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Block C - Circulation > Histology Lecture 2 -- Blood Vessels > Flashcards

Histology Lecture 2 -- Blood Vessels Flashcards

1
Q

What are the efferent vessels?

A

Arteries

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2
Q

Artery function

A

Conduct oxygen and nutrients to the tissues which diffuse out through a capillary network

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3
Q

What are the afferent vessels?

A

Veins

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4
Q

Vein function

A

Convey the product of metabolism of tissues such as waste products and CO2 to the heart

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5
Q

3 distinct layers of the walls of arteries and arterioles

A

Intima
Media
Adventitia

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6
Q

What does the adventitia often merge with?

A

Dense or loose connective tissue surrounding the vessels

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7
Q

Describe the walls of veins or venules

A

Equivalent layers to arteries and arterioles are generally difficult to identify, or boundaries are poorly defined

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8
Q

Location of capillaries

A

Between metarterioles and postcapillary veins

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9
Q

Dimensions of capillaries

A

1 mm in length

8 - 10 micrometers in diameter

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10
Q

Approximate number of capillaries in myocardium

A

2000 per cubic mm

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11
Q

Histology of capillaries

A

Simply squamous endothelium with tight junctions sitting on a basement membrane and surrounded by reticular fibers

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12
Q

What support do capillaries have structure-wise?

A

Intermediate vimentin filaments within endothelial cells

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13
Q

Describe the adventitia of capillaries

A

Absent or minor

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14
Q

What is the relative area of the capillary network?

A

800 times larger than the area of the aorta

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15
Q

Blood flow in the capillary network

A

0.3 mm/s

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16
Q

Blood flow in the aorta

A

320 mm/s

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17
Q

What substances increase the permeability of capillaries

A

histamine

bradykinin

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18
Q

4 roles of capillaries

A

Gas exchange
Thermoregulation
Regulation of blood pressure
Inflammation

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19
Q

3 classifications of capillaries plus 2 subclassifications

A

Impermeable
Continuous
Permeable (fenestrated, sinusoid)

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20
Q

How are arteries and veins classified?

A

According to their size and histological features

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21
Q

4 types of arteries

A

Large elastic arteries
Muscular arteries
Arterioles
Metarterioles

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22
Q

4 types of veins

A

Large veins
Medium and small size veins
Venules
Postcapillary venules

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23
Q

Function of muscular arteries

A

Distribute blood to organs

Help regulate blood pressure by contracting or relaxing smooth muscle

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24
Q

Location of smooth muscle in arteries

A

Media

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25
Q

Location of muscular arteries

A

Branching tree between the large elastic arteries and arterioles

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26
Q

Accompanying veins for muscular arteries

A

Medium and small size veins

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27
Q

Shape of muscular arteries

A

Circular/oval profile

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28
Q

Shape of medium and small veins

A

Irregular profile, often larger collapsed lumen

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29
Q

Muscular arteries: 3 layers of the intima

A

Endothelium (with gap and tight junctions)
Sub-endothelial layer (thin)
IELM (Internal Elastic Limiting Membrane; or internal elastica)

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30
Q

Muscular arteries: media

A

4 - 10 layers of smooth muscle cells

Collagen type III

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31
Q

Muscular arteries: adventitia

A

Dense connective tissue containing (or not) small blood vessels (vasa vasorum(

32
Q

Medium and small size veins: intima

A

Endothelium (with gap and tight junctions)
Sub-endothelial layer (thin or absent)
Poorly defined IELM

33
Q

Medium and small size veins: media

A

Incomplete layers (usually 2) of smooth muscle cells

34
Q

Medium and small size veins: adventitia

A

Dense C.T. with or without vasa vasorum

35
Q

Largest vessels of the body

A

Elastic arteries and large size veins

36
Q

Most prominent feature of large elastic arteries

A

Thick media in which elastic lamellae (fenestrated membranes) alternate with layers of smooth muscle cells

37
Q

What are the large elastic arteries?

A

Aorta

Carotid

38
Q

How many elastic lamellae in adult aorta?

39
Q

What is the effect of hypertension on the media layers of elastic arteries?

