Intestines

Question 1

Anatomical Ways to Increase SA and Absorption

Answer 1

Plicae circularis (core of submucosa) folds in walls
Villus (core of lamina propria)
Microvillus (cellular projections on enterocytes)
Glycocalyx (on microvilli) enzymes for digest of proteins

Question 2

Intestinal Villus Composition

Answer 2

• simple columnar epithelium with goblet cells
  (enterocytes + terminal web + microvilli)
• intestinal glands (continuous epithelium into lamina)
• blood supply in villus
• lacteal in villus – blind-ended + smooth muscle covers

Question 3

Nutrient Absorption and Transport

Answer 3

Inactive enzymes (trypsinogen/proelastase)
Enterokinases on microvilli cleave to activate
Active enzymes (trypsin/elastase) = protein –> aa

enterocyte of villus absorb – blood pick up – portal vein
chylomicrons enters lacteal – lymphatic vessel

Question 4

Cells of the Intestinal Epithelium

Answer 4

Goblet Cell (out) + Enterocyte (in)
Microfold Cell
- with lots of lymph tissue + no microvilli
Enteroendocrine Cell
- secretin/cholecystokinin to in = pancreas action
Paneth Cell
- lysozyme to out = digest bacteria wall (eosin granule)

Question 5

Features of 3 Intestinal Regions

Answer 5

Duodenum = submucosal gland (mucus w/ bicarbonate)
Jejunum
Ileum = Peyer’s Patches (lymph nodules in lamina propria and submucosa)

Question 6

Colon Function and Features

Answer 6

Absorb water and electrolytes

Tenia Coli = thickened longitudinal muscularis externa
Haustra = space to slow down waste
Plica Semilunaris = separate Haustra

Question 7

Colon Composition

Answer 7

• enterocytes with lots of goblet cells
• intestinal glands (continuous surface epithelium down)
• NO Villi

Question 8

Cell Renewal in Intestines

Answer 8

Mainly Unidirectional Cell Flow
- stem cells differentiate up towards tip
- some differentiate down into Paneth’s cells