the structure and function of arteries, capillaries and veins 2.5 Flashcards
what does the cardiovascular system consist of
the heart, blood vessels and the blood which they contain
function of the cardiovascular system
to exchange substances between different structures in the body and to exchange substances between the body and its environment
where does oxygenated blood go
leaves the heart through arteries which branch off into capillaries
what happens to the pressure of blood as it moves away from the heart
decreases
what is the central cavity of blood vessels lined with
a layer of cells called the endothelium
what surrounds the endothelium in the blood vessel central cavity
layers of tissue which varies in composition on which blood vessels it’s found in
arteries
-carry blood away from the heart at a high pressure
-thick walls and relatively narrow lumen
-the outer layer of connective tissue contains elastic fibres and the inner layer (thick muscular wall) contains smooth muscle with more elastic fibres
-when the heart contracts, surges of high pressure blood move into the arteries
-the elastic walls of the arteries stretch and recoil to accommodate the surge in blood after each contraction of the heart (this can be felt as a pulse)
-these fibres recoil between beats, so maintaining the high pressure of blood in arteries
vasoconstriction
the control blood flow the smooth muscle surrounding arteries can contract
vasodilation
the control blood flow the smooth muscle surrounding arteries can relax
veins
-carry blood back to the heart at a low pressure
-thin walls and a wider lumen
-have an outer layer of connective tissue containing elastic fibres but a much thinner inner muscular wall than arteries containing smooth muscle with more elastic fibres
-have valves that prevent the back flow of blood as blood is moving out at a low pressure and generally against gravity
capillaries
-allow exchange of substances to occur between the blood and tissues
-have a lumen and very thing walls (only a one cell thick endothelium) which allows efficient exchange
what is blood made up of
red blood cells, white blood cells and platelets bathed in plasma
what is plasma
a watery yellow fluid that contains many dissolved substances
-glucose
-amino acids
-respiratory gases
-plasma proteins
capillary beds
when blood is carried to the tissue in arteries which divide into many arteriols they then divide again into a capillary network/ bed
where do capillary networks run
inbetween cells of the body tissues
pressure filtration
-blood in the arteriols is at a higher pressure than blood in the capillaries the blood reaches the capillaries it causes pressure filtration
-this forces plasma out of the capillaries and into the space which surrounds tissues and cells
-plasma is now called tissue fluid and it bathed the cells
-since every cell in the body is close to a blood capillary it is surrounded by tissue fluid
tissue fluid
-tissue fluid doesn’t contain plasma proteins as they’re too big to fit through the membrane
-it contains high concentrations of glucose and oxygen which diffuse into cells
-waste products such as carbon dioxide and waste substances such as urea diffuse out of cells into the tissue fluid
-most tissue fluid returns to the capillaries by diffuse and osmosis
-excess tissue fluid enters lymph vessels and passes into the lymphatic system and is now called lymph
lymph vessels
-have think walls and valves
-lymphatic vessels absorb excess tissue fluid and return the lymph fluid to the circulatory system
