Small Intestine Structure and Function

10 Questions

What are the three regions that constitute the small intestine?

Duodenum, jejunum, ileum

What is the length of the small intestine?

5 m

What are the folds in the lining of the small intestine called?

Plicae circularis

Which cells in the intestinal glands have microvilli forming the brush border?

Absorptive cells

Which cell type in the intestine is primarily responsible for producing mucus?

Goblet cells

What can a deficiency of disaccharidases lead to?

Digestive disturbances

What is the main function of Paneth cells in the intestine?

Secreting lysozyme for antibacterial activity

Microfold cells specialize in which one of the following processes?

Endocytosing antigens and transporting them to lymphoid cells

Which of the following intestinal cell types secretes regulatory peptides?

Enteroendocrine cells

Where are the number of Goblet cells most likely to increase in the intestinal tract?

Near the ileum

Study Notes

Small Intestine (S.I.)

The small intestine is the site of terminal food digestion, nutrient absorption, and endocrine secretion.
The process of digestion is completed in the small intestine, and the products of digestion are absorbed.
The small intestine is approximately 5 meters long.
It is divided into three regions: duodenum, jejunum, and ileum.

Structure of Small Intestine

The lining of the small intestine has many folds called plicae circularis, composed of mucosa and submucosa.
Villi are small, finger-like projections that are 0.5-1.5 mm long.
Intestinal glands, also called crypts of Liberkuhn, are located between villi.

Intestinal Cell Types

Absorptive cells: These cells are columnar, with a nucleus in the basal half of the cell, and have a brush (striated) border at the apex.
Absorptive cells have approximately 3000 microvilli, which increase the absorptive surface area.
Enzymes in absorptive cells hydrolyze disaccharides and dipeptides to facilitate absorption.
Deficiency of disaccharidases leads to digestive disturbances, which can be genetic in origin.
Goblet cells: These cells are interspersed between absorptive cells, increasing in number towards the ileum.
Goblet cells produce acid proteins that form mucus, protecting and lubricating the intestinal lining.
Paneth cells: These cells secrete lysozyme, which has antibacterial activity and helps control intestinal flora.
Microfold cells: These cells are specialized epithelial cells overlying lymphoid follicles of Peyer's patches.
Microfold cells can endocytose antigens and transport them to underlying lymphoid cells, initiating an immune response.
Enteroendocrine (Argentafin) cells: These cells secrete regulatory peptides that regulate gastric secretion, intestinal motility, and pancreatic secretion.