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Gi System > GI physiology > Flashcards

GI physiology Flashcards

1
Q

Describe the 4 layers of the GI system

A

Mucosa: Epithelium, Lamina propria, Muscularis mucosae
Submucosa
Muscularis externa
Adventitia

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2
Q

Describe the epithelium of the mouth, oesophagus and anal canal

A

Mouth, oesophagus, anal canal - Stratified squamous

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3
Q

Describe the epithelium of the Stomach, Small & Large intestine

A

Stomach, Small and large intestine - Simple columnar

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4
Q

Describe the muscosa roles

A
  • Separates Lumen from alimentary canal
  • Synthesis and secretion of digestive enzymes
  • Absorb products of digestion
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5
Q

Describe the submucosa

A
  • Contains Meissners plexus (parasympathetic)

-

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6
Q

Describe the muscularis externa

A
  • Two distinctive layers, Longitudinal and Circular
  • Inner layer circular - constricts lumen
  • Outer layer longitudinal - shortens lumen
  • Auerbachs(Myentirc) plexus between two layers
  • ENS = Messiers + Myentric nervous systems
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7
Q

Describe the parasympathetic innervation by the vagus nerve

A

Stimulatory

  • Increases gut motility
  • Increases secretion
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8
Q

Describe the sympathetic innervation by the splanchnic nerve

A

Inhibitory

  • Decrease secretion
  • Decreases gut motility
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9
Q

Describe the Salivary innervation of the alimentary system

A 
Facial nerve (VII) - Parotid gland
Glossopharyngeal (IX) - Submandibular and sublingual
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10
Q

Describe the basic monosaccharides

A

Glucose, galactose, fructose - Hexose Sugars

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11
Q

Describe the basic polysaccharides and how they are linked

A

Maltose = glucose + glucose
Sucrose = glucose + fructose
Lactose = glucose + galactose
Linked by α 1,4 glycosidic bonds - hydrolysed by amylase

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12
Q

What is starch, and what is it linked by?

A

Plant storage of glucose, linked by α 1,4 glycosidic bonds

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13
Q

Describe cellulose, what is it linked by and

A

Constinuant of plant cell wall, Unbranched glucose chain linked by B, 1,4 glycosidic bonds

Only broken by cellulase

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14
Q

What enzyme is used to break polysaccharides and where is it secreted?

A

a - amylase used to break down α 1,4 glycosidic bonds

secreted by saliva and pancreas

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15
Q

What is glycogen and how is it stored?

A

How animals and humans store glycogen monomers,

linked by α 1,4 glycosidic bonds

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16
Q

Describe how glucose gets into the blood?

A

Using SGLT transporter to pass into the apical membrane, along with sodium then using then using the GLUT-2 transporter, this method uses facilitated diffusion as it requires Na

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17
Q

Describe how fructose passes into the blood?

A

Fructose passes via the Glut - 5 transporter and then the GLUT-2 transporter into the blood

18
Q

How are proteins linked?

A

Polymers of amino acids are linked together by peptide bonds CO,NH

19
Q

What breaks down proteins?

A

Proteases and peptidase

20
Q

How are amino acids absorbed into the cell?

A

Amino acids are absorbed into the cell via the SAAT1 transporter, which uses sodium

21
Q

Why is there an acid microclimate?

A

Abundance of hydrogen to drive peptides into the cell

22
Q

How is fat formed and what is it broken down by?

A

Fat is formed as triacyglycerol and is broken down by pancreatic lipase

23
Q

What is emulsification and what prevents droplets from reforming?

A

Emulsification is the break down of large lipid droplets into small lipid droplets, emulsifying agents prevent small droplets reforming into large ones (Phospholipids and bile salts)

24
Q

What is the process of large lipid droplets going into small lipid droplets?

A

Mechanical disruption

25
Q

What does the breakdown of triacyglycerol result in?

A

2 fatty acids and monoglycerol

26
Q

What is a micelles?

A

Miscelle are similar to emulsion droplets but smaller
micelle = bile salt + monoglyceride + fatty acid + phospholipid
They travel to the membrane of the enterocytes, miscelles themselves are not absorbed!

27
Q

What happens in the smooth endoplasmic reticulum in the epithelial cells?

A

Monoglycerides and fatty acids are reformed into triacylglycerols

28
Q

What is a chylomicron?

A
  • Inside the lumen of the smooth ER, cholestrol and phospholipids also aggregate with the tracyglcerols forming chylomicrons
  • They pass through lacteals
29
Q

What are the fat souble vitamins?

A

Vitamins A, D, E, K

All follow the same absorption route as a fat molecule

30
Q

What are the water souble vitamins?

A

Vitamins B,C and folic acid

Either passive diffusion or carrier mediated transport

31
Q

What is vitmain B12? What does it bind to and where is it absorbed?

A
  • B12 is a large charged molecule which binds to intrinsic factor
  • It is absorbed in the distal ilium
32
Q

What does vitamin B12 deficiency result in?

A
  • Pernicious anemia, which is the failure of the red blood cell to mature
33
Q

What does iron bind too and how is it absorbed?

A

Iron binds to ferratin and is absorbed in duedenal enterocytes via a DMT1 transporter

34
Q

What does Iron in blood bind too?

A

Transferrin

35
Q

Describe Hyperaemia and anaemia?

A

Hyperaemia - Increased ferratin levels, More iron in enterocytes
Anemaia - Decreased ferratin levels, more iron in blood

36
Q

What is the content of saliva?

A

Water, Mucins, Amalyse, Lyzomes, Electrolytes

37
Q

Describe salivary secretion control

A

Parasympathetic -
(Cr N VII & IX) - Stimulation profuse watery secretion

Sympathetic-
Small volume, more viscous
High mucus content - alpha 1 adrenoreceptor
High amaylse content - alpha 1 adrenoreceptor

38
Q

Describe the muscularis externa in the oesophagus and the lining of the oesophagus?

A
  • Upper 1/3 is skeletal muscle, Superior
  • Lower 2/3 is smooth muscle, Lower
  • Mucosa lined by stratified squamous epithelium
39
Q

Describe the process of swallowing?

A 
Oral phase
- Bolus pushed to the back of the mouth
Pharyngeal phase
- Presence of bolus, sequence of reflex contractions of pharyngeal muscles
- Co-ordination of swallowing centre
- Soft palate reflected backwards and upwards (nasopharynx closed off)
As bolus approaches oesophagus
- Upper oesophageal sphincter relaxes and the epiglottis covers the larynx
- Upper oesophageal sphincter closes 
Oesophageal phase
- Propulsion of bolus to stomach
- Perastaltic wave sweeps across entire oesophagus
- Propelled to stomach
- Bolus nears stomach LOS relaxes
Relaxtion of stomach
- Stomach volume goes from 50 - 1500ml
40
Q

List the functions of the stomach?

A
  • Temporay storage of ingested material
  • Dissolve food particles initiate digestive control
  • Control delivery of contents to small intestine
  • Sterilise ingested material
  • Produce intrinsic factor (B12)

Gi System (16 decks)

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