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Y1 LSS Alimentary System > Oesophagus and stomach > Flashcards

Oesophagus and stomach Flashcards

Oesophagus; Gastrooesophageal sphincter; Stomach; Gastric gland; Gastric acid secretion

1
Q

Where does the oesophagus start and end?

A

C5 to T10

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2
Q

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

A

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

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3
Q

How long is the oesophagus?

A

approx 25cm

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4
Q

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

A 
stratified squamous
Lubricate bolus by mucous secreting glands & saliva
Non-keratinising
Protect from:
-temperatures
-acidity
-textures
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5
Q

What kind of muscle is found in the oesophagus?

A

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

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6
Q

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

A

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)

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7
Q

What are the stages of swallowing?

A

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

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8
Q

What does the upper oesophageal sphincter consist of?

A

Constrictor pharangeus medius (circular)

Constrictor pharangeus inferior (longitudinal)

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9
Q

What are the 3 phases of gastric acid secretion?

A

Cephalic
Gastric
Intestinal

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10
Q

What are the afferents and efferents of the cephalic phase?

A 
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
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11
Q

What are the afferents and efferents of the gastric phase?

A 
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
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12
Q

What are the afferents and efferents of the intestinal phase?

A 
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
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13
Q

What is the role of the gastro-oesophageal sphincter?

A

Ensures one way traffic

Z line border separates stomach acid from vulnerable oesophagus

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14
Q

How does the diaphragm aid the gastro-oesophageal sphincter?

A

prevents reflux

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15
Q

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

A

Internal - oesophageal wall

External - diaphragm

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16
Q

What are the 3 key functions of the stomach?

A

Digestion of nutrients
Storage reservoir for food
Immunological protection

17
Q

What is the stomach lined with?

A

Columnar epithelia

Invaginations into gastric pits that contain specialist exocrine and endocrine cells

18
Q

What are the 5 sections of the stomach?

A 
Cardia
Fundus
Body
Pyloric antrum
Pyloric canal
19
Q

Which sections of the stomach secrete mucous?

A

Pyloric canal
Cardia
Body
Fundus

20
Q

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

A

Body

Fundus

21
Q

Which section of the stomach secretes gastrin?

A

Pyloric antrum

22
Q

What is the purpose of rugae?

A

Folds allow a large increase in sfa and volume

Allows distension

23
Q

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

A 
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
24
Q

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

A

Secrete bicarbonate rich mucous to:

  • protect stomach lining
  • keep pH near lining around 7
  • protect against active lipase & proteases
25
Q

What is the purpose of parietal cells?

A

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

26
Q

How do features of the parietal cell aid secretion?

A

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

27
Q

What is the purpose of enterochromaffin-like cells?

A

Neuroendocrine cells

Secrete histamine to stimulate acid secretion from parietal cells

28
Q

What is the purpose of chief cells?

A

Produces a protease zymogen - pepsinogen

Produces gastric lipase to remove fatty acids from triglycerides

29
Q

How is HCl secreted?

A

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

30
Q

What are features of a chief cell?

A

Abundant golgi and RER

Masses of apical secretion granules

31
Q

What is the purpose of D cells?

A

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

32
Q

What is the purpose of G cells?

A

Release gastrin into bloodstream in response:

  • Vagus nerve stimulation
  • Presence of peptides in stomach
  • Stomach distension
33
Q

What does gastrin do?

A

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

34
Q

What is the purpose of gastric stem cells?

A

Pluripotent

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

Y1 LSS Alimentary System (7 decks)

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