WEEK 17 Digestion and Absorption

Flashcards covering key concepts of digestion and absorption processes, phases, and physiological roles.

What is the difference between chemical and mechanical digestion?

Chemical digestion breaks down food with enzymes, while mechanical digestion involves physical processes.

What are the regulatory mechanisms of digestion?

Neural (long and short reflexes) and hormonal mechanisms.

Explain the four processes involved in the GI tract.

Digestion: breaking down food; Absorption: nutrients entering the bloodstream; Motility: movement of food; Secretion: digestive juices.

What are the main secretory cells in the stomach and their functions?

Mucous cells secrete mucus; Parietal cells secrete HCl and intrinsic factor; Chief cells secrete pepsinogen and gastric lipase.

What are the phases of digestion?

Cephalic: triggered by senses; Gastric: triggered by food; Intestinal: triggered by chyme.

Match enzymes with their substrates: Amylase, Pepsin, Lipase.

Amylase - starch; Pepsin - protein; Lipase - fats.

What gives food nutritional value?

Food must be digestible and absorbable to provide nutritional value.

List the functions of the digestive system.

Ingestion, digestion, propulsion, secretion, absorption.

What are macronutrients and micronutrients?

Macronutrients: carbohydrates, lipids, proteins; Micronutrients: vitamins and minerals.

Differentiate between long and short reflexes in neural regulation.

Long reflexes involve the central nervous system; short reflexes are localized responses from the enteric nervous system.

What roles does the autonomic nervous system play in digestion?

The parasympathetic nervous system stimulates motility and secretion.

What are the functions of sensory neurons in the enteric nervous system?

They detect food through mechanoreceptors and chemoreceptors.

What are the effects of digestive hormones?

They alter GI secretion and motility, and stimulate enzyme release.

List the four basic digestive system processes.

Digestion, absorption, motility, secretion.

What happens during the cephalic phase?

Parasympathetic activation via senses triggers salivation and gastric secretions.

What are the functions of saliva during the cephalic phase?

Moistens food, digests starch, aids taste, and provides antibacterial action.

What are the functions of the stomach?

Storage, secretion, churning, and defense.

What stimulates mucous cells to secrete their product?

Mucus is stimulated by tonic secretion and irritation.

What are the stimuli for parietal cells?

ACh (acetylcholine), gastrin, and histamine stimulate the secretion of HCl and intrinsic factor.

What do chief cells secrete?

Pepsinogen and gastric lipase; stimulated by ACh and acidic environment.

What is the role of G cells?

They secrete gastrin; stimulated by ACh, peptides, and amino acids.

What happens during the gastric phase?

Distension of the stomach and gastrin release stimulate secretions.

What is the role of HCl in the stomach?

HCl denatures proteins, activates pepsinogen, and provides defense against pathogens.

What is the function of pepsin?

Pepsin breaks down proteins into smaller peptides.

What does gastric lipase do?

Begins the digestion of fats.

How much absorption occurs in the stomach?

Very limited due to mucus and incomplete digestion.

What are the histological layers of the intestines?

Mucosa, submucosa, muscularis externa, and serosa.

What is the function of the major duodenal papilla?

It delivers bile and pancreatic enzymes into the duodenum.

What is the function of villi in the small intestine?

Villi increase surface area for absorption.

What are the sections of the small intestine?

Duodenum, jejunum, and ileum.

Where are the jejunum and ileum located?

Jejunum: upper left quadrant; Ileum: lower right quadrant.

What are plicae circulares?

Permanent mucosal folds that increase surface area and cause spiraling of chyme.

How do plicae circulares differ between jejunum and ileum?

Jejunum has larger and more numerous plicae circulares; Ileum has smaller and fewer.