Module 5: Digestive system: Small intestine

Question 1

sections of small intestine in order from stomach

Answer 1

duodenum, jejunum, ileum

Question 2

main function of small intestine

Answer 2

absorption of digestion products from GI tract

Question 3

2 types of intestinal digestion

Answer 3

Luminal

Membrane

Question 4

Luminal digestion

Answer 4

mixing of chyme with pancreatic enzymes (molecular breakdown)

Question 5

Membrane digestion is enhanced by 4 things

Answer 5

1) long length (4-6m)
2) presence of plicae circulares
3) villi on plicae circulares; Crypts of Lieberkuhn
4) extensive microvilli on surface of each intestinal lining cell

Question 6

Lymphoid aggregations in small intestine are called

Answer 6

peyers patches

They sample antigens are deliver to macrophages/lymphocytes in patch. Important for forming IgA-producing plasma cells

Question 7

Primary defence for small intestine

Answer 7

secretory IgA that is produced and is present of the free surface of the epithelium
IgA is able to lower the ability of bacteria to adhere to cell surface and neutralize bacterial and viral toxins

Question 8

Intestinal villi are lined by

Answer 8

simple columnar epithelium (same as crypts)

Question 9

2 types of cells of epithelium

Answer 9

Enterocytes (membrane digestion and absorption; tall columnar cells)

Goblet cells (mucous secreting)

Question 10

Crypts of Lieburkuhn

Answer 10

produce new cells so that intestinal lining is replaced every 3-5 days

Contain Paneth cells (source of lysozyme, an antibacterial enzyme)

Question 11

2 specialized secretory functions of duodenum

Answer 11

1) Presence of chyme stimulates Brunners glands (compound coiled branched tubular glands in submucosa of duodenum) to secrete alkaline mucous to neutralize acidic chyme

2)Chyme stimulates release of secretin and CCK from endocrine cells
Both stimulate pancreatic secretion into pancreatic duct and CCK stimulates contraction of gallbladder to propel bile into duodenum