E4 L26 The stomach, small intestine, liver, pancreas, & large intestine

Three functional regions of the stomach

fundus

body

antrum

fundus

upper portion of the stomach, flexible, thin

Body of the stomach

secretes mucus, pepsinogin, and HCl

Antrum of the stomach

lower portion of the stomach, mixing and grinding, secretes mucus, pepsinogen, and gastrin

Gastric pits secrete _______

gastric juice

6 cell types within gastric pits

mucus cell

parietal cell

ECL cell

Chief cell

D cell

G cell

Chyme =

juice + bolus

Mucus cells

secrete mucus

Parietal cells are _____ glands

exocrine (p)

Parietal cells secrete

acid, intrinsic factor

ECL cells are ________ glands

paracrine

ECL cells secrete

histamine

Chief cells are ________ glands

exocrine

Chief cells secrete

pepsinogen

D cells are ________ glands

Endocrine (D)

D cells secrete

somatostatin

G cells are _________ glands

Endocrine

G cells secrete

gastrin

HCl production and secretion by parietal cells

CO2 + H2O -> carbonic acid

Bicarb to blood

H+ to stomach joins with Cl

Alkaline shift

Bicarb from parietal cells creates a basic pH around the stomach

What are the four factors that regulate HCl secretion from parietal cells

Gastrin

Histamine

ACh

Somatostatin

Gastrin/histamine/ACh regulation of HCl

increased secondary messengers that increase H/K ATPase to stomach increasing HCl

Somatostatin regulation of HCl

Decrease the amount of secondary messengers decreasing the number of H/K ATPases decreasing amount of HCl produced

Drugs that affect HCl production impact

Acid production, heart burn, GERD

OTC antiacid tablets/solution examples

TUMS, rolaids, pepto

OTC antiacid tablets/solution mechanism of action

Neutralize HCl but do not alter the production

Histamine blocker examples

Tagamet, zantac

Histamine blocker mechanism of action

reduce the secondary cascade, decrease H secretion, decrease vesicle fusion, decrease H/K pumps

Proton pump inhibitors examples

Prilosec, Nexium

Proton pump inhibitors mechanism of action

inhibits the H/K pumps, decreased H release, strongest!

What 5 things can regulate parietal cell secretion

Somatostatin

Histamine

Gastrin(increased histamine and increased parietal)

Gastric phase

Enteric neural activity (cephalic phase)

The presence of nutrients in the SI has an ________ effect on both the stomach's secretion and motility

inhibitory

Control of HCl during a meal

Cephalic

Gastric contents/phase

Intestinal contents/phase

Pathway of cephalic control of HCl secretion during a meal

Parasympathetic increases HCl

Pathway of Gastric Phase control fo HCl during a meal

long and short reflexes, increase HCl

Pathway of intestinal phase to control HCl secretion during a meal

Long and short reflexes, SECRETIN, CCK, DECREASE HCl secretion

Secretin

A hormone secreted by the duodenum in response to low pH (from stomach acid), promotes the release of bicarbonate from the pancreas

How is pepsinogen activated in the stomach

Released from chiefs, activated by H+ OR autocatalysis (pepsin)

How is pepsin inactivated

by alkaline pH in SI

Why is pepsin non-essential

the pancreas proteases are adequate to break down proteins into peptides

What does intrinsic factor do

Absorbs vitamin B12 in ileum

Motilities of the stomach (4)

Receptive relaxation

Peristalsis

Retropulsion

Gastric emptying

Retropulsion

occurs in the antrum in the opposite direction of peristalsis

AP waves of the GI tract are depolarized and hyper-polarized by

location of the bolus

ENS

Hormones

ANS

Tension in the stomach develops as the AP wave ________

goes above threshold

Gastric emptying is promoted by

full stomach stretch

chyme fluidity

Gastric emptying is inhibited by

Enterogastric reflex (CCK and Secretin)

