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Gastrointestinal / General Surgery > Physiology 1 > Flashcards

Physiology 1 Flashcards

1
Q

Which of the 6 sphincters in the GI tract are made of skeletal muscle?

A

Upper oesophageal sphincter (UOS)

External anal sphincter

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2
Q

Which of the 6 sphincters in the GI tract are made of smooth muscle?

A

Lower oesophageal sphincter (LOS)
Pyloric sphincter
Ileocaecal valve
Internal anal sphincter

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3
Q

Where does carbohydrate begin and with what?

A

Mouth

Salivary amylase

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4
Q

Where does protein digestion begin and with what?

A

Stomach

Pepsin and HCl (hydrochloric acid)

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5
Q

How does the duodenum delay gastric emptying until it is ready to receive chyme?

A

Neuronal response –> enterogastric reflex

Hormonal response –> cholecystokinin (CCK)

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6
Q

Which factors within the duodenum prompt a delay in gastric emptying?

A
  • Fat: delay required for digestion and absorption
  • Acid: time required for neutralisation of gastric acid by bicarbonate secreted from pancreas
  • Hypertonicity of carbohydrate and protein breakdown products
  • Distension
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7
Q

Which factors are released from the fundus and body of the stomach?

A 
HCl
Pepsinogen
Intrinsic factor
Gastroferrin
Histamine
Mucus
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8
Q

Which factors are released from the pylorus and antrum area of the stomach?

A

Gastrin
Somatostatin
Mucus

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9
Q

Where are gastrin and somatostatin released from and where do they go?

A

Gastrin released from G cells
Somatostatin released from D cells
–> into the blood

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10
Q

What is the function of gastrin?

A

Stimulates HCl secretion

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11
Q

What is the function of somatostatin?

A

Inhibits HCl secretion

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12
Q

Where is pepsinogen released from?

A

Chief cell

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13
Q

What is pepsinogen?

A

Inactive precursor of pepsin (a peptidase)

–> activated by HCl

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14
Q

Which factors are released from gastric parietal cells?

A

HCl
Intrinsic factor
Gastroferrin

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15
Q

What is the role of HCl?

A
  • activates pepsinogen to pepsin
  • denatures protein
  • kills most (not all) micro-organisms ingested with food
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16
Q

What is the role of intrinsic factor?

A

Binds vitamin B12, facilitating subsequent absorption

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17
Q

What is the role of gastroferrin?

A

Binds Fe2+, facilitating subsequent absorption

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18
Q

Where is histamine secreted from and what is its role?

A

Secreted from enterochromaffin-like cells

Acts on parietal cells to stimulate HCl secretion

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19
Q

Which 3 factors induce acid secretion from the parietal cells?

A

ACh
gastrin
histamine

20
Q

Which 2 factors inhibit acid secretion?

A

Somatostatin

Prostaglandins

21
Q

What are the three phases of gastric acid secretion and inhibition?

A

Cephalic phase - in the head
Gastric phase
Intestinal phase

22
Q

How does the cephalic phase work?

A

Prepares stomach to receive food

  • -> driven by CNS and vagus nerve
  • -> causes release of gastric acid inducing factors
23
Q

How does the gastric phase work?

A

When food in stomach, distension activates reflexes that –> acid secretion

24
Q

How does the intestinal phase work?

A

Chyme entering upper small intestine –> stimulation of acid secretion

25
Q

Where does the majority of digestion and absorption occur?

A

Small intestine

26
Q

What are the three parts of the small intestine?

A

Duodenum
Jejunum
Ilium

27
Q

How does pancreatic juice and bile enter the small intestine?

A

Via the sphincter of Oddi

28
Q

How is the surface area of the small intestine increased?

A

Circular folds
Villi
Microvilli (the brush border)

29
Q

What is segmentation?

A

The mixing of chyme with digestive juices

Due to alternating contraction and relaxation of circular muscle

30
Q

What is the gastroileal reflex?

A

Segmentation in the empty ileum is triggered by gastrin from the stomach

31
Q

What is the migrating motor complex?

A

Strong peristaltic contraction slowly passing the length of the small intestine between meals to ‘clear’ it
Triggered by motilin

32
Q

Why do macrolide antibiotics e.g. erythromycin cause GI disturbance?

A

They mimic the effect of motilin

33
Q

Which hormones does the small intestine secrete into the blood and where from?

A

Gastrin - G cells of gastric antrum (mainly) and duodenum
Secretin - S cells of duodenum
Cholecystokinin (CCK) - I cells of duodenum and jejunum
Gastric inhibitory peptide (GIP) - K cells of duodenum and jejunum
Glucagon-like peptide-1 (GLP-1) - L cells of small intestine
Motilin - M cells of duodenum and jejunum
Ghrelin - Gr cells

34
Q

What is the function of secretin?

A

Released in response to H+ and fatty acids in lumen

Promotes secretion of pancreatic and biliary HCO3

35
Q

What is the function of CCK?

A

Released in response to monoglycerides, free fatty acids, amino acids and small peptides in the lumen

  • inhibits gastric emptying
  • causes secretion of pancreatic enzymes
  • relaxation of sphincter of Oddi + contraction of gall bladder
  • potentiates secretin
36
Q

What is the function of GIP?

A

Stimulates release of insulin from pancreatic beta-cells in response to glucose in lumen

37
Q

What is the function of GLP-1?

A
  • stimulates insulin secretion
  • inhibits glucagon secretion from pancreatic alpha-cells
  • decreases gastric emptying and appetite
38
Q

What is the function of motilin?

A

Secreted during fasting state

Initiates the migrating motor complex

39
Q

What is the function of ghrelin?

A

Stimulates appetite (hunger)

40
Q

What does small intestine secretion (juice) contain?

A

Mucus

Aqueous salt

41
Q

What are the endocrine pancreatic secretions?

A

Insulin
Glucagon
–> secreted into blood

42
Q

What are the exocrine pancreatic secretions?

A

Digestive enzymes –> acinar cells
Aqueous NaHCO3 solution –> duct dells

–> secreted into duodenum as ‘pancreatic juice’

43
Q

What is the function of the aqueous NaHCO3 solution?

A

Alkaline solution neutralises acidic chyme entering duodenum

  • provides optimum pH for pancreatic enzymes
  • protects mucosa from erosion by acid
44
Q

Which enzymes are released from acinar cells in the pancreas?

A 
Active:
- pancreatic amylase
- pancreatic lipase
Inactive:
- trypsinogen
- chymotrypsinogen
- procarboxypeptidase A and B
45
Q

How are the inactive pancreatic enzymes activated?

A

Enterokinase in the duodenum

Gastrointestinal / General Surgery (4 decks)

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