BIO 107 - Structure and Function of The Small Intestine

What events take place in the small intestine?

• final events of digestion

• where absorption takes place (mostly for nutrients)

What are the 3 segments of the small intestine?

• duodenum

• jejunum

• ileum

Which is segment of the small intestine is the shortest segment and is retroperitoneal?

duodenum

Where is the ileocecal valve/sphincter located?

where the ileum joins the large intestine

Which gastric hormone causes the relaxation (opening) of the ileocecal valve?

Gastrin

What facilitates the process of digestion and absorption?

Special features of both the mucosa and the submucosa

The length of the structure of the small intestine provides what for digestion and absorption?

Large surface area

Name the 3 structural modifications of the small intestinal wall that make it ideal for its function in absorption?

Circular folds (plicae circulares)

• deep, permanent folds of the mucosa and submucosa

Villi

• finger-like projections of the mucosa that greatly increase the surface area available for absorption

Microvilli (brush border)

• tiny projections of the plasma membrane of the absorptive cells (facing the lumen) of the mucosa (also known as the brush border)

What matches this description?

• deep, permanent folds of the mucosa and submucosa

Circular folds (plicae circulares)

What matches this description?

• finger-like projections of the mucosa that greatly increase the surface area available for absorption

Villi

What matches this description?

• tiny projections of the plasma membrane of the absorptive cells (facing the lumen) of the mucosa (also known as the brush border)

Microvilli (brush border)

Where are the intestinal capillaries and lacteals found?

Within the villi of the small intestine

What is the role of capillaries and lacteals in absorption?

The nutrients absorbed by the epithelial cells covering the villus pass through the wall of a capillary or a lacteal to enter blood or lymph respectively

Which one will carry the absorbed material to the liver?

The capillary (through hepatic portal vein)

What and where are the Crypts of Lieberkuhn located? What role do the crypt of lieberkuhn play?

They are shallow invaginations between the villi and they secrete salt and water

What are the functions of the crypts?

1. Nursery for the stem cells (non-specialized, undifferentiated) that regularly replace the epithelial lining of the small intestine

2. the Paneth cells present produce lysozyme and defensins

What is the function of Paneth cells?

They present produce lysozyme and defensins