Ch 13 Digestion

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the main function of ductile cells in the pancreas?

Producing sodium bicarbonate to neutralize acidic gastric contents (correct)

Regulating blood sugar levels

Storing pancreatic enzymes

Producing digestive enzymes

What percentage of the pancreas mass is devoted to the islets of Langerhans?

15%

10%

2% (correct)

Which of the following pancreatic enzymes breaks down polysaccharides into disaccharides?

Carboxypeptidase

Trypsin

Pancreatic lipase

Pancreatic amylase (correct)

What is the function of enterokinase in the small intestine?

Activating trypsinogen into trypsin Signup and view all the answers

What does the parasympathetic nervous system do to pancreatic secretion?

Increases it Signup and view all the answers

What percentage of the pancreas mass is devoted to its exocrine function?

98% Signup and view all the answers

Which pancreatic enzyme breaks down triglycerides into fatty acids?

Pancreatic lipase Signup and view all the answers

What is the purpose of producing pancreatic enzymes in their inactive forms?

To minimize the risk of self-digestion within the pancreas Signup and view all the answers

What stimulates the vagus nerve, leading to acid secretion in the stomach?

Distension of the stomach Signup and view all the answers

What is the primary effect of gastrin secretion on the stomach?

Stimulation of acid secretion Signup and view all the answers

Which of the following inhibits gastrin secretion?

Decrease in pH of gastric juice Signup and view all the answers

What is the primary function of parietal cells in the stomach?

Production of acid Signup and view all the answers

What is the primary function of the enterogastric reflex?

Inhibition of gastric acid secretion Signup and view all the answers

What is the primary stimulant of acid secretion in the stomach?

Vagus nerve stimulation Signup and view all the answers

What is the function of secretin in the regulation of gastric acid secretion?

Inhibition of gastric acid secretion Signup and view all the answers

What is the primary stimulus for the intestinal phase of gastric acid secretion regulation?

Acidic chyme entering the small intestine Signup and view all the answers

What is the primary function of G cells in the stomach?

To secrete a hormone called gastrin Signup and view all the answers

Which type of digestion is initiated by pepsin in the stomach?

Protein digestion Signup and view all the answers

What is the primary function of the cephalic phase of gastric secretion regulation?

To stimulate gastric secretion through parasympathetic nerves Signup and view all the answers

What is the result of the mixing, chemical digestion, secretion, and absorption in the stomach?

A yellowish paste called chyme Signup and view all the answers

What is the role of intestinal gastrin in regulating gastric secretion?

To inhibit gastric secretion Signup and view all the answers

What type of substances can be absorbed in the stomach?

Small and fat-soluble substances Signup and view all the answers

What is the role of gastric lipases in chemical digestion?

To break down certain lipids like butterfat Signup and view all the answers

What regulates the activities of gastric glands in the stomach?

Both nervous and hormonal mechanisms Signup and view all the answers

Study Notes

G Cells and Gastric Secretion

G cells secrete a hormone called gastrin, which stimulates parietal cells and overall gastric secretion.

Chemical Digestion and Absorption in the Stomach

Carbohydrate digestion is continued with gastric amylase, resulting in disaccharides.
Protein digestion begins with pepsin (activation of pepsinogen by HCl), resulting in peptides.
Lipid digestion begins with gastric lipases, which can only break down certain lipids such as butterfat, resulting in fatty acids.
Absorption in the stomach is limited, where only small and fat-soluble substances can be absorbed (water, alcohol, aspirin, and certain drugs).
The result of all these mixing, chemical digestion, secretion, and absorption is a yellowish paste called chyme, which will be passed on to the small intestine.

Regulation of Gastric Secretion

Regulation of gastric secretion and activities is by both nervous and hormonal mechanisms.
Food moving along the oral cavity and esophagus stimulates the parasympathetic nerves to activate the secretion in gastric glands.
Gastrin hormone from G cells stimulates the gastric glands for more activities ("positive feedback").
When food is emptying from the stomach, sympathetic nerves inhibit the gastric glands and gastrin, and a hormone called intestinal gastrin (released by small intestine) inhibits other gastric activities.

Phases of Gastric Regulation

Cephalic Phase: involves special senses detecting food and using parasympathetic nerves in the vagus nerve to stimulate gastric activities.
Gastric Phase: involves the distension of the stomach and stimulates its own activities by the vagus nerve.
Intestinal Phase: involves acidic chyme passing into the small intestine, which secretes intestinal gastrin hormone to inhibit gastric activities.

Pancreas

Pancreas produces most pancreatic enzymes as inactivate molecules, or zymogens, to minimize self-digestion.
More than 98% of the pancreas mass is devoted to its exocrine function: the secretion of pancreatic juice by the pancreatic acini and their ductile cells.
Ductile cells produce sodium bicarbonate, which helps neutralize the acidic gastric contents.
Acinar cells of the exocrine pancreas produce a variety of digestive enzymes to break down food substances into smaller absorbable molecules.

Pancreatic Enzymes

Pancreatic amylase: digests polysaccharides into disaccharides.
Pancreatic lipases: digest triglycerides into fatty acids.
Pancreatic nucleases: digest nucleic acids into nucleotides.
Pancreatic proteinases: digest peptides into amino acids, including trypsin, chymotrypsin, aminopeptidase, and carboxypeptidase.

Pancreatic Secretion

The parasympathetic nervous system increases pancreatic secretion.
Sight, smell, and taste of food cause stimulation of vagus nuclei in the brain, which stimulates acid secretion.
Vagus stimulates acid secretion directly and indirectly through gastrin secretion.

Regulation of Gastric Emptying

Distension of the stomach and small intestine stimulates the vagus nerve, which inhibits gastric activity.
Amino acids and peptides in the stomach lumen stimulate acid secretion.
Intestinal gastrin hormone inhibits gastric activity.
Secretin, a hormone secreted by the duodenum, inhibits gastric acid secretion in response to fat in chyme.
The enterogastric reflex: a neural reflex that inhibits gastric activity when the duodenum is filled with chyme.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

This quiz covers the functions of G cells and gastric cells in the stomach, including the digestion of carbohydrates, proteins, and lipids.