Structure of the blood vessels Brought to you

Structure of the blood vessels Brought to you by Brought to you by Brought to you by Brought to you by Brought to you by Brought to you by Brought to you by artery vein lumen.Structure of the blood vessels Brought to you by Brought to you by Brought to you by Brought to you by Brought to you by Brought to you by Brought to you by artery vein lumen.

Structure of the blood vessels

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artery vein

Artery with thick muscle layer

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Layers of the wall of an artery

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Comparison of artery and vein

artery

vein

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Relatively small lumen Thick muscle layer Brought to you by

Relatively large lumen Thin muscle layer Brought to you by

Artery and vein compared

Artery Vein

Semi-lunar pocket valve

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Words to use to complete the sheet describing the structure of arteries and veins

(some words may be used once, some more than once and some not at all)

HighLowPresentAbsentThinThickSqueezeNarrow

BackflowLargeSmallFrictionSmoothElasticFibresMuscles

And helps to maintain the blood flow

By controlling the diameterAlso prevents over-expansion to maintain the pressure

Anchors the vessels in the tissues

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Describe, and account for, the similarities and

differences in the structure of arteries and veins

To be done in continuous prose (no tables, no bullet points)

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Capillary networks in tissues

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Checkpoint 1.2 How the structure of an

artery, a vein and a capillary is related to the

function of the vessel.

• Refer to Fig 1.10 B

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Outer layer of connective

tissue with fibres of collagen

(a strong fibrous protein)

Thick walls containing lots of elastic fibres (made from a protein called

elastin) and smooth muscle cells

Artery.

makes the outer wall tough to

prevent over-stretching and to

protect against the pressure

exerted by other organs

rubbing against it

•Elastic fibres allow walls to stretch when blood pumped at high speed and high pressure into arteries by contraction of ventricles; elastic recoil when the pressure drops as the ventricles relax pushes the blood forward to maintain the flow and the pressure.

•The smooth muscles contract to control how far the artery stretches and so controls the diameter of the artery, which also maintains the pressure (NB

The muscles do not contract to pump the blood in the arteries!)

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No valves

The narrow lumen

helps maintain the blood

at higher pressure.

because forward blood flow is maintained by the heart and elastic recoil of the arteries.

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Vein Outer layer of connective

tissue with fibres of collagen

(a strong fibrous protein)

makes the outer wall

tough to prevent

over-stretching and to protect

against the pressure

exerted by other organs

rubbing against it

Thin walls with few elastic fibres and smooth muscle

Wide lumen

Blood flows slowly under low pressure; there is no

pulse so the walls do not need to stretch and recoil.

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Distribution of blood in the circulatory system

Has pocket valves that prevent the backflow of blood.

Blood in the vein is pushed forward by the increase in pressure

produced by the contraction of the nearby skeletal muscles which

the vein run through

When the muscles relax and stop pressing the pressure

drops and the valves prevent the blood flowing

Lie close to all cells in the body

Narrow diameter slows down blood flow

to allow time for exchange between blood and surrounding cells to take

place more efficiently

Thin walls only one cell thick

to ensure maximum rate of transfer between blood and

surrounding tissue fluid

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Atherosclerosis Light micrograph of a cross section through an artery

