Small Intestine Function

Question 1

What is the three parts of the small intestine and their sizes

Answer 1

Duodenum - 24cm

Jejnum 2.5m

Illeium 3.5m

Question 2

What is the three overall functions of the duodenum

Answer 2

Gastric neurtralisation

Digestion

Iron absorption

Question 3

Where does majority 95% of nutrient absorption occur

Answer 3

Jejnum

Question 4

Why is the jenjum considered the flat and pink

Answer 4

Flat as mostly empty due to constant detriment absorption

and pink due to well established vascular system present for aximum absorption

Question 5

What is the main process occurring in the ileum and what is the purpose

Answer 5

NaCl and Water absorption

Necessary for chyme dehydration

also vitamin B 12 absorption,

Question 6

What enhance the absorptive surface of the small intestine from 0.33m2

Answer 6

Circular fold - Plicae (1m2)

Villi (10m2)

Microvilli (200m2)

Question 7

What is the cell surface of a Villus

Answer 7

Simple columnar epithelium

Question 8

What runs up the core of each individual Villi

Answer 8

Lacteal duct surrounded by a capillary network

• takes products of fat digestion to the blood

Question 9

What is found at the base of villi extending down lamina proper

Answer 9

Crypt of lieberkuhn

Question 10

What cells are present in villi and what do they produce

Answer 10

Goblet cells producing mucus

Question 11

What is the purpose of the crypt of lieberkuhn

Answer 11

Produces stem cells that rapidly develop and move up crypt lumen axis shed onto the epithelium and replenishing it

Question 12

Why is the crpyt of lieberkuhn important

Answer 12

Important due to cell renewal as epithelial cells on the intestine have an average 5 day life span

Question 13

What is the importance of mucus production from goblet cells in the small intestine

Answer 13

Mucus protects the surface of the small intestine

Question 14

What do Villi enterocyte cells absorb across the small intestine

Answer 14

NaCl
Monosaccharides
Amino acids
Peptides
Fats
Vitamins
Minerals
Water

Question 15

What is secreted by the crypt cells in the villi

Answer 15

secretes Cl and water

Question 16

How do most products of digestion enter the intestinal cell

glucose, galactose, amino acids+ nucleotides

Answer 16

Through a NA coupled secondary active transport

Question 17

How is chloride transported across the intestinal cell and into the lumen

Answer 17

Through the Na-K-Cl cotransporter into intestinal cell then through CFTR channel ono the intestinal villi membrane into the lumen

Question 18

How does water moves across and into the villi membrane

Answer 18

Water moves passively

As chloride moves into the lumen creates an osmotic gradient so water diffuses through tight junctions following that osmotic gradient

Question 19

How much water on average does the small intestine secrete and where does this secretion come from

Answer 19

Small intestine secretes ~1500ml H2O per day

H2O secretion comes from epithelial cells lining crypts of Lieberkuhn

Question 20

How is water important for normal digestive process

Answer 20

Maintains lumenal contents in liquid state

Promotes mixing of nutrients with digestive enzymes

Aids nutrient presentation to absorbing surface

Dilutes and washes away potentially injurious substances

Question 21

How is water secretion recycled

Answer 21

as is re-asborbed with the villi enterocyte cells

Question 22

What is the exact pathway that allows CL to leave to intestinal cell and into the lumen

Answer 22

CFTR channels opens to transport CL whenIt is activated by cAMP dependent phosphorylation which is gated by the binding of ATP

Question 23

What is the two forms of Intestinal movement

Answer 23

Segmentation

Pertalisis

Question 24

When does the movement of segmentation most likely occur

Answer 24

Whilst eating

Question 25

How does segmentation occur

Answer 25

Due to the contraction and relaxation of short intestinal segments

Question 26

What is the purpose of segmentation

Answer 26

Give a thorough mixing of stomach contents with digestive enzymes Bring chymes into contents with absorbing surface

Question 27

What is the movement of chyme in segmentation

Answer 27

``` Contraction lasting a few seconds moves chyme (up & down) into adjacent areas of relaxation ``` Whilst relaxed areas then contract and push chyme back (one bit contracts the other relaxes moving chyme around)

Question 28

How is Segementation contraction initiated

Answer 28

There is a constant depolarisation by the pace makes cells in the longitudinal muscle layer creating a basic electrical rhythm Contraction occurs when threshold is reached by AP stimuli

Question 29

What is the frequency of segementation determined by

Answer 29

Basic electrical rhythm

Question 30

What determines the strength of contractions in segmentation

Answer 30

The frequency of Action potentials

Question 31

What happens to the basic electrical rhythm as you move down the from the intestine to the rectum, What is the reason for this

Answer 31

Decreases Creating a net migration of the material, so there is a slow migration of chyme towards the large bowel

Question 32

What is the affect of parasympathetic and sympathetic intervention on segmentation

Answer 32

Parasympathetic increases contractions Sympathetic decreases contraction

Question 33

What affect does the autonomic NS have on basic electrical rhythm

Answer 33

No effect

Question 34

When does Pertalisis begin

Answer 34

Following absorption of nutrients: segmentation stops and peristalsis starts

Question 35

Define the Migrating Motility Complex

Answer 35

Pattern of peristaltic activity travelling down small intestine from gastric antrum to ileum when one MMC ends in ileum another begins

Question 36

When food arrives in the stomach what affect does this have on segmentation and peristalsis

Answer 36

cessation of MMC and initiation of segmentation

Question 37

What is the purpose of the Migrating Motility Complex

Answer 37

Move undigested material into large intestine | Limit bacterial colonisation of small intestine

Question 38

What hormone is involved in the initiation of Migrating Motility Complx

Answer 38

Moltin

Question 39

Where is the autonomic control for perstalisis mediates

Answer 39

In the myenteric plexus

Question 40

Explain how the law of Intestine means that food will forever travel in the direction of mouth to anus

Answer 40

If intestinal smooth muscle is distended (eg by bolus of chyme): Muscle on oral side of bolus contracts and Muscle on anal side of bolus relaxes Therefore Bolus is moved into area of relaxation towards colon

Question 41

What stimulates the gatroilleal reflex

Answer 41

Gastric emptying increasing the segmentation activity of the ileum

Question 42

What occurs in the gastroileal reflex

Answer 42

Opening of ileocaecal valve/sphincter chyme enters into large intestine Distending colon Resulting in a Reflex Causing contraction of ileocaecal sphincter

Question 43

What is the purpose of the Gastroilleal reflex

Answer 43

prevents backflux into small intestine