large intestinal function Flashcards
for carnivores, ruminants, horses and birds, describe the order of the digestive tract and where the bulk of digestion occurs
which large intestine belongs to which species
discuss where water is stored in the body
- 60-70% body mass
- intracellular (30-40%)
- extracellular (20-40%)
give examples of extracellular fluid
- plasma
- lymph
- interstitial
- gastrointestinal
- synovial
- peritoneal
- pleural
how much blood is in the body per kg
90-100 ml/kg
discuss water exchange in the GI tract
- most of the water absorbed from the GIT has come from intestinal secretions
- there is a continuous process of secretion and absorption of large volumes of fluid across the intestinal wall
- most of the water is secreted in the proximal (small intestine) and absorbed both in the small and large intestine
what causes disorders in water exchange in the GIT
increases or decreases in secretion and absorption and by changes in motility
which changes of water exchange can cause diarrhea
- decrese in absorption of water in the small intestine
- increase in secretion
- increased motility
which changes in GIT water exchange will cause constipation
- increased absorptions
- decreased secretions
- decreased motility
fill out
define muscularis of intestine
muscle layer of intestine consisting of an inner circular muscular layer and a longitudinal outer muscular layer. The coordinated contractions of these layers is called peristalsis, which propels the food through the GI tract.
what is chyme
semi-fluid mass of partly digested food that is expelled by an animals stomach
what is peristalsis
- involuntary contraction and relaxation of the muscles of the intestine creating wave like movements to push the contents forwards
what is anti-peristalsis
contractions of the intestine that force the contents in the opposite direction to the normal
what is segmentation
a muscular activity that divides and mixes the chyme by alternating between backward and forward movement of the GIT contents. predominently in the SI and LI
define mass movements
the downhill movement of material under the force of gravity
what are the muscular layers in the muscularis
- inner circular layer
- longitudinal outer muscualr layer
- myenteric nerve plexus found between longitudinal and circular layers
where is the myenteric plexus located
in between circular and longitudinal layers of the muscularis
what are the interstitial cells of cajal
- pacemakers of the gut
- within the tunica muscularis
- mediators of enteric neurotransmission
what type of muscle is in the intestinal tract
smooth muscle
what are the main types of motility in the caecum and colon
haustral contraction and mass movement
where will you find the pelvic flexure in the horse
in the left half of the abdomin in contact with the abdominal wall and close to the pelvic inlet
- between left ventral colon and left dorsal colon
describe the lcation of the sternal flexure in the horse
sits on the sternum in xiphoid region
- transition from left to right ventral colon
where is the diaphragmatic flexure in the horse
- between left dorsal and right dorsal colon
- turns in caudal direction at level of diaphragm
what effect does sympathetic stimulation have on motility ?
- decreased peristalsis and gut motility
- decreased secretions such as mucus
- inhibition of gastrointestinal sphincters
what effect does parasympathetic stimulation have on motility ?
- increases digestive productivity
- increases gut motility
- increases secretions
- relaxation of sphincters
outline the process involved in emptying the rectum
- after the mass movements of the large intestine, the rectum becomes filled with faeces.
- This stimulates pressure sensitive cells in the wall of the rectum and initiates the defeacation reflex.
- reflex causes a forceful contraction of the rectum, and relaxation of the internal anal sphincter.
which species have voluntary control over emptying the rectum
- carnivores
- primates
not herbivores
what are the products of microbial fermentation in the hundgut
- volatine fatty acids
- lactic acid
- fructans (into fructose and lactic acid)
- absorption of fatty acids is accompanied by absorption of water and electrolytes
- carbohydrates make VFAs and lactic acid
what are the benefits of microbial digestion
- Up to half the fibre in grass cannot be digested in the horse without microbial digestion
- The bacteria synthesise essential amino acids
- Microbial digestion produces water soluble B and K vitamins
- Rabbits and rats are coprophagic to increase their intake of protein (amino acids) and B vitamins
list factors important in hind gut digestion
- Type of bacteria (lactobacillus, streptococci)
- Correct pH 5-6 (BIC and Na buffers from small intestine)
- Anaerobic environment
- Fluid movement
- Retention of food - up to 65 hours
where foes microbial digestion occur in the horse
caecum and ventral colon
where does microbial digestion occur in the rabbit
caecum
how important is the large intestine in the horse
- 30% protein digested and absorbed
- 15-30% soluble carbohydrate digested and absorbed
- 75-85% structural carbohydrate (cellulose) digested and absorbed
- Most of the electrolytes absorbed
- 90% of water absorbed
infrequent feeds for horses will cause what chemical changes
- decrease pH
- increase lactate
- massive influx of water rather than continuous low level
changhes in bacterial flora of the equine LI leads to:
- enteritis
- colitis
- laminitis
changes to water balance in the equine LI leads to
impactions
