3.8-3.10 Key Points Review

What enzyme breaks down triglycerides in the small intestine?

Pancreatic lipase

Where do chylomicrons go after being packaged in enterocytes?

Lacteals → lymph → thoracic duct → left subclavian vein → bloodstream

What vitamin is water-soluble and not stored in fat?

Vitamin C

Trypsinogen is activated by what enzyme on the brush border?

Enteropeptidase

CCK is released in response to what?

Fats and proteins in the duodenum

What is GIP’s primary function?

Stimulates insulin release (in response to glucose in the small intestine)

Gastroileal reflex triggers what?

Relaxation of the ileocecal valve (small intestine → large intestine)

Gastrocolic reflex causes what?

Mass movement of feces into the rectum

Enterogastric reflex does what?

Slows gastric emptying when chyme enters the duodenum

What triggers the defecation reflex?

Stretch of the rectum → parasympathetic contraction of rectum, relaxation of internal anal sphincter

What cell secretes GLP-1?

L cells (in the small intestine)

What cell secretes GIP?

K cells (small intestine)

What cell secretes gastrin?

G cells (in the stomach)

What triggers secretin release?

Low pH in the duodenum

What are the main actions of CCK?

↑ gallbladder contraction, ↑ pancreatic enzymes, ↓ gastric emptying

What’s the role of GLP-1 in digestion?

↑ insulin release and promotes satiety (acts on brain)

What’s the role of secretin?

↓ stomach acid production, ↑ bicarbonate secretion from pancreas/liver

What do micelles carry?

Fatty acids and monoglycerides (after emulsification by bile)

How do micelles get lipids into cells?

Simple diffusion across enterocyte membrane

What happens to fats once inside enterocytes?

Reassembled into triglycerides → packaged into chylomicrons → exocytosed into lacteals

What enzyme digests nucleic acids?

Ribonuclease (RNA) & Deoxyribonuclease (DNA)

Vitamin B12 needs what to be absorbed?

Intrinsic factor (from parietal cells) → absorbed in ileum via endocytosis

Which vitamins are fat-soluble?

A, D, E, K

Which vitamins are water-soluble?

C, B-complex(12) vitamins

Which structure increases surface area the most in the small intestine?

Microvilli (on absorptive cells)

How are glucose and galactose absorbed into enterocytes?

Via Na+ cotransporters (secondary active transport)

How is fructose absorbed?

Via facilitated diffusion

What is absorbed through receptor-mediated endocytosis in the ileum?

Vitamin B12 (bound to intrinsic factor)

Which molecules enter blood capillaries, not lacteals?

Monosaccharides, amino acids, short-chain fatty acids

Which molecules are absorbed into lacteals?

Chylomicrons (fats reassembled in enterocytes)

What does the gastroileal reflex do?

Opens the ileocecal valve, letting contents enter the large intestine

What does the gastrocolic reflex trigger?

Strong peristaltic wave that moves feces into the rectum

What does the enterogastric reflex do?

Inhibits gastric emptying when the duodenum is full/stretching

What triggers the defecation reflex?

Stretch of the rectum → parasympathetic response → rectal contraction & internal sphincter relaxation

What hormone is released in response to fats & proteins in the duodenum?

CCK (cholecystokinin)

What hormone is released in response to low pH in the duodenum?

Secretin

What hormone stimulates insulin release and promotes satiety?

GLP-1 (glucagon-like peptide 1)

What hormone is released in anticipation of glucose?

GIP (glucose-dependent insulinotropic peptide)

What does gastrin do?

Increases stomach acid secretion & motility

Which cells secrete GLP-1?

L cells (found in small intestine)

Which cells secrete GIP?

K cells (also in small intestine)

Which cells release secretin?

S cells

Which cells release gastrin?

G cells (in the stomach)

What is the liver’s functional unit?

The liver lobule

What are Kupffer cells?

Specialized phagocytes in liver sinusoids

Where is bile produced?

In the liver (by hepatocytes)

Where is bile stored?

In the gallbladder

What are sinusoids in the liver?

Capillary-like spaces where blood from hepatic artery & portal vein mix