simple stomach Flashcards
monogastrics and hind gut fermenters have a
simple single-chambered stomach
hind gut fermenters digest cellulose in the
large intestine and caecum with aid of micorbiota
what is the function of simple stomach
receives boluses of food from
the oesophagus, mixes the food with secretions of the stomach wall, stores
it, and then releases it into the duodenum at a controlled rate, to maximise digestion and absorption
simple stomach receives bolus from
esophagus
rate of simple stomach releases food into duodenum is controlled by
volume and composition of contents of the duodenum
greater curvature
convex and curves to left
lesser curvature
concave and to right generally facing in dorsal direction
the stomach curvatures connect the 2 extremitites
- cardiac extremity; left (entrance from esophagus)
- pyloric extremity; right (exit into duodenum)
so when dog is lying on back and you are looking at the stomach you see pylorus on left (but RHS of dog) and esophagus/ cardiac region on right
4 major zones of stomach
1) cardiac region, around entrance of esophagus
2) fundus: bulges cranially to insertion of esophagus
3) body; major part
4) pyloric antrum; leading to exit (pyloric sphincter) into duodenum
2 surfaces of stomach
- parietal; faces liver and diaphragm, cranioventral in dog, protected by ribs
- visceral; facing intestine and spleen, dorsocaudally in dog
the pancreas is closely associated w the
stomach and extends along the duodenum
the duodenum (first part of small intestine) leave pylorus via the
pyloric sphincter
first part of duodenum is ____, second part is _____
descending, ascending
the stomach is inbetween two double folds of peritoneum called the
greater omentum and lesser omentum
the greater omentum
a long loose fold along the greater curvature
the lesser omentum
along the lesser curvature, extends to the liver
the lesser omentum is also called the
hepatogastric ligament although it is loose and rather fragile
the peritoneum (the omentums) also extend over the stomach as a
serous coat
carnivores stomach location in body when empty and full
- empty: completely under ribs
- full: extends caudally beyond ribs, displacing intestines, spleen etc
2 types of mucosa in the simple stomach
nonglandular and glanadular
non glandular mucosa in simple stomach (colour, type of epithelium)
- white
- stratified squamous epithelium
- often folded, may be thick and cornified
- involved w storage
glandular mucosa in simple stomach (colour, type of epithelium)
- reddish to yellow
- covered w simple columnar epithelium
- may have folds (rugae)
- involved w digestion
the surface area of glandular stomach is increased by folding into _____, these are dotted by ______
rugae, especially when stomach is empty, dotted by gastric pits (foveolae)
three types of glandular mucosa based on types of glands present in the lamina propria
1) proper gastric glands or fundic glands
2) cardiac glands
3) pyloric glands
proper gastric gland aka fundic gland
(type of glandular mucosa)
tubular glands, produce a secretion specific to the stomach that contains hydrochloric acid and enzymes
comprised of a neck, a body and a base aka the fundus
have 3 main types of secretory cells; mucous neck cells, chief cells and parietal cells
cardiac glands
(type of glandular mucosa)
simple branched tubular glands which mainly produce mucous which contains large amount of diffuse and nodular lymphoid tissue, protective role
pyloric glands
(type of glandular mucosa)
short, branching and coiled glands, open into deep gastric pits and produce mucus and gastrin (hormone)
need EM to identify
internal morphology of carnivore stomach in reference to the diff types of mucosa (either non glandular, cardiac, fundic or pyloric)
- non glandular; none of v small, v little storage in carnivores
- cardiac; small
- fundic; major part, thick reddish (in dog distal half is darker)
- pyloric; extensive
chemical digestion of food occurs w the presence of
H+ and pepsin
the epithelial layer of stomach mucosa produces
protective layer of mucous since the cells lining the stomach are not immune to the chemical digestion process
describe epithelium of stomach that produces the mucous to protect the surface from acid and enzymes
include where cells are produced
- tall columnar cells
- no prominent microvilli
- mucous granules apically (towards lumen)
- high cell turnover
- cells produced in deep gastric pits
stomach mucosa epithelia contains many shallow indentations called
gastric pits, which open at bottom into gastric glands
so gastric pits lead into gastric glands and kind of intertwined within we see the
(i think the pits and glands are actually WITHIN it)
lamina propria, a loose, elastic connective tissue layer that has lots of lymphocytes, eosinophils, plasma cells and mast cells
the lamina propria is packed with the 3 types of glands, which open into the gastric pits:
fundic, cardiac and pyloric glands
fundic glands have 3 main types of secretory cells:
(type of glandular mucosa)
mucous neck cells, chief cells and parietal cells
mucous neck cells
(type of secretory cell of the fundic glands)
- only found in neck (recall fundic glands have a neck, body and base)
- basal nucleus
- mucus granules
- secrete alkaline mucous that protects epithelium against shear stress and acid
- stain w PAS
chief cells are _____ secreting cells, which means
(type of secretory cell of the fundic glands)
zymogen-secreting cells
they secrete in inactive substance which is converted into an enzyme when activated by another enzymes
chief cells secrete
(type of secretory cell of the fundic glands)
pepsinogen and prorenin
which are converted to active enzymes pepsin and rennin in the gastric lumen (both peptidases ie they break down protein)
why does rennin production decrease after weaning?
