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Life support > CVS Different Types of Capillaries, Functions and Solute Movement > Flashcards

CVS Different Types of Capillaries, Functions and Solute Movement Flashcards

1
Q

What are cell memrbanes?

A

Cell membranes are a barrier to solute transport

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2
Q

What does it mean by semi permeable membrane?

A

Allow movement of water

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3
Q

What do cell membranes provide?

A

Provide support and protection

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4
Q

What do cell membranes control?

A

Controls what enters or leaves the cell – e.g. ion movement in nerves

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5
Q

What do cell membranes regulate?

A

Regulates cell function – e.g. Insulin-mediated glucose uptake

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6
Q

What layers does the cell membrane consist of?

A

Consists of two layers of amphipathic
phospholipids

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7
Q

What is the state of phosphate head?

A

Phosphate head is polar (hydrophilic)

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8
Q

What is the state of fatty acid tail?

A

Fatty acid tail is non-polar (hydrophobic)

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9
Q

What does a cell membrane form in solution?

A

Form bilayers in solution

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10
Q

Where does most solute and fluid movement occur?

A

Most solute and fluid movement occurs at capillaries

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11
Q

How thick is the endothelium of capillaries?

A

Endothelium only – 1 cell thick

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12
Q

What do capillaries connect?

A

Vessels that connect arterioles to venules

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13
Q

What is passive movement?

A

– Movement of molecules DOWN a gradient

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14
Q

Does passive transport require energy?

A

No

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15
Q

What is active transport?

A

Movement of molecules AGAINST a gradient

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16
Q

What are the four passive transport processes?

A
  1. Diffusion
  2. Convection
  3. Osmosis
  4. Electrochemical flux
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17
Q

How does diffusion work?

A

Concentration gradient

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18
Q

How does convection work?

A

Pressure gradient

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19
Q

How does osmosis work?

A

Osmotic pressure (water) gradient

20
Q

How does electrochemical flux work?

A

Electrical and Concentration gradient
e. g. ion flow during an action potential in a nerve

21
Q

What does convection require?

A

Requires pressure gradient, functioning heart – appropriate CO etc.

22
Q

What does osmosis require?

A

Requires balance of filtration, reabsorption and functioning lymphatics
(see Fluid movement and oedema session)

23
Q

What does electrochemical flux require?

A

Requires active and other transport mechanisms to create electrochemical
gradients, needs ion channels to provide ion movement across membranes

24
Q

What does properties of the solute that affect transport?

A

-Concentration gradient
-Size of the solute
-Lipid solubility of solute (lipophilic,
lipophobic nature)

25
Q

What are the properties of the membrane affecting transport?

A

-Membrane thickness/composition
-Aqueous pores in the membrane
-Carrier-mediated transport
-Active transport mechanisms

26
Q

What are the 4 factors that determine solute movement?

A
  1. D = Diffusion coefficient of solute - how easy it moves through solvent
  2. Area
  3. deltaC/x
  4. x(distance0
    Js = - DAdeltaC/x
27
Q

What are the 3 distinct types of capillaries?

A
  1. Continuous capillaries
  2. Fenestrated capillaries
  3. Discontinuous capillaries
28
Q

What are the 3 distinct types of capillaries?

A
  1. Continuous capillaries
  2. Fenestrated capillaries
  3. Discontinuous capillaries
29
Q

What is the permeability like for continuous capillaries?

A

Moderate permeability

30
Q

How are the gaps like between continuous capillaries?

A

Tight gaps between neighbouring cells

31
Q

What type of constant membrane does continuous capillaries have?

A

Constant basement membrane

32
Q

What is the permeability like for fenestrated capillaries?

A

High water permeability

33
Q

What is the basement membrane like in fenestrated capillaries?

A

Modest disruption of basement membrane

34
Q

What structures do discontinuous capillaries have?

A

Very large fenestration structures

35
Q

What is the basement membrane
like for discontinuous capillaries?

A

Disrupted basement membrane

36
Q

What are the 3 structural features of capillary walls that can influence solute transfer?

A
  1. Intercellular cleft
  2. Glycocalyx
  3. Caveola-vesicle system
37
Q

How wide is the intercellular cleft?

A

10-20 nm wide

38
Q

What does the glycocalyx cover?

A

covers endothelium

39
Q

What does glycocalyx acts as?

A

acts as sieve for
solute permeation and access to transport mechanisms

40
Q

What are caveolae and vesicles involved in the movement of?

A

movement of large molecules,

41
Q

What processes does glucose transport occur via across membrane from capillaries into tissues?

A

Glucose transport across membrane from capillaries into tissues
occurs by either passive diffusion or filtration

42
Q

What is glucose concentration in blood plasma?

A

Glucose concentration in blood plasma is 1 g / litre

43
Q

Via what process is the majority of glucose transport into interstitial space?

A

98% of glucose transport into interstitial space
via passive diffusion
- via GLUT carrier system -

44
Q

How does increased blood flow increase diffusion rate?

A

Increases concentration of solutes in capillaries
Less time for equilibration between interstitial spaces and plasma in capillaries
of highly membrane permeable solutes, e.g. O2/CO2

45
Q

How does a fall in interstitial concentration increase diffusion rate?

A

Increases the concentration difference
Also, metabolism increases blood flow - metabolic hyperaemia -  O2 delivery

46
Q

How does recruitment of capillaries increase diffusion rate?

A

Dilation of arterioles - Increased number of capillaries perfused
Increases total surface area A for diffusion (Fick’s law)
Shortens diffusion distance deltax (faster diffusion)

47
Q

What is permeability?

A

Permeability is the rate of solute transfer by diffusion
across area of membrane per concentration difference

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