Question

Describe how microvilli, lacteal and capillary structures of the small intestine are involved in digestion and/or absorption.

Answer 1

Microvilli are microscopic cellular membrane protrusions that increase the surface area for diffusion and minimize any increase in volume and are involved in plethora of functions such as absorption,secretion,cellular adhesions and mechanotransduction.

Lacteals are lymphatic capillaries found in the villi of the small intestine.They absorb and transport large molecule ,fats,and lipids in the digestive system mainly in the form of lipoproteins.This chyle is carried by the lacteals to the lymph vessels in the intestinal wall.

Capillaries -Each villus has a network of capillaries and fine lymphatic vessels called lacteals close to its surface.The epithelial cells of the villi transport nutrients from the lumen of the intestine into the capillaries.

Digestion in the small intestine

The small intestine is the part of gastro intestinal tract between the stomach and the and the large intestine responsible for the major part of digestion.Also absorption of nutrients and minerals taken place.

Digested nutrients moves to the blood vessels through the procss of diffusion.The inner wall of the intestine ie lined with columnar epithelium.These mucosa is covered with wrinkles calles plicae circulares these are permenent featurs in the wall of intestine.

From this plicae circulares microscopic fingers like projections called villi ,these individual epithelial cells are also called micro villi ,These are increase the amount of surface area available for the absorption of nutrients.These are the primary surface oof nutrient absorption.For this function these microvilli are filled with enzymes that helps in the breakdown of complex nutrients into simpler compounds and aids in easy absorption.

In case of lacteals these absorb dietary fats.Triglecerides are emulsified by bile and hydrolized by the enzyme lipase resulting in mixture of fatty aciods and monoglycerides.due to the larger diameter than blood capillaries fat molecules are absorbed by lacteals from the intestine.

These lacteals are surrounded by the capillaries.Digested nutrients pass into the blood vessels in the wall of the intestine through a process of diffusion.The epithelial cells of villi transport nutrients from the lumen of the intestine into these capillaries and lacteals.