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Blood vessels Flashcards

1
Q

Distinguish between micro and macrovasculature

A

Micro: <0.1mm e.g. arterioles, capillaries, venules

Macro: >0.1mm e.g. arteries and veins

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2
Q

What is meant by a portal system?

A

Blood carried from one capillary bed to another through

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3
Q

What constitutes a portal venous system?

A

Both capillary beds and blood vessels connecting them

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4
Q

2 examples of portal systems?

A

Hepatic portal system (GI tract to liver)

Hypothalamic pituitary system (hypothalamus to anterior pituitary)

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5
Q

Features of arteries?

A

Thick muscular walls

Branch into arterioles

Round in histological section

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6
Q

What is the role of the thick walls of the arteries?

A

Facilitate constriction and dilation to modulate blood pressure and flow

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7
Q

What do capillaries do?

A

Distribute blood from arterioles throughout tissue (important exchange unit)

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8
Q

What are features of capillaries?

A

Thin wall (one endothelial cell thick)

Don’t contract

Only have endothelium

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9
Q

Describe course of veins from capillary bed

A

Drain capillary bed as venules, these converge to form veins carrying blood to heart

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10
Q

What are features of veins?

A

Valves prevent retrograde flow/back flow

Some vascular smooth muscle (not as much as arteries)

Usually less circular/collapse in a section

Contraction of surrounding skeletal muscle aids venous return

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11
Q

What aids venous return to heart?

A

Valves prevent back flow

Contraction of surrounding skeletal muscle aids venous return

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12
Q

What are the 3 layers of walls of arteries and veins?

A

Tunica intima (endothelium)

Tunica media (muscular tissue/elastic)

Tunica adventita (connective tissue)

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13
Q

Which layers are more developed in arteries than veins?

A

Tunica intima and media

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14
Q

Endothelium is what sort of epithelial layer?

A

Squamous

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15
Q

What is tunica intima composed of?

A

Single layer of squamous epithelial cells and basal lamina

Sub endothelial layer contains connective tissue and internal elastic lamina

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16
Q

What separates tunica intima and media?

A

Internal elastic lamina of tunica intima

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17
Q

What layer of blood vessel is thickest?

A

Tunica media

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18
Q

What is tunica media composed of? (how is this different in large small arteries) (3)

A

Smooth muscle cells around lumen (in smaller arteries)

Replaced by elastic in elastic (larger) arteries

Type 3 collagen and proteoglycans dispersed within layers.

External elastic lamina

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19
Q

What separates tunica media and tunica adventitia?

A

External elastic lamina of tunica media

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20
Q

What is tunica adventitita composed of?

A

Fibroelastic connective tissue (fibroblast, type 1 collagen, elastic fibres, small blood vessels) arranged longitudinally with adipose tissue.

Blends with surrounding connective tissue

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21
Q

How is the fibroelastic connective tissue arranged in the tunica adventitia?

A

Longitudinally

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22
Q

True or false, external elastic lamina of tunica media is always distinguishable

A

False

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23
Q

Where are internal elastic lamina and external elastic lamina found?

A

Tunica intima

Tunica media

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24
Q

When is internal elastic lamina not visible?

A

Tunica media is muscular (smaller arteries)

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25
Q

Where is tunica media not found?

A

Capillaries

Post capillary venules

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26
Q

What is the blood supply to walls of large arteries and veins from?

A

Vasa vasorum

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27
Q

What are vasa vasorum?

A

Small arteries entering and branching to supply walls of large arteries and veins

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28
Q

What cells do vaso vasorum supply?

A

Tunica media and adventitia

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29
Q

Why are vasa vorum prevalent in veins?

A

Blood contains less oxygen and nutrients, less received through diffusion

30
Q

Classify arteries by size (3 sizes)

A

Largest: Conducting arteries = elastic (elastic layers in tunica media + muscle)

Middle: distributing arteries = muscular (smooth muscle in tunica media)

Arterioles

31
Q

Give examples of elastic arteries

A

Pulmonary artery and aorta

32
Q

How do walls of aorta and pulmonary artery look, why?

A

Yellow, abundant elastin.

Wall has thick layer of elastic (concentric layers) occupying most of tunica media

33
Q

What is benefit of elastic arterioles?

