pathophys Final

The GI tract is called

alimentary canal

GI tract pathway

mouth, pharynx, esophagus, stomach, small intestine, large intestine, rectum, anus

ascessory organs

teeth, toungue, salivary glands, liver, pancreas

alimentary canal histology layers

serosa (outer)

muscularis externa

submucosa

mucosa

mini brain of the alimentary cancal

enteric nervous system

enteric nervous system two parts

short

long

short enteric nervous system

only enteric neurons,

sensory neurons (stretch, osmolarity, PH)

to interneurons

to motor neurons which are the effectors to muscles and glands

long enteric nervous system

involves the CNS, sympathetic and parasympathetic nervous system

what do sensory neurons in the enteric nervous system do

the sense stretch, osmolarity, and PH

what mouth do

ingestion, mechanical breakdown, initiates propulsion, starts digestion

what begins breakdown of food

mastication

what saliva do

cleans mouth, lubricates food, dissolves food chemicals, compacts food into bolus, contains amylase (breakdown of food), protection against microorganisms

salvation happens at

thought of food

salivary glands contain

amylase, IgA, water, K+, Na+

what are effectors in the enteric nervous system

smooth muscle, glands, and endocrine cells of GI tract

peristalis and segmentation

extrinsic salavary glands

outside oral cavity

parotid

submandibular

sublingual

intrinsic salivary glands

buccal, labial, palatine

where does food go after mouth

pharynx

two types of pharynx

oropharynx and laryngopharynx

what closes the larynx

epiglottis

what is esophagus lined with

stratified squamous epithelium

what do esophageal glands secrete

mucus to aid in bolus movement

Deglutition

swallowing

two phases of deglutition

buccal phase, pharyngeal-esophageal phase

buccal phase of deglutition is (voluntary/involuntary)

voluntary, occurs in the mouth, food is formed into a bolus, the bolus is forced into the pharynx by the tongue

ends when food leaves mouth

the pharyngeal-esophageal phase of deglutition is (voluntary/involuntary)

Involuntary - primarily vagus nerve

Control center in the medulla and lower pons

food passes from oropharynx to stomach in less than 8 seconds

buccal phase drawing steps

mandible depresses or opens, tongue elevates, downward slope (pushes food), UES is closed during buccal phase

pharyngeal phase drawing steps

to prevent bolus from going to the larynx the epiglottis covers, to prevent bolus from going to nasopharynx, the uvula and soft palate rises

the UES is open during pharyngeal phase

Esophogial phase drawing steps

UES closes to prevent upwards movement

peristalis propels food down the esophagus

gastoesophageal sphincter opening

LES/ gastroesphageal sphincter opens

what is peristalsis controlled by

pacesetter cells which surround lumen of the GI tract, trigger APs in smooth muscle

what is the lower esophageal sphincter called

gastroesophageal sphincter

what is bolus converted to in stomach

chyme

what is mostly digested in the stomach

large proteins

what break down the proteins in stomach

HCL and pepsin, pepsin digests proteins into smaller proteins

what is also digested in the stomach (not the top one the other two)

lipids by lingual lipase, and carbs (SOME digestion)

what can be absorbed in the stomach

little absorption but lipid soluble compounds can be absorbed like aspirin and alc

how do peristaltic contractions move in stomach

move from fundus to pylorus, with vigorous peristalsis occuring in pyloris

how does chyme move into small intesting

pyloric sphincter opens, chyme moves into the duodenum, when pyloric sphincter closes, it creates rethopulsion

mucous cells in stomach

produce bicarbonate-rich alkaline mucus to protect the stomach from acidity and stress

parietal cells of stomach

secrete HCl (increase acidity and digests proteins)and intrinsic factor (B12 absorbtion)

chief cells of stomach

secrete pepsinogen which will be converted to pepsin for protein digestion.

G cells of stomach

- release gastrin --> stimulate parietal cells --> release HCl

how does stomach protect itself

mucous coat, tight junctions, epithelial cell replacement

gastritis

inflammation of the stomach lining if anything breaches mucusal barrier, ulcers, H pylori

3 phases of gastric secretion

cephalic, gastric, intestinal

cephalic phase produces __ of gastric juices

1/3

when does cephalic phase begin

before bolus enters stomach, sight and smell of food stimulate the vagus nerve to start cephalic phase

gastric phase produces ___ of gastric juices

2/3

What does the cephalic phase do?

prepares your body for digestion, vagus nerve innervates parietal cells to extrete HCL and intrinstic factor, cheif cell to secrete pepsinogen,

What is the role of the gastric phase?

