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Year 1: Alimentary System > 1. The Oesophagus & Stomach > Flashcards

1. The Oesophagus & Stomach Flashcards

1
Q

Define digestion

A

The process of breaking down macromolecules to allow absorption

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2
Q

Define absorption

A

The process of moving nutrients and water across a membrane

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3
Q

Describe the structure of the gut wall from the lumen

A

Mucosa (Epithelium, lamina propria, muscularis mucosae), submucosa, muscularis, serosa/adventitia

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4
Q

What is the lamina propria?

A

This is the loose connective tissue beneath the epithelium

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5
Q

What layers make up the mucosa?

A

The epithelium and lamina propria

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6
Q

What is the submucosa?

A

This is location of most of the nerves (contains nerve plexus) which innovate into the mucosa

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7
Q

What is the muscularis?

A

This contains the circular and longitudinal smooth muscle. Also contains nerve plexus

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8
Q

What is the serosa/adventitia?

A

Lining of connective tissue. Serosa is found on loose parts of the gut while the adventitia is on parts of the gut wall that is fixed

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9
Q

What types of glands are found in the stomach?

A

sub-mucosal glands

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10
Q

How long is the oesophagus?

A

26cm

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11
Q

What does the oesophagus connect?

A

Pharynx to stomach

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12
Q

That vertebral level does the oesophagus start and end at?

A

Starts at C5 and ends at T10 (passes through the abdomen at T10)

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13
Q

Describe the arrangement of the oesophagus

A

The oesophagus starts behind the trachea, moves behind the aorta and then twists back round the front of the aorta. Most of the oesophagus is in the thorax

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14
Q

List 2 clinical concerns of the oesophagus

A

The recurrent laryngeal nerves lie next to the oesophagus, so any surgery could damage these nerves
The pericardium is also very close. Any cancers could spread to the pericardium

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15
Q

What is the function of the oesophagus?

A

Conduit for food, drink and swallowed sections from pharynx to stomach

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16
Q

What is the structure and function of the epithelium lining the oesophagus?

A

Non-keratinising stratified squamous epithelium - this can resist ‘wear and tear’ of food bolus’. There are also lots of glands secreting a lot of mucus for lubrication (saliva as well). Together it helps get food through the oesophagus

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17
Q

How does the oesophagus close off?

A

There are two sphincters the upper and lower oesophageal sphincters.

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18
Q

How does the upper oesophageal sphincter close off?

A

3 muscles

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19
Q

How does the lower oesophageal sphincter close off?

A

Diaphragm

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20
Q

Why does the oesophagus have sphincters?

A

This is prevent air from entering the oesophagus (stomach) and the food from coming back up from the stomach

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21
Q

What does it mean when the oesphageal sphincters are tonically active?

A

They are usually closed off

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22
Q

What muscle is found in the upper and lower oesophagus?

A

Upper: skeletal muscle (voluntary)
Lower: skeletal and smooth muscle (under the control of the enteric nervous system)

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23
Q

What causes the sphincter muscles to relax?

A

The process of swallowing

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24
Q

What is peristalsis?

A

Moving of the food bolus with smooth and longitudinal muscle down the oesophagus. A second wave of peristalsis will occur to ensure the food gets to the stomach.

25
Q

What marks the transition from oesophagus and stomach?

A

The zigzag line, shows the epithelial transition

26
Q

What is the epithelium of the stomach?

A

Simple columnar

27
Q

What is the name of the gastric folds of the stomach?

A

Rugae

28
Q

What is the cause of gastro-oesophageal reflux?

A

Failure of the lower oesophageal sphincter. Allows acid to come up from the stomach

29
Q

What is the purpose of the epithelial transition?

A

The stomach needs an epithelium that is suited for a secretory role not for ‘wear and tear’. Hence the change from stratified squamous epithelium to simple columnar epithelium

30
Q

Why are gastric folds present?

A

Increases surface area, allows the stomach to stretch when there is food

31
Q

What is the function of the stomach?

A

Break food down into smaller particles stored ( due to acid & pepsin); hold food and release at a controlled steady rate into duodenum, kill parasites and certain bateria

32
Q

What are the three major regions of the stomach in terms of secretion?

A

Antrum (gastrin), Body & Fundus (Mucus, HCL, pepsinogen), Cardia & Pyloric (mucus only)

33
Q

What is a gastric gland?

