Lesson 68 - Monogastric Stomach structure

How many chambers is monogastric?

one

What is pepsin?

digestive enzyme produced in the stomach that breaks down proteins into smaller peptides

What is cardia?

upper region of the stomach where the food enters from the esophagus

What is fundus?

part of the stomach that expands to store food and secretes digestive enzymes

What is the pylorus?

lower part of the stomach that regulates the movement of partially digested food into the small intestine

What is chyme?

semi-liquid mixture of partially digested food and gastric juices that passes from the stomach to the intestines

What are parietal cells?

cells in the stomach lining that produce hydrochloric acid

What are chief cells?

cells in the stomach lining that secrete pepsinogen

What are mucous cells?

cells that produce mucous to protect the stomach lining from acid and digestive enzymes

What is gastrin?

hormone that stimulates acid secretion in the stomach

What is bloat?

digestive disorder in which gas accumulates in the stomach, leading to distension and discomfort

What is the pyloric sphincter?

muscular valve that controls the passage of chyme from the stomach to the small intestine

What animals are monogastric?

pigs, dogs, cats, horses, rabbits

What are characteristics of monogastric animals?

limited fiber digestion, enzyme-based digestion, fast digestion, omnivorous vs carnivorous diets

What is the function of the monogastic stomach?

food storage, mechanical digestion, chemical digestion, fat digestion, carbohydrate digestion, regulation of digestion

What enzyme is doing protein digestion?

pepsin

What enzyme is doing carbohydrate digestion?

amylase

What enzyme is doing fat digestion?

lipase

What are the regions of the stomach?

fundus, body, pylorus

What structure can be seen inside the stomach?

rugae

What animal has a more pronounced angular notch?

cats

What is ventriculus/gaster?

another name for stomach

What part of the stomach has the cardia?

fundus

What sphincter is in the cardia?

cardiac sphincter

Where is the stomach located in the body?

transversely from rib 9-12

What part of the stomach is on the left side?

fundus and body

What part of the stomach is on the right side?

pylorus

What is unique about stomach location in cats?

most of the stomach is on the left side of the midline; only pyloric canal is on the right

What is the only fixed point of the stomach?

cardia at the 9th intercostal space

What are the connecting peritoneum?

greater and lesser omentum

Where is the greater omentum?

between body wall and greater curvature of the stomach

Where is the lesser omentum?

between the liver and lesser curvature of the stomach

What is the gastrosplenic ligament?

greater omentum

What is another name for the greater omentum?

abdominal policeman

What are the functions of the omentum?

fat storage and energy reserve, immune and protective function, infection and wound healing, lubrication and reduction of friction

How does the omentum help with the immune system?

contains macrophages and lymphoid tissue that help in immune response

What is the clinical importance of the greater omentum?

can be used in surgical repairs, helps contain tumors and abscesses, excessive fat deposition is linked to obesity disorders

What is the main artery that supplies the stomach?

celiac artery

What are the major branches of the celiac artery?

hepatic, splenic, and left gastric artery

Where does the right gastric artery come from?

hepatic artery

What arteries supply the lesser curvature of the stomach?

left and right gastric artery

What arteries supply the greater curvature of the stomach?

left and right gastroepiploic artery

Where does the left gastroepiploic artery come from?

splenic artery

Where does the right gastroepiploic artery come from?

hepatic artery

What are the major tributaries of the hepatic portal vein?

splenic, left gastric, gastroduodenal, right gastric, cranial and caudal mesenteric veins

Where does the sympathetic innervation to the stomach orginate from?

thoracic spinal cord (T5-T12)

What nerve travels from the thoracic spinal cord?

splanchnic nerve and lesser splanchnic nerve

Where does the splanchnic nerve come from?

T5-T9

Where does the lesser splanchnic nerve come from?

