The small intestine

Question 1

how is the pancreas attached to the small intestine

Answer 1

via the common bile duct

Question 2

what is the function of the brush border enzymes

Answer 2

intergral memnbrane proefins
on surfaces of microvilli
break down material n contact with brush border

Question 3

what is peristalsis

Answer 3

waves of muscular contraction which move contents along the length of the GIT

Question 4

describe the muscles involved in peristalsis

Answer 4

circular muscles contract behind bolus while circular muscles ahead of bolus relax
longitudinal muscles ahead of the muscles contract shortening adjacent segments
wave of contraction in circular muscles forces bolus forward

Question 5

which muscles contract first in peristalsis

Answer 5

longitudinal then circular behind the bolus

Question 6

what is segmentation

Answer 6

alternative contraction of neighbouring segments which churn and mix contents with intestinal secretions

Question 7

describe the migrating motor complex

Answer 7

when the gut is empty
MMC’s generate every 90 mins stimulated by motion (22 aa peptide secreted by M cells and erythromycin)
these are to help clean the gut, slow strong peristaltic waves

Question 8

what inhibits MMC’s

Answer 8

feeding

Question 9

what hormones are secreted from APUD cells

Answer 9

CCK from I cells
secretin from S cells
MOtilin from M cells
gastrin from G cells

Question 10

where does bicarbonate come from

Answer 10

pancreas

Question 11

where does mucus come from

Answer 11

goblet cells

Question 12

what foods must be digested before absorption

Answer 12

carbs
lipids
proteins

Question 13

describe carb digestion

Answer 13

soluble amylases only break down internal a1-4 bonds, remaining short china carbs are broken down by enzymes on the brush border
glucose and galactose actively absorbed by SGLT1
fructose passively via GLUT5 transporter

Question 14

where does protein digestion start

Answer 14

in the stomach -15% but pepsin is inactivated in the duodenum

Question 15

where is enterkinase secreted from

Answer 15

crypt cells

Question 16

what is the role of trypsinogen (released from the pancreas) in protein digestion

Answer 16

converted to trypsin by enterokinase which converts proenzymes to the active enzymes

Question 17

what are 5 proenzymes in protein digestion

Answer 17

trypsinogen 
chymotrypsinogen 
proelastase 
procarboxypeptidase a
procarboxypeptidase b

Question 18

what are large proteins digested by within the protein chain

Answer 18

typsin
chymotrypsin
elastase

Question 19

what is the role of carboxypeptidases

Answer 19

cut at the last peptide bond

Question 20

what is the specific role of carboxy A

Answer 20

cuts peptide with C terminal neutral AA such as serine

Question 21

what is the specific role of carboxy b

Answer 21

peptide cut with C terminal basic AA such as arginine

Question 22

how are amino acids taken up into the cell

Answer 22

via sodium linked secondary active transporters

Question 23

how are di/tri peptides taken up by cells

Answer 23

proton linked secondary active transport

Question 24

what is the role of M cells in protein absorption

Answer 24

phagocytose large proteins into cells

Question 25

how are fats digested

Answer 25

bile slats break up lipid droplets increasing surface area as fats cannot dissolve in water amphipathic bile slats causes emulsification

Question 26

what is the role of the pancreas in fat digestion

Answer 26

pancreatic lipase cells off outside fatty acids leaving a monoglyceride plus 2 free fatty acids

Question 27

once fats are turned into monglycerides or mixed with bile salts what happens to them

Answer 27

diffuse close to the brush border and are resythesised and packaged in into chylomicra which are exocytosied which drain into lymphatic lacteals

Question 28

describe bile salt recycling

Answer 28

conjugated bile salts are actively absorbed in the distal ileum

Question 29

describe how iron is absorbed

Answer 29

absorbed in fe 2 state and starts in the duodenum Dcytb reduces iron from fe3+ either absorbed within haem or via cotransport with H+ iron leaves the cell via FP1 and ends to plasma transferrin bilirubin is a bi product of absorbing iron

Question 30

how is calcium absorbed

Answer 30

actively reabsorbed in the dude which is regulated by vit D in the rest of the small bowel it is reabsorbed paracellularly Ca binds to calbindin in the cell leaves cell via na / ca anti porter

Question 31

how are fat soluble vitamins absorbed

Answer 31

ADEK | absorbed with lipids as they are dissolved in lipid droplets and enter into chylomicrons

Question 32

how are water soluble vitamins absorbed

Answer 32

require special transport proteins usually Na+ linked

Question 33

how is Vit B12 absorbed

Answer 33

absorbed only hone bound to intrinsic factor which is released from gastric parietal cells in the ileum

Question 34

what is the role of aldosterone in digestion

Answer 34

absorption of Na and K secretion in colon are aldosterone regulated

Question 35

what happens to acidity as you move through the GIT

Answer 35

acid in stomach and becomes more alkaline

Question 36

how much is absorbed in the small intestine compared to large

Answer 36

7L/day | 1.9L/day