Intestinal Secretion and Absorption

Question 1

What is the principal task of the digestive system?

Answer 1

absorption of nutrients

Question 2

Why does the small intestine carry out most of the nutrient absorption?

Answer 2

it has a large surface area

Question 3

What part of the digestive system has the fastest absorption rate?

Answer 3

the duodenum and upper jejunum

Question 4

When can the rate of caloric absorption be adjusted?

Answer 4

at the ingestion step

Question 5

What are the 3 ways to increase the surface area of the small intestine?

Answer 5

• folds
• villi
• microvilli

Question 6

How much of the water and electrolytes presented to it does the small intestine absorb?

Answer 6

99%

Question 7

What does failure to absorb water and nutrients by the small intestine lead to?

Answer 7

rapid dehydration and circulatory collapse

Question 8

What regulates water transport?

Answer 8

regulation of electrolyte transport

Question 9

What is the mucus in the small intestine used for?

Answer 9

to protect the surface against acid and pepsin

Question 10

What is mucus secretion in the small intestine stimulated by?

Answer 10

• parasympathetic nerve impulses
• 3 major GI hormones (gastrin, CCK and secretin)

Question 11

Why are enzymes present in the small intestine?

Answer 11

as a result of cell degeneration not secretion

Question 12

What do death cells release into the small intestine?

Answer 12

• maltase
• sucrase
• lactase
• L-glucosidase
• enterokinase

Question 13

What is intestinal juice compared to plasma?

Answer 13

isotonic with higher HCO3- and lower Cl- due to the HCO3/Cl- exchanger

Question 14

What is intestinal juice secretion in the small and large intestine stimulated by?

Answer 14

• mechanical irritation of the mucosa
• distension of the gut
• ACh and gastrin (leads to Ca2+ release)
• secretin, CCK and GIP (leads to cAMP release)

Question 15

What is the function of intestinal juice?

Answer 15

maintain chyme fluidity and a slightly alkaline pH

Question 16

What is the variation in pH throughout the GIT?

Answer 16

1.5-8

Question 17

What does the colon contain?

Answer 17

microflora, an agent for the metabolism of various substrates

Question 18

What does the colon secrete?

Answer 18

mucus and intestinal juice

Question 19

Why does the intestinal juice in the colon have high levels of K+ and HCO3-?

Answer 19

• K+ since not a major K+ excretion site
• HCO3- to act as a buffer against H+ produced by bacterial fermentation

Question 20

How is secretion of intestinal juice decreased in the colon?

Answer 20

sympathetic stimulation

Question 21

What does failure to absorb electrolytes in the intestines lead to?

Answer 21

congenital Cl- diarrhoea due to decreased activity of the Cl-/HCO3- exchanger

Question 22

What does failure to absorb nutrients in the intestines lead to?

Answer 22

carbohydrate malabsorption syndromes

Question 23

What does hypermotility of the intestine lead to?

Answer 23

less absorption time and enhanced secretion of water and electrolytes

Question 24

What can enhanced secretion of water and electrolytes in the intestine lead to?

Answer 24

secretory diarrhoea which can be treated by oral rehydration therapy