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The Heart > Histology of Blood Vessels > Flashcards

Histology of Blood Vessels Flashcards

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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
main blood vessels + brief explanation
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
26
what are the layers of vessels called?
tunics
27
three tunicas
tunica intima, tunica media and tunica adventitia
28
structure and location of tunica intima
squamous epithelium endothelium adjacent to lumen of blood vessel sub-endothelial layer of connective tissue internal elastic lamina
29
tunica intima main function
acts as a principal barrier to plasma from exiting lumen of blood vessels
30
structure of connective tissue + function
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
31
Internal elastic lamina of tunica intima structure
composed of elastin, with holes allowing the better diffusion of substances from the blood deeper into the wall
32
tunica media structure and location
middle layer, composed of concentric layers of helically arranged smooth muscle may also contain elastic fibres, elastic lamellae, reticular fibres and proteoglycans
33
what produces the non muscular components of the tunica media?
smooth muscle cells
34
what does the tunica media contain in arteries?
an external elastic lamina
35
function of tunica media
collagen provides restraint
36
Tunica adventitia structure
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
How do arteries compare to veins under a TEM ?
veins appear collapsed
38
Vasa vasorum definition
the microvasculature of large vessels
39
vasa vasorum function
formed of small arteries that enter the vessel and branch profusely serve cells located in the tunica media and adventitia with blood supply
40
which has more vasa vasorum: arteries or veins? + why?
veins- they carry deoxygenated blood, so less oxygen able to diffuse from the blood within the lumen
41
where does the tunica intima receive oxygen?
the blood carried in the vessels
42
Two different types of arteries
elastic- conducting muscular- distributing
43
where are the elastic arteries situated relative to the muscular?
elastic close to the heart, further from the heart the amount of elastin decreases and media becomes more muscular
44
examples of elastic arteries
pulmonary and aorta
45
examples of muscular arteries
include most vessels originating from the aorta, such as femoral and carotid
46
structure of elastic arteries
thick layer of elastic tissue formed of concentric layers of elastin within the tunica media
47
function of elastic arteries
make blood flow more uniform by stretching during systole and rebounding passively during diastole
48
structure of muscular arteries
thick tunica media composed of mainly smooth muscle, with up to 40 layers of cells prominent internal elastic lamina
49
when is an external elastic lamina present?
only in larger muscular arteries
50
function of muscular arteries
regulate blood pressure
51
levels of vasculature during blood flow
from artery to arteriole to capillary to venule to vein
52
2 common features of microvasculature
discontinuous smooth muscle cells- individual cells pericytes
53
what are pericytes?
multitasking cells with remarkable plasticity and range of activities-
54
functions of pericytes
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
Explain how pericytes aid wound healing
can differentiate into fibroblasts, smooth muscle cells and macrophage
56
what can a loss of pericytes cause?
vessels to become hyperdilated and haemorrhagic - lead to oedema and diabetic retinopathy
57
explain angiogenesis
normal and vital proess in growth and development, wound healing and granulation tissue fundamental step in transition from benign to malignant tumours
58
arteriole definition
smallest of arterial branches, with around three to four layers of tunica media smooth muscle
59
arteriole structure
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
function of arterioles
principal resistance vessel- control arterial blood pressure controls distribution of blood to whole capillary beds
61
what is present at the arteriole and capillary junction?
pre-capillary sphincters
62
structure and function of pre-capillary sphincters
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
what are arterioles controlled by?
sympathetic autonomic nerves
64
three different types of capillaries
continuous (most popular), fenestrated and sinusoidal
65
structure of capillaries
approximately 50 micrometres in length diameter 8-10μm squamous epithelium and pericytes
66
continuous capillary structure+ function
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
fenestrated capillaries structure and function
pores that are 60-80nm in diameter permeable to small ions and other molecules pores bridged by diaphragms formed of proteoglycans
68
sinusoidal capillaries structure and function
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
structures of capillary beds
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
How is blood pushed?
sphincters contract and relax cyclically, with 5-10 cycles per minute causing blood to pass through in a pulsatile manner
71
Where are each capillaries located?
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
What enables capillary beds to be bypassed?
arteriovenous anastomoses
73
How are veins classified?
on the basis of their diameter and wall thickness- small, medium, large and low pressure
74
Brief structure compared to arteries
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
venule structure
walls similar to capillaries- thin endothelium surrounded by reticular fibres and pericytes
76
function of venules
site of migration of neutrophils macrophages- especially during diapedesis
77
medium vein structure and function
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
large veins structure and function
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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