Processing the ingested materials by acid and enzymes.

When does the gastric phase begin?

when food enters the stomach

what happens during gastric phase

stretch further stimulates vagus nerve

G cells--> gastrin--->stimulates parietal cells to secrete more HCL and intrinsic factor---> produce gastric juices

What is the role of the intestinal phase?

control the rate of gastric emptying, largely inhibitory

first step of intestinal phase

peptones (smaller protein fragnments) stimulate intestinal G cells, produces gastrin, act on parietal cells, more gastric juices

second step of intestinal phase

fatty acids and glucose enter the small intestine and stimulate S cells ---> secretin (inhibit stomach g cells)

and also stimulate I cells---> CCK (inhibit parietal cells) so there are mo more gastric juices

what do fatty acids and glucose stimulate in the small intestine

S and I cells

S--> secretin

I---> CCK

what inhibits G cells from prodcuing gastrin in the gastric phase

sympathetic nervous system and high acidity

how much absorbption occurs in the small intestine

90%

duodenum main function

neutralize acidic chyme and begin absorbtion

where is most nutrient absorbtion

jejunum

sugars, amino acids, fatty acids,

what increases absorbtion in the jejunum

plicae circulares (muscular flaps) and villi

where does the illeum end

ileocecal valve

what does the illeum absorb

what was missed by jejunum, B12, bile salts, sugars

enterocytes

small intestine cells, absorb nutrients and electrolytes in the vili, secree intestinal juives to absorb nutrients in chyme

goblet cells

in small intestine, secret mucus

paneth cells

in small intestine, secrete defensins and lysozomes, which kill certain bacteria

enteroendocrine cells

I and S, secrete secretin and CCK

what movement happens in small intestine

peristalsis and segmentation

what does segmentation do

mix chyme with bile and enzymes moving both directions, nonajacent segments of small intestine contract

peristalsis in small intestine is driven by what

the enteric nervous system (myenteric plexus) PNS and distension

migrating motility complex

sweeps intestines clean between meals, peristalsis that occurs in the fast state, begins 90-120 minutes after meal, stops when food is eaten, pulls everything into large intestine

what is migrating motility complex stimulated by

motilin---> released in small intestin in between meals

large intestine divided into

ascending colon, transverse colon, descending colon, sigmoid colon, rectum

what is large intestine separated by

flexures, making feces

what happens in large intestine

very luttle digestin, form and propel feces, absorb water and electrolytes left over, prodice and absorb vitamains

how are vitamains K, biotin, and pantothenic acid created

by bacteria in large intesting

what is gut bacteria creating

vitaman k, biotin, pantothenic acid

vitamin k

blood clotting, used by liver to synthasize prothrombin

Biotin

glucose metabolism, and fat synthesis

Pantothenic Acid (B5)

a component of co-enzyme A, which is fatty acid synthesis and other metabolic processes

intestinal bacteria

ferment indigestible carbs, break down fiber, could be linked with dementia, provide protective and metabolic functions like vitamins K and B

ascending colon

processes chyme delivered by the ileum, some vitamins produced here

how to ascending colon move chyme

peristalsis

what does ascending colon absorb

water to solidify stool

transverse colon absorbing?

water and electrolyte absorbtion

what does transverse colon do

stores solid feces

how does feces move through transverse colon

haustration

haustration

involuntary, sluggish contraction of the haustra, back and forth movement but slowly,

what is power propulsion

in transverse colon, used to move feces over longer distance, pushing it out faster, used when recieving lots of chyme

descending colon function

prepares waste for eliimination, channel between transverse and sigmoid

sigmoid colon function

store fecal wastes(reservoir) until they are ready to leave the body

final reabsorption of vitamins and mineral and water, pushes feces into the rectum

rectum function

stores and expels feces, temporary storage, movement of fecal matter into the rectum triggers urge to defecate

anus

anal orfice, anal canal connects anus and rectum, releases feces

defecation reflex first step

stretch receptors detect movement of feces into the rectum

defecation reflex second step

parasympathetic motor fibers stimulate contraction of rectum and relaxation of internal anal sphincter

defecation reflex third step

voluntary motor neurons open external anal sphincter allowing feces to pass

blood in stool and urgency

large intestine

liver function

energy metabolism (maintains blood glucose and blood lipids)

produces proteins

drug metabolism

storage of fat sikuble vitamins and iron

produces bile

carb energy metabolism liver

glucose convert to glycogen, stored in liver

fructose and galactose also taken up by liver

gluconeogenesis