physiology of small intestine & accessory organs 2

Question 1

what are the parts of the small intestine

Answer 1

• duodenum
• jejunum
• ileum

Question 2

what are the parts of the large intestine

Answer 2

• caecum
• colon
• rectum

Question 3

what does the mucosa secrete

Answer 3

• maltase and sucrase
• end and exopeptidase

Question 4

what does the submucosa secrete

Answer 4

mucous to
- protect intestinal wall
- neutralise acidic chyme

Question 5

what do both the submucosa and mucosa secrete

Answer 5

ions, water and mucous for lubrication and protection from enzymes

Question 6

what is the function of villi

Answer 6

• folds of mucosa & submucosa increase surface area
• microvilli increase surface area further
• transport of nutrients

Question 7

what does each villus have

Answer 7

• arteriole
• capillary bed
• venule
• lymphatic

Question 8

what is in intestinal juices

Answer 8

water
mucous
enzymes

Question 9

what stimulates and regulates secretion of intestinal juices

Answer 9

• stimulated by presence of chyme
• regulated by CCK and secretin

Question 10

what starts the chemical digestion process

Answer 10

salivary amylase
stomach pepsin

Question 11

what allows digestive process to be complete in small intestine

Answer 11

combined actions of
- pancreatic juice
- bile
- intestinal juice

Question 12

what converts starch to disaccharides

Answer 12

pancreatic amylase

Question 13

what converts disaccharides to monosaccarides

Answer 13

glycosidase

Question 14

can monosaccharides be absorbed

Answer 14

yes

Question 15

what catabolises polypeptides arriving from stomach

Answer 15

pancreatic trypsin and chymotrypsin

Question 16

what completes digestion of proteins

Answer 16

peptidases released from glandular epithelium

Question 17

where is most fat absorbed

Answer 17

jejunum

Question 18

how do peptidases cleave peptides

Answer 18

• carboxypeptidases act at “carboxyl” end
• aminopeptidases act at “amino” end
• dipeptidases convert dipeptides to amino acids

Question 19

how does bile help digest fat

Answer 19

fat globules in duodenum are coated with bile salts to create emulsion and disperse large fat globules into smaller entities.

Question 20

what does emulsification allow in digestion of fats

Answer 20

breakdown of triglycerides by increasing the surface area for water soluble pancreatic lipases to act upon and produce monoglycerides and free fatty acids.

Question 21

what is absorption in the small intestine

Answer 21

the process by which digestion products are transported across epithelial cells and into blood

Question 22

where does almost all absorption occur

Answer 22

in the small intestine

Question 23

how does general absorption through intestinal mucosa occur

Answer 23

active transport
diffusion

Question 24

what are carbohydrates broken into in small intestine

Answer 24

monosaccharides

Question 25

what are proteins broken into in small intestine

Answer 25

peptides and amino acids

Question 26

what are fats broken into in small intestine

Answer 26

monoglycerides and free fatty acids

Question 27

how are glucose and galactose (monosaccharides) absorbed

Answer 27

- absorbed into epithelial cell by co-transport with Na+ via sodium-glucose transporters

Question 28

how do glucose and galactose (monosaccharides) enter blood

Answer 28

leave epithelial cell and enter blood by facilitated diffusion via glucose transporters (GLUTs)

Question 29

how is fructose (monosaccharides) absorbed

Answer 29

absorbed into and leave cells by facilitated diffusion via GLUTs

Question 30

how are peptides absorbed into small intestine

Answer 30

- uptake thought to be linked to H+ influx - broken down to constituent amino acids inside epithelial cell

Question 31

how are amino acids absorbed into small intestine

Answer 31

- uptake into epithelial cells by Na+-dependent co-transport (active) - leave epithelial cell by facilitated diffusion

Question 32

how are fats absorbed

Answer 32

monoglycerides and free fatty acids associate with bile salts to form micelles/emulsion and diffuse passively into cells

Question 33

where do bile salts remain after fats are absorbed

Answer 33

remains in lumen of gut then re-cycled by enterohepatic circulation

Question 34

where do lipids accumulate and how do they leave

Answer 34

lipids accumulate in the vesicles of the smooth ER epithelial cell they leave the cell by fusing with the plasma membrane.

Question 35

how do chylomicrons leave the intestine

Answer 35

in lymph since they are too large to enter the circulation immediately. they are eventually delivered into venous circulation

Question 36

what does the lymphatic system do

Answer 36

absorbs nutrients, electrolytes, fluid and protein from interstitial spaces. chylomicrons too large to enter capillaries but lacteals have large pores. removal of haemorrhaged red blood cells from tissue and invading bacteria

Question 37

what are lymphatic vessels of the small intestine called

Answer 37

lacteals

Question 38

what does the intestine act as to the lymphatic system

Answer 38

a lymphoid organ in addition to its absorptive role

Question 39

where can lymphatic tissue be seen

Answer 39

close to epithelial surface and as large aggregates

Question 40

does the lymphatic pathway cross the liver

Answer 40

no, allows nutrients/drugs are delivered into the systemic circulation close to the heart

Question 41

can lymphatic system hold a large capacity

Answer 41

yes

Question 42

when would drugs get involved in the lymphatic system

Answer 42

is solubility of drugs in triglycerides is around 50mg/ml or more

Question 43

what allows lymphatic circulation

Answer 43

muscular movements of smooth muscle in walls of lymphatics pushing lymph along by peristalsis

Question 44

where are electrolytes absorbed

Answer 44

along the intestine

Question 45

how must fat soluble vitamins (A,D,E,K) be absorbed

Answer 45

in micelles (similar to fat)

Question 46

how are water soluble vitamins (B,C) involved

Answer 46

by diffusion

Question 47

how is vitamin B12 absorbed

Answer 47

it requires presence of intrinsic factor which is produces by stomach