Cardiovascular L7: Blood vessel properties cont.; lymphatic system

Question 1

What is the function of capillaries?

Answer 1

sites of exchange

Question 2

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

Answer 2

diffusion

Question 3

What are 3 ways diffusion can be increased?

Answer 3

1. Minimal distance
2. Maximal surface area
3. Maximal time

Question 4

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

Answer 4

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

Question 5

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

Answer 5

High numbers (10-40 billion) = 600m2

Question 6

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

Answer 6

Velocity is slow due to extensive branching

Question 7

What is flow rate?

Answer 7

volume of blood per unit of time

Question 8

What is flow velocity?

Answer 8

distance of blood travelled per unit of time

Question 9

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)

Answer 9

stable; closed; equal

Question 10

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

Answer 10

varies; inversely proportional

Question 11

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

Answer 11

Has a larger CSA

Question 12

What are 3 characteristics of capillary permeability?

Answer 12

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

Question 13

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

Answer 13

Endothelial

Question 14

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

Answer 14

endothelial; water-filled

Question 15

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

Answer 15

True

Question 16

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

Answer 16

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

Question 17

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

Answer 17

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

Question 18

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

Answer 18

Called reconditioning organs

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

Question 19

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

Answer 19

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)

Question 20

What are reconditioning organs or organs that get excess blood?

Answer 20

1. Intestine
2. Kidney
3. Liver

Question 21

What are sinusoids?

Answer 21

very large inter- and intra-cellular spaces

Question 22

What are fenestrations?

Answer 22

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

Question 23

What are 4 characteristics to control blood flow through capillaries?

Answer 23

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

Question 24

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

Answer 24

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

Question 25

What is interstitial fluid?

Answer 25

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

Question 26

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

Answer 26

1. Interstitial fluid (80%) 2. Plasma (20%)

Question 27

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

Answer 27

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

Question 28

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

Answer 28

1. Diffusion 2. Bulk flow

Question 29

What is diffusion?

Answer 29

allows for individual solute exchange between blood & cells

Question 30

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

Answer 30

passive; down

Question 31

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

Answer 31

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

Question 32

\_\_\_\_\_\_regulates distribution of ECF between plasma & interstitial fluid, i.e. maintains plasma volume

Answer 32

Bulk flow

Question 33

What is the function of bulk flow?

Answer 33

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

Question 34

What does bulk flow not play a major role in?

Answer 34

individual solute exchange

Question 35

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

Answer 35

1. Hydrostatic pressure 2. Oncotic pressures

Question 36

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

Answer 36

interstitial fluid; reabsorbed

Question 37

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

Answer 37

ultrafiltration; reabsorption 1. Capillary blood pressure &plasma proteins 2. Interstitial fluid & proteins

Question 38

What is ultrafiltration?

Answer 38

Fluid goes out

Question 39

What is reabsorption?

Answer 39

Fluid comes in

Question 40

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

Answer 40

Interstitial fluid will flow in to compensate

Question 41

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

Answer 41

‘pores’ to allow fluid to pass through

Question 42

#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?

Answer 42

Net inward pressure is increased so fluid moves from interstitial fluid into plasma. * Decreased ultrafiltration * Increased reabsorption

Question 43

What is the main function of the lymphatic system?

Answer 43

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.

Question 44

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

Answer 44

1. Defense against disease 2. Transport absorbed fat

Question 45

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

Answer 45

Question 46

What happens between blood flow and lymph flow?

Answer 46

Question 47

What is oedema?

Answer 47

accumulation of interstitial fluid --\> reduced exchange between blood & cells

Question 48

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

Answer 48

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)

Question 49

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

Answer 49

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

Question 50

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

Answer 50

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.

Question 51

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

Answer 51

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