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Gastrointestinal and Liver Disorders (GIL) > 2.1 Anatomy and Physiology > Flashcards

2.1 Anatomy and Physiology Flashcards

1
Q

What is the role of the GI tract and what are its requirements of its role ?

A

Absorption of nutrients (and drugs) and excretion of waste products

Requires:

  1. Breakdown large molecule (mechanical and chemical)
  2. Secretion of enzyme
  3. Transport mechanisms
  4. Secretion of compounds to aid absorption
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2
Q

What happens when the circular smooth muscle of the GI tract contracts ?

A

The lumen becomes smaller

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3
Q

What happens when the longatudinal smooth muscle contracts ?

A

Helps the movement of contents in lumen

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4
Q

What is peristalsis ?

A

Is a series of synchronised and wave-like smooth msucle contrations and relaxations that move food unidircetionally through the GI tract.

The contractions and relaxations of the smooth muscles causes the lumen to dialate and constrict.

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5
Q

What resides between the circular smooth muclee and the longitudinal smooth muscle and what is its function?

A

The nerve plexus (myenteric plexus)

This is a nerve network which co-ordinates the contraction-relaxation cycle at a local level

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6
Q

What are interstitial cells of cajal and what are their roles?

A

They serve as electrical; pacemacker and generates sponmtaneous electrical slow waves in the GIT. This helps co-ordinate contraction of GI smooth muscle.

They intergate signals from enteric nerves to smooth muscle

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7
Q

True/false. The top of the GIT contracts and the bottom relaxes to move food down the tract? The same thing applies to the small intestine.

A

True

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8
Q

What controls the mixing and propulation in the GIT and what are their local controls?

A

Enteric nervous system which has local controls of ACh, NA, 5-HT, NO and ATP

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9
Q

What does the autonomic nervous system act on ?

A

Enteric nerves and direct on smooth mucles

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10
Q

What does the parasympathetic nervous system release and what does it act on?

A

Releases ACh, acts on muscarinic receptors to stimulate contractions

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11
Q

Breifly summerise what happens when an ACtion potential arrives at the smooth mucle ?

A
  1. Action potential causes depolarisation
  2. Channels open within the membrane
  3. Ca2+ comes into the cell
  4. Vesicals containing ACh merge to the membreane
  5. ACh is released out of the menrin and acts on receptors on the mooth mucle
  6. This causes a contraction
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12
Q

What muscarinic receptor subtypes are on smooth mucle on the GIT?

A

M2: causes smooth mucle contraction

M3: which are on the smooth mucle too

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13
Q

What neurotransmitters (chemicals) can act on the pre-synaptic receptors on the nerve cells ? Do they stimulate or supress the release of ACh

A

Opioid acts on m- inhibit

Dopamine acts on D2receptor -inhibit

5-HT acts on 5-HT4 receptor - stimulate

In terms of smooth muscle opioid and dopamine causes SM to relax and 5-HT cause SM to contract

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14
Q

What are the two ways in which the GI motility can be controlled therapeutically ?

A
  1. Stmilation and antagonist of the muscarinic receptors

2. Stimulation or antagonist of the pre-synaptic receptors

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15
Q

Describe the three stages of mastication and salivation

A
  1. Grinding and breakup food for swallowing
  2. Mix food with saliva (enzymes)
  3. Stimulates taste buds
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16
Q

What are the 4 functions of the stomach?

A
  1. Storage of food
  2. Initiation of digestion of proteins and CHO
  3. Kill ingested bacteria (via acid)
  4. Formation of chyme, before transfer to small intestine
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17
Q

True/false? Stomach absorbs food not alcohol

A

False, stomach absorbs alcohol but not food

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18
Q

What does the duodenum recieve from the stomach?

A

Chyme

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19
Q

What enzymes are delivered to the duodenum from the acinar cells in the pancreas? And what do the enxymes breakdown?

A 
Lipase- Fats
Amylase- Carbohydrates
Proteases- Protiens (trypsin, chymotrypsin,carboxypeptidases)
Nucleases- Nucleic acids 
HCO3- Nutralises acids
20
Q

Why might patients with cyctic fibrosis need PERT (pancreatic enzyme replacement therapy)?

A

Pancreatic sercretion depends on Cl- exchange and this is inpaired in patients with cystic fibrosis. This means that fat and protein digestion is imparied.

Can result in undernutrition

21
Q

Where are most nutrients absorbed?

A

In the duodenum and jejunum

22
Q

Where does B12 and Bile absorption occur?

A

Terminal ileum

23
Q

What would happen if the small intestine was inflammed in terms of the absorption of nutrients ?

A

Inflamation causes flattening of the villi,

Reduces the surface area hence reduced the absorption of nutrients

24
Q

What is the role of tight junctions ?

A

Limits the transport of contents between cells

25
Q

If drugs can cross the elithelial cells that line the vili, where can they be absorbed ?

A

Lymphatic circulation as well as blood circulation

26
Q

What is payers patches and what are their roles ?

A

Collection of sub-epithelial lymphoid follicles which acts as immune sensors .

Together with M cells, theyplay an important role in detecting pathogens in the GIT

27
Q

How are fats digested?

A

By bile, which is a digestive fluid

28
Q

What is bile made from?

A

Cholesterol

29
Q

Where is bile synthesised?

A

Liver

30
Q

Where is bile stored?

A

Gall bladder

31
Q

Where is bile secreted ?

A

Duodenum

32
Q

What does bile do?

A

Emulsifies fat and helps form micelles to aid fat absorption

33
Q

What is entrohepatic recycling?

A

Reuptake of bile back into the liver

34
Q

How much bile is produced a day?

A

1-2L

35
Q

What chemicals are cholesterols synthesised into to make bile salts?

A

Cholesterol —> 7-hydroxycholestrol: —> cholate and chenodeoxycholate

36
Q

What is the role of the portal vein and what is portal circulation?

A

Drains almost all of the blood from the digestive tract and empties directly into the liver

Portal circulation is the circulation of nutrient-rich blood between the gut and liver

37
Q

Briefly describe the process of the transport of micelles in enterocytes and then into blood circulation

A

Miecelles (bile salts and fatty acid) are actively transported across the cells.

This is broken down into cholesterol and FA

Chylomicrons then transport this outside of the cell into blood circulation

38
Q

Breifly describe the absorption of proteins and carbohydrates into enterocytes

A

Protiens are broken down into AA which is then transported into the cell via a Transpoter

Polysaccharides (aka carbohydrates) are broken down into glucose.
A symporter transports Na+ as well as glucose inside the cell

39
Q

What is prenicious anemia caused by?

A

Lack of intrinsic factor that causes impaired uptake of vit B12

40
Q

Breifly describe calcium uptake in enterocytes

A

Ca+ diffused into enterocytes via calcium channels.
This is passive diffusion

CaBP binds to Ca2+ and is transported out of the enterocyte via ATPase into the blood circulation

41
Q

What prevents bacteria in large intestine from infecting small instestine ?

A

Ileocecal junction which is between the small and large intestine

42
Q

What does colonic bacteria in the large intestine digest?

A

Non-starch polysacharrides - fibre and increases faecal bulk

43
Q

True/False. More water and NA+ is extracted from the contents within the large intestine

A

True

44
Q

Does digestion take place in the large intestine ?

A

NO

45
Q

Breifly decribe the absorption of water through enterocytes

A

Osmosis

Gastrointestinal and Liver Disorders (GIL) (25 decks)

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