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Physiology 1 : cardiovascular > Capillaries I - Solute exchange > Flashcards

Capillaries I - Solute exchange Flashcards

1
Q

What does metabolism create?

A

→ A need to transport solute and fluids

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2
Q

What do cell membranes consist of?

A

→ Phosphate head (Polar)

→ Fatty acid tail (non-polar)

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3
Q

What do cell membranes form?

A

→ Bilayers in solution

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4
Q

What are the functions of cell membranes?

A

→ Provide support and protection
→ Cell-to-cell recognition
→Controls what enters and leaves the cell
→ Regulates cell function

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5
Q

What are properties of Passive transport?

A

→ Movement of molecules down a gradient
→ Concentration/pressure/osmotic/electrical
→ Does not require energy
→ Simple (O2/CO2) or facilitated (ions/glucose)

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6
Q

What are properties of Active transport?

A

→Movement of molecules against a gradient

→ Requires energy (uses ATP)

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7
Q

What gradient does diffusion use and give an example

A

→ concentration gradient

→ O2 uptake from the lungs into the blood

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8
Q

What gradient does convection use and give an example

A

→Pressure gradient

→ blood flow from heart to blood vessels

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9
Q

What gradient does osmosis use and give an example

A

→ Osmotic pressure gradient

→ Water uptake by cells

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10
Q

What gradient does electrochemical flux use and give an example

A

→ Electrical and concentration gradient

→ Ion flow during an action potential in a nerve

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11
Q

Where does solute and fluid exchange occur?

A

→ At capillaries

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12
Q

What do capillaries connect?

A

→ Connect terminal arterioles to venules

→ Extension of inner lining of an arteriole

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13
Q

How thick are capillaries?

A

→ 1 cell thick

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14
Q

Where are capillaries found?

A

→ found near every cell in the body

→higher density in highly active tissues (muscles, liver, heart, kidneys, brain)

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15
Q

What is the function of capillaries?

A

→ Solute exchange
→ Fluid exchange
→ Regulation of plasma and interstitial fluid

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16
Q

What controls the rate of solute transport?

A

→Properties of passive diffusion
→Properties of solutes and membranes
→ Properties of capillaries

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17
Q

What are properties of passive diffusion?

A

→Does not require any energy
→ molecules move randomly
→ Move from areas of high to low concentrations
→ transport of lipid soluble solutes over short distances

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18
Q

What are properties of the solute that affect transport?

A

→ Concentration gradient
→ size of solute
→ Lipid solubility of solute

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19
Q

What are properties of the membrane that affect transport?

A

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

20
Q

What is Fick’s law?

A

→solute movement (mass per unit time) can be determined by four factors:

→the diffusion coefficient of the solute (the ease of movement through the solvent)
→the area
→the concentration gradient (C1 - C2)
→ the distance (between C1 and C2)

21
Q

What value does Fick’s law have down a concentration gradient?

A

→ a negative value

22
Q

What are the three types of capillaries?

A

→ Continuous capillaries
→ Fenestrated capillaries
→ Discontinuous capillaries

23
Q

What are properties of continuous capillaries?

A

→Moderate permeability
→Tight gaps between neighboring cells
→ constant basement membrane

24
Q

What are properties of fenestrated capillaries?

A

→ High water permeability
→ Fenestration structures
→ modest disruption of the membrane

25
Q

Where are fenestrated capillaries found?

A

→ in high water turnover tissues

→ salivary glands, kidneys, synovial joints, anterior eye, choroid plexus, gut mucosa

26
Q

Where are continuous capillaries found?

A

→ blood-brain barrier

→ Muscle, skin, fat, connective tissue

27
Q

What are properties of discontinuous capillaries?

A

→ Very large fenestration structures

→ disrupted membrane

28
Q

Where are discontinuous capillaries found?

A

→ When the movement of cells is needed

→ RBCs in liver, spleen + bone marrow

29
Q

How wide is the intercellular cleft?

A

→ 10-20nm wide

30
Q

What are the caveolae + vesicles?

A

→ large pore systems

31
Q

What is the glycocalyx?

A

→ Covers the endothelium
→ -vely charged
→ Blocks solute permeation and access to transport mechanism
→ highly regulated
→ dynamic and can be broken down and remade as required

32
Q

What is permeability?

A

→ Permeability is the rate of solute transfer by diffusion across a unit area of membrane per unit concentration difference
(ie. how freely a solute crosses a membrane).

33
Q

How does a porous membrane interfere with the diffusion of lipid insoluble solutes?

A

→ a reduction in the area for diffusion (A)
→an increased path length through the membrane (x)
→ restricted diffusion in the pore produces hydrostatic issues (D)

34
Q

What is filtration?

A

→going through gaps, pores and fenestrations

→ as fluid moves through the dissolved glucose goes with it

35
Q

What is the glucose concentration in plasma?

A

→ 1g/liter

36
Q

What is the total volume of plasma filtrate flowing into tissues per day?

A

→ 8 liters

37
Q

What is the maximum filtration of glucose per day?

A

→ 8g/day

38
Q

What does filtration transport account for?

A

→ 2% of glucose transport

39
Q

How does 98% of glucose get transported?

A

→ into the interstitial space via passive diffusion

→ via GLUT transporter

40
Q

How does blood flow control diffusion rate?

A

→More blood brings more solutes

→ Increased blood volume means less time for equilibration to occur across capillaries

41
Q

What is flow limited diffusion?

A

→ slow flow in a long capillary

→ O2/CO2 equilibrate over the proximal section and there is little diffusion across the rest of the vessel

42
Q

When can flow limited diffusion occur and what can this lead to ?

A

→ In sepsis when blood pressure and flow are low

→ can lead to ischaemia

43
Q

How can a fall in interstitial concentration affect diffusion rate?

A

→More solute is used up
→ increases the concentration difference
→metabolism increases blood flow
→Increased O2 delivery controlled by arterioles

44
Q

How can recruitment of capillaries affect diffusion rate?

A

→ Dilation of arterioles leads to more perfused capillaries
→ Increases total SA for Fick’s Law
→ Shortens diffusion distance between capillary and cell

45
Q

During strenuous exercise how much does O2 transport to the muscle increase by?

A

40x

Physiology 1 : cardiovascular (18 decks)

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