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G.I. Block > G.I. Physiology 1 > Flashcards

G.I. Physiology 1 Flashcards

1
Q

Name the components of the mucosa

A

Epithelium, lamina propria and muscularis mucosa

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2
Q

Which plexus lies in the submucosa?

A

Meissener’s (Submucosal) plexus

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3
Q

Name the components of the muscularis propria.

A

Circular muscle, auerbach’s (Myenteric) plexus and longitudinal muscle

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4
Q

Name the 4 major tunics of the digestive tract.

A

Mucosa, Submucosa, Muscularis Propria and Adventitia/Serosa

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5
Q

Which parts of the digestive tract contain moist stratified squamous epithelium?

A

Mouth, Oropharynx, Oesophagus and anal canal. The rest have simple columnar epithelium

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6
Q

What is the lamina propria?

A

The lamina propria is a loose connective tissue layer that forms prt of the mucosa.

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7
Q

What two specialised cell types are found in the mucosa? What do they do?

A

Mechanoreceptors - involved in peristaltic reflexes

Chemoreceptors - detect the chemical composition of food

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8
Q

Which parts of the digestive tract lack a submucosal plexus?

A

Oesophagus and Stomach

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9
Q

What kind of muscle makes up the muscularis mucosae?

A

Smooth muscle

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10
Q

Name the 2 exceptions to the general composition of the muscularis propria

A

Upper Oesophagus - contains striated muscle

Stomach - contains 3 layers of smooth muscle

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11
Q

Where is the Myenteric Plexus found?

A

Between the circular and longitudinal muscle of the muscularis propria.

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12
Q

What is the role of interstitial cells within the myenteric plexus?

A

They act as pacemakers which promote rhythmic contractions of the smooth muscle along the digestive tract.

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13
Q

When is the outer tunic called serosa and when is it called adventitia?

A

Serosa - when parts of the digestive tract protrude into the peritoneal cavity, they will have an outer tunic of serosa - i.e. thin layer of connective tissue and a simple squamous epithelium
Adventitia - when the outer layer of the digestive tract is derived from adjacent connective tissue. It consists of a connective tissue covering that blends with the surrounding connective tissue. These include oesophagus and retroperitoneal organs

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14
Q

Name the 3 paired glands of the mouth.

A

Sublingual, Parotid and submandibular glands

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15
Q

What type of gland is the Parotid Gland?

A

A serous gland; produces mostly a watery saliva

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16
Q

What does serous saliva contain?

A

Salivary Amylase
Bicarbonate ions
Lysozyme
Immunoglobulin A

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17
Q

What do mucus salivary secretions contain?

A

Mucin - a proteoglycan that gives a lubricating quality to the secretions of the salivary gland

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18
Q

Which two nerves of the parasympathetic fibres increase salivary secretions?

A

Facial (VII) and Glossopharyngeal (IX)

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19
Q

Name the 3 phases of swallowing.

A

Voluntary
Pharyngeal
Oesophageal

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20
Q

How can the lower oesophageal sphincter be identified when it is not anatomically distinct from the rest of the oesophagus?i

A

It remains tonically constricted to prevent reflux of stomach contents into lower oesophagus

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21
Q

What is the parasympathetic supply to the oesophagus?

A

Vagus Nerve (X)

22
Q

What is the arterial supply of the thoracic oesophagus?

A

Branches of the bronchial, intercostal and descending aortic arteries and the superior and inferior thyroid arteries

23
Q

What is the arterial supply of the abdominal oesophagus?

A

Left gastric, left inferior phrenic and splenic arteries.

24
Q

What is the venous drainage of the thoracic oesophagus?

A

Azygous and to a lesser extent, the hemiazygous, intercostal and bronchial veins

25
Q

What is the venous drainage of the abdominal oesophagus?

A

Left gastric vein to the portal circulation or azygous vein to systemic circulation

26
Q

What is the venous drainage of the cervical oesophagus?

A

The inferior thyroid vein

27
Q

Describe the pathogenesis of oesophageal varices.

A

This condition most commonly occurs in people with serious liver disease. Oesophageal varices develop when normal blood flow to the liver is blocked by a clot or scar tissue in the liver. To go around the blockages, blood flows into smaller vessels that aren’t designed to carry large volumes of blood. The vessels can leak blood or even rupture, causing life-threatening bleeding.

28
Q

What is an oesophageal varice?

A

Oesophageal varices are abnormal, enlarged veins in the oesophagus normally seen in people with serious liver disease

29
Q

What is a Sengstaken-Blakemore tube?

