Stomach Functions, Gastric Phase, and Secretion

What are the functions of the stomach?

- Mixing chamber

- Holding reservoir

What happens to food in the stomach?

Food is liquefied into chyme

What does the stomach secrete?

The stomach secretes gastric juice.

What does the stomach digest and absorb?

- Digests proteins and fats

- Absorbs water, alcohol, and ions

What is the gastric phase?

Food entering the stomach activates stretch and chemoreceptors.

What happens when food enters the stomach?

- Sensory signals activate the parasympathetic and enteric nervous systems.

- Results in increased gastric motility and secretion.

What happens when food enters the stomach and activates stretch and chemoreceptors?

- G cells are activated to secrete gastrin.

- This increases gastric motility and secretion.

What are gastric pits?

Gastric pits contain gastric glands which secrete gastric juice.

What stimulates the secretion of gastric juice?

- Food entering the stomach

- Activation of G cells, mucous cells, parietal cells, and chief cells

What are exocrine cells?

Exocrine cells secrete substances into ducts (e.g., mucous cells, parietal cells, chief cells).

What are endocrine cells?

Endocrine cells secrete hormones into the bloodstream (e.g., G cells secrete gastrin).

What do Enteroendocrine cells (G cells) secrete?

G cells secrete gastrin

What does gastrin do in the stomach?

• Gastrin stimulates the formation of gastric juice.

• Stimulates mucous, parietal, and chief cells.

• Positive feedback: Gastrin secretion is enhanced by the acid already in the stomach, leading to more gastric juice being secreted. This process continues until digestion is complete.

What do Mucous cells in the stomach secrete?

Mucous cells secrete mucus.

What is the function of mucus in the stomach?

Mucus protects the stomach lining from acidic damage.

What do Parietal cells secrete in the stomach?

Parietal cells secrete HCl and Intrinsic factor (IF).

What does HCl do in the stomach?

- Denatures proteins

- Activates enzymes

- Kills bacteria

- Liquefies food

What does Intrinsic factor (IF) do in the stomach?

Intrinsic factor (a glycoprotein) aids in the absorption of Vitamin B12, which is essential for hemoglobin synthesis.