T10-T12

Where do the preganglionic fibers synapse?

celiac ganglion which is part of the celiac plexus

What type of information travels through the sympathetic fibers?

motor and sensory

Where does the parasympathetic innervation to the stomach originate from?

dorsal motor nucleus in the medulla oblongata

What nerve travels from the dorsal motor nucleus?

vagus nerve

What does the vagus nerve split into?

dorsal and ventral vagal trunks

Where do the parasympathetic fibers synapse?

ganglions in the wall of the stomach

What type of information travels through the parasympathetic fibers?

motor and sensory

What plexuses are in the muscularis layer of the stomach wall?

myenteric plexus

What plexuses are in the submucosal layer of the stomach wall?

submucosal plexus

What is another name for the myenteric plexus?

Auerbach's

What is another name for the submucosal plexus?

Meissner's

What does the sympathetic nervous system do to the pyloric sphincter?

contracts to delay gastric emptying

What can excessive vagal stimulation lead to?

increased acid production contributing to gastric ulcers and acid reflux

What is the outer muscular layer?

longitudinal

What is the middle muscular layer?

circular

What is the inner muscular layer?

oblique

What are the sphincters made of?

thickenings of the circular muscle layer

What does the mucosa and submucosa of the stomach contain?

folds and various glands

What animal has a larger area of cardiac glands?

pig

What is the stomach lined by?

simple columnar epithelium

What are gastric pits?

invagination of epithelium, lined by simple columnar epithelium

What are gastric glands?

simple branched, coiled tubular gland densely packed within the lamina propria

What does the cardiac gland region look like?

shallow gastric pits, simple, branched, tubular, mainly mucous secretion

What does the fundic gland region look like?

deeper gastric pits, simple, branched, mucus neck cells, chief/zymogen cells, parietal cells

What are the endocrine/ argentaffin cells?

cells wedged between the basement membrane and the chief cells in the fundic gland region

What is the function of the endocrine/argentaffin cells?

produce serotonin

What stain is needed to see the argentaffin cells?

silver stain

What does the pyloric gland region look like?

deeper gastric pits, simple branched coiled tubular, G cells, D cells, few parietal cells

What do G cells do?

secrete gastrin, which stimulates parietal cells in fundic glands to produce HCl

What do D cells do?

secrete somatostatin which inhibits gastrin secretion and reduces acid production

What is receptive relaxation?

when food enters the stomach relaxes and expands to accommodate the meal without increasing pressure

What is another name for receptive relaxation?

accomodation

What controls the receptive relaxation phase?

vagus nerve and nitric oxide

Where does receptive relaxation occur?

proximal stomach

Where does propulsion occur?

distal stomach

What is the propulsion phase?

strong peristaltic contractions move food toward the pylorus

What regulated the propulsion phase?

pacemaker cells; the interstitial cells of cajal in the greater curvature

What is the frequency of contractions in the propulsion phase?

3 cycles per minute

Where does the grinding and mixing occur?

antrum and pylorus

What is the grinding and mixing phase?

large food particles are mechanically broken down by strong contractions; chyme is mixed with gastric secretions

What is retropulsion?

some chyme is forced back into the stomach body due to pyloric sphincter resistance

What is gastric emptying?

chyme is sufficiently processed, and pyloric sphincter relaxes allowing small amounts of chyme into the duodenum

What hormone increases gastric motility?

gastrin

What hormones inhibit gastric emptying when chyme enters the duodenum?

cholecystokinin, secretin, gastric inhibitory peptide

What is the trigger for the cephalic phase?

sight, smell, thought of food

What happens in the cephalic phase?

stimulates vagus nerve to release acetylcholine to release HCl from parietal cells and pepsinogen from chief cells and gastrin released

What is the trigger for the gastric phase?

presence of food in the stomach

What happens in the gastric phase?

stretch receptors in the stomach detect food activating the vagus nerve to release gastrin and HCl and pepsinogen

What triggers the intestinal phase?

when chyme enters the duodenum

What happens in the intestinal phase?

short burst of gastric secretion from duodenal stretch, but then secretin, cholecystokinin, and GIP are released to inhibit gastric secretion

What does the parasympathetic nervous system do to gastric secretion?

promotes secretion of acid, pepsinogen, and mucus