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PHYL2062 EOS > Cardiovascular L7: Blood vessel properties cont.; lymphatic system > Flashcards

Cardiovascular L7: Blood vessel properties cont.; lymphatic system Flashcards

1
Q

What is the function of capillaries?

A

sites of exchange

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2
Q

Exchange occurs across capillary walls by _________ – no carrier-mediated transport systems (except for the blood-brain barrier)

A

diffusion

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3
Q

What are 3 ways diffusion can be increased?

A
  1. Minimal distance
  2. Maximal surface area
  3. Maximal time
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4
Q

How can minimal distance in capillaries be a way that diffusion can be increased? List 3 reasons

A
  1. Single layer of endothelial cells
  2. Thin wall (1 μm) & small diameter (7 μm)- red blood cells are 8 μm = (push plasma against walls)
  3. Proximity to cells
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5
Q

How can maximal surface area of capillaries be a way that diffusion can be increased?

A

High numbers (10-40 billion) = 600m2

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6
Q

How can maximal velocity in capillaries be a way that diffusion can be increased?

A

Velocity is slow due to extensive branching

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7
Q

What is flow rate?

A

volume of blood per unit of time

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8
Q

What is flow velocity?

A

distance of blood travelled per unit of time

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9
Q

Flow rate is _____ at all levels of vascular tree - CVS is a ____ loop so the volume of blood, (i.e. the flow rate), must ____ the CO (~5L/min at rest)

A

stable; closed; equal

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10
Q

Flow velocity _____ at all the levels of the vascular tree – it is ______ (directly proportional/inversely proportional) to the total cross sectional area of all vessels

A

varies; inversely proportional

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11
Q

How does the the structure of arteries and capillaries change? What effect does that have?

A

Has a larger CSA

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12
Q

What are 3 characteristics of capillary permeability?

A
  1. Endothelial cells fit together like a jigsaw to form the capillary wall
  2. The majority of capillaries have tightly joined endothelial cells with narrow water-filled spaces between them
  3. This allows for passage of small water-soluble substances
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13
Q

________ cells fit together like a jigsaw to form the capillary wall

A

Endothelial

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14
Q

The majority of capillaries have tightly joined ____ cells with narrow ______ spaces between them

A

endothelial; water-filled

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15
Q

The tightness of endothelial cells fit varies between organs. True or false.

A

True

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16
Q

In the cerebrum, how does the tightness of the endothelial cell fit vary?

A

tight junctions so no clefts are present –> blood-brain barrier

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17
Q

In skeletal muscles and lung (and most other), how does the tightness of the endothelial cell fit vary?

A

water-filled clefts (4nm) –> small, water soluble substances pass (ions, glucose, amino acids) but large water-soluble substances cannot (proteins via vesicular transport)

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18
Q

In the kidneys and intestines, how does the tightness of the endothelial cell fit vary?

A

Called reconditioning organs

water-filled clefts + fenestrations (20-100nm) –> ‘leaky’ capillaries (allow molecules to move through quickly)

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19
Q

In the liver, how does the tightness of the endothelial cell fit vary?

A

water-filled clefts (10-1000nm) + fenestrations (not between endothelial cells- there are holes within the endothelial cells) –> very large inter- &intra-cellular spaces, known as sinusoids

The liver is the site of protein formations (which are very big and can’t go through the water-filled clefts)

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20
Q

What are reconditioning organs or organs that get excess blood?

A
  1. Intestine
  2. Kidney
  3. Liver
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21
Q

What are sinusoids?

A

very large inter- and intra-cellular spaces

22
Q

What are fenestrations?

A

Holes that are within the endothelial cells (not between the endothelial cells)

23
Q

What are 4 characteristics to control blood flow through capillaries?

A
  1. No smooth muscle
  2. Pre-capillary sphincters are smooth muscle cells that spiral capillaries: myogenic tone (not innervated) & sensitive to local metabolic factors
  3. If metabolic activity increases, sphincters relax –> increase flow
  4. If metabolic activity decreases, sphincters contract –> flow is bypassed
24
Q

What are the 2 main factors that blood flow through an organ is regulated by? What are the other 3?

A
  1. Number of open capillaries
  2. Degree of arteriolar resistance
  3. radius (only one that changes- out of the 3)
  4. viscosity
  5. length
25
Q

What is interstitial fluid?

A

a component of ECF- space between blood vessels and cells within an organ (tissue)

26
Q

What are 2 components that make up ECF? What is the percentage of each?

