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GASTROINTESTINAL PHYSIOLOGY > Small Intestine Function > Flashcards

Small Intestine Function Flashcards

1
Q

How long is the duodenum?

A

~25cm

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2
Q

What is the function of the duodenum?

A

Neutralise acid
Digestion
Absorption of Fe

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3
Q

What is the function of the jejunum?

A

~95% of nutrient absorption?

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4
Q

What is the function of the ileum?

A

Absorption of NaCl to dehydrate Chyme

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5
Q

What structures increase the surface area of the small intestine?

A

Folds
Villi
Microvilli

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6
Q

What structure lies at the bottom of Villi?

A

Crypts

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7
Q

What is the function of small intestinal crypts?

A

Growth of villi endothelial cells

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8
Q

What are plicae circularis?

A

Circular folds inside the small intestine

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9
Q

How tall are microvilli?

A

1um

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10
Q

What types of cells are found on the surface mucosa of villus?

A

Simple columnar epithelium

Goblet cells

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11
Q

What vessels are found within a villus?

A

Capillary networks

Lacteals

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12
Q

What is the function of crypt cells of the small intestine?

A

Secretion of Cl and Water

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13
Q

Why is Cl secreted by Crypt cells?

A

So water will follow the osmotic gradient and keep the mucus watery

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14
Q

Villus cells absorb what?

A

Everything

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15
Q

How is Sodium absorbed into the cell in the small intestine?

A

Coupled with:
Glucose/Galactose
AAs
Nucleosides

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16
Q

How is Na taken from the small intestinal epithelial cells to the blood?

A

Na-K ATPase

17
Q

How much water is secreted by the small intestine each day?

A

1500ml

18
Q

What is the purpose of of secreting water into the small intestine?

A

Lumenal contents liquidity
Mixing of nutrients and enzymes
Dilutes injurious surface

19
Q

How is chloride taken from the blood into small intestinal epithelial cells?

A

2 Cl- ions coupled with 1 K+ and 1 Na+

20
Q

How does Cl- enter the lumen of the small intestine?

A

CFTR channel protein triggered by cAMP –> PKA

21
Q

What is the purpose of pumping Cl- into the small intestinal lumen?

A

Passive diffusion of water

22
Q

What types of movements occur in the intestines?

A

Segmentation

Peristalsis

23
Q

What is segmentation?

A

Contraction and relaxation lengthways up intestinal surface

24
Q

What is the purpose of segmentation?

A

Move chyme back and forwards, mixing contents with enzymes

Bringing chyme into contact with BBM

25
Q

How are segmentation contractions triggered?

A

Depolarisation generated by pacemaker cells (longitudinal muscle layer)

26
Q

Action potential frequency in the longitudinal muscle layer determines what?

A

Strength of contraction

27
Q

What determines the strength of segmentation?

A

Basic electrical rhythm

Distance down intestine (–> rectum)

28
Q

Is segmentation fast or slow?

A

Slow

29
Q

What is the effect of the Parasympathetic NS on segmentation?

A

Increased contractility

30
Q

What is the effect of the Sympathetic NS on segmentation?

A

Decreased contractility

31
Q

When does peristalsis begin?

A

When nutrients are absorbed (segmentation stops)

32
Q

What is the Migrating Motility Complex

A

Pattern of peristaltic activity from antrum to terminal ileum

33
Q

What causes the Migrating Motility Complex to stop?

A

Arrival of food into the stomach

34
Q

What is the purpose of the Migrating Motility complex?

A

Move undigested material into the large intestine

Limit bacterial colonisation of SI

35
Q

What is the function of Motilin?

A

Initiation of MMC

36
Q

What is the law of the intestine?

A

Muscle on oral side of bolus contracts

Muscle on anal side of bolus relaxes

37
Q

The law of the intestine is mediated by what?

A

Myenteric plexus

38
Q

What is the gastroileal reflex?

A 
Gastric emptying increases segmentation
Ileocaecal valve opens
Chyme --> LI
Colon distended
Reflex contraction of Ileocaecal valve to prevent backflux

GASTROINTESTINAL PHYSIOLOGY (10 decks)

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