Histology of blood vessels

Question 1

What are the components of the blood vascular system?

Answer 1

elastic arteries
muscular arteries
arterioles
capillaries
postcapillary and collecting venules
muscular venules
muscular veins

Question 2

What are the three layers of blood vessels?

Answer 2

Tunica intima
Tunica media
Tunica adventitia

Question 3

What does the tunica intima consist of?

Answer 3

lining of simple squamous endothelial cells supported by a thick layer of connective tissue
bounded by the internal elastic lamina

Question 4

What does the tunica media consist of?

Answer 4

smooth muscle cells
some collagen and a variable amount of elastin
may be an external elastic lamina

Question 5

What does the tunica adventitia consist of?

Answer 5

supporting layer of dense, fibroelastic connective tissue

may contain vasa vasorum and nerves

Question 6

What are elastic arteries?

Answer 6

major distribution vessels closest to the heart

Question 7

Examples of elastic arteries

Answer 7

aorta, brachiocephalic, carotid, subclavian and pulmonary

Question 8

how do elastic arteries function?

Answer 8

elastic wall expands to receive blood expelled from the heart during systole
smooth muscle contracts
elastic recoil helps maintain blood pressure during diastole

Question 9

What is the tunica intima of elastic arteries like?

Answer 9

single layer of squamous endothelial cells
subendothelial collagenous connective tissue rich in elastin
contains fibroblasts and smooth muscle like cells

Question 10

What is the tunica media of elastic arteries like?

Answer 10

concentric fenestrated sheets of elastin separated by collagen and smooth muscle cells

Question 11

What is the tunica adventitia of elastic arteries like?

Answer 11

collagenous connective tissue

contains vasa vasorum and a plexus of autonomic nerves

Question 12

Structure of muscular arteries

Answer 12

thin tunica intima
tunica media almost entirely made of circumferential smooth muscle cells
Elastin reduced to an internal elastic lamina and sometimes less distinctive EEL

Question 13

function of tunica intima in muscular arteries

Answer 13

withstand pressure

vary lumen diam to regulate flow - smooth uscles do not contract to assist blood flow

Question 14

how can pressure that can be sustained by artery be measured

Answer 14

proportional to wall thickness / dia

Question 15

what is the structure of an arteriole like

Answer 15

tunica intima is thin and may contain IEL
tunica media less than 6 layer of smooth muscle cells
insignificant tunica adventitia

Question 16

what is the main factor in regulation of blood flow

Answer 16

control of flow through arterioles

Question 17

what happens if you halve the diameter of an arteriole

Answer 17

resistance increases by 16 fold

this is as viscous resistance to flow is inversely proportional to radius^4

Question 18

size of capillaries

Answer 18

vary from 3-4 um to 30-40 um, less than 1 mm in length

Question 19

what are large diam capillaries called

Answer 19

sinusoids

found in liver, spleen, bone marrow and some endocrine glands

Question 20

what do capillaries consist of?

Answer 20

single layer of endothelial cells

Question 21

what are the 3 types of capillaries?

Answer 21

continuous
fenestrated
discontinuous

Question 22

what are the properties of continuous capillaries?

Answer 22

tube of endothelial cells resting on a thin basal lamina
no tunica I , M OR A
adjacent endothelial cells are linked by tight junctions (permeability barriers)
embraced by pericytes

Question 23

what does permeability to substances that pass through continuous capillaries rely on?

Answer 23

tightness of tight junctions between endothelial cells
very tight - blood brain barrier
less tight in most other places

Question 24

what is the importance of pericytes that surround continuous capillaries?

Answer 24

important in the stabilisation and survival of endothelial cells

Question 25

where are fenestrated capillaries found?

Answer 25

sites where there is rapid movement of macromolecules in/out of bloodstream e.g. small intestine, kidney

Question 26

what is the structure of fenestrated capillaries?

Answer 26

luminal and basal plasma membranes of endothelial cells come together to form round windows which are around 80nm fenestrations usually closed by a diaphragm basal lamina continuous across fenestrations pericytes usually absent

Question 27

where are discontinuous capillaries found?

Answer 27

found in sinusoids of liver and spleen

Question 28

structure of discontinuous capillaries

Answer 28

large gaps between endothelial cells basal lamina also discontinuous allows free passage of large macromolecules or even RBCs

Question 29

what is micro-circulation?

Answer 29

part of circ system concerned with the exchange of gases, fluids, nutrients and waste products

Question 30

where does microcirculation occur?

Answer 30

mainly in capillaries and all active cells ,must lie within 150um of a capillary

Question 31

where do capillaries drain into?

Answer 31

post capillary venules, collecting venules and muscular venules

Question 32

how is blood flow into capillaries controlled?

Answer 32

by arterioles and pre capillary sphincters metarterioles are transitional vessels with a discontinuous layer of smooth muscle cells that regulate flow into the capillary arteriovenous shunts provide direct connections between arterial and venous systems - can bypass capillaries

Question 33

how does venous drainage occur?

Answer 33

several capillaries unite to form post-capillary venules main site for entry and exit of WBCs post capillary venules until to form collecting venules - more pericytes collecting venules drain into muscular venules (1-2 layers of smooth muscle cells)

Question 34

what are veins formed from?

Answer 34

union of muscular venules

Question 35

what is the structure of the vein?

Answer 35

recognisable tunica I,M,A TI - little more than endothelium TM- 2 layers of smooth muscle cells or more TA- broadest layer wall much thinner than artery of similar diam

Question 36

how does blood return from capillaries to the heart

Answer 36

veins - low pressure collecting system - blood flow is passive - assisted by -ve pressure within chest during inspiration - return from limbs aided by muscular contraction and compression of veins - backflow prevented by valves

Question 37

where are valves present?

Answer 37

in veins of above 2mm dia

Question 38

functions of endothelial cells

Answer 38

permeability barrier synthesise components of basal lamina synthesise materials that promote blood clotting on injury synthesise molecules that prevent inappropriate clotting secrete vasoactive factors that promote or inhibit vasodilation produce inflamm mediators produce some growth factors

Question 39

How does fluid enter the lymphatic system?

Answer 39

due to hydrostatic pressyre at the arterial end of blood capillaries, water, electrolytes and some proteins leak into extracellular space (TF) fluid drains into lymphatic vessels and then back into the blood vascular system

Question 40

where are lymphatic vessels found?

Answer 40

all tissues except - CNS, cartilage, bone, bone marrow, placenta, cornea and teeth

Question 41

properties of lymphatic vessels

Answer 41

have extremely flattened endothelial cells, basic basal lamina and lack of pericytes no RBCs backflow prevented by delicate semi lunar valves

Question 42

what is angiogenesis?

Answer 42

formation of new blood vessels from pre existing capillaries

Question 43

how do new blood vessels form - angiogenesis?

Answer 43

begins as capillary sprout involves migration and proliferation of endothelial cells, their assembly into tubes and recruitment of smooth muscle cells, pericytes and fibroblasts from arteries and veins

Question 44

Why might be a benefit of inhibition of angiogenesis?

Answer 44

attractive option for new anti cancer drugs as it is induced by tumour cells this will reduce chances of metastasis at the moment not successful as it is not isolated and angiogenesis of other blood vessels not in tumours is being prevented