overview of the GI tract pt.2 (lecture)

Question 1

What % of ingested water is absorbed in the small intestine ?

Answer 1

80%

Question 2

List all the categories of things that the small intestine absorbs …

Answer 2

• water
• electrolytes
• vitamins
• minerals
• carbohydrates (monosaccharides)
• proteins (dipeptides, amino acids)
• lipids (micelles, chylomicrons, fatty acids, monoglycerides)

Question 3

What type of digestive enzymes does the small intestine secrete?

Answer 3

• peptidases
• sucrases
• malfasse
• lactase
• saccharidases
• lipase
• nucleases

Question 4

Where does the majority of nutrient digestion and absorption take place ?

Answer 4

Small intestine

Question 5

Where do the majority of digestive enzymes used in the small intestine come from ?

Answer 5

pancreas

Question 6

What substance aids pancreatic enzymes to carry out digestion ?

Answer 6

bile

Question 7

How long is the average adult duodenum?

Answer 7

25cm

Question 8

Which is the shortest section of the small intestine?

Answer 8

duodenum

Question 9

Where is all of ingested iron absorbed?

Answer 9

Duodenum

Question 10

Where does the majority of carbohydrate absorption occur ?

Answer 10

Duodenum

Question 11

Where is vitamin B12 (cobalamin) absorbed ?

Answer 11

ileum

Question 12

What is another name for Vitamin B12 ?

Answer 12

Cobalamin

Question 13

Where are the vast majority of bile salts absorbed ?

Answer 13

ileum

Question 14

What structures are found on the columnar epithelial cells of the small intestine ?

Answer 14

microvilli

Question 15

What are the mucosal folds called that line the small intestine ?

Answer 15

villi

Question 16

What feature of the small intestine creates a larger surface area for absorption ?

Answer 16

villi and microvilli

Question 17

Describe the mechanism of glucose absorption in the small intestine …

Answer 17

co-transport of glucose

1. Na-K pump in basement membrane removes Na from cell, decreasing charge in cell
2. negative charge drives the co-transport of Na into the cell followed by glucose via co-transport protein in apical membrane
3. glucose leaves into blood stream via glucose channel protein in basement membrane

Question 18

Describe the mechanism of lipid absorption in the small intestine …

Answer 18

1. bile salts emulsify fat globules in duodenum
2. bile salts coat the fat droplets
3. pancreatic lipase hydrolyses droplets into fatty acids and monoglycerides
4. form micelles (fatty acid heads + bile salts on outside, monoglycerides inside)
5. micelles assimilate into epithelium and release fatty acids + monoglycerides into the cell
6. inside the cell, fatty substances become chylomicrons in the lacteal (lymph system)

Question 19

Where is bile produced ?

Answer 19

in the liver

Question 20

What is “Orlistat” used for ?

Answer 20

targeting weight loss

more of a ‘weight pill’, not an nhs recognised medication

Question 21

Which enzyme does ‘Orlistat’ target?

Answer 21

inhibits pancreatic lipase to significantly reduce fat absorption

Question 22

When is bariatric surgery indicated ?

Answer 22

• cases of severe obesity (last resort in debilitating cases)
• **BMI >40 **
• unable to maintain weight loss by any other method over a period of months/years

Question 23

What are the different techniques of bariatric surgery ?

Answer 23

• gastric banding
• gastric bypass
• biliopancreatic diversion

Question 24

What is gastric banding ?

Answer 24

placing a sleeve around the stomach to functionally reduce capacity of stomach

Question 25

What is the aim of bariatric surgery ?

Answer 25

• shorten small intestine
• reduce capacity of stomach

Question 26

What is gastric bypass surgery ?

Answer 26

• create a smaller stomach pouch
• shorten intestine (without removal

Question 27

What is biliopancreatic diversion surgery ?

Answer 27

• remove part of stomach
• divert bile and pancreatic enzymes