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BMS10 > Histology of Blood Vessels > Flashcards

Histology of Blood Vessels Flashcards

1
Q

What does the systemic circulatory system do?

A

Carries oxygenated blood from the heart to tissues

Returns deoxygenated blood to heart

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2
Q

What does the pulmonary circulatory system do?

A

Carries deoxygenated blood from heart to lungs

Returns oxygenated blood to heart

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3
Q

Which circulatory systems depend on a pump?

A

Systemic

Pulmonary

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4
Q

What helps move blood around the portal circulatory system?

A

Movement and pressure changes in the body

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5
Q

What does the lymphatic system do?

A

Drains extracellular fluid back into the circulatory system

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6
Q

What three layers are present in a typical blood vessel?

A

Tunica intima

Tunica media

Tunica adventitia

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7
Q

What is the tunica intima?

A

Lining of simple squamous endothelial cells supported by a basal lamina

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8
Q

What marks the boundary between the tunica intima and the tunica media?

A

Internal elastic lamina

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9
Q

What is the tunica media comprised of?

A

Smooth muscle cells

Some collagen

Variable elastin

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10
Q

What marks the boundary between the tunica media and the tunica adventitia?

A

External elastic lamina

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11
Q

What is the tunica adventitia?

A

Supporting layer of dense fibroelastic connective tissue

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12
Q

What is a vasavasorum?

A

Smaller blood vessel networks that supply large blood vessels

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13
Q

Where are elastic arteries mainly found and why?

A

Closest to heart

Elastic walls can stretch to withstand high pressure and recoil to maintain flow

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14
Q

When do the elastic artery walls stretch?

A

Systole

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15
Q

When do the elastic artery walls recoil?

A

Diastole

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16
Q

Describe the tunica intima of elastic arteries (4)

A

Simple squamous endothelial cells

Subendothelial collagenous connective tissue

Rich in elastin

Fibroblasts and smooth muscle-like myointimal cells

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17
Q

Describe the tunica media of elastic arteries

A

Concentric, fenestrated sheets of elastin separated by sheets of collagen and smooth muscle cells

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18
Q

Describe the tunica adventitia of elastic arteries

A

Collagenous connective tissue

Vasavasorum and autonomic plexuses

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19
Q

Give an example of an elastic artery

A

Aorta

Common carotid

Pulmonary artery

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20
Q

Describe the tunica media of a muscular artery

A

Almost entirely circumferential smooth muscle cells

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21
Q

Where is elastin found in a muscular artery?

A

Only in the internal elastic lamina and maybe a less distinct external elastic lamina

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22
Q

What is the function of smooth muscle in a muscular artery?

A

Withstand pressure

Vary lumen diameter to regulate flow

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23
Q

What stimulates the smooth muscle cells to contract in muscular arteries?

A

Sympathetic NS

Adrenaline

Local factors in response to vessel injury

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24
Q

What is the pressure that can be sustained in a muscular artery proportional to?

A

Wall thickness / diameter

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25
Q

What are arterioles?

A

Terminal branches of arterial system

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26
Q

What is the diameter of an arteriole?

A

<0.1mm

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27
Q

Describe the structure of an arteriole (4)

A

Thin tunica intima

May have a thin internal elastic lamina

<6 layers of smooth muscle cells in tunica media

Insignificant tunica adventitia

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28
Q

What is the relationship between pressure and radius?

A

(Pressure = resistance to flow / Rf)

Rf = k / r^4 or inversely proportional to r^4

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29
Q

What is the main factor used in the regulation of systemic blood pressure?

A

Control of blood flow through arterioles

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30
Q

What occurs in microcirculation?

A

Exchange of gases, fluids, nutrients and waste products

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31
Q

What is the order of blood vessels from the microcirculation?

A

Capillaries

Post-capillary venules

Collecting venules

Muscular venules

32
Q

What controls flow into capillaries?

A

Arterioles

Pre-capillary sphincters

33
Q

How close must an active cell be to a capillary?

A

150um

34
Q

What is a true capillary?

A

Single layer of endothelial cells (and basal lamina) only

35
Q

What is a metarteriole?

A

Transitional vessels (arteriole to capillary)

Discontinuous layer of smooth muscle cells

36
Q

What are arteriovenous shunts?

A

Direct connections between arterial and venous systems

37
Q

What is the diameter of a capillary?

A

Varies from 3-4um to 30-40um

Average is 8-10um

38
Q

How long is a capillary?

A

<1mm

39
Q

What are sinusoids?

