Physiology Of The Small Intestine

Question 1

GI Tract Functions

Answer 1

Ingestion
Mechanical processing
Digestion
Secretion
Absorption
Excretion

Question 2

How does the LI join to the SI

Answer 2

Ileocecal valve

Question 3

First part of the SI joining from the stomach

Answer 3

Duodenum

Question 5

What are the folds in the small intestines

Answer 5

Plica circulares

Question 6

What are the folds upon the plica circulares called

Answer 6

Villi

Question 7

Layers of the small intestine from inside to outside

Answer 7

Mucosa (innermost with villi)
Submucosa
Muscularis externa (motility)
Serosa peritoneum (visceral peritoneum)

Question 8

What do villi and microvillli do?

Answer 8

Amplify the SA for available interaction with food

Question 9

What do the crypts of lieberkuhn do? Where are they?

Answer 9

Secrete bicarbonate rich fluid - between microvilli

Question 10

What do brush boarder enzymes do? Wehere are they?

Answer 10

Integral membrane proteins on surfaces of micro villi which breakdown materials in contact with brush boarder.

Question 11

What is peristalsis

Answer 11

Waves of muscular contractions which move contents along the GI tract length

Question 12

What muscles are there inn the small intestine

Answer 12

Circular muscles
Longitudinal muscles

Question 13

Describe muscle contraction in the SI

Answer 13

Circular muscles contract behind bolus
Longitudinal muscles ahead of bolus contract, shortening adjacent segments
Wave of contraction in circular muscles force bolus forward

Question 14

What is segmentation in SI motility

Answer 14

Alternate contraction of neighboring segments
Churn and fragment the bolus
Mixes contents with intestinal secretions

Question 15

Which hormones are secreted from the SI - and from what cells

Answer 15

From the crypts of liberkuhn/ dueodenal submucosal Brunners glands:

• CCK (I cells)
• secretin (S cells)
• motility (M cells)
• gastrin (G cells)

Question 16

Where is mucus secreted form

Answer 16

Goblet cells

Question 17

Where does bicarbonate come from

Answer 17

Secreted from pancreatic duct cells

Question 18

What nutrients must be digested before absorption can occur?

Answer 18

• carbohydrates
• proteins
• lipids

Too big! Complex!

Question 19

What essential nutrients can be absorbed without processing

Answer 19

Water
Electrolytes
Vitamins

Question 20

How are carbohydrate chains broken down (side by side)

Answer 20

Soluable amylases break internal alpha 1,4 bonds

Question 21

How are the short chain carbohydrates (with alpha 1,6) bonds broken down?

Answer 21

• specific enzymes on brush boarder membrane

Question 22

Is glucose and galactose actively absorbed?

Answer 22

Yes - high conc inside of cell

Question 23

What are glucose and galactose absorbed by?

Answer 23

SGT1

Question 24

Is fructose absorbed actively

Answer 24

No

Question 25

What protein transports fructose into cell

Answer 25

Glut5 transporter

Question 26

How much of protein is digested in stomach?

Answer 26

15%

Question 27

What pancreatic enzymes do the pancreas secretes

Answer 27

Trypsinogen Chymotryosinogen Proteolastase Procarboxypeptidase A and B

Question 28

Which enzyme turns inactive pancreatic enzymes into active stomach enzymes

Answer 28

Enterokinase on epithelial cells

Question 29

Action of endopeptidases

Answer 29

Cut proteins within chain - trypsin, chymotrypisn, elastase

Question 30

Action of exopeptidases?

Answer 30

Cut last peptide bond - carboxopeptodases

Question 32

Bile action

Answer 32

Fat absorption: - bile breaks up lipid droplets = increased SA

Question 33

Lipase action

Answer 33

Panc enz Cleaves off external fatty acids = 2 fatty acids + mono glyceride

Question 34

Micelles

Answer 34

Move to brush boarder, devliver contents to membrane, endocytosis

Question 35

What happens to contents of micelles once inside of epithelial cells

Answer 35

- triglycerides resynthesised - all packages into chylomicrons - chylomicrins are excocytosed into interstitium

Question 36

What makes poo brown

Answer 36

Bile acids

Question 37

Where does fat exit the epithelial cells to

Answer 37

Lymph vessels

Question 38

When does iron abs happen

Answer 38

Early duodenum

Question 39

What enhanced iron absorption

Answer 39

Vitamin c

Question 40

What protein helps iron andorbtion in blood stream

Answer 40

Plasma transferrin

Question 41

What vitamin regulates ca2+ absorption

Answer 41

D

Question 42

Fat soluable vitamins

Answer 42

ADEK

Question 43

Water soluabe vitamins how absorbed

Answer 43

Need transport proteins (Na+ linked)

Question 44

What is special about Vitamin B12

Answer 44

Absorbed only when bound to intrinsic factor - secreted by gastric parietal cells Not absorbed till ileum (LATE just before colon!)