Stomach Phys and Path

Question 1

What is the stomach?

Answer 1

a J-shaped enlargement of GI tract directly inferior to diaphragm in abdomen

Question 2

what is the most distensible part of the GI tract?

Answer 2

stomach

Question 3

what are the functions of the stomach

Answer 3

• serves as reservoir for food before release into SI
• mixes saliva, food, and gastric juice to form chyme

Question 4

what are the 4 main regions of the stomach?

Answer 4

• cardia
• fundus
• body
• pyloric

Question 5

what are the 2 sphincters of the stomach?

Answer 5

• lower esophageal
• pyloric

Question 6

what are the 2 main curvatures of the stomach?

Answer 6

• lesser
• greater

Question 7

the main arterial supply comes from where?

Answer 7

celiac trunk of aorta

Question 8

what are the 4 main arterial supply to the stomach?

Answer 8

• Hepatic artery
  – right gastric
  – right gastro-omental
• celiac trunk
  –left gastric
• splenic artery
  – left gastro-omental

Question 9

which veins does the stomach drain into?

Answer 9

drain into hepatic portal vein or superior mesenteric vein

Question 10

specifically, tell me the vein and where it drains into

Answer 10

○ Left gastric vein
§ Hepatic Portal Vein
○ Right gastric
§ Hepatic Portal Vein
○ Left gastro-omental vein
§ Superior Mesenteric Vein
○ Right gastro-omental
§ Superior Mesenteric Vein

Question 11

in terms of innervation of the stomach, the parasympathetic supply comes from?

Answer 11

anterior and posterior vagal trunks from vagus nerve

Question 12

in terms of innervation of the stomach, the sympathetic supply comes from?

Answer 12

from T5-T9 segments of sympathetic trunk, passes to celiac plexus via greater splanchnic nerve

Question 13

what is part of the mucosa of the stomach

Answer 13

• epithelium
• lamina propria
• muscularis mucosae

Question 14

epithelium and lamina propria are arranged into ?

Answer 14

glands

Question 15

glands have 3 regions:

Answer 15

• pit
• neck (isthmus)
• base

Question 16

what are the different cell types of the stomach glands?

Answer 16

• surface mucus cells
• parietal cells (oxyntic)
• chief cells (zymogenic)
• enteroendocrine cells

Question 17

what lines the surface of the stomach and gastric pits

Answer 17

simple columnar epithelium

Question 18

surface mucus cells have lots of what ? which are large glycoprotein

Answer 18

mucin granules

Question 19

what are found within the neck of gastric glands/mucus neck cells

Answer 19

simple columnar epithelium

Question 20

parietal cells are what shape?

Answer 20

rounded/pyramidal shape

Question 21

what are the functions of these parietal cells?

Answer 21

produce HCL and IF

Question 22

where are parietal cells mainly found

Answer 22

in upper half of gastric gland

Question 23

where are chief cells found?

Answer 23

in lower regions of gastric glands

Question 24

what is the function of the chief cells?

Answer 24

pepsinogen secretion

Question 25

where are enteroendocrine cells found?

Answer 25

found deep within gastric pits

Question 26

what are the different types of enteroendocrine cells?

Answer 26

- enterochromaffin-like cells - G-cells - D- cells

Question 27

what does enterochromaffin-like cells secrete?

Answer 27

histamine

Question 28

what does G-cells secrete

Answer 28

gastrin

Question 29

what does D-cells secrete

Answer 29

somatostatin

Question 30

the submucosa is made up of ?

Answer 30

dense, irregular collagenous CT

Question 31

what are the 3 layers of muscularis externa

Answer 31

- inner oblique - middle circular - outermost longitudinal

Question 32

what are the 4 different stages of the stomach motility

Answer 32

1. food entry into stomach 2. storage in fundus 3. mixing (aka churning) 4. emptying into small intestine

Question 33

what are the functions of the lower esophageal sphincter?

Answer 33

- controls movement of food into the stomach - also prevent reflux of gastric contents into the esophagus

Question 34

what is required of the sphincter to facilitate entry of food into the stomach?

Answer 34

relaxation

Question 35

what is initiated for the relaxation of the lower esophageal sphincter?

Answer 35

initiated by a vasovagal reflex called receptive relaxation which is triggered by swallowing and esophageal distension

Question 36

where is the food stored in the stomach?

Answer 36

fundus

Question 37

what is gastric accommodation

Answer 37

the presence of food stretches the stomach walls and reduces the tone in muscular wall of body of the stomach

Question 38

what initiates mixing waves of food in the stomach?

Answer 38

gastric pacemakers

Question 39

what is it called when waves start in mid- to upper portion and move toward pyloric antrum

Answer 39

propulsion

Question 40

the contractions in pyloric antrum "grinds" the food bolus called?

Answer 40

grinding

Question 41

the pylorus opening is very small so antral contents are pushed back upstream toward body of stomach, this is called?

