Lecture 6 - Bile acids

Step 1 of Bile acid recycling

Bile acids synthesized within heptaocyte and transported across apical surface by 1 active transport into canicular networks that darin into bile ducts and enter gallbladder or SI

Step 2 of bile acid recycling

Bile acids enter lumen of SI, digest food then move to ileum and move into portal circulation. Absorbed by epithelial cells thru Na dependent secondary active transport

Step 3 of bile acid recyling

Bile acids in portal blood are carried into heptocytes thru secondary active transport for cycle to continue

What are gallstones and how are they formed?

Caused by excess cholesterol and is insoluble with water. It is kept in the micelle solution with bile acids. High cholestrol conc. will precipitate out

What are pigment stones?

Another type of gallstone where excess RBC breakdown will lead to increased bile pigments that precipiates with calcium

What are consequences of gallstones?

Cause major obstruction/infection of gallbladder, liver and pancrease

How can gallstones be treated?

Cholecystectomy (removal of gallbladder), remove the stones, opr drugs to dissolve it

What is the small intestine?

Divided into three parts and helps with digestion/absorption of protein, fat, carbs, electrolytes, water, iron, vitamins

What is the duodenum?

Mixes digestive enzymes and bile with food, absorption of nutrients, iron, and calcium, release of secretin and CCK

What is the jejunum?

Digestion and absorption

What is the ileum?

Digestion and absorption of bile acids and B12

How is SA increased in the SI?

There are fold of Kerckring covered with villi, microvilli, and crypths within

What are within the crypths of SI?

Stems cells that can divide into paneth, endocrine, goblet, or enterocytic cells

What are absorptive cells (enterocytes)?

Microvilli at apical surface also called brush borderWh

What are goblet cells?

Secretion of mucus for food and protection

What are enteroendocrine cells?

Produce hormone I and S cells

What are paneth cells?

Secrete antibacterial peptides to protect GIT

What is a brush border enzyme?

Anchored to brush border and has catalytic activity in lumen. Breaks for carbs and peptides into sugars and amino acids

How do brush border enzymes work with amylase?

Helps break down products from amylase since amylase only works on glucose

What is sucrase?

Brush border enzyme that breaks down sucrose into glucose and fructose

What is lactase.

Brush border enzyme that breaks down lactose into glucose and galactose

How is glucose and galactose absorbed?

Same pathway and move across apical membrane through SGLT and across basolateral enterocyte through GLUT

How is fructose absorbed?

Moves across apical membrane though GLUT5 and basolateral surface through GLUT2

What is carboxypeptidase and aminopeptidase?

Pancreatic protease; brush border enzyme

What is the role of carboxypeptidase and aminopeptidase?

THey can cleave the amino-portion and carboxy-terminal peptide bonds