A

Large diameter capillaries

40
Q

Where are sinusoids found?

A

Liver

Spleen

Bone marrow

Some endocrine glands

41
Q

Describe a continuous capillary

A

Tube of endothelial cells resting on a thin basal lamina

Tight junctions

Embraced by pericytes

42
Q

How are substances transported across capillary membranes?

A

Small molecules (eg. O2) simply diffuse through endothelial cells

Permeability to other molecules depends on ‘tightness’ of tight junctions

Large molecules and fluids involves transcytosis across endothelial cells

43
Q

What is transcytosis?

A

Calveolae bud off vesicles which cross the cell and fuse with calveolae on the opposite side of the cell

44
Q

What are calveolae?

A

Flask-like pits on endothelial cells lined by calveolin

45
Q

What is the purpose of fenestrated capillaries?

A

Rapid movement of macromolecules

46
Q

Where are fenestrated capillaries found?

A

Small intestine

Kidney

Some endocrine glands

47
Q

Describe a fenestra (of a capillary)

A

Basal lamina and basal membranes of endothelial cells come together to form fenestrae

Fenestrae closed by diaphragm (continuous basal lamina)

48
Q

What is the average diameter of a fenestra?

A

50nm

49
Q

Where are discontinuous capillaries found?

A

In sinusoids of liver and spleen

50
Q

What is the purpose of discontinuous capillaries?

A

Allows free passage of large macromolecules or even cells

51
Q

Describe a discontinuous capillary

A

Large gaps between endothelial cells with a discontinuous basal lamina

52
Q

What is the difference between a post-capillary venule and a capillary?

A

(Similar structure but) larger diameter

53
Q

What occurs at post-capillary venules?

A

Entry and exit of white blood cells

54
Q

What is the difference between a collecting venule and a post-capillary venule?

A

Larger diameter

More pericytes

55
Q

How many layers of smooth muscle cells are in muscular venules?

A

1-2

56
Q

What vessels come together to form veins?

A

Muscular venules

57
Q

Describe the structure of a vein

A

Tunica intima is little more than endothelium

Tunica media is 2+ layers of smooth muscle cells

Tunica adventitia is the broadest layer

58
Q

How could you tell the difference between an artery and a vein on a micrograph?

A

Veins have a larger diameter to smooth muscle/wall ratio

59
Q

How can you tell the difference between a blood vessel and a lymphatic vessel on a micrograph?

A

No red blood cells in a lymphatic vessel

60
Q

How does blood move through the vein system?

A

Passively

Assisted by negative pressure within chest/right atrium during inspiration

Assisted by muscle contractions causing vein compression from limbs/skeletal pump

61
Q

What prevents backflow in veins?

A

Valves

62
Q

What is the structure of a valve in a vein?

A

2 semilunar projections of fibroelastic tissue extending from tunica intima

63
Q

When do you find valves in veins?

A

When the vein is larger than 2mm in diameter

64
Q

What is the function of the endothelial cells?

A

Permeability barrier

Synthesise and secrete substances

65
Q

What do endothelial cells synthesise/secrete? (5)

A

Blood clotting factors

Molecules that prevent inappropriate blood clotting

Vasoactive factors (promote/inhibit vasodilation)

Inflammatory mediators

Some growth factors

66
Q

At which end of the microcirculatory system is the hydrostatic pressure highest?

A

Arterial end

67
Q

Where does the lymphatic system drain into?

A

Subclavian veins

68
Q

Where are lymphatic vessels not found? (6)

A

CNS

Cartilage

Cornea

Bone and bone marrow

Placenta

Teeth

69
Q

What is a lymphatic vessel similar to in structure?

A

Sinusoids

70
Q

What does high hydrostatic pressure in the microcirculation cause?

A

Water, electrolytes and some proteins to leak into extracellular space

71
Q

Describe the structure of a lymphatic vessel

A

Extremely flattened endothelial cells and basal lamina (no pericytes)

Delicate semilunar valves prevent backflow

72
Q

What is angiogenesis?

A

Formation of new blood vessels from pre-existing capillaries

73
Q

When does angiogenesis occur?

A

Menstrual cycle

Placental growth

Wound healing

Inflammation

74
Q

Briefly describe angiogenesis

A

Capillary sprout

Migration and proliferation of endothelial cells

Assembly into tubes

Recruitment of smooth muscle cells, pericytes and fibroblasts

75
Q

What type of cell can induce angiogenesis?

A

Tumour cells

BMS10 (13 decks)

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