Transcript Document
Small Intestinal Wall
Mucosa, submucosa,muscularis, serosa
Mucosa – increased surface area due to many villi
Each villus contains thousands of ___________
(brush border)
Microvilli have both digestive enzymes and
carrier molecules for nutrients, vitamins, and
minerals embedded in cell membranes
_______- invaginations of mucosa around each
villus. New cells are produced and pushed
from bottom of crypt to replace cells of villus
Goblet cells present. Mucus helps with flow of
ingesta.
Nervous System and Small Intestines
_____________ nervous system provides stimulation for
intestinal motility, secretions, and blood flow.
_____________ nervous system decreases circulation to the
intestines.
Intestinal tract is constantly functioning and is never at rest.
Small intestine Motility
Peristalsis
Circular contractions prevent backflow of ingesta, longitudinal
muscles propel ingesta caudally
Dilation of bowel with ingesta stimulates peristalsis
CCK and Prostaglandins can both affect motility.
Fats/protein in the intestine stimulate the mucosa to release CCK,
which increases intestinal motility (opposite of the effect on the
stomach)
Prostaglandins can increase GI motility and secretions which can lead
to colic.
Segmental contractions slow the movement of ingesta to
allow time for it to be both mixed with intestinal enzymes and
absorbed through the intestinal wall.
Many times diarrhea is caused not due to increased peristalsis, but
lack of segmental contractions.
Small Intestine Digestion
_____________, _____________, _____________
Absorbed intact across SI wall
_____________, _____________, _____________
Chemically digested via enzymes in the lumen and enzymes
on the microvilli b/c they are too large to pass through the
mucous membrane
Starch is broken into disaccharides by amylase found in the saliva and from the
pancreas
Disaccharides are broken down into monosaccharides by enzymes (lactase,
sucrase, and maltase) in microvilli
Monosaccharides can then be transported across microvilli and absorbed into
blood
Microvilli enzymes are dependent on diet (Lactose-intolerant animals/diarrhea)
Carbohydrate Digestion
Food
Starch
Enzyme
Amylase
Lactase
Sucrase
Maltase
Source
Broken into Fate
Saliva, Pancreas Disaccharides
lactose
sucrose
maltose
Brush border Monosaccharides
glucose Absorbed
galactose Absorbed
fructose Absorbed
Protein chains are broken into smaller polypeptides by pepsin
Polypeptides are broken down into peptides (several amino acids) by
pancreatic proteases
Peptides are broken down into amino acids, dipeptides, and some
tripeptides by peptidases are then absorbed
Protein Digestion
Food
Protein
Enzyme
Source
Broken into Fate
Pepsin
Stomach
Polypeptides
Proteases
SI (Pancreas)
Peptides
Peptidases Brush border Amino acids Absorbed
di-peptides Absorbed
tri-peptides Absorbed
Agitation of the pyloric antrum emulsifies (breaks down) fat globules
(triglycerides) into smaller droplets
Bile acids from the liver coat the fat droplets in duodenum
Keeps them from re-forming into globules again
Arranges them to make them more water soluble
Pancreatic lipases (fat-digesting enzymes) penetrate bile acid coating
Digest triglycerides to form glycerol, fatty acids, and monoglycerides (micelles)
which are absorbed through the microvilli
Vitamins A, D, E, K are often absorbed with the micelles
Fat Digestion
Food
Lipids
Enzyme
Bile acids
Lipases
Source
SI (Liver)
Broken into Fate
small fat droplets
SI (Pancreas)
glycerol
Absorbed
fatty acids
Absorbed
monoglycerides Absorbed
Species variation in structure
Components
1. ________ - blind sac at
ileocecal junction
2. ________
3. ________
Primary functions Store feces
Recover fluid and
electrolytes
Hindgut fermentation
(non ruminant herbivores)
Equine, guinea pigs, rats,
rabbits, swine
Large Intestine
Large Intestines
____________: simple, tubular
colon; poorly developed cecum
__________ __________: very large
colon and cecum (hindgut)
Fermentation site
Modifications of cecum and colon
allow fermentative digestion in
hindgut
similar to rumen
VFA’s (produced by microbes)
absorbed from cecum and colon for
energy needs (similar to rumen)
Possible areas of impaction
Flexures, Small colon
Cause of colic
Consists of 4 sections:
Cecum, Ventral colon (right and left
halves), Dorsal colon (right and
left halves), Small colon
Cecum is composed of:
Base, Main body, Apex
Cecum and dorsal and ventral colons
have longitudinal bands that separate
the structure into a series of sacs called
________
The role of the small colon is to
absorb electrolytes, water, and any
VFA’s that were not previously
absorbed.
Horse Hindgut
Terminal portion of the large
intestine; an extension of
colon
Rectum
Capable of more expansion
than colon
Mucus-secreting glands
___________ feces to aid
their passage
Has sensory receptors that
detect stretching or
distention and stimulates
defecation response.
Internal sphincter under ________ control
(Parasympathetic system causes
relaxation, Sympathetic system causes
constriction)
External sphincters under __________
control
As rectum distends, stretch receptors
cause partial relaxation of internal
sphincter. Fecal material moves into
the Internal Sphincter Canal which
stimulates more stretch receptors
increasing urge to defecate.
Stretching of Anal mucosal receptors
increase the sense or need for defecation
Surgery or disease in anal region can
damage sphincter muscles and nerves,
causing incontinence
Anus
Liver’s Role in the GI Tract
________, __________, and/or ___________
materials absorbed from GI tract before they
reach blood.
Removes toxins, infectious agents, old
blood cells that enter the body via the GI
tract.
Glucose, amino acids, and vitamins are
stored or metabolized.
Glucose absorbed by the GI tract can be
stored in the liver as _____________
(glycogenesis). When glucose is needed in
the blood, glycogen is broken down by the
liver (glycogenolysis).
_____________________ is the process of
glucose being made in the liver by using
amino acids.
Major source of blood __________
Albumin
Gallbladder
The liver produces _______ which
contains bile acids, cholesterol,
and bilirubin
Bile is secreted into bile ducts, which
lead to the hepatic duct, which leads
to the ____________for storage (not
horse)
The gallbladder stores bile until it is
stimulated by CCK (due to fat in SI),
causing it to contract.
Contraction forces bile down the
common bile duct into the
duodenum, where it aids in the
digestion of fat.
Pancreas’ Role in the GI Tract
Exocrine and endocrine gland
Exocrine functions:
Produces _________, _________,
___________
Secretes _____________ (HCO3-)into
duodenum
Neutralizes acidity of stomach contents
and maintains pH in duodenum needed
for proper enzyme function
Endocrine functions:
Produces ___________ & _________
Regulates blood glucose levels:
Insulin moves glucose from the
blood to the body’s tissues.
Glucagon stimulates
gluconeogenesis and glycogenolysis
in the liver.