Gastric Anatomy and Physiology

Question 1

Gastric Anatomy

Answer 1

• Fundus (storage)
• Body (storage and mixing)
• Antrum (grinding)

Question 2

Gastric cell types and function

Answer 2

• Mucous neck cell: secretes mucous and bicarbonate.
• Parietal cells: secretes HCL and Intrinsic factor (Calcium absorption)
• ECF-like cells: secretes histamine (stimulates acid)
• Chief cells: secretes Pepsinogen and Gastric lipase.
• D-cells: Secretes somatostatin (inhibits acid)
• G cells: secretes Gastrin (stimulates acid)

Question 3

Gastric Cell types and Location

Answer 3

• Body: pit foveolar cells (secrete mucous), also parietal cells (secrete acid), cheif cells, and enteroendocrine cells.
• Antrum: pit foveolar epithelial cells, endocrine cells, basal gland cells

Question 4

Gastric acid secretion

Answer 4

• Both neuro and endocrine stimulation of release of gastric acid.
• Nervous system: stimulates release of Calcium via AcH
  Gastrin from G cell binds and stimulates Ca release.
  Histamine also stimulates cAMP. Somatstatin inhibits this.

Question 5

Regulation of Gastric secretion

Answer 5

• Cephalic phase: see food, smell food, taste food. Parasympathetic system: enteric neurons release Ach, stimulates G cells and enteroendocrine cells to produce histamine. This stimulates gastric acid secretion.
  Somatostatin releaseing cells sense the lower pH, and release somatostatin.

-Gastric phase: food in stomach. this buffers the acid, increases the pH, this has a negative effect on somatostatin releasing cells.
Distension activates enteric neurons. activates Ach.
Release of peptides stimulates gastrin release and histamine release. This stimulates gastric acid secretion.

-Intestinal phase: food in intestine, increase H+, distension, osmolarity and fat; all of this stimulates enterogastron release (CCK, secretion, GLP-a, GIP) this inhibits gastrin and histamine release. Enteric nervous system inhibits Ach release in stomach. Somatostatin is released. This leads to decrease in acid release. intestinal enzymes cannot handle acidic pH

Question 6

Gastroduodenal defense

Answer 6

Preepithelial:
- Mucus, Bicarb, Surface active phospholipids.
Epithelial:
- Cellular resistance, restitutio, growth factors, prostaglandins, cell proliferation.
Subepithelial: blood flow, leukocyte.