found along lumen brush border

innermost layer

-stratified suamous cells

-simple columnar cells

absorption and secretion here

composed of dense irrecular connective tissue

binds mucosa with muscularis

highly vascularized

innervated by MEISSENERS PLEXUS

-structural and immune cells

responsible for peristalsis

smooth mucsle except esophagus

auerbachs MYENTERIC plexus

GI motility

-muscle for motility

outermost layer

serous membrane: produces fluids

simple squamous epithelium

ADVENTIA (no cavity) layer

-interfac with body

pulls and stores nutrients especially glucose

from oxygen rich hepatic artery

nutrient rich porta vein

fenestrated blood vessels

kupffer cells are found here

macrophages that break down old RBC

broken down to iron and bilirubin

processed to bile salts and stored in gall bladder

circulated many times a day in GIT

actively absorbed in Ileum

portal blood leads back to liver

free fatty acids and monoglycerides

which are them converted and reabsorbed as triglycerides

broken down by amylase

absorbed in mono-disaccharide form

absorption coupled with Na

broken down by stomach acid, pepsin, trypsin

absorbed as AA and small peptides

coupled with Na

emulsified by bile in liver

broken down to FFA and monoglycerides

broken down by lipases too

absorbed in small intestine

LDL

low density lipoprotein

bad cholesterol

remains in cicrulation promotes plaque formation

mevacor, zocor, lipitor,crestor

bind to HMG CoA reductases to reduce cholesterol synthesis by liver

increase HDL lowers LDL

blocks absorption of cholesterol that comes from food

reduces cholesterol body makes naturally

8,500ml, largest area of absorption

most important gI organ

involves brain in GI regulation

system is a feedback mechanism

vagus nerve is major stimulator

activates meissners ans auerbachs plexus

splachnic nerves (NE E)

control of motor activity in gut

smooth muscle funtion

mucosal functions

secretion, absorption and regulates local blood flow

made from G cells

responds to distension of stomach or presence of AA, peptides

increases acid secretion

made from S cells in duodenum

responds to duodenal activty

increases bicarbonate secretion

made from I cells in duodenum

responds to fat and protein digestion products in duodenum

contracts gall bladder increases enzyme secretion

activated by sight, smell, taste or act of eating food

mediated by vagus nerve

vagal reflex

increased gastric motility, enzyme and HCL secretion

initiated by entry of food to stomach

vagus nerve stimulation is augmented by gastrin

-local reflex, depends on food in stomach

-increase HCL and pepsinogen secretion

initiated by entry of food to duodenum

accounts for 70-80% of pancreatic secretory response to meal, mediated by release of secretin

autoregulation of the GIT

activates exocrines glands and smooth muscle galnds along tract

accessory organs

produces saliva that lubricates and compacts

compound acinar glands (amylase & lipase)

serous (watery)

secretes waterm enzymes and ions

mixed

produces mucous, ions, enzymes and water

mucous producing cells for lubrication and protection

top portion of stomach

sphincter helps prevent acid reflux

peptic gland region

covered with gastric pits

has chief and parietal cells

mucous secreting cells

endocrine G cells

controls emptying of stomach to S.I

pyloric sphincter controls its actions

rotates at slow rate to allow S.I absorption

opening of pyloric sphincter is reflexive

HCL acid production

intrinsic factor for vit B12 absorption

converts pepsinogen to pepsin

important for protein digestion

if always active for pepsin formation causes cell to autolyse

gastrin production

increases GI motility

causes parietal cells to increase acid production

histamine production

acid secetion stimulator

somatostatin production

an acid secretion inhibitor

shuts down insulin and glucagon production

release due to duodenal fillin and acid

inhibits gI motility and acid production

gives time for absorption

back and forth mixing of chimes and enzymes

brings digestive nutrients into contact with villi and microvilli

slow stationary ans ocsillatory movement

forward propulsion of chime along small intestine

pumpimg up and dowm of villi by muscularis mucosa

varicose veins in anal canalitching, bleeding

destroys by burning or cutting in rubber banding

absorption of water, electrolytes

vitamin production by bacteria

expulsion of feces by mass peristalsis

(cecum, colon & rectum)

-exo and endocrine functions

-sphincter of oddi keeps pancreatic fluid and bile from entering SI except during meals

-endocrne: reg blood sugar w/insuln & glucagon

-exocrine: secretions of product to duct, digestive enzyme alkaline juice (tyrpsin, lipase, nucleic acids)

-acinar cells: prod pancreatic juice

inhibit acid production (AcH antagonist)

cimetidine, tagamet, zantac, pepcid