(chief cells secrete pepsinogen and proreninwhich are converted to active enzymes pepsin and rennin in the gastric lumen (both peptidases ie they break down protein))
(chief cells type of secretory cell of the fundic glands)
because Rennin is involved in curdling milk in young mammals
parietal cells
(type of secretory cell of the fundic glands)
- found throughout glands
- pyramidal, narrow apically, fried egg appearance because of central nucleus
- eosinophilic (stain v pink)
- SA increased by deep infolding of apical surface, these secretory canaliculus subdivides into many smooth-surfaced canalicli which are in close contact w large numerous mitochondria
- secrete hydrochloric acid
neuroendocrine (argentaffin) cells
- take up silver salts
- found throughout stomach around gastric glands
- v small cells and pyramidal
- difficult to see without silver stains
- secrete serotonin into bloodstream
neuroendocrine (argentaffin) cells secrete
serotonin into blood stream
stem cells occur in the ____ region of glands and differentiate to replace both:
- neck
- neck and glandular cells
cats have a layer deep to the lamina propria called the
- lamina subglandularis (name makes sense bc lamina propria has many glands)
- has inner and outer layer
layers of the lamina subglandularis (the layer found in cats that sits deep to lamina propria)
- inner layer; stratum granulosum (fibroblasts)
- outer; stratum compactum (dense collagen)
what is the function of the layer lamina subglandularis found in cats (think cat diet)
to prevent penetration of shards of bone through stomach mucosa
summary of the tunica mucosa of the stomach
-the surface epithelium.
- Then the lamina propria, which is packed with fundic, cardiac and pyloric glands, which open into the gastric pits
- In cats, beneath this lies the lamina subglandularis
- then muscularis mucosae, which is made up of two or three layers of smooth muscle cells, oriented in circular or longitudinal directions (Thin strands may extend into the lamina propria between the glands)
recall in lamina propria we have fundic glands (consisting of mucous neck cells, chief cells and parietal cells), cardiac glands and pyloric glands
tunica muscularis of stomach is thickest in
pyloric region and near esophagus
describe the fibers in the tunica muscularis of the stomach
- longitudinal fibers: 2 bands along greater and lesser curvatures, aka external oblique, run obliquely in parietal and visceral surfaces
- circular fibers; in body and pyloric parts, thickest at pyloric and cardiac sphincters
- internal oblique fibers; mainly fundus and cardia, extend along lesser curvature to pylorus, form cardiac sphincter along with circular muscle fibers
storage occurs in what region of stomach
mechanical and chemical digestion occurs in what region of stomach
proximal
distal
describe muscular activity in proximal stomach (storage)
- maintains tone in wall
- relaxes as food enters and is stored
- increases tone slightly to move ingesta to distal stomach
strong, slow waves of peristaltic contractions migrate from
middle of stomach towards the pylorus
as slow waves approach the pylorus, the pylorus _____, which means that
contracts/ constricts, means that only liquid and smallest particles can enter the duodenum, at same time pyloric region is crushing and grinding food aiding in mechanical digestion
CNS
brain and spinal cord
PNS
entire nervous system outside of brain and spinal cord
split into somatic (voluntary control of skeletal muscle) and autonomic (involuntary control of glands and smooth muscle)
autonomic is further split into parasympathetic (rest and digest) and sympathetic (fight or flight)
sensory/ ______ as well as motor / _____ neurons
afferent (sensory): info coming in
efferent (motor); info going out
heart:
sympathetic stimulation (fight or flight)
parasympathetic stimulation (rest and digest)
- S: Increased rate, increased force of
contraction (whole heart) - P: Decreased rate, decreased force of
contraction (of atria only)
blood vessels
sympathetic stimulation (fight or flight)
parasympathetic stimulation (rest and digest)
- S: constriction
- P: Dilation of vessels supplying the penis and clitoris only
lungs
sympathetic stimulation (fight or flight)
