Physiology 1

Question 1

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

Answer 1

Upper oesophageal sphincter (UOS)

External anal sphincter

Question 2

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

Answer 2

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

Question 3

Where does carbohydrate begin and with what?

Answer 3

Mouth

Salivary amylase

Question 4

Where does protein digestion begin and with what?

Answer 4

Stomach

Pepsin and HCl (hydrochloric acid)

Question 5

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

Answer 5

Neuronal response –> enterogastric reflex

Hormonal response –> cholecystokinin (CCK)

Question 6

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

Answer 6

• 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

Question 7

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

Answer 7

HCl
Pepsinogen
Intrinsic factor
Gastroferrin
Histamine
Mucus

Question 8

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

Answer 8

Gastrin
Somatostatin
Mucus

Question 9

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

Answer 9

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

Question 10

What is the function of gastrin?

Answer 10

Stimulates HCl secretion

Question 11

What is the function of somatostatin?

Answer 11

Inhibits HCl secretion

Question 12

Where is pepsinogen released from?

Answer 12

Chief cell

Question 13

What is pepsinogen?

Answer 13

Inactive precursor of pepsin (a peptidase)

–> activated by HCl

Question 14

Which factors are released from gastric parietal cells?

Answer 14

HCl
Intrinsic factor
Gastroferrin

Question 15

What is the role of HCl?

Answer 15

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

Question 16

What is the role of intrinsic factor?

Answer 16

Binds vitamin B12, facilitating subsequent absorption

Question 17

What is the role of gastroferrin?

Answer 17

Binds Fe2+, facilitating subsequent absorption

Question 18

Where is histamine secreted from and what is its role?

Answer 18

Secreted from enterochromaffin-like cells

Acts on parietal cells to stimulate HCl secretion

Question 19

Which 3 factors induce acid secretion from the parietal cells?

Answer 19

ACh
gastrin
histamine

Question 20

Which 2 factors inhibit acid secretion?

Answer 20

Somatostatin

Prostaglandins

Question 21

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

Answer 21

Cephalic phase - in the head
Gastric phase
Intestinal phase

Question 22

How does the cephalic phase work?

Answer 22

Prepares stomach to receive food

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

Question 23

How does the gastric phase work?

Answer 23

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

Question 24

How does the intestinal phase work?

Answer 24

Chyme entering upper small intestine –> stimulation of acid secretion

Question 25

Where does the majority of digestion and absorption occur?

Answer 25

Small intestine

Question 26

What are the three parts of the small intestine?

Answer 26

Duodenum Jejunum Ilium

Question 27

How does pancreatic juice and bile enter the small intestine?

Answer 27

Via the sphincter of Oddi

Question 28

How is the surface area of the small intestine increased?

Answer 28

Circular folds Villi Microvilli (the brush border)

Question 29

What is segmentation?

Answer 29

The mixing of chyme with digestive juices | Due to alternating contraction and relaxation of circular muscle

Question 30

What is the gastroileal reflex?

Answer 30

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

Question 31

What is the migrating motor complex?

Answer 31

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

Question 32

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

Answer 32

They mimic the effect of motilin

Question 33

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

Answer 33

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

Question 34

What is the function of secretin?

Answer 34

Released in response to H+ and fatty acids in lumen | Promotes secretion of pancreatic and biliary HCO3

Question 35

What is the function of CCK?

Answer 35

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

Question 36

What is the function of GIP?

Answer 36

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

Question 37

What is the function of GLP-1?

Answer 37

- stimulates insulin secretion - inhibits glucagon secretion from pancreatic alpha-cells - decreases gastric emptying and appetite

Question 38

What is the function of motilin?

Answer 38

Secreted during fasting state | Initiates the migrating motor complex

Question 39

What is the function of ghrelin?

Answer 39

Stimulates appetite (hunger)

Question 40

What does small intestine secretion (juice) contain?

Answer 40

Mucus | Aqueous salt

Question 41

What are the endocrine pancreatic secretions?

Answer 41

Insulin Glucagon --> secreted into blood

Question 42

What are the exocrine pancreatic secretions?

Answer 42

Digestive enzymes --> acinar cells Aqueous NaHCO3 solution --> duct dells --> secreted into duodenum as 'pancreatic juice'

Question 43

What is the function of the aqueous NaHCO3 solution?

Answer 43

Alkaline solution neutralises acidic chyme entering duodenum - provides optimum pH for pancreatic enzymes - protects mucosa from erosion by acid

Question 44

Which enzymes are released from acinar cells in the pancreas?

Answer 44

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

Question 45

How are the inactive pancreatic enzymes activated?

Answer 45

Enterokinase in the duodenum