A
  1. Interstitial fluid (80%)
  2. Plasma (20%)
27
Q

Movement between blood and cells is not direct. What are the 2 features?

A
  1. Movement in or out of cells can be passive or active
  2. Movement in or out of capillary endothelial cells is mostly passive (move down a concentration gradient)
    • similar composition between arterial blood & interstitial fluid, except proteins
28
Q

What are the 2 mechanisms that the exchange between blood and organs can occur?

A
  1. Diffusion
  2. Bulk flow
29
Q

What is diffusion?

A

allows for individual solute exchange between blood & cells

30
Q

Diffusion is ___ (active/passive) and goes __ (up/down) a concentration gradient.

A

passive; down

31
Q

In this picture, explain what happens to glucose, O2 and CO2?

A

Glucose INTO cell:

  1. Passively diffuses down its concentration gradient (from plasma)
  2. to interstitial fluid
  3. Enters cells via glucose transport on surface of membrane

O2 INTO cell:

  1. Passively diffuses down its concentration gradient (from plasma)
  2. to interstitial fluid
  3. Enters cells via glucose transport on surface of membrane

CO2 OUT OF cell:

  1. Exits out of cell
  2. to interstitial fluid
  3. Goes into the plasma
32
Q

______regulates distribution of ECF between plasma & interstitial fluid, i.e. maintains plasma volume

A

Bulk flow

33
Q

What is the function of bulk flow?

A

regulates distribution of ECF between plasma & interstitial fluid, i.e. maintains plasma volume

34
Q

What does bulk flow not play a major role in?

A

individual solute exchange

35
Q

What are 2 types of pressures that influence bulk flow via ultrafiltration and reabsorption?

A
  1. Hydrostatic pressure
  2. Oncotic pressures
36
Q

Protein free plasma flows out of capillaries and mixes with ______ and is then _____.

A

interstitial fluid; reabsorbed

37
Q

Hydrostatic & oncotic pressures influence bulk flow via ______& ________. What are 2 things that are related to this?

A

ultrafiltration; reabsorption

  1. Capillary blood pressure &plasma proteins
  2. Interstitial fluid & proteins
38
Q

What is ultrafiltration?

A

Fluid goes out

39
Q

What is reabsorption?

A

Fluid comes in

40
Q

if the interstitial fluid is too low in capillaries, what is a compensatory technique?

A

Interstitial fluid will flow in to compensate

41
Q

Capillaries are the only vessels that have ___________. What does that allow?

A

‘pores’

to allow fluid to pass through

42
Q

In the context of bulk flow, what would happen in response to a haemorrhage (severe blood loss- blood out of capillaries)? (Hint: a reduction in plasma volume reduces capillary blood pressure). What happens to ultrafiltration and reabsorption?

A

Net inward pressure is increased so fluid moves from interstitial fluid into plasma.

  • Decreased ultrafiltration
  • Increased reabsorption
43
Q

What is the main function of the lymphatic system?

A

return excess fluid & protein that leaked out of capillaries back into the venous system

Acts as a back up to pick up the excess interstitial fluid and protein that hasn’t been absorbed.

44
Q

What are the 2 other functions of the lymphatic system (apart from returning fluid)?

A
  1. Defense against disease
  2. Transport absorbed fat
45
Q

What happens once it enters the lymphatic system? The relationship of the lymphatic system compared to the circulatory system.

A
46
Q

What happens between blood flow and lymph flow?

A
47
Q

What is oedema?

A

accumulation of interstitial fluid –> reduced exchange between blood & cells

48
Q

What are 3 causes of reduced concentration of plasma proteins (abnormal physical force)?

A
  1. Kidney disease (increased protein in urine = less in plasma)
  2. Reduced liver function (should be response for proteins = less)
  3. Protein-deficient diet (not eating enough protein)
49
Q

What is the cause of increased permeability of capillary walls (abnormal physical force)?

A

Histamine- inducing widening of pores (blisters and hives) Cause swelling, redness and increased fluid

50
Q

What is the cause of increased venous pressure (abnormal physical force)?

A

backflow of blood in LL –> increase capillary hydrostatic pressure > extra ultrafiltration > extra fluid in ECF > oedema.

e.g. Pregnancy - growing uterus compress on veins, make it harder to return blood upwards. Also heart failure.

51
Q

What is the cause of a blockage of lymph vessels (abnormal physical force)?

A

Surgical removal of nodes (or possible type of mosquito- rare) - difficult to take up lymph

PHYL2062 EOS (13 decks)

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