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The Heart > Histology of Blood Vessels > Flashcards

Histology of Blood Vessels Flashcards

1
Q

What does the composition of blood vessels depend upon?

A

mechanical factors- such as blood pressure and metabolic factors reflecting the local needs of tissues

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2
Q

What structure do all blood vessels have?

A

Endothelium

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3
Q

Endothelium definition

A

A specialised epithelium that acts as a semi-permeable barrier between two major internal compartments, the blood and interstitial fluid

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4
Q

Structure of endothelial cell epithelium

A

squamous, polygonal and elongated, with the long axis in the direction of blood flow

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5
Q

Endothelium functions

A

nonthrombogenic surface, vascular tone and blood flow, inflammation and local immune response, growth, strength

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6
Q

Explain nonthrombogenic surface

A

actively secrete agents that control local clot formation- such as heparin, von Willebrand agent and tissue plasminogen activator. Prevents blood from clotting

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7
Q

explain the control of vascular tone and blood flow

A

secrete various factors that stimulate smooth muscle contraction, such as endothelin-1, NO and angiotensinconverting enzyme

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8
Q

explain inflammation and local immune responses

A

Endothelial cells in venules induce specific white cells to stop and undergo transendothelial migration at sites of injury or infection. Under those conditions, p-selectin is expressed rapidly.

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9
Q

Explain growth

A

secrete various growth factors that include inducing the proliferation of immune cells and cells that make up the vascular wall

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10
Q

explain strength

A

secretes collagen

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11
Q

Important growth factor and function

A

VEGF- vascular endothelial growth factor

stimulates formation of vascular system from embryonic mesenchyme (vasculogenesis) and angiogenesis

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12
Q

What enzyme is present + function?

A

membrane bound angitoensin converting enzyme ACE- converts angiotensin 1 to angiotensin 11, which is a vasoconstrictor

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13
Q

Functions of blood vessels

A

O2 delivery, CO2 removal

nutrient delivery and waste removal

delivery of hormone signals to tissues

regulate blood flow, with specialised functions in certain tissues such as kidneys

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14
Q

Two components of the circulatory system

A

lymphatic system and blood vessels

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15
Q

lymphatic system function

A

collects lymph (extracellular tissue fluid) and delivers it back to he cardiovascular system

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16
Q

macrovascular definition

A

vessels that are greater than 0.1mm in diameter, such as arteries and veins

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17
Q

microvascular definition

A

vessels that are less than 0.1mm in diameter, such as arterioles, venules and capillaries

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18
Q

2 different circuits and their passage

A

pulmonary- carries blood to and from the lungs

systemic circuit- carries blood to and from the organs and tissues of the body

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19
Q

what is an exception to this?

A

A portal system

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20
Q

portal system definition

A

blood carried from one site to another without directly involving the heart

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21
Q

2 examples of portal systems

A

hepatic portal system- gastrointestinal tract to liver- through the hepatic portal vein

hypothalamic-pituitary portal system- hypothalmus to anterior pituitary

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22
Q

Explain how blood flows through a portal system

A

occurs when a capillary bed pools into another capillary bed through veins, without first going to the heart.

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23
Q

How is the hepatic portal vein formed?

A

From the superior mesenteric vein and the splenic vein

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24
Q

resistance and pressure in both ciruits

A

pulmonary- low resistance, low pressure

systemic- high resistance, high pressure

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25
Q

main blood vessels + brief explanation

A

arteries- thick walled vessels that transport blood away from the heart, branch into smaller and smaller arterioles

capillaries- thin walled vessels that form capillary beds where substances pass between blood and tissue

veins- drain capillary beds- venules. Form larger and larger blood vessels that lead back to the heart, also have pocket valves

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26
Q

what are the layers of vessels called?

A

tunics

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27
Q

three tunicas

A

tunica intima, tunica media and tunica adventitia

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28
Q

structure and location of tunica intima

A

squamous epithelium endothelium adjacent to lumen of blood vessel

sub-endothelial layer of connective tissue

internal elastic lamina

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29
Q

tunica intima main function

A

acts as a principal barrier to plasma from exiting lumen of blood vessels

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30
Q

structure of connective tissue + function

A

collagen fibres in subendothelial layer

elastic fibres provide the resiliency required for the vascular wall to expand under pressure

various levels of proteoglycans and hyaluronates dependent on vessel function

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31
Q

Internal elastic lamina of tunica intima structure

A

composed of elastin, with holes allowing the better diffusion of substances from the blood deeper into the wall

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32
Q

tunica media structure and location

A

middle layer, composed of concentric layers of helically arranged smooth muscle

may also contain elastic fibres, elastic lamellae, reticular fibres and proteoglycans

33
Q

what produces the non muscular components of the tunica media?

A

smooth muscle cells

34
Q

what does the tunica media contain in arteries?

A

an external elastic lamina

35
Q

function of tunica media

A

collagen provides restraint

36
Q

Tunica adventitia structure

A

fibroelastic connective tissue comprised predominantly of type-1 collagen, small blood vessels and elastic fibres

arranged longitudinally with adipose tissue
adventitia is continuous with and bound to the stroma of the organ through which the blood vessels run

autonomic nerve fibres synapse, vasomotor nerves, that release vasoconstrictor norepinephrine

37
Q

How do arteries compare to veins under a TEM ?

A

veins appear collapsed

38
Q

Vasa vasorum definition

A

the microvasculature of large vessels

39
Q

vasa vasorum function

A

formed of small arteries that enter the vessel and branch profusely

serve cells located in the tunica media and adventitia with blood supply

40
Q

which has more vasa vasorum: arteries or veins? + why?

