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6380747
The Circulatory System
Descrição
parts of the circulatory system
Sem etiquetas
heart
arteries
veins
biology
year 3
Mapa Mental por
Caramel Kitty
, atualizado more than 1 year ago
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Criado por
Caramel Kitty
quase 8 anos atrás
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Resumo de Recurso
The Circulatory System
Heart
blood is kept circulating throughout the body by means of a muscular pump; the heart
relaxes
fills up with blood
contracts
blood is squeezed out
blood circulates through blood vessels which direct blood flow round the body
Arteries
blood vessels that carry blood away from heart
need to be able to withstand the immense pressure of the blood as it is forced out of the heart
have thick, muscular and elastic walls
elastic layer is much thicker in arteries near the heart
elasticity enables artery wall to stretch and recoil or spring back
this helps to push the blood in spurts along the artery and also gives rise to the pulse
constricts
lumen becomes narrower & less blood flows through per unit time
dilates
lumen becomes wider & more blood flows through it per unit time
most arteries carry oxygenated blood
except pulmonary arteries
carry deoxygenated blood from heart to lungs
Arterioles
aorta -> arteries -> arterioles -> capillaries
Blood Capillaries
found between the cells of almost all tissues
have walls made up of only a single layer of flattened cells (endothelium)
endothelium is partially permeable
enables certain substances to diffuse quickly through the capillary walls
branch repeatedly
numerous branches provide a large surface area for exchange of substances between blood & tissue cells
total cross-sectional area increases when arteriole branch into capillaries
this lowers blood pressure in capillaries
flow of blood is slowed down, giving more time for exchange of substances
Venules
before the capillaries leave an organ or tissue, they unite to form small veins called venules
Veins
venules in turn join to form bigger veins
carry blood back to the heart
blood pressure in veins is much lower than in the arteries
blood flows more slowly and smoothly
walls do not need to be as thick and muscular as of those arteries of about the same size
contain less elastic tissue
semi-lunar valves
prevent blood from flowing backwards
Anexos de mídia
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