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Flashcards in deck_485971 Deck (66):
1

How does exchange occur between blood and tissues?

Diffusion

2

Give three factors which affect rate of diffusion

Area available for exchangeDiffusion 'resistance' Concentration gradient

3

What affect does increased capillary density have and why?

Increased rate of diffusion as larger surface area for diffusion

4

What do highly metablolically active tissues have?

A high capillary density

5

Why is area available for exchange conisdered a maximum?

Because not all capillaries are perfused

6

In the body is areaa) Rate Limitingor b) Not rate limiting

It is b, not rate limiting

7

What are the three factors which affect diffusion resistance?

Nature of molecules crossing the capillariesNature of the barrierPath length

8

How do lipophillic molecules reach cells from capillaries?

By directly crossing capillary wall due to the nature of the lipid bilayer of endothelial cells

9

How do hydrophillic molecules reach cells?

Pass through pores, which offer little resistance

10

What property do small moleules posses when compared to large?

Diffuse more easily

11

How the nature of the barrier affect diffusion?

Increasing pore size and number facilitates the diffusion of large and hydrophillic molecules

12

What does path length depend on?

Capillary density and interstitial space

13

How does conc gradient affect diffusion?

The greater the concentration gradient, the greater the rate of diffusion. Must be maintained in order for exchange to continue.

14

What is the conc gradient in capillaries between?

Capillary contents and nearby cells

15

What is the most important variable in conc grad?

The flow of blood

16

What happens if blood is not supplied at appropriate rate?

Conc grad driving exchange will dissipate, and nutrients will not be supplied at the right rate

17

What is the cardiac output of an average male at rest?

5 l/min

18

What is the minimum rate of blood flow required by the brain?

750 ml/min

19

What three organs must have blood at ALL times?

Kidney, heart muscle and brain

20

What are the four main components of circulation?

PumpDistribution vesselsFlow controlCapacitance

21

What is the bodies pump?

Take a guess, wise guy.

22

What is the bodies main distribution vessels for circulation?

Arteries

23

What type of vessels are used in flow control?

Resistance vessels, such as arterioles and pre-capillary sphincters

24

What two things do resistance vessels ensure?

Blood flow to areas of the body which are difficult to perfuseBlood flow is restricted to areas which are easy to perfuse

25

What is capacitance?

Store of blood to be called upon to cope with temporary imbalances between the amount of blood returning to the heart and the amount that is required to pump out.

26

Where is capacitance generated?

In the veins

27

What is the function of an artery?

Carry blood away from the heart to the capillary beds

28

Give two types of artery

Elastic (conducting) or muscular (distributing)

29

What are arterioles?

Arteries with a diameter of less than 0.1mm

30

What are capillaries?

Vessels 7-10 micrometers in diameter

31

What is a post capillary venule?

Receive blood from capillaries, have a diameter of 10-30 micrometers and are even more permeable than capillaries

32

What is a merging venule?

Diameter more than 50 micrometers. Tunica media reappears

33

describe a vein

Very large diameterThin wall with more connective tissuesFewer elastic and muscle fibresUsually have semi-lunar valves

34

What are veins and arteries comprised of?

Three layersTunica intima, media and adventitia

35

Describe the tunica intima of elastic arteries

Endothelial cells with long axes parallel to axis of arteryNarrow subendothelium of CT with discontinuous internal elastic limina

36

Why do epithelial cells in tunica intima of elastic arteries have endothelial cells with long axes parallel to axis of artery

to reduce friction

37

Why does the tunica intima of elastic arteries have a narrow subendothelium of CT with discontinuous internal elastic lamina?

to allow for expansion

38

Describe the structure of the media of elastic arteries

40-70 layers of fenstrated elastic membrane, with smooth muscle and collagen between these lamellae.

39

How is the smooth muscle in the media of elastic arteries controlled?

Smooth muscle is involuntary and allows for controlled contraction in order to move the blood through the lumen

40

Describe the adventitia of elastic arteries

Thin layer of fibroelastic CT containing lymphatic vessels and nerve fibers

41

Describe the intima of muscular arteries

Endothelium, subendothelium, thick internal elastic lamina

42

Describe the media of muscular arteries

40 layers of smooth muscle cells connected by gap junctions Prominent external elastic lamina

43

Why is does the media of muscular arteries have 40 layers of smooth muscle cells connected by gap junctions?

For coordinated contraction

44

Describe the structure of the adventitia of muscular arteries

Thin layer of fibroelastic CT with nerve fibersVasa vasorum

45

Why does the adventitia of the arteries have nerves?

For vasoconstriction and dilation

46

What are vasa vasorum?

Dekiever blood to tissues in muscular artery which are inadquately nourished by luminal blood

47

Describe the structure of the intima of arterioles

Endothelium and thin subendothelium

48

Describe the structure of the media of arterioles

1 to 3 layers of smooth muscle

49

Describe the structure of the adventitia of arterioles

Hardly present

50

How do metarterioles differ from arterioles?

Smooth muscle layer discontinuous. spaced apart and encircle endothelium of capillary arising from metarterioles, forming pre-capillary sphincter

51

What is a pre-capillary sphincter?

Formed from metarterioles, can contract and prevent blood flow into capillary bed

52

Describe the structure of capillaries

Single layer of endothelium with basement membrane

53

Give three types of capillary

Continous, fenstrated and sinusoidal

54

what is a fenstrated capillary?

Interruptions between thin parts of endothelium

55

What is a sinusoidal capillary?Where are they found?

Large diameter, special linings and an incomplete basal lamina which allows blood cells to enter tissue space.Liver, spleen and bone marrow

56

Why are venules more permeable than capillaries?

Lower pressure so fluids tend to drain into them

57

Describe the structure of merging venules

Intima - endothelium or thin smooth muscle form thin wallValves which are thin extensions of intima and prevent backflowMedia - 2 to 3 layers of smooth muscle

58

Describe the intima of veins

Thicker tunica intima than venules (smooth muscle, valves)

59

Describe the media of veins

2 to 3 laers of smooth muscle

60

When does the media of veins differ?

In superficial veins of leg, where muscle thick to resist distension caused by gravity

61

Adventitia of veins?

Well developed

62

What is a vena comitante?

A vein or usually a pair of veins found either side of and artery whose pulsations aid venous return

63

What happens to veins if pressure is not maintained?

They collapse

64

How is pressure in arteries maintained?

Systolic blood flow

65

How is blood pressure in veins maintatined?

The muscle pump action in the leg and pressure factor in abdominal and thoracic cavity

66

Name three structures blood vessels do not reach in body

Cartilage, epithelia and cornea