A

Number increases

40
Q

Elastic arteries: intima

A

Well developed
Endothelium: endocytic vessels, gap junctions, tight junctions
Sub-endothelial layer: thin
IELM: fenestrated (difficult to differentiate from media elastic membranes)

41
Q

Elastic arteries: media

A

Approximately 50 layers of smooth muscle cells in adults intercalated with layers of perforated elastic membranes
Rich in collagen type III and chondroitin SO4 proteoglycans

42
Q

Elastic arteries: adventitia

A

Dense connective tissue rich in elastic fibres and collagen type I
Vasa vasorum

43
Q

Purpose of alternating layers of smooth muscle and elastic fibers in elastic arteries’ media

A

Solidity and resilience of the wall since these arteries are submitted to the strong rhythmic pulsations of the heart

44
Q

Notable feature of large veins

A

Presence of valves

45
Q

Where do the valves of the large veins come from?

A

Projections of the intima

46
Q

Large veins: intima

A

Endothelium
Connective tissue
Diffuse small muscle cells
Internal elastic is undefined or absent

47
Q

Large veins: media

A

Five layers (or less) or smooth muscle cells separated by connective tissue and collagen

48
Q

Large veins: adventitia

A

Often the thickest layer.
Dense connective tissue
Vasa vasorum

49
Q

Diameter of arterioles

A

Less than 0.1 mm

50
Q

Describe the internal elastic of the arteriole intima

A

absent or fibrous

51
Q

How are functional bypasses formed?

A

When arterioles anastamose directly to venules

52
Q

What special function does the smooth muscle of metarterioles have?

A

Sphincter function (may direct blood to venules via the functional bypass)

53
Q

Major role of arterioles

A

Regulation of systemic blood pressure

54
Q

Arterioles: intima

A

Endothelium (gap and tight junctions)
Subendothelial (thin-absent)
Fibrous IELM

55
Q

Arterioles: media

A

One or two layers of smooth muscle cells may be present

56
Q

Arterioles adventitia

A

Thin without vasa vasorum

57
Q

Shape of arterioles

A

Regular shape

58
Q

Venules intima

A

Endothelium (gap and tight junctions)
Absent subendothelial layer
Absent IELM

59
Q

Venules media

A

Incomplete

Pericytes

60
Q

Venules adventitia

61
Q

Shape and diameter of venules

A

Larger diameter than arterioles, but irrgular shape

0.2 mm to 20 micrometers

62
Q

4 function categories of the endothelium

A

Permeability
Metabolic
Production of vasoactive factors
Antithrombogenic

63
Q

2 metabolic functions of the endothelium

A

Conversion of angiotensin I to angiotensin II

Inactivation of bradykinin

64
Q

2 vasoactive factors produced by the endothelium

A

Endothelins and nitric oxide

65
Q

Describe the antithrombogenic function of the endothelium

A

Desquamation of endothelial cells –> fibrin aggregation and formation of thrombi

66
Q

Describe lymphatic vessels

A

Anastomic network of vessels that start as blind tubules that converge into larger lymphatic vessels, which drain into large veins

67
Q

Function of lymphatic vessels

A

Conduct lymph

68
Q

What is lymph?

A

Plasma enriched with immunoglobulins and lymphocytes produced by lymphatic organs

69
Q

Describe the lymphatic endothelium

A

Very thin with no occluding junctions

70
Q

Describe the basement membrane of the lymphatic endothelium

A

Absent or partial

71
Q

Valves are sometimes found in lymphatic vessels. What are they made of?

A

Folds on endothelium

72
Q

Where can smooth muscle be found in terms of lymphatic vessels?

A

In the walls of large lymphatics (i.e. thoracic duct)

73
Q

Where do thoracic duct lymph vessels empty into?

A

The venous system at the junction of jugular and subclavian veins

74
Q

Define varicose veins

A

Veins whose valves cannot close completely, thus causing retrograde flow

75
Q

5 potential causes for varicose veins

A 
High BP in superficial veins from:
Obesity
Pregnancy
Lack of movement
Smoking
Genetic predisposition

Block C - Circulation (26 decks)

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