A

veins- they carry deoxygenated blood, so less oxygen able to diffuse from the blood within the lumen

41
Q

where does the tunica intima receive oxygen?

A

the blood carried in the vessels

42
Q

Two different types of arteries

A

elastic- conducting

muscular- distributing

43
Q

where are the elastic arteries situated relative to the muscular?

A

elastic close to the heart, further from the heart the amount of elastin decreases and media becomes more muscular

44
Q

examples of elastic arteries

A

pulmonary and aorta

45
Q

examples of muscular arteries

A

include most vessels originating from the aorta, such as femoral and carotid

46
Q

structure of elastic arteries

A

thick layer of elastic tissue formed of concentric layers of elastin within the tunica media

47
Q

function of elastic arteries

A

make blood flow more uniform by stretching during systole and rebounding passively during diastole

48
Q

structure of muscular arteries

A

thick tunica media composed of mainly smooth muscle, with up to 40 layers of cells

prominent internal elastic lamina

49
Q

when is an external elastic lamina present?

A

only in larger muscular arteries

50
Q

function of muscular arteries

A

regulate blood pressure

51
Q

levels of vasculature during blood flow

A

from artery to arteriole to capillary to venule to vein

52
Q

2 common features of microvasculature

A

discontinuous smooth muscle cells- individual cells

pericytes

53
Q

what are pericytes?

A

multitasking cells with remarkable plasticity and range of activities-

54
Q

functions of pericytes

A

support blood vessels, regulate vascular tone and tissue perfusion, act as macrophage like scavangers

detect that blood is not going through the vessel which leads to their strangulation

angiogenesis, wound healing

55
Q

Explain how pericytes aid wound healing

A

can differentiate into fibroblasts, smooth muscle cells and macrophage

56
Q

what can a loss of pericytes cause?

A

vessels to become hyperdilated and haemorrhagic - lead to oedema and diabetic retinopathy

57
Q

explain angiogenesis

A

normal and vital proess in growth and development, wound healing and granulation tissue

fundamental step in transition from benign to malignant tumours

58
Q

arteriole definition

A

smallest of arterial branches, with around three to four layers of tunica media smooth muscle

59
Q

arteriole structure

A

lumen often less than 0.1mm in diameter, lumen as wide as the wall is thick

subendothelial layer is very thick, elastic laminae are absent

very thin adventitia

60
Q

function of arterioles

A

principal resistance vessel- control arterial blood pressure

controls distribution of blood to whole capillary beds

61
Q

what is present at the arteriole and capillary junction?

A

pre-capillary sphincters

62
Q

structure and function of pre-capillary sphincters

A

a ring of muscle surrounding the blood vessel

controls the dilation and constriction of resistance vessels and can effectively open or close the capillary, thus facilitating shunting

63
Q

what are arterioles controlled by?

A

sympathetic autonomic nerves

64
Q

three different types of capillaries

A

continuous (most popular), fenestrated and sinusoidal

65
Q

structure of capillaries

A

approximately 50 micrometres in length

diameter 8-10μm

squamous epithelium and pericytes

66
Q

continuous capillary structure+ function

A

have junctional complexes, tight junctions to control trans-endothelial transport

prevent passage of many molecules

substances may move across by active transport

important in blood brain barrier

67
Q

fenestrated capillaries structure and function

A

pores that are 60-80nm in diameter

permeable to small ions and other molecules

pores bridged by diaphragms formed of proteoglycans

68
Q

sinusoidal capillaries structure and function

A

large pores that are not linked to diaphragms

enhances exchange between blood and tissue

allows leukocytes to pass between organs where they are produced to mature and to mediate a response in the tissues

irregular channels conforming to a shape of structure in which they are located

highly discontinuous basement membrane

large diameter 30-40 μm which slows blood flow

69
Q

structures of capillary beds

A

supplied by terminal arteriole branches called metarterioles

metarterioles are continuous thoroughfare channels connected with postcapillary venules

the metarteriole smooth muscles act as precapillary sphincters

70
Q

How is blood pushed?

A

sphincters contract and relax cyclically, with 5-10 cycles per minute causing blood to pass through in a pulsatile manner

71
Q

Where are each capillaries located?

A

continuous- connective tissue, lungs, exocrine glands and nervous tissue

fenestrated- found in organs with rapid exchange of materials- kidneys, intestine, choroid plexus

sinusoidal- liver, spleen and some endocrine organs and bone marrow

72
Q

What enables capillary beds to be bypassed?

A

arteriovenous anastomoses

73
Q

How are veins classified?

A

on the basis of their diameter and wall thickness- small, medium, large and low pressure

74
Q

Brief structure compared to arteries

A

same 3 layers as arteries but elastic not as well developed

connective tissue more pronounced

boundary between tunica media and intima not clear

medium sized veins have valves

75
Q

venule structure

A

walls similar to capillaries- thin endothelium surrounded by reticular fibres and pericytes

76
Q

function of venules

A

site of migration of neutrophils macrophages- especially during diapedesis

77
Q

medium vein structure and function

A

less than 1cm in diameter

smooth muscle cells of tunica media are loosely organised with collagen fibres and fibroblasts

tunica adventitia is the thickest of the tunicas

78
Q

large veins structure and function

A

low pressure, high capacitance system

have pocket valves to prevent back flow

thin tunica media

few have a well developed smooth muscle layer

superficial veins have well developed muscle to resist distention caused by gravity

well developed tunica adventitia

The Heart (11 decks)

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