DS- Lecture 28

Duodenum

1st of 12 inches of small intestine

-before jejunum

-contains brush boarder

(tiny hair like projections)

Intestinal Phase Enzymes

duodenal signals:

-bile

-pancreatic enzymes

-brush boarder enzymes

Duodenal Signals: Acid

produce secretin—>

-slows stomach motility

-also triggers bicarbonate release from the pancreas

-neutralizes acid

Duodenal Signals: Carbohyrates

makes gastric inhibitory peptide (GIP)

glucagon-like peptide 1 (GLP-1)

-both tell the pancreas to make insulin

-ensure there is not too much glucose in blood (prepares for carbohydrates)

Duodenal Signals: Fats

cholecystokinin (CCK)

-triggers contraction of gallbladder

-delivers bile into duodenum

-also tells pancreas to release digestive enzymes

Pancreas

takes C02 and sending bicarbonate out and proton bacj into blood—> reserves what stomach does= makes more acidic

Ghrelin

is an appetite stimulus by stomach= increase appetite

Bile

accumulates in gallbladder

-digest fats

Bile Salts

=amphipathic

(hydrophilic and lipophilic)

-water gets out between/ fat molecules in water (lipophilic)

become cluster—> bile salts split fat molecules —> into smaller balls of fat= emulsification

Pancreatic Zymogens

lipases, amylases, nucleases, peptidases- trypsinogen (protein digesting enzyme)

-all made in inactivated form—> get peptidase and get activated later

Enteropeptidase in Pancreas

brush border has this enzyme that works to break the safety cap of trypsinogen

trisinogen + enteropeptidase

=

activation of lipase, amylases, nuclease, and peptidase

Gallstone

Enzymes cant get out of the pancreas —> enzymes can’t activate an get acute pancreatis

(inflammation)

Brush Boarder Continued

Maltose (Glu+ Glu)

Sucrose (Glu+ Fru)

Lactose (Glu+ Gal)

can’t absorb any—> need enzymes sucrase, maltase, lactase

Na+ based symports

as disaccharides pass through duodenum—> brush boarder enzymmes break maltose into seperate glucose, sucrose into fructose, and lactose into glucose and galactose.

Absorption: Carbohydrates

monosaccharides SGLT and GLUT transporters

Absorption: Proteins

amino acids (Cl-3) Na+ symporters

Absorption: Nucleic Acids

nucleotides—> transport proteins

Absorption: Fats

gets broken down into glycerol + 2 fatty acids—> move into enterocyte—> get put back together into triglycerides—> gather into chylomicrons( protein+ fats) export from cell—> lacteals take it out through lymph—> into blood

Cephalic Phase

sensory or cognitive aspects of food

-activity in parasympathetic NS on the Vagus nerve to abdominal cavity to the stomach

think and hunger is activated

“long vagal reflex”

increased motility and secretion (gets ready for food)

-prepares for food and opens slightly

Saliva

secretion of salivary glands

-mostly, water, mucus, antibodies (disinfectant)

-one of first defenses

-lysosome, anti-bacteria

-salivary amylases, lingual lipase -both work best at ph of (6-7) salivary Ph

Amalyse

enzymes in which break up polysacharides (starch)—> can break down to level of maltose

Lapase

enzyme which breaks down fats—> triglycerides—> monoglyerides+ fatty acid

Gastric Glands

G cells—> gastrin

Parietal Cells

produce hydrochloric acid & intrinsic factor

Hydorchloric Acid

kills microorganisms

denatures proteins

makes Ph of stomach 2

Intrinsic Cells

protects vitamin b-12 from acid, enables b12 absorbtio inintestine

ECL Cells

secrete histamine

Chief Cells

pepsinogen—> (with acid)= endopeptidase

gastric lipase,

Gastric Phase System

sensory stimuli food from stomach—> G cells—> gastrin

can activate ECL cells to make histamine—→ parietal cells

OR

gastrin—> parietal cells—> acid—> make chief cells

OR

parietal cells—> intrinsic factor

chief cells—> make intrinsic factor

or gastric lipase

Peptidase

enzyme which breaks down proteins

Intestinal Phase

stomach being emptied into the duodenum

acid in the duodenum—> duodenum secretes secretin

—> causes the pancrease to release bicarbonate and pancreatic enzymes into the duodenum

=slow stomach emptying

Carbohydrates in duodenum

duodenum secretes GTP—> slows + GLP-1

GTP- slows down stomach emptying

GLP-1 - slows down the stomach, suppressing appetite, triggers insulin production

Fats in duodenum

duodenum secretes CCK—> powerful appetite suppressant and stimulates gallbladder contraction to release bile for fat digestion.

Proteins

= peptidase —>

1-3 amino acids

—>

Na+ based symports

Nucleic Acids

=nucleases —>

nucleotides—>

Na+ based symports

Carbohydrates

starches or disaccharides—>

starches, maltose, sucrose, lactose