parasympathetic stimulation (rest and digest)
- S: Dilation of bronchioles
- P: Constriction of bronchioles
digestive tract
sympathetic stimulation (fight or flight)
parasympathetic stimulation (rest and digest)
- S: Decreased motility, Contraction of sphincters
- P: Increased motility, Relaxation of sphincters, Stimulation of digestive secretions
urinary bladder
sympathetic stimulation (fight or flight)
parasympathetic stimulation (rest and digest)
- S: relaxation
- P: contraction (emptying)
eye
sympathetic stimulation (fight or flight)
parasympathetic stimulation (rest and digest)
- S: dilation of pupil
- P: constriction of pupil
liver (glycogen stores)
sympathetic stimulation (fight or flight)
parasympathetic stimulation (rest and digest)
- S: glucose released (glycogenolysis)
- P: none
adipose cells (fat stores)
sympathetic stimulation (fight or flight)
parasympathetic stimulation (rest and digest)
- S: fatty acids released (lipolysis)
- P: none
somatic efferent pathway
somatic motor system, there’s a motor neuron that goes from the spinal cord, directly to the skeletal muscle. So there’s one myelinated nerve, travelling from the spinal cord, to the muscle
autonomic efferent pathway
Efferent neurons are made up of two neurons, a preganglionic nerve, and a postganglionic nerve. The preganglionic nerve is myelinated, and the postganglionic one isn’t.
The length of these pre- and postsynaptic fibres is different in the sympathetic and parasympathetic nervous systems.
sympathtic nervous system synaspes in sympathetic chain ganglia, aka the
sympathetic trunk
sympathetic ganglia location vs parasympathtic ganglia location
what does this mean in terms of the presynaptic vs postsynaptic nerve lengths for each
- synapses in sympathetic ganglia chain (sympathetic trunk) made up of paravertebral ganglia located next to spinal column in thoracic and abdominal cavities
- parasympathetic synapses in autonomic ganglia that is close to the tissue it is going to be innervating, emerge from craniosacral region
- so presynaptic vs postsynaptic nerves going to be diff lengths: sympathetic has short pre and long post, parasympathetic has long pre and short post
parasympathetic nervous system involved in
house keeping functions
in GIT parasympathetic nervous system serves to
increase motility and secretions
parasympathetic nervous system originates from
the brain (cranial nerves) or the pelvic region (pelvic nerves)
parasympathetic supply to abdomen leaves the brain as fibers in
CN X, the vagus nerve
vagus nerve travels with
(parasympathetic innervation)
sympathetic fibers, next to carotid artery on way to head, known as the vagosympathetic trunk
in thoracic cavity the vagus nerve
(parasympathetic innervation)
continues alongside esophagus and splits into dorsal and ventral vagus
(since cranial nerves are paired there is a left and right vagus nerve so 4 total atp)
how does the vagus nerve pass through the diaphragm
(parasympathetic innervation)
with the esophagus through the esophageal hiatus (the left and right dorsal vagus nerves join and the left and right ventral vagus nerves join)
sympathetic nervous system _____ activity of GIT
decreases
sympathetic nerves originate from the
spinal cord in thorax and abdomen
the sympathetic chain runs
in the fascia near hypaxial muscles in the thoracic and abdominal cavities (easier to see in thoracic cavity)
some preganglionic sympathetic fibres pass through the sympathetic chain without synapsing, instead they synapse at ganglia which are associated with
the 3 major blood vessels that supply to GIT: (ganglia named after blood vessels they lie on)
- coeliac artery; coeliac ganglion
- cranial mesenteric artery; cranial mesenteric ganglion
- caudal mesenteric artery; caudal mesenteric ganglion
sympathetic innervation; those preganglionic fibers that DON’t pass through the chain and instead lie on the 3 major arteries supplying the GIT;
anyways
The coeliac and cranial mesenteric ganglion lie near one another in the abdominal cavity and there is a dense network of nerve fibres that branch and communicate between the two ganglia. Sometimes they might be referred to as
the coeliac and cranial mesenteric
plexuses.
