13 - Stomach-Peritoneum

Question 1

What is the enteric nervous system

Answer 1

brain of the gut
consists of >100 million neurons from the esophagus to the anus
(sensory, motor, interneurons)

capable of generating local reflexse

Question 2

What are the plexuses of the enteric nervous system

Answer 2

influenced by autonomic input

myenteric plexus – controls motility (ex. perstalsis)
- between circular and longitudinal muscle layers

submucosal plexus – controls secretions
- in submucosa

Question 3

What nerve controls the parasympathetic plexuses of the ENS

Answer 3

vagus nerves (CN X)

Question 4

What controls the sympathetic plexuses of the ENS

Answer 4

celiac, sup & inf mesenteric ganglia

Question 5

What is the peritoneum

Answer 5

largest serous membrane of the body

Question 6

What are the layers of the peritoneum

Answer 6

parietal peritoneum
visceral peritoneum

Question 7

What do the peritoneal folds do

Answer 7

support the abdominal organs by acting as a highway for nerve, bv and lympahtics

Question 8

What are the five folds of the peritoneum

Answer 8

falciform ligament – between left and right lobe of liver

lesser omentum – from inferior surface of liver to lesser curvature of stomach

greater omentum – from greater curvature of stomach to transverse colon

mesocolon – from posterior abdominal wall to transverse and sigmoid colon

messentery – suspends most of small intestine for posterior wall

Question 9

What are the retroperitoneal organs

Answer 9

organs only covered by peritoneum on their anterior surface

abdominopelvic cavity
- pancreas
- duodenum
- ascending and descending colon
- kidneys

Question 10

What are the four layers of the gastric walls

Answer 10

same layers in esophagus

mucosa (inside) – contains rugae (innermost, oblique muscle layer)
submucosa
muscularis
serosa - lubricating fluid

Question 11

What does the stomach do

Answer 11

holding reservoir and mixing chamber – no absorption

Question 12

What does the stomach connect
Where is it located

Answer 12

esophagus to duodenum

inferior to the diaphragm

Question 13

What are the four main regions of the stomach

Answer 13

cardia (closest to the heart)
fundus (tip of stomach)
body (major part)
pylorus (at pyloric sphincter)

Question 14

What does rugae do

Answer 14

accomodates the stretching of the mucosa

Question 15

Where does the most intense churning occur

Answer 15

pyloric antrum

Question 16

Where does the stomach receive blood from

Answer 16

branches of the celiac trunk

Question 17

What arteries lie at the lesser curvature of the stomach

Answer 17

right and left gastric arteries

Question 18

What arteries lie at the greater curvature of the sotmach

Answer 18

left and right gastroomental arteries

Question 19

What are the layers of the muscularis

Answer 19

muscularis (longitudinal layer) – outermost
circular layer
oblique layer – innermost

Question 20

What are the parts of the pylorus

Answer 20

pyloric antrum (the blender)
- connects to the body of the stomach

pyloric canal
- connects to the duodenum

Question 21

what does the submucosa of the gastric wall do

Answer 21

provides innervation and blood supply to the overlying mucosa

Question 22

What do gastric pits do

Answer 22

specialized cells that secrete gastric juice (2-3 liters a day) and a protective muscous

Question 23

What is the pH of gastric secretions

Answer 23

1.5 and 3.5

Question 24

What are the cell types in gastric pits

Answer 24

mucus cells - secrete bicarbonate-rich mucus to protect the gastric lining from stomach acid

parietal cells - secrete hydrochloric acid and intrinsic factor (vit B12 absorption)

chief cells - secrete pepsinogen (digestive enzyme pepsin) and gastric lipase

G cells - secrete the endocrin hormone gastrin
- gastrin increases parietal and cheif cell secretion // increases gastric motility (more churning) and LES tone (nice and tight) // decreases pyloric sphincter tone

Question 25

How is HCl produced

Answer 25

chloride anion and a proton combined seperately in the lumen of the stomach
- makes pH really low in the stomach

Question 26

What is HCl secretion regulated by

Answer 26

gastrin (from enteroendocrin G cells)
ACh (from parasympathetic fibers)
- tells stomach to make more acid
Histamine (from mast cells)
- glue epithelium down
- protection –> makes more acid
Cortisol (from adrenal cortex)
- slows down stomach in stress

Question 27

What causes gastric ulcers to form

Answer 27

form on the mucosal lining of the stomach if protective mucus production is insufficient or gastric acid secretion is excessive

• can lead to perforation of the gastric wall

Question 28

What are the phases to digestion

Answer 28

1. cephalic
   - receptors for sight, smell, and taste of food activated
   - thoughts of food
   (cortex & hyopthalamus –> medulla oblongata –> parasympathetic output)
2. gastric
   - stretch receptors detect distention of the stomach
   - chemoreceptors detect increased pH of gastric juice
   (submucosal plexus
3. intestinal
   - stretch receptors detect distension of the duodenum
   - chemoreceptors detect fatty acids and glucose in the duodenum

Question 29

How do neural and endocrine signals help regulate digestion

Answer 29

regulating motility and digestive enzyme secretion

Question 30

What are the factors promoting gastric emptying

Answer 30

neural
- parasympathetic (vagus)

hormonal
- gastrin

composition of chyme
- carbohydrates & water –> quick emptying

Question 31

What are the factors inhibiting gastric emptying

Answer 31

neural
- sympathetic
- enterogastric reflex

hormonal
- CCK
- secretin

composition of chyme
- high protein = moderate emptying
- high fat = slow emptying