with mild atheroma The artery wall is pink The formation of a fatty

plaque or atheroma (grey, centre) has greatly narrowed the size of the

artery lumen (white, centre) This causes a considerable reduction in

blood flow When this occurs in the arteries leading to the heart

symptoms of angina pectoris (gripping pains in the chest) are frequently

experienced In severe cases heart attacks or strokes may occur

Atherosclerosis is principally caused by high fat diets, cigarette smoking,

obesity and inactivity

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Atheroma & thrombus

Coloured light micrograph of a

section through an artery almost

completely blocked by

atherosclerosis and a thrombus

The large red mass in the centre

is a thrombus, an abnormal blood

clot This is attached to a part of

the arterial wall that has

thickened with atheroma

(yellow-red), a fatty deposit containing

fibrous tissue, dead cells &

cholesterol Atherosclerosis is the

biggest cause of death in the UK

It causes progressive narrowing

of the arteries by deposits of

atheroma, and encourages the

formation of abnormal clots that

can block arteries Fatal

complications of atherosclerosis

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Atherosclerosis Light

micrograph of a cross section

through an artery obstructed

with an atheroma plaque The

artery (at upper left) has a

central lumen (black), where

blood flows Bordering the

lumen is a fibrous and fatty

deposit of a plaque on the

arterial wall This can be seen

as a dark grainy irregular

deposit on the inner wall

Surrounding the plaque is the

dark artery wall muscle with an

inner layer of lighter

endothelium Atherosclerosis,

the thickening of the artery

walls, is mainly due to a fatty

diet high in cholesterol This can

result in clot formation or severe

artery blockage which may lead

to heart attack

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Atheroma Cutaway illustration of

the inside of a human artery showing

fatty plaques of atheroma The artery

has three distinct layers The tunica

adventitia (outer layer) is fibroelastic

and the tunica media (middle layer)

is muscular The inner layer, the

tunica intima, is composed of a layer

of endothelial cells (large, orange)

supported by connective tissue

Atheroma (green and yellow, centre

right) is a mixture of low- density

lipoproteins, decaying muscle cells,

fibrous tissue, blood platelets and

cholesterol It has narrowed the

artery and caused thinning and

damage to the endothelial layer

(atherosclerosis)

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Heart disease Coloured 3-D computed tomography (CT) scan of the heart of sixty

year old patient with heart disease The left coronary artery (pink) is on the top of the heart, and it supplies the heart with oxygenated blood The left hand branch is the

anterior interventricular artery, which has become narrowed near the top (highlighted area) Stenosis, or narrowing, of arteries leads to reduced blood flow to the areas

served by the artery If the artery becomes completely blocked these areas die,

causing myocardial infarction, or heart attack Risk factors for stenosis include obesity, smoking, diabetes and a family history of the condition

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Coloured angiogram taken

during a percutaneous

transluminal coronary

angioplasty (PTCA) to the

right coronary artery It is

done to treat a severe

stenosis (narrowing, upper

centre left) caused by

plaques of atheroma

lining the inside of the

artery; the blood flow is

also impaired by a clot

seen in the same area just

below the stenosis

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Heart disease Coloured 3-D computed tomography (CT) scan of the heart of sixty

year old patient with heart disease The left coronary artery (pink) is on the top of the heart, and it supplies the heart with oxygenated blood The left hand branch is the

anterior interventricular artery, which has become narrowed near the top (highlighted area) Stenosis, or narrowing, of arteries leads to reduced blood flow to the areas

served by the artery If the artery becomes completely blocked these areas die, causing myocardial infarction, or heart attack Risk factors for stenosis include obesity,

smoking, diabetes and a family history of the condition

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Heart disease Coloured angiogram (X-ray) of the coronary (heart) arteries of a

patient with heart disease Coronary arteries (orange) supply the heart muscle with

oxygenated blood Stenosis (narrowing) of the blood vessels is seen at left Stenosis is

usually due to atherosclerosis, where fatty deposits of atheroma form on the inner walls

of arteries It may also be due to abnormal blood clots (thrombi) blocking part of an

artery Lack of blood to the heart muscle causes angina (severe chest pain) and can

lead to a heart attack (death of part of the heart muscle) Atherosclerosis is usually

caused by a high-cholesterol diet, but smoking and inactivity are also risk factors

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Heart bypass grafts Artwork of a heart that has had a blockage of the coronary

arteries treated by coronary artery bypass graft (CABG) surgery The coronary arteries are the smallblood vessels seen running over the outer surface of the heart They

supply oxygenated blood to keep the heart muscle pumping, and a blockage can cause

a fatal heart attack The solution is to harvest arteries from elsewhere in the body and use them to bypass the blockage Three grafts are seen running from the aorta, the main body artery, back to the coronary arteries, secured by sutures (black) Three

grafts makes this a triple bypass operation, indicating an advanced state of heart

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