A

Invaginations into the mucosa where the bottom of the gastric gland has secretory cells will secrete products

34
Q

What does the body & fundus regions secrete?

A

Pepsinogen, HCl, Mucus, Mucus + HCO^3-

35
Q

What does the cardia & pyloric regions secrete?

A

HCl, Mucus + HCO^3-

36
Q

What does the antrum region secrete?

A

HCl, Gastrin (endocrine secreting cells), Mucus + HCO^3-

37
Q

How much acid is produced by the stomach in a day?

A

2L/day

38
Q

What drives peristalsis?

A

ANS

39
Q

What percentage of stomach contractions is peristalsis?

A

20%

40
Q

What percentage of stomach contractions is segmentation?

A

80%

41
Q

What drives segmentation?

A

Enteric nervous system. When the stomach is stretching it activates the enteric nervous system making sure the content of the stomach is mixed together

42
Q

What is primary protein secreting cell in the stomach and what does it secrete?

A

Chief cell - pepsinogen

43
Q

Describe the structure of a gastric chief cell?

A

Abundant RER, lots of golgi for packing and modifying for export, masses of apical secretory granules.

44
Q

What cell type in the stomach can exist in two states and what are the states?

A

Parietal cell: Resting and secreting

45
Q

Describe the parietal cell in the resting state

A

Many mitochondria (requires lots of ATP), cytoplasmic tubulovesicles (contain H+/K+ ATPase), internal canaliculi (extend to apical surface)

46
Q

Describe the parietal cell in the secretory state

A

1) Canaliculi connect together and out into the lumen of the stomach
2) The tubulovesicles project into the canaliculi
This creates a canal where H+ ions can be secreted into and passed into the lumen of the stomach

47
Q

Describe the process of the secretion of H+ ions in parietal cells

A

1) H+ and HCO3- is produced in the parietal cell catalysed by carbonic anhydrase.
2) K+ is driven into the gastric lumen by Na+/K+ ATPase.
3) HCO3- is exchanged for Cl- ions, where the Cl- ions are pumped into the gastric lumen. They are pumped from the blood
4) Mitochondria produces lots of ATP allowing for the secretion of H+ into the gastric lumen in exchange for potassium.

48
Q

What is consequence of inhibiting carbonic anhydrase

A

Inhibit acid production in the parietal cells of the stomach

49
Q

What happens to pepsinogen when it comes in contact with HCl

A

Pepsinogen is cleaved by the acid forming pepsin which is the protease which can digest proteins. Autocatalysis - Pepsin it self can also cleave pepsinogen.

50
Q

What are gastrins?

A

Local peptide hormones which stimulate histamine release from chromaffin cells (lamina propia). Major role is to stimulate acid secretion

51
Q

What does histamine do?

A

Powerful stimulator of acid secretion

52
Q

Phases of gastric secretion?

A

Cephalic, gastric, intestinal

53
Q

What is the cephalic phase of secretion?

A

Thought, sight, smell & taste of food. Activtates the medulla which activates the vagus (parasympathetic) to the stomach. Increases HCl, pepsin and gastrin production

54
Q

What is the gastric phase of secretion?

A

Food in stomach - stretch and chemoreceptors. Stomach wall stretches, sends signals to the brain, activation of the vagus resulting in the same increase in the secretions as the cephalic phase

55
Q

What is the intestinal phase of secretion?

A

1) The chyme enters the small intestine via peristalsis. The low pH of the chyme and high fat content causes afferent nerves to send signals up into the brain resulting in the cessation of production of HCl and pepsin.
2) Enterocytes in the intestine secrete endocrine factors into the blood (secretin, cholecystokinin and gastric inhibitory peptide). These return to the stomach to inhibit acid production.
3) When food leave the stomach via the pyloric sphincter it also causes the inhibition of stomach contents. Local enteric nervous system mediated effect

56
Q

What is chyme

A

The contents that has left the stomach

57
Q

What is intestinal phase reflex called?

A

Enterogastric reflex

58
Q

What drug is a proton pump inhibitor?

A

Omeprazole

59
Q

What drug is a histamine receptor inhibitor?

A

Ranitidine - blocks the receptor

Year 1: Alimentary System (15 decks)

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