GI Tract II

Question 1

Why do we chew?

Answer 1

• Fruit and veg have indigestible walls
• To increase SA:V
• Finer particles prevent blockages

Question 2

Distribution of skeletal and smooth muscle in the oesophagus

Answer 2

Upper 1/3 - skeletal

Lower 2/3 - smooth

Question 3

Location of the oesophagus

Answer 3

Runs posterior to trachea, heart and lungs, anterior to vertebrae and pierces the diaphragm before entering stomach

Question 4

What is primary peristalsis?

Answer 4

Continuation of peristaltic wave that commences in oropharynx and spreads to oesophagus

Question 5

What is secondary peristalsis?

Answer 5

Sweeps down any remaining food. Trigger is distension of oesophagus

Question 6

Which cranial nerves innervate the skeletal muscle of the upper 1/3 of the oesophagus?

Answer 6

CN IX and CN X

Question 7

Which cranial nerves innervate the smooth muscle of the lower 2/3 of the oesophagus?

Answer 7

CN X

Question 8

What is a hiatus hernia?

Answer 8

Loss of fat by the plug between oesophagus and stomach. Acid refluxes and enters bottom of oesophagus –> heartburn

Question 9

Give an example of a disease associated with the oesophagus

Answer 9

Barrett’s oesophagus

Question 10

What is Barratt’s oesophagus?

Answer 10

Metaplasia (abnormal change) of cells lining lower oesophagus

Question 11

What change occurs in Barratt’s oesophagus?

Answer 11

The normal stratified squamous epithelium is replaced by simple columnar epithelium with goblet cells (found in stomach)

Question 12

Symptoms of Barrett’s oesophagus

Answer 12

None but associated with acid reflux

• heart burn
• dysphagia
• Haematemesis
• Erosion of teeth

Question 13

How can you treat Barratt’s oesophagus?

Answer 13

Get rid of acid
-Proton pump inhibitor
Endoscopic surveillance
oesophagus resection

Question 14

The main way to manage Barratt’s oesophagus is to get rid of the acid but what would be an adverse effect of this?

Answer 14

More susceptible to food poisoning

Question 15

What kind of circles does food in the stomach form?

Answer 15

Concentric circles - old food by the wall, newest food in the centre

Question 16

What do G cells in the stomach secrete?

Answer 16

Gastrin

Question 17

What is gastric juice secreted by?

Answer 17

Gastric glands that cover almost the entire lumen of the stomach

Question 18

Which GI tract structure provides the most potent signals in controlling stomach emptying?

Answer 18

Duodenum

Question 19

Factors that increase rate of stomach empyting

Answer 19

• Increased food volume in the stomach
• Gastrin - hormone produced by G cells in the astral mucosa. Mainly increase production of gastric juice. Also stimulates motor activity of pyloric pump

Question 20

Factors that decrease rate of stomach emptying

Answer 20

Stretch of duodenal wall

• directly inhibits pyloric pump via enteric nervous system in the gut wall
• vagus nerve to brainstem –> inhibit excitatory signals to stomach

Question 21

Give an example of a pathology of the stomach

Answer 21

Peptic ulcer

Question 22

What is a peptic ulcer?

Answer 22

Damage to the wall of the stomach by stomach aid

Question 23

What lines the inside of the stomach so that it doesn’t get damaged?

Answer 23

Mucus

Question 24

Causes of peptic ulcers

Answer 24

Helicobacter pylori —> chronic inflammation in the astral mucosa
- acid secretion –> erosion of gastric wall

Non-steroid anti-inflammatory drugs e.g. ibuprofen (long term/high doses)

Question 25

How could you treat peptic ulcers?

Answer 25

• Proton pump inhibitor
• ‘triple therapy’ if caused by Helicobacter pylori
  Lamoxicillin, Clarithromycin and PPI

Question 26

Where does gastric cancer develop from?

Answer 26

Lining of the stomach

Question 27

What are the folds that increase the surface area for absorption in the GI tract and where are they most well-developed?

Answer 27

Folds of Kerckring

Well-developed in the duodenum and jejunum

Question 28

What are fats broken down into?

Answer 28

Monoglycerides and free fatty acids

Question 29

Breaking down fat mechanism

Answer 29

1. Micelles carried to the brush border and penetrate the recesses in between the agitating microvilli
2. The monoglycerides and free fatty acids diffuse out of the micelle into the interior of the epithelial cell. Micelles remains in chyme and emulsifies more fats acting as a ‘ferry’
3. Monoglycerides and free fatty acids are taken up by smooth ER, converted into triglycerides and released to form chylomicrons through the basolateral membrane, up through the thoracic lymph duct and emptied to the blood

Question 30

What are Peyer’s patchers?

Answer 30

Areas of lymphoid tissue for local immune protection

Question 31

Why does the colon have a high concentration of goblet cells?

Answer 31

Mucus secretion

Question 32

What are haustra?

Answer 32

The pockets which give the colon a segmented appearance

Question 33

What are the tenia coli?

Answer 33

3 bands of longitudinal muscle seen on the ascending, transverse, descending and sigmoid colon

Question 34

What does aldosterone enhance at the large intestine?

Answer 34

Na+ absorption

Question 35

What happens at the colon when dehydrated?

Answer 35

Lots of aldosterone secreted by the cortices of the adrenal gland

Question 36

Composition of faeces

Answer 36

3/4 water and 1/4 solid matter

Question 37

What gives faeces their brown colour?

Answer 37

Stercobilin and urobilin