Stomach and rumen Flashcards
What is the principal of hox genes ?
hox gene sequence on the DNA is in the same order in which they are used from head to tail and changes in hox genes cause valves , sphincter changes in diameter and function
What structures derive from the foregut section of the gut tube ?
oral cavity , tongue
oesophagus
stomach
duodenum
upper and lower resp tract
liver
pancreas
tonsils , salivary glands
thyroid
thymus
anterior pituitary
What structures in the adult derive from the midgut section of the gut tube ?
rest of small intestine and part of large intestine
What structures of the adult derive from the hindgut part of the gut tube ?
rest of large intestine
Where does the gut tube derive from ?
forms from endoderm which then forms the epithelial lining of the digestive tract and parts of liver and pancreas
What does the mesoderm form in terms of the gut tube ?
mesoderm forms muscular and peritoneal components of the gut
what does the gut tube develop from ?
ventral invaginations at either end of the embryo that elongate and fuse along the ventral midline to form straight tube
What is mesentery ?
fold or membrane that has bv , nerves and lymphatics to and from visceral structures
What does mesentery refer to ?
mesojenjunum
What does greater omentum refer to ?
greater omentum that supports the stomach also known as the mesogastrium
Name developmental defects
-viteline fistula
-viteline cyst
-meckels diverticulum
-umbilical hernia due to faulty closure of abdominal wall leaves larger opening
-clefts - abnormal growth processes e.g hernia , spina bifida ( split vertebral column ) , schistosoma reflexum ( open body wall and dislocation of organs ) palatoschisis ( cleft lip and palate )
-aplasia - absence of part or all of an organ
-hypoplasia - reduced development of an organ
What is the septum transversum ?
junction between amniotic ectoderm and yolk sac endoderm
Describe the factors that regulate appetite in domestic species
-age - slower metabolism as get older
-environment - stress fight/ flight
-exercise - lifestyle
- multi- animal household - compete for food
-repro status pregnant/lactating
-genetics - no POMC gene - overeat
-type food
-hormones
outline hormones that stimulate appetite
ghrelin
neuropeptide Py
agouti-related peptides
Name appetite decreasing hormones
leptin
peptide YY
glucagon like peptide
What happens to the gastrointestinal sphicter under parasympathetic control
relaxes - decreases retention allows food to move through GI tract
What happens to gastrointestinal sphincter under sympathetic control ?
contraction of the gastrointestinal sphicters - increase retention and stop movement of food through GI tract
What are the splanchnic nerves ?
-thoracic - sympathetic , supply abdomen and pelvis ,greater splanchnic ( stomach , spleen, liver , pancreas , gallbladder , adrenal medulla ) , lesser splanchnic ( midgut ) , Least splanchnic nerve ( renal plexus ) , arise T1-L2 enter coeliac plexus
- pelvic - parasympathetic , reg emptying of bladder ( opening and close urethral sphincter ) ,innervates repro organs , motility to rectum , arise from s2-4 enter sacral plexus
Parasympathetic supply in abdomen
- originate from vagus nerve
-ventral vagus plexus - liver and stomach - hepatic branches form plexus at liver to cystic duct,gal bladder , l lateral lobe of liver and bile duct
- dorsal vagal trunk p– cardiac region of stomach - forms plexus to pylorus
ENS plexuses in the GIT
myenteric plexus
submucosal plexus
Outline how an action potential is generated
-stimulus reach threshold (membrane potential -55)for activation
-depolarisation 40 mV rapid rise caused by opening of Na channels large influx of Na+
-action potential
-repolarisation - Na channel inactivation and large influx of K+ as K channels are activated
- hyperpolarisation - efflux of K + when K channels close causing decreases in membrane potential below -70
- returns to resting state -70
Func and distribution of ENS ?
-all down wall of GI tract from lower oesophagus to rectum
- myenteric plexus - sit between longitudinal and circular muscle layers - regulate GI motility
- submucosal plexus - sit in lamina submucosal layer - control secretions and blood flow
-using short reflex arch they can alter motor func and secretion due to changes in ph, stretch walls and osmolarity
Overall ENS func
-motility
-exocrine and endocrine secretions
- reg immune and inflammatory processes
- microcirculation
intrinsic enteric ENS
ENS fibres in smooth muscle of GIT act independently via interstitial cells of cajal ( pacemaker ) = modified smooth muscle cells that initiate waves of partial depolarisation that facilitate peristalsis.( need action potential to cause full contraction and action potential )
extrinsic autonomic innervation
sympathetic and parasympathetic fibres of the GIT - outside GI smooth muscle
What is electrocoupling how does it relate to the gi tract ?
electrocoupling is where gap junctions are continuous through cells allowing the spread of electrical signals that trigger contractions. smooth muscle cells of the GI tract are connected via gap junctions . the rhythmic contractions all food to move through GIT
Biophysical characteristics of GI tract smooth muscle
-Gi smooth muscle autonomous - interstitial cells of cagal so can generate electrical activity without input of nerves ( cagal cells only in circular muscle - slow waves )
-contractile activity is determined by input of enteric motor neurones
define slow wave
periodic depolarisation that sets up electrical conditions for smooth muscle cells to contract in response to release of ach from myenteric excitatory motor neurons
difference between segmentation and propulsive peristalsis
-segmentation = mixing and churning of chyme , rhythmic back and forth , circular muscle of intestinal wall ,local ENS
-peristalsis = moving of chyme through intestine ,wave like pattern , circular and longitudinal ,local and central from ENS and ANS , triggered by expansion of the stomach
-segmentation first ( digestion and absorption ) then peristalsis becomes stronger ( wave from stomach down intestine )
How is the stomach emptied ?
