whitfield lecture 1 & 2

other words for GI tract

gut

bowel

intestinal tract

digestive system

Why is poop brown?

bile and dead RBCs

Gi tract is a doughnut…

hole through the animal

stuff goes in → processes it → stuff comes out

types of stomachs

monogastrics

ruminants

monogastrics

single chambered stomach

ruminants

rumen, reticulum, omasum, abomasum (“true stomach”)

sites of fermentation

hind-gut fermenters

forestomach

hind-gut fermenters

monogastrics but specialized for fermentation in large intestine

forestomach

ruminants

camelids

flow of feed

mouth → esophagus → stomach (forestomach ruminants) → small intestine → large intestine → rectum/anus

large intestine sections

cecum

colon

rectum

anus

3 parts of colon

ascending

transverse

descending

straight line GI

dog/person/carnivore

coiled GI

cow/ruminant

extended, some loops GI

horse

stomach major functions

mechanical digestion

acidic digestion

some enzymatic digestion

small intestine function

enzymatic digestion

absorption

immune functions

organ most similar among species

small intestine

large intestine functions

fermentation

absorption

cecum functions

blind pouch ?

descending colon/rectum/anus functions

storage

absorption/transport ?

mucosa function

epithelium that lines the lumen of the GI tract

submucosa function

underlying connective tissue - collagen with blood vessels and nerves

muscularis function

smooth muscle that produces wave-like contractions (peristalsis)

serosa function

connective tissue

outermost covering

peristalsis

progression of coordinated contractions and relaxations of the smooth muscles of the GI tract to propel food

enteric nervous system (ENS) controls…

nearly all aspects

motility secretions blood flow

ENS is the second

brain

ENS can operate independently of

CNS

ENS: two interconnected systems of ganglia

myenteric (Auerbach)

submucosal (meissner)

myenteric (auerbach)

between muscle layers

regulates motility

submucosal (meissner)

regulates secretions from mucosa

sensory neurons

interneurons

connect myenteric and submucosal ganglia

two main components of ANS

sympathetic and parasympathetic

parasympathetic input

vagus nerve

and some pelvic splanchnic n.

sympathetic input

thoracic/lumbar splanchnic n.

para innervation

vagus

pelvic in terminal colon

para neurotransmitter

Ach

para function

rest

relax

digest s

symp innervation

postganglionic fibers

splachnic n

symp neurotransmitter

norepinephrine

symp function

fight or flight

gut’s local control system =

enteric nervous system

sphincters

ring of muscle surrounding and serving to guard or close an opening or tube

GI sphincters

upper esophageal

lower esophageal

pyloric