Anatomy and Physiology of Digestion Flashcards
Digestion
physical, chemical, and enzymatic processes that prepare a feedstuff for absorption
physical digestion
mastication (chewing)
peristalsis (smooth muscle contraction)
chemical digestion
acid (HCl) in stomach or abomasum
enzymatic digestion
enzymes to break down chemical bonds
produced in various locations in the GI tract
- mouth, pancreas, small intestine, bacteria in rumen, cecum or colon
types of digestive systems
monogastric, avian, ruminant, pseudo-ruminant, hind gut fermentation
monogastric
one simple stomach
carnivores - cats, dogs
omnivores - humans, pigs, avian too
herbivore fermentation strategies
pregastric, pseudo ruminant, post gastric
ruminant
pre-gastric
"polygastric" characteristics -slower digestion carbohydrates are fermented to VFAs -acetate, propionate, butyrate VFAs absorbed and transported to liver
acetate
2 carbon
propionate
3 carbon
butyrate
4 carbon
microbial protein
high biological value
rumen microbes break down plant protein and make microbial protein
they then pass down digestive tract, die and are digested
major AA source for ruminants
true ruminants
4 chambered stomach
rumination
cattle, sheep, goats, deer, buffalo, antelope, gazelles, giraffe
pseudoruminant
3 chambered stomach (rumen+reticulum combined also have glandular HCl stomach)
function like a true ruminant
rumination fermentation of CHO to VFAs
post gastric (hind gut) fermentation
microbial protein lost in feces
energy obtained from absorption of VFAs
steps of digestion
prehension
mastication
salivation
deglutition
prehension
bring food into mouth
mastication
chewing
salivation
salivary gland secretion
deglutition
swallowing
rumination
regurgitation
reinsalvation
remastication
redeglutition
mouth
contains organs of: prehension (teeth tongue) mastication (teeth jaws) salivation (salivary glands) deglutition (palate throat epiglotis)
saliva
contains:
amylase - starch digestion
bicarbonate - buffering
esophagus
tube connecting mouth to stomach
function:
-transports ingesta from mouth to stomach
-peristalsis - moves food to stomach
-lower esophageal sphincter - prevents acid reflux
stomach
functions:
-mixing and storage
-mucus secretions
-HCl very strong acid environment to denature proteins and be an acid barrier to microbes
-enzymes
- lipase - triglyceride
- pepsin - protein
pyloric sphincter regulates passage of digesta to intestinessmall intestine
major site of enzymatic digestion, absorption, and intestinal juices
many segments
provides surface area for absorption (folds villi microvilli)
liver
secretion of bile
“detergent” to emulsify fat
pancreas
secretes:
- bicarbonate
- digestive enzymes (lipase, protease, amylase)
segments of the small intestine
duodenum, jejunum, ileum
duodenum
short segment buffers and enzymes enter via bile and pancreatic secretions
jejunum
main site of absorption
ileum
connects to large intestine
large intestine
functions:
-fermentation
-absorption of water, VFAs, minerals, B vitamins
microbial protein lost in feces
some species practice cecotrophy (rabbits)
digestion of proteins
hydrolyzed to AA by peptidases and absorbed and transported in blood
digestion of carbohydrates: monogastrics
amylase cleaves starch chains into monosaccharides (glucose) and some disaccharides (maltose)
intestinal disaccharides complete digestion into monosaccharides which can then be absorbed
digestion of carbohydrates: ruminants
fermentation to VFA
VFA absorbed from rumen into blood
digestion of lipids
fat and fat soluble vitamins
mostly triglycerids in diet
hydrolyzed to fatty acids monoglycerides
absorbed and reformed into triglycerides
packaged w/ protein complexes “lipoproteins”
transported to bloodstream via lymphatic system @ thoracic duct
avian digestive system
monogastric type enzymatic digestion no teeth crop proventriculus ventriculus (gizzard) ceca cloaca
crop
esophageal distention which serves to store moisten and soften ingesta
proventriculus
glandular stomach
HCl and enzymes
ingesta passes thru quickly, little digestion occurs
ventriculus (gizzard)
stones, grit
particle reduction
b/c no teeth
ceca
paired structures
fermentation
cloaca
common opening for digestive and reproductive systems
agents of rumen fermentation
microbes!
bacteria, protozoa, archea
reticulum
honeycomb, hardware stomach
ingesta moves freely btwn rumen and reticulum
rumen
the major fermentation chamber
lined w/ papillae
omasum
manyplies, dry contents, function not clear
abomasum
true or glandular stomach similar to nonruminant stomach acid secretion (HCl)
esophageal groove
milk fed calves folds of reticulum which can close to form a tube allowing liquid to bypass the fore stomachs stimulated by suckling preruminant stage of life similar to monogastrics
factors affecting rumen development
age, diet, VFA
eructation
belching
rumen stratification
top layer = gas
middle layer = fiber mat
bottom layer = liquid
vitamin products of rumen fermentation
vit K and B