A

It is a medical device inserted through the nose or mouth and used occasionally in the management of upper GI haemorrhage due to oesophageal varices

30
Q

What type of muscle makes up the pyloric sphincter

A

Smooth muscle

31
Q

Outline the 5 types of epithelium found in the stomach mucosa.

A

Surface Mucous Cells; produce an alkaline mucus on surface which neutralises acid and is a barrier to the digestive enzymes
Mucus Neck Cells: produce mucus
Parietal Cells: produce HCl and intrinsic factor
Chief Cells: produce pepsinogen
Endocrine Cells: produce regulatory hormones and paracrine factors

32
Q

Name some endocrine cells of the epithelium of the stomach mucosa and what they release

A

Enterochromaffin-like cells; produce histamine. This in turn stimulates acid secretion by parietal cells
Gastrin-containing Cells (G Cells); secrete gastrin
Somatostatin-Containing Cells (D Cells); secrete somatostatin which inhibits gastrin and insulin release

33
Q

How can smooth muscle of the stomach stretch without an increase in tension?

A

Because a reflex integrated within the medulla oblongata inhibits muscle tone in the body of the stomach

34
Q

Describe the mixing of the stomach contents.

A

Invested food is thoroughly mixed with stomach gland secretions to form chyme. This mixing is accomplished by gentle mixing waves, which are peristaltic like contractions that occur about every 20 seconds, proceeding the body of the stomach towards the pyloric sphincter. Peristaltic waves occur less frequently, are significantly more powerful than mixing waves, and force the chyme near the periphery of the stomach toward the pyloric sphincter. The more solid material near the centre of the stomach is pushed superiorly towards the cardiac part for further digestion. Roughly 80% of contractions are mixing waves and 20% are peristaltic waves.

35
Q

What does Intrinsic Factor do?

A

Intrinsic factor is released from parietal cells and binds vitamin B12 to allow its absorption

36
Q

What are the functions of Gastric Acid?

A

Converts inactive pepsinogen to the active enzyme pepsin and kills a large amount of bacteria that enter stomach.

37
Q

What stimulates acid secretion?

A

Histamine; acts in H2 receptor on parietal cells
Gastrin; acts in CCK2 receptor on parietal cells
Acetylcholine; acts on acetylcholine muscarinic receptor on parietal cell

38
Q

What was the problem with vagotomy as a treatment for excess acid secretion?

A

The vagus nerve is also responsible for peristalsis and emptying. Therefore, a side effect was a delay in emptying. It had to be performed with a pyloroplasty or gastroenterostomy

39
Q

How does Cimetidine work?

A

It is an H2 receptor antagonist

40
Q

Name some proton pump inhibitors and name an unwanted effect.

A

Omeprazole, lansoprazole, esomeprazole.
They are associated with increased risk of noscomial infections including Clostridium difficile as gastric acid kills a large number of bacteria

41
Q

What duodenal enterogastrones are released to stop acid secretion?

A

GIP
Secretin
CCK

42
Q

Name the 3 phases of stomach secretion.

A

Cephalic
Gastric
Intestinal

43
Q

Describe the action of gastrin.

A

Gastrin acts on parietal and chief cells where it stimulates additional hydrochloric acid and pepsinogen secretion. In always stimulates enterochromaffin like cells to release histamine, which stimulates parietal cells to secrete hydrochloric acid.

44
Q

Which hormone has the greatest stimulatory effect on gastric acid secretion?

A

Histamine

45
Q

What are the primary stimuli of the gastric phase of Digestion?

A

Distention of the stomach

Presence of amino acids and peptides

46
Q

Which foods directly stimulate gastrin?

A

Protein/peptides
Coffee
Calcium rich foods

47
Q

Name the 4 epithelial cell types of the duodenal mucosa

A

Absorptive cells - contain microvilli that produce digestive enzymes and absorb digested food
Goblet cells - produce a protective mucus
Granular Cells/Paneth Cells - may help to protect the intestinal epithelium from bacteria
Endocrine Cells - produce regulatory hormones

48
Q

Where would you find Brunner’s Glands and what do they do?

A

In the submucosa of the duodenum. They open into the base of the intestinal glands.they secrete bicarbonate

49
Q

How is chyme mixed and propulsed in the small intestine?

A

By segmental and peristaltic contractions of the smooth muscle in the wall of the small intestine

50
Q

Name the secretions of the small intestine.

A
  • NaCl/NaHCO3- - neutralises gastric HCl
  • Amylase - Starch digestion
  • Enteropeptidase - activates trypsinogen

-Brush Border Enzymes - Digestion

51
Q

Which hormone stimulates pancreatic enzyme release?

A

Cholecystokinin (CCK)

G.I. Block (13 decks)

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