Question

describe the structures in the small intestine wall and what they do?

is this question asking about the duodenum, jejunum, and ileum or about the microvilli ?

Answer 1

Answer

Small intestine is the major organ of digestive system involved with digestion and absorption of nutrients.  

- The outermost layer of intestinal wall is serosa : It secretes serous fluid.

- Second layer is muscularis : It contains smooth muscles that contract for peristalsis (longitudinal muscles) and segmentation (circular muscles) in order to facilitate digestion of the nutrients in chyme.

- Third layer is submucosa : It is made up of dense irregular connective tissue and functions to support the underlying mucosa layer.

- The innermost layer of the small intestine wall is mucosa.

It contains three major adaptations that helps small intestine in its function

1) Villi : Villi are the finger projections of the simple columar cells in the mucosa layer of intestinal wall.

2) Microvilli : They are numerous small projection on each villus.

3) Plicae circulares : Numerous folds present in the mucous membrane of small intestine.

All these structures facilitate the process of nutrient absorption by providing more surface area.

Some other structures of intestinal wall are :

• Lacteals : Small lymphatic vessels surrounding each villi. Lipids after digestion are packed into chylomicrons and transported into lactals before it enters blood circulation.
  
  
• Crypts of Lieberkuhn : It possess stem cells for regenration of the intestinal epithelium.