A

Stabilise blood flow and maintain arterial blood pressure

34
Q

How does composition of arteries change the further away from heart?

A

Less elastin and more muscular tunica media

35
Q

Give examples of muscular arteries?

A

Most vessels arising from aorta e.g. femoral

36
Q

Are elastic or muscular arterioles thicker?

A

Elastic

37
Q

What does muscular artery allow?

A

Selective distribution of blood to different organs and muscle tone to maintain blood pressure

38
Q

What type of cells support microvasculature?

A

Smooth muscle cells around arterioles, venules and small veins (discontinuous)

Pericytes

39
Q

What is the function of pericytes?

A

Support and stabilise arteries and veins

Regulate vascular tone
Its processes wrapped around capillary endothelium

40
Q

What is unique about pericytes?

A

Are plastic and can differentiate to fibroblast, SMC and macrophages

41
Q

Describe diameter of arterioles

A

<0.1mm

42
Q

How many layers of SM do arterioles have?

A

1-2

43
Q

What does arteriole control, how?

A

Distribution of blood to whole capillary beds, through sympathetic autonomic nerves

44
Q

What are pericytes sensitive to?

A

Low oxygen

45
Q

What are pre-capillary sphincters?

A

Band of SM that adjust blood flow into capillary bed

46
Q

What are precapillary sphincters controlled by?

A

Local metabolic products

47
Q

3 types of capillary

A

Continuous, fenestrated, discontinuous (sinusoidal)

48
Q

Describe dimensions of capillary?

A

50 micrometer length, 8-10 micrometer diameter

49
Q

Describe structure of capillaries

A

Squamous epithelium (endothelium) walls only one cell thick

Pericytes outside regulate blood flow

Posses no smooth muscle

50
Q

Where are continuous capillaries found?

A

Skin, muscle, lungs, nerve tissue (i.e. where no need for protein passage)

51
Q

Describe feature of continuous capillaries in terms of pores, how come?

A

No pores in their walls - have junctional complexes so tight control of trans endothelial transport

52
Q

Describe permeability of continuous capillary

A

Moderate

53
Q

How can substances move across continuous capillary?

A

Active transport, diffusion

54
Q

Do capillaries exhibit vasomotor activities?

A

No

55
Q

Describe structure of fenestrated capillaries, including size of pores.

A

60-80nm pores, bridged by diaphragm

56
Q

What is a diaphragm (fenestrated capillary)?

A

Diaphragm consists of radially oriented fibrils that allows small molecules and limited amounts of protein to diffuse.

57
Q

What is fenestrated capillary permeable to?

A

Small ions and proteins

58
Q

Where are fenestrated capillaries found?

A

High water turnover tissue and where protein passage needed

E.g. kidney, synovial joint, intestine, pancreas, , endocrine glands, anterior eye

59
Q

Describe sinusoidal capillaries structure

A

Discontinuous epithelial cells

Large fenestrae without diaphragm (30-40 micrometer)

60
Q

Describe permeability of sinusoids

A

Permeable to proteins and cells (e.g. RBCs)

61
Q

Where are sinusoids found?

A

Bone marrow, liver, spleen , lymphoid organs

62
Q

What is the glycocalyx?

A

Structure made of GAGs that exists inside of the endothelium on the lumenal side

63
Q

What forms around the gylcocalyx and why?

A

GAGs have many negative charges (heavily sulfated) collect Na+ ions which lowers the water potential around the calyx, leading water to gather around to form a gel like substance.

64
Q

How much of the capillary lumen does the glycocalyx cover?

A

~1/10th

65
Q

Compare the connective tissue components of arteries and veins

A

More pronounced in veins

66
Q

Describe the boundary between tunica intima and media in veins

A

Not clear

67
Q

Describe structure of venule walls

A

Similar to capillaries, thin endothelium surrounded by reticular fibres and pericytes

68
Q

What forms the valve in veins?

A

Folds of the tunica intima

69
Q

Describe structure of medium veins

A

<1cm

SMC of tunica media loosely organised with collagen fibres and fibroblasts

Tunica adventita is thickest layer (contains collagen and elastic)

70
Q

Describe diameter of arterioles and medium vein lumen

A

Medium vein lumen wider

71
Q

Describe structure of large veins in terms of layers

A

Tunica media thin

Tunica adventitia well developed

Tissues (13 decks)

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