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Alimentary System: Physiology SA > Small Intestine Function > Flashcards

Small Intestine Function Flashcards

1
Q

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

A

Duodenum - 24cm

Jejnum 2.5m

Illeium 3.5m

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2
Q

What is the three overall functions of the duodenum

A

Gastric neurtralisation

Digestion

Iron absorption

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3
Q

Where does majority 95% of nutrient absorption occur

A

Jejnum

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4
Q

Why is the jenjum considered the flat and pink

A

Flat as mostly empty due to constant detriment absorption

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

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5
Q

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

A

NaCl and Water absorption

Necessary for chyme dehydration

also vitamin B 12 absorption,

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6
Q

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

A

Circular fold - Plicae (1m2)

Villi (10m2)

Microvilli (200m2)

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7
Q

What is the cell surface of a Villus

A

Simple columnar epithelium

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8
Q

What runs up the core of each individual Villi

A

Lacteal duct surrounded by a capillary network

  • takes products of fat digestion to the blood
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9
Q

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

A

Crypt of lieberkuhn

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10
Q

What cells are present in villi and what do they produce

A

Goblet cells producing mucus

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11
Q

What is the purpose of the crypt of lieberkuhn

A

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

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12
Q

Why is the crpyt of lieberkuhn important

A

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

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13
Q

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

A

Mucus protects the surface of the small intestine

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14
Q

What do Villi enterocyte cells absorb across the small intestine

A 
NaCl
Monosaccharides
Amino acids
Peptides
Fats
Vitamins
Minerals
Water
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15
Q

What is secreted by the crypt cells in the villi

A

secretes Cl and water

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16
Q

How do most products of digestion enter the intestinal cell

glucose, galactose, amino acids+ nucleotides

A

Through a NA coupled secondary active transport

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17
Q

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

A

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

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18
Q

How does water moves across and into the villi membrane

A

Water moves passively

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

19
Q

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

A

Small intestine secretes ~1500ml H2O per day

H2O secretion comes from epithelial cells lining crypts of Lieberkuhn

20
Q

How is water important for normal digestive process

A

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

21
Q

How is water secretion recycled

A

as is re-asborbed with the villi enterocyte cells

22
Q

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

A

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

23
Q

What is the two forms of Intestinal movement

A

Segmentation

Pertalisis

24
Q

When does the movement of segmentation most likely occur

A

Whilst eating

25
Q

How does segmentation occur

A

Due to the contraction and relaxation of short intestinal segments

26
Q

What is the purpose of segmentation

A

Give a thorough mixing of stomach contents with digestive enzymes

Bring chymes into contents with absorbing surface

27
Q

What is the movement of chyme in segmentation

A 
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)

28
Q

How is Segementation contraction initiated

A

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

29
Q

What is the frequency of segementation determined by

A

Basic electrical rhythm

30
Q

What determines the strength of contractions in segmentation

A

The frequency of Action potentials

31
Q

What happens to the basic electrical rhythm as you move down the from the intestine to the rectum,

What is the reason for this

A

Decreases

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

32
Q

What is the affect of parasympathetic and sympathetic intervention on segmentation

A

Parasympathetic increases contractions

Sympathetic decreases contraction

33
Q

What affect does the autonomic NS have on basic electrical rhythm

A

No effect

34
Q

When does Pertalisis begin

A

Following absorption of nutrients: segmentation stops and peristalsis starts

35
Q

Define the Migrating Motility Complex

A

Pattern of peristaltic activity travelling down small intestine from gastric antrum to ileum

when one MMC ends in ileum another begins

36
Q

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

A

cessation of MMC and initiation of segmentation

37
Q

What is the purpose of the Migrating Motility Complex

A

Move undigested material into large intestine

Limit bacterial colonisation of small intestine

38
Q

What hormone is involved in the initiation of Migrating Motility Complx

A

Moltin

39
Q

Where is the autonomic control for perstalisis mediates

A

In the myenteric plexus

40
Q

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

A

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

41
Q

What stimulates the gatroilleal reflex

A

Gastric emptying increasing the segmentation activity of the ileum

42
Q

What occurs in the gastroileal reflex

A

Opening of ileocaecal valve/sphincter

chyme enters into large intestine

Distending colon

Resulting in a Reflex

Causing contraction of ileocaecal sphincter

43
Q

What is the purpose of the Gastroilleal reflex

A

prevents backflux into small intestine

Alimentary System: Physiology SA (9 decks)

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