the GIT has its own intrinsic nervous system called
enteric nervous system
the enteric nervous system is represented by the
the myenteric (Auerbach’s) and submucosal (Meissner’s) plexuses in the gut wall.
Auerbach’s plexus (ENS)
found between the muscle layers of the tunica muscularis, where it forms an almost continuous network of nerve fibres (plexus) and nerve cell bodies (ganglion)
meissner’s plexus (ENS)
found in the submucosa and receives input from Auerbach’s plexus but is more intermittent and can be hard to find. The fibres of the vagus and the coeliac and the cranial and caudal mesenteric ganglia then pass along blood vessels to the stomach, and synapse with the Auerbach’s and Meissner’s plexuses in the wall of the GIT to influence the activity of the enteric nervous system.
coeliac artery (first major unpaired branch of abdominal aorta) has 3 main branches:
- left gastric
- spelnic
- hepatic
what is first major unpaired branch of abdominal aorta
coeliac artery
the venous blood in gastric veins flows through the
hepatic portal vein to the liver
left gastric artery
(branch of coeliac artery)
THE MAIN blood supply to the stomach is from the left gastric artery
The left and right gastric arteries run along the lesser curvature and anastomose
main blood supply from stomach is from
left gastric artery
major blood supply to spleen is from
splenic artery
splenic artery
The splenic artery traverses to the spleen on the left hand side of the
abdomen and supplies the spleen as well as giving off the left
gastroepiploic artery.
splenic artery branches into the
left gastroepiploic artery
major blood supply to liver
hepatic artery
hepatic artery
The hepatic artery goes off to the right hand side of the abdomen to supply the liver and gives off the right gastric artery and the right gastroepiploic artery (and the gastroduodenal artery).
hepatic artery branches (3)
- Right gastric
- Right gastroepiploic
- Gastroduodenal
Lymphatics of the stomach drain to nodes in the
coeliac lymph centre
Efferent lymphatics join together at the
cysterna chyli, and lymph reaches the
bloodstream through the thoracic duct
efferent lymphatics –> cysterna chyli –> thoracic duct
Which region of the stomach surrounds the entrace of the oesophagus?
cardia
Where does the stomach exit into the duodenum?
pylorus
Which surface of the stomach faces the intestines and the spleen?
visceral
In the glandular regions of the simple stomach, which layer of the tunica mucosa is packed with gastric glands?
lamina propria
Which of the following is also known as the proper gastric glands?
fundic glands
epithelium of glandular mucosa is
simple columnar epithelium
The secretions produced by the gastric glands function
aid in chemical digestion of food
Pepsinogen is secreted by which cell type?
chief cells
In the GI tract, an increase in parasympathetic stimulation:
Increases motility and secretions
Which of the following statements regarding the enteric nervous system is INCORRECT?
A.
The enteric nervous system is the intrinsic nervous system in the gastrointestinal tract
B.
It is comprised of the myenteric (Auerbach’s) and submucosal (Meissner’s) plexuses in the gut wall
C.
It is comprised of nerves that originate from the spinal cord in the thorax and abdomen
D.
Sympathetic and parasympathetic stimulation influence the activity of the enteric nervous system
C
The main blood supply to the stomach is from the:
left gastric artery
