Lecture 12 The Digestive System

Question 1

Mucosa

Answer 1

• Inner most mucous membrane, with glands that face the lumen
• Epithelium
• Lumen, lamina propria/connective tissue (thin smooth muscle)

Question 2

Submucosa

Answer 2

-Layer outside of the mucosa, connective tissue=elasticity, blood/lymph vessels, nerves

Question 3

Muscularis externa

Answer 3

• Outside of submucosa
• Smooth muscle coat, circular inner/longitudinal outer layers
• Nerves

Question 4

Serosa

Answer 4

• Outer most layer
• Connective tissue
• Secretes serous fluid, with mesentery

Question 5

Exocrine cells in gastric pits

Answer 5

Mucous, chief, parietal, stem

Question 6

Mucous cells

Answer 6

line gastric pits and gland entrance; thin mucus

Question 7

Chief cells

Answer 7

deep numerous; pepsinogen

Question 8

Parietal cells

Answer 8

• deep; intrinsic factor (absorb vitamin B12 in small intestine) HCl
• Breakdown connective tissue, muscle (meat)
• Denatures protein
• Antimicrobial
• Cleaves (activates) pepsinogen

Question 9

Stem cells

Answer 9

• midway; becomes all types of cells in pit/epithelium

- Replace mucosa every 3 days

Question 10

Pepsinogen

Answer 10

• Hydrolysis of proteins
• Stored in inactive form to prevent protein damage
• Autocatalytic

Question 11

Regulation of gastric juice production

Answer 11

• Gastrin: hormone (made by G cells), secreted in blood, returns to stomach; stimulate parietal, chief, and ECL cells
• Somatostatin: paracrine, negative feedback; stimulated by acid, stops the signal
• Histamine: paracrine positive feedback
• ACh from enteric nerves (and some from parasympathetic nervous system): stimulates all cells
• Secretion gradually decreases as chyme exits