CCK senses what in the SI

fat content

Secretin senses what in the stomach

acidity

Digestion and abs in the stomach

mechanical, chemical (proteins to peptides, HCL), not much abs only weak acids

Where does the SI begin

pyloric sphincter

Three sections of the SI

duodenum, jejunum, ileum

Where does the SI end

ileocecal valve

What causes the large surface area of the SI

Coils, circular folds, villi, microvilli

Enteroendocrine cells

Cells of the SI that secrete CCK, secretin, and GIP

Where in the SI does abs occur

microvilli

Three secretions into the SI lumen

water/mucus/NaCl

bile

pancreatic (bicarb, enzymes)

What type of secretions are secreted into SI

exocrine

What is NaCl important for in the SI

secondary active transport

What does bile help to digest

fats

the __________ duct becomes the _____________ and merges with the _________ duct to be released through the sphincter of oddi

common hepatic, common bile, main pancreatic

Two exocrine cells of the pancreas

acinar and duct cells

Acinar cells secrete

pancreatic enzymes

Duct cells secrete

bicarb

How is bicarb secreted from the pancreas

H20 + CO2 = carbonic acid = H and bicarb

Bicarb to duct lumen, H to ISF

Acidic shift

occurs near pancreas due to H release from creating bicarb

5 types of pancreatic enzymes

Tripsin/chymotripsin/elastase

carboxypeptidase

lipase

amylase

ribonuclease/deoxyribose

What activates pancreatic enzymes

membrane bound enterokinases

Tripsin/chymotripsin/elastase

break proteins down into peptides

carboxypeptidase

break down terminal amino acid from protein

lipase

forms two fatty acids and a monoglyceride

amylase

breaks down polysaccarides into maltose

ribonuclease/deoxyribose

splits nucleic acids into nucleotides

Increased acid in the stomach will cause pancreas to do what

Increase secretin from SI, increase bicarb from pancreas duct cells

Increased fatty acids and amino acids in the SI will cause the pancreas to do what

SI increased CCK secretion

Pancreas increases enzymes from acinar cells

Four roles of CCK

Inhibit gastric emptying

Increase enzyme secretion from acinar cells

Eject bile from gal

Relax sphincter of oddi

Bile salts

made from cholesterol, emulsify fats

How are carbs digested/abs in the SI

polysacchariddes are converted to monosaccharides (fructose, glucose, galactose), transported via GLUT or Na/SGLT co, then GLUT along apical mem, Na/K ATPase on apical

Fructose, glucose, galactose to the liver for processing

How are proteins abs/digested in the SI

Proteins broken down into small peptides/amino acids, amino/Na co, pep/H co

In epithelial cell pep to amino, then transported to ISF via amino acid transporter

Na/K ATPase basal

Steps of lipid digestion/abs

emulsify

digestion

form absorbable units

resynthesize trigly to form chylomicrons

TO LYMPH SYSTEM

How are fats emulsified in the SI

Bile salts

How are fats digested in the SI

Pancreatic lipase

How are fats formed into absorbable units?

broken into fatty acid and monoglycerides

Where do chylomicrons exocytosis into

lacteals, in the lymphatic system

How are hydrophilic substances abs from the SI

Capillaries surrounding GI, to hepatic portal vein (processing), hepatic vein, inferior vena cava

Two motilities of the SI

Segmentation

Migrating Myoelectric Complex (MMC)

MMC

intestinal housekeeper sweeping

Pathway of the large intestine

Cecum

Ascending colon

Transverse colon

Descending colon

Sigmoid colon

Rectum

Function of the LI

storage and water reabs

What is the function of the ileocecal valve/sphincter

keep bacteria from large from getting into the small

Secretions of the LI

Alkaline mucus with bicarb and K+

Digestion of the LI

bacterial breakdown of complex polysaccharides (plant walls

Absorptions of the LI

products of bacterial metabolism

vitamin K

NaCl

1.4 L H2O / day

Three motilities of the Large Intestine

Segmentations of haustrations

Mass movement via peristalsis

Defecation

What is mass movement of the LI stimulated by

Gastrin

What stimulates defication

stretch