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