The Stomach

Stomach

What is the stomach and where is it located

The stomach is a hollow muscular sac located in the left upper quadrant under the diaphgram

Funciton of the stomach (3) and what does it produce

Food storage, mechanical digestion by liquifying food, and begining chemical digestion of protein and fat

produces chyme

Chyme

acidic and soupy mixture of semi digested food produced by the stomach

What are the 4 regions of the stomach

cardiac region (cardia), fundic region (fundus), body, and pyloric region

Fundus region of stomach

Body of stomach

cardia of stomach

Phyloric region of stomach → connecst to the duodenum part of the small intestine

What are the two margins of the stomach

greater and lesser curvature
image is lesser curvature
greater curvature is the other side

Circulation - where does blood going to digestive organs come from

Stomach receives blood from the branches of the celiac trunk (from the aortic artery)

Circulation → where does blood from the stomach and intestine go

hepatic portal circulation → filtered through the liver before returnign to heart

How is the musclaris externa layer from the 4 basic layers (mucosa submucosa musclaris externa and serosa) different in the stomach

There are actually 3 layers instead of 2

before (outer longitudinal, inner circular)

in the stomach → outer longitudinal, middle circular, inner oblique) → stronger and better churning

Gastric rugae

folds of the mucosa and submucosa layer of the stomach → folds when stomach is empty and flattens when stomach is full to expand

Mucosa of the stomach produces what

mucus that traps bicarbonate rich fluid

Mucosa of stomach contains what

Gastric pits that lead into tubular glands

Gastric Pits and what do they have

Depressions on the gastric mucosa (deepest layer of the mucosa) → each has 2-3 tubular glands at the bottom

Gastric glands/ tubular glands

glands at the bottom of gastric pits that contain different cells that produce gastric juice

What are the three types of gastric glands

cardiac, pyloric, and gastric glands

What are the four gastric pit cell types (in the glands)

mucosa, parietal, chief, and enteroendocrine cells

mucous cells secrete what + in which glands

secrete mucous

mainly in pyloric and cardiac gland

called mucosal neck cells in gastric glands because they get stuck at neck

What 3 things do parietal cells secrete

intrinsic factor, ghrelin, and HCl

Which cell secretes this and what do each of these do
ghrelin, intrinsic factor, HCl

Parietal cells

Intrinsic factors→ allows small intestine to absorb vitamin b12

ghrelin - hunger hormone

HCl (really acidic)- denatures protein, kills bacteria, and activate pepsin

Chief cells - what do they secrete (2) which do what

Pepsinogen → pepsin → gets activated by HCl to take part in digestion of mainly protein

• pepsin can activate more pepsin (positive feedback)

Gastric lipase → digests fat

Which glands are chief cells in

In the lower half of gastric glands - none in cardiac or pyloric gland

Enteroendocrine cells - also called what - release what

also called G cells

secrete chemical messengers

• Paracrine - histamine and seretonin

• Hormone - G cells (gastrin and somatostatin) that regulate mobility and secretion

which cells are which (left is pyloric and right is gastric gland)
blue, light pink, dark pink, orange

blue - mucus, light pink is chief cell, dark pink is G (enteroendocrine) cell, and orange is parietal cell

which gland is which left and right

left is pyloric gland because it doesn’t have chief cells

right is gastric gland because it has all 4 cells and the mucous cells are at the neck

How does the stomach protect itself from gastric juice (pepsin, HCl) and not digest itself → 3 things
what happens if they fail

mucous (traps bicarboniate rich fluid under it), tight junctions, epithelial cell replacement

failure → inflmation / ulceration

What two system regulates gastric motility and secretion and what is the goal

endocrine and nervous system

increase gastric secretion and motility when there is food and limit them when there isn’t

What are the three phases that control gastric activity and what does it mean that thye are concurrent

cephallic, gastric, intestinal

concurrent - happening at the same time

Cephalic phase of gastric control

cephalic = head/ brain

stimulus comes from inside or outside GI tract like senses or thinking about food → CNS → hypothalamus → medulla oblongata → vagus nerve → enteric nervous system → stimulates gastric secretion

Gastric phase of gastric control

Presence of food in stomach = stimulus

stretches the stomach and activates short myenteric reflex (through myenteric plexus) and long vagovagal reflex (through vagus nerve)

this increases gastric secretion

ACh, histamine, gastrin

stimulates gastric secretion in the gastric phase (in stomach)

Receptive-Relaxation (Reflex-Mediated) Response

when swallowing → brain → vagus nerve tells stomach to relax to make room

resist stretching then relaxes

Gastric accomodation - stress relaxation response

allows muscle to stretch without contracting reflexively (immediately)

Enteric pacemaker cells (cells of cajul) → BER

cells in the stomach that produce basic electrical rhythm → produces peristaltic waves → push chyme from fundus to pylorus

some chyme gets pushed from pylorus of stomach to duodenum of small intestines while most of it gets sent back to the stomach (which helps with mixing)

Intestinal phase of gastric control

chyme enters duodenum of intestine and regulates the gastric activity through hormones and reflexes

Intestinal phase - stimulatory (what is it and what ar ethe two)

sends chyme down to intestines faster

• vagovagal reflex

• gastrin enzyme

Intestinal phase - inhibitory (what is it and what are the 3)

slows down gastric activity (chyme entering intestine slower)

• entericgastric reflex

• secretin

• cck

Emesis + involve what center where

Vomitting - > protective reflex

involves emetic center in medulla

forces food out of stomach