-peristaltic waves
- systolic contractions in pylorus - lower freq contractions create pressure gradient
- reduction in size of the stomach
Factors effecting stomach emptying
- digestible components and nutrient density - high fat content take longer to digest
- solid or liquid - liquids faster
- volume of ingesta - higher volume takes longer
- viscocity of ingesta - increase vis decrease rate of emptying
- excercise intensity - increased intensity blood diverted away from GI tract ( sympathetic )
-temp - warmer food increase rate of digestive enzymes
-enterogastric reflex
-gastric inhibitory and excitatory hormones released from pancreas and intestine
What is the enterogastric reflex ?
stimulated by acid ph change
cause release of acids and control release of gastrin
if gastrin stops secretion of hcl from parietal cells stops
ph goes up
how osmolarity and chemical composition of ingesta effect gastric emptying ?
- higher osmolarity ( more solute particles ) , higher chemical composition ( effect osmolarity more concentrated ) - take longer to digest
- osmo and chemoreceptors detect this and delay gastric emptying ( change patterns of gastric motility )
Vomiting reflex
-stimulus to medulla - vomiting center
- vomiting center coordinates reflex through cranial nerves
-hypersalivation , sweat , tachycardia
-glottis closes, soft palate rises
-deep inspiration , diaphragm contracts
-cardiac sphincter an fundus relax
-abdominal muscles contract forcefully
-antiperistaltic waves
- increase pressure forces chyme upwards from stomach out of mouth
what receptors does the vomiting center have ?
muscarinic
What is the CTZ ?
chemoreceptor trigger zone that stimulates the vomiting centre ( dopamine 2 receptors )
Outline the origin and activity of major gastrointestinal hormones ( what stimulates their release )
-gastrin - stimulated by vagus nerve and peptides in stomach , from G cells , stim HCL and mucosa to develop in s and I , stim ECL , dilate pyloric sphicter
-Histamine is stimulated by gastrin , come from ECL cells , stimulate parietal cells by binding to H2 receptor
-secretin - stim by duodenum enteroendocrine cells when ph drops , reduces secretions( stop high acidity ) - inhibits parietal and chief cells and stim buffer , stops stomach from continually secreting
-somatostatin - stim by delta cells ( when ph drops ) , inhibit release of gastrin and HCL , inhibit release cholecytokinin and secretin from duodenum
-cholecystokinin - released by epithelial cells in si ( I cells ) when lipid and carbs present in duodenum and hypothalamus satiety center when stomach expand
- gastric inhibitory peptide - stim by ingestion of food especially fat , inhibit gastric motility and hcl secretion and insulin secretion ( lipolysis to lipogenesis)
Influence of chloecystokinin and secretin on pancreatic secretions
-CCK - stim release of pancreatic digestive enzymes and fluid
-secretin - inhibits secretion of pancreatic digestive enzymes and fluid
outline Fore stomachs of the cow and their epithelial tissue
rumen - rumen take up a lot of it
reticulum - section of rumen much smaller than whole rumen , conical papillae
omasum - spherical with slightly flattened sides , laminae covered in conical papillae( 3 different sizes/heights )
-lined stratified epithelium
Outline the true stomach of the cow and its epithelium
abomasum - fundus , body and pylorus
longitudinal rugae
simple columnar epithelium - some goblet
-mucin, pepsinogen and hcl
-fundic gland - renin coagulates casein ( milk protein ) then pepsin completes digestion
What do rumen-reticulo contractions do ?
stir, redistribute and mechanically grind
partition fibre for re-chewing ( long at top so can go into oseophagus opening )
structure and func of ruminal papillae
leaf-shaped , keratinised
conical papillae in reticulum
increase surface area for flora and absorption
less at the top of the rumen so the long fibres that need rechewing can go back up oesophogus
What factors effect size and shape of papillae ?
age, diet , location
What happens when reticula croove contracts ?
edges curl up and create tunnel between oesophagus and the reticulo-omasal orifice
What stimulates the reticular groove reflex ?
suckling milk , noises associated with feeding routine – vagus nerve stim to contract
Where does the abomasum usually sit in the cow and how does this change with LDA ?
usually sits on right however when distended pulled over to the left ( ping auscultated on left )
What makes it possible for abomasum to dislocate when distended ?
abomasum is loosley suspended by omentum so it can move from left to right its pushed onto left side
What can cause distention of abomasum?
diet - grain
competing - eat very quickly
-the more calving’s and first few weeks of lactating it can occur
How can you evaluate rumen health ?
ping
ausultation - 3contractions every 2 m
abdominal silhouette - ruminal bloat , vagal indigestion , LDA
faeces
ruminal fluid
