus is richly supplied by blood capillaries and lacteal.• Lacteals a vessel of lymphatic system with a covering of epithelial cells.• Each villus has countless microvilli which can only be seen by electron microscope.• These are closely packed cylindrical processes which form brush border .
Functions of villi• Due to these villi and micro villa, absorptive surface becomes incredibly large.
Absorption of sugars and amino acids.• By diffusion• By active transport• Sugars and amino acids are absorbed into blood stream.
Absorption of fatty acids and glycerol• They enter the epithelial cells of villi and recombine in to fats.• These fats enter lacteals.• There are proteins in lacteals.• These protein meet up with fats and form lipo proteins• These lipoproteins enter blood stream via thoracic lymphatic duct.
lipoproteins• These lipoproteins go to blood and enzymes in plasma (part of blood) hydrolyse them.• After that they can enter body cells.• These hydrolysed lipo proteins can be used in respiration(breathing) or can be stored in liver and under the skin as fat.
• Contents of intestine are pushed along digestive tract by peristaltic activity.• At the end of ileum where there is ileo caecal valve .• Contents enter large intestine through this valve/sphincter.