Answer 41

retropulsion

Question 42

what can only leave the stomach through the pyloric sphincter

Answer 42

only liquid

Question 43

gastric acids are released from ?

Answer 43

parietal cells

Question 44

what is the pH of gastric acid?

Answer 44

pH of 1-2

Question 45

gastric acid is composed of?

Answer 45

- hydrochloric acid - large amounts of KCI and small amounts of NaCl

Question 46

what are the functions of gastric acid?

Answer 46

- digestions of denaturation of protein - bacteriostatic - needed for conversion of pepsinogen to pepsin

Question 47

what is the secretion mechanism of gastric acid?

Answer 47

- Water dissociates into H+ and OH- in cell cytoplasm - CO2 combines with OH- to form bicarbonate ions by enzyme: carbonic anhydrase - H+ is pumped into lumen of canaliculus via H+/K+ ATPase - H+/K+ ATPase is blocked by the class of drugs called “proton pump inhibitors” - Cl- transported passively from cytoplasm of parietal cell into lumen of canaliculus - Parietal cells can be stimulated by several sources: ○ Acetylcholine acting on Muscarinic receptors § Parasympathetic stimulation ○ Gastrin acting on CCK2 receptors ○ Histamine acting on H2 receptors

Question 48

Histamine is stored and released form ? of the stomach

Answer 48

enterochromaffin-like cells

Question 49

what are the functions of histamine

Answer 49

- acts on H2 receptors on parietal cells - stimulates release of gastric acid - stimulates vasodilation

Question 50

gastrin is secreted by ?

Answer 50

G cells

Question 51

gastrin is secreted in response to?

Answer 51

- stomach distension - vagal stimulation - presence of partially digestion proteins (peptides and amino acids)

Question 52

what are the functions of gastrin?

Answer 52

○ Acts on ECL cells to stimulate release of histamine ○ Directly stimulates parietal cells by binding to CCK receptor

Question 53

Parietal cells can be inhibited by?

Answer 53

- somatostatin - prostaglandins

Question 54

somatostatin is also known as ?

Answer 54

growth hormone inhibiting hormone

Question 55

somatostatin is released from what?

Answer 55

D cells

Question 56

what are the functions of somatostatin?

Answer 56

- acts on parietal cells to reduce secretion of gastric acid - also reduce release of gastrin, secretin, and histamine - suppresses released of pancreatic hormones

Question 57

somatostatin is secreted in response to?

Answer 57

luminal H+ which is negative feedback

Question 58

the phases of gastric acid secretion after meals can be divided into 3 phases which are?

Answer 58

- cephalic - gastric - intestinal

Question 59

the cephalic phase is triggered by ?

Answer 59

smell, sight, taste, thought and swallowing food

Question 60

the cephalic phase is primarily mediated by the ?

Answer 60

vagus nerve

Question 61

the vagus nerve releases ?

Answer 61

Ach

Question 62

what does the Ach do?

Answer 62

§ Ach acts directly on parietal cells to release H+ § Ach acts on ECL cells to release histamine § Ach acts on D cells, inhibiting release of somatostatin

Question 63

Vagus nerve also releases ? to induce gastrin release from G cells

Answer 63

GRP

Question 64

food enters the stomach, distending the gastric mucosa and activating what?

Answer 64

vagovagal reflex and local ENS reflex

Question 65

partially digested proteins stimulate G cells to produce ?

Answer 65

gastrin

Question 66

what stimulates D cells to secrete somatostatin, which inhibits gastrin production (think negative feedback)

Answer 66

low luminal pH

Question 67

explain the intestinal phase of gastric acid secretion

Answer 67

- Presence of amino acids and partially digested peptides in proximal intestine ○ Stimulates G cells in duodenum to secrete gastrin

Question 68

what are some intrinsic factors for secretion of gastric acid

Answer 68

glycoprotein and pepsinogen

Question 69

glycoprotein is secreted by ?

Answer 69

parietal cells

Question 70

what is the function of glycoprotein

Answer 70

required for the absorption of vitamin B12 in the ileum

Question 71

pepsinogen is secreted by ?

Answer 71

chief cells

Question 72

pepsinogen is spontaneously cleaved to ? in the presence of HCI

Answer 72

active pepsin

Question 73

how is pepsinogen secretion stimulated?

Answer 73

§ Ach release from vagus nerve or ENS □ Ach bind to M receptors on chief cells □ *Most important stimulus § Presence of acid in the duodenum triggers secretin from S cells □ Secretin also stimulates chief cells to release more pepsinogen

Question 74

the gastric diffusion barrier is maintained by:

Answer 74

- mucus gel layer on surface epithelium - bicarbonate microclimate adjacent to surfacce epithelial - tight junctions in gastric glands

Question 75

mucus combines with phospholipids, electrolytes, and water to form a ?

Answer 75

gel layer

Question 76

the gel layer protects against:

Answer 76

acid, pepsin, bile acid, and ethanol

Question 77

what is mucin secretion induced by?

Answer 77

- vagal stimulation - chemical irritation