Oesophagus and stomach

Question 1

Where does the oesophagus start and end?

Answer 1

C5 to T10

Question 2

What two important structures ensure food and air get to the correct destination?

Answer 2

Epiglottis
Upper oesophageal sphincter
@ rest spincter tonically active and epiglottis is upright
During swallowing sphincter relaxes and epiglottis covers trachea

Question 3

How long is the oesophagus?

Answer 3

approx 25cm

Question 4

What kind of epithelium is found in the oesophagus and what is its purpose?

Answer 4

stratified squamous
Lubricate bolus by mucous secreting glands & saliva
Non-keratinising
Protect from:
-temperatures
-acidity
-textures

Question 5

What kind of muscle is found in the oesophagus?

Answer 5

Skeletal at start, mix of skeletal and smooth in middle, smooth at end

Question 6

What are the 4 main components of the oral cavity and their purposes?

Answer 6

Teeth - biting and ripping food
Muscles - movement of the jaw
Salivary glands - produce saliva containing enzymes
Tongue - form bolus, eating and taste (intrinsic and extrinsic muscles)

Question 7

What are the stages of swallowing?

Answer 7

0-Oral - chewing and saliva prepare bolus for swallowing, both sphincters constricted
1-Pharyngeal - pharyngeal musculature guides bolus towards oesophagus, both sphincters open
2-Upper oesophageal - upper sphincter closes, superior circular muscle rings contract as inferior ones constrict, sequential contractions of longitudinal muscle help guide food down gullet
3-Lower oesophageal - as food passes through lower sphincter, it closes & peristalsis pushes food into stomach

Question 8

What does the upper oesophageal sphincter consist of?

Answer 8

Constrictor pharangeus medius (circular)

Constrictor pharangeus inferior (longitudinal)

Question 9

What are the 3 phases of gastric acid secretion?

Answer 9

Cephalic
Gastric
Intestinal

Question 10

What are the afferents and efferents of the cephalic phase?

Answer 10

Afferents:
-sight
-smell
-taste
-thought
Efferents:
-Vagus nerve stimulates secretion via submucosal plexus
-parietal secretion stimulated by G and ECL cells
Effects:
-small secretion for a few minutes

Question 11

What are the afferents and efferents of the gastric phase?

Answer 11

Afferents:
-reduced pH
-stomach distension
-chemoreception of nutrients
Efferents:
-Vagus nerve stimulates submucosal plexus and myenteric plexus
-Gastrin and histamine from G cells and ECL cells stimulates parietal cell secretion
Effect:
-mechanical digestion for 3-4 hours

Question 12

What are the afferents and efferents of the intestinal phase?

Answer 12

Afferents:
-Duodenal stretch
-Reduced pH
-Duodenal distension
Efferents:
-Cholecystokinin from I cells
-Secretion from S cells
-Inhibited gastric motility and emptying
-Decreased parietal secretion
-Stretch receptors input to the enteric nervous system to decrease activation of stomach
Effects:
-Gastric emptying slows
-Gives time for downstream organs to deal with contents

Question 13

What is the role of the gastro-oesophageal sphincter?

Answer 13

Ensures one way traffic

Z line border separates stomach acid from vulnerable oesophagus

Question 14

How does the diaphragm aid the gastro-oesophageal sphincter?

Answer 14

prevents reflux

Question 15

What are the two components of the gastro-oesophageal sphincter?

Answer 15

Internal - oesophageal wall

External - diaphragm

Question 16

What are the 3 key functions of the stomach?

Answer 16

Digestion of nutrients
Storage reservoir for food
Immunological protection

Question 17

What is the stomach lined with?

Answer 17

Columnar epithelia

Invaginations into gastric pits that contain specialist exocrine and endocrine cells

Question 18

What are the 5 sections of the stomach?

Answer 18

Cardia
Fundus
Body
Pyloric antrum
Pyloric canal

Question 19

Which sections of the stomach secrete mucous?

Answer 19

Pyloric canal
Cardia
Body
Fundus

Question 20

Which sections of the stomach secrete HCl, mucous and pepsinogen?

Answer 20

Body

Fundus

Question 21

Which section of the stomach secretes gastrin?

Answer 21

Pyloric antrum

Question 22

What is the purpose of rugae?

Answer 22

Folds allow a large increase in sfa and volume

Allows distension

Question 23

What are the cell types found in the gastric gland and where?

Answer 23

in increasing depth order:
Surface mucous cell
Mucous neck cell
Parietal cell
Enterochromaffin-like cells (ECL cells)
Chief cell (body and fundus)
D cells
G cell
Gastric stem cells

Question 24

What is the purpose of surface mucous cell and mucous neck cells?

Answer 24

Secrete bicarbonate rich mucous to:

• protect stomach lining
• keep pH near lining around 7
• protect against active lipase & proteases

Question 25

What is the purpose of parietal cells?

Answer 25

Secrete acid to: -kill ingested pathogens -activate protease zymogens -alter protein structure to aid digestion Secrete intrinsic factor - a glycoprotein to aid absorption of B12

Question 26

How do features of the parietal cell aid secretion?

Answer 26

Lots of canaliculi that extend to apical surface When secreting, cytoplasmic tubulovesicles fuse with membrane and microvilli project into canaliculi to create a large sfa for acid secretion Rich in mitochondria to provide energy for membrane transport

Question 27

What is the purpose of enterochromaffin-like cells?

Answer 27

Neuroendocrine cells | Secrete histamine to stimulate acid secretion from parietal cells

Question 28

What is the purpose of chief cells?

Answer 28

Produces a protease zymogen - pepsinogen | Produces gastric lipase to remove fatty acids from triglycerides

Question 29

How is HCl secreted?

Answer 29

1) CO2 diffuses down concentration gradient into parietal cell 2) CO2 + H2O → H+ + HCO3- by carbonic anhydrase 3) HCO3- exchanged with Cl- in interstitial space 4) Cl- diffuses down concentration gradient into stomach lumen via Cl- channels 5) Na+/K+ exchanger in basolateral membrane and Cl- channels in apical membrane enable K+ to be pumped into cell in exchange for H+ 6) K+ re-enters cell via K+ channels 7) Secreted H+ combines with Cl- = HCl

Question 30

What are features of a chief cell?

Answer 30

Abundant golgi and RER | Masses of apical secretion granules

Question 31

What is the purpose of D cells?

Answer 31

Enteroendocrine cells that sercrete somatostatin Inhibitory effect on GI function: -Somatostatin inhibits ECL production of histamine and parietal cell activity ∴ inhibit HCl secretion

Question 32

What is the purpose of G cells?

Answer 32

Release gastrin into bloodstream in response: - Vagus nerve stimulation - Presence of peptides in stomach - Stomach distension

Question 33

What does gastrin do?

Answer 33

Travels in blood to receptor cells in stomach: -Stimulates gastric secretion and motility - stronger contractions and opening of pyloric sphincter Also binds to receptors in pancreas and gall bladder: -increase secretion of pancreatic juice and bile

Question 34

What is the purpose of gastric stem cells?

Answer 34

Pluripotent | Differentiate into all the stomach cell types under influence of different factors