3.1.2 c blood vessels Flashcards
what are the components used in the blood vessels?
elastic fibres composed of elastin that can stretch and recoil giving the walls flexibility
smooth muscle which contracts or relaxes changing the size of the lumen
collagen that provides structural support to maintain the shape and volume of the vessel
function of the arteries
carry blood away from the heart to the tissues of the body
what type of blood do they carry?
oxygenated blood except in the pulmonary artery which carries deoxygenated blood from the heart to the lung and the umbilical artery that carries deoxygenated blood from the foetus to the placenta
what do artery walls contain?
elastic fibres, smooth muscle and collagen
what do the elastic fibres allow?
enable the arteries to withstand the force of the blood pumped out of the heart and stretch to take a larger blood volume
what happens to the elastic fibres in between contractions of the heart?
the elastic fibres recoil and return to their original length which helps to even out the surges of blood pumped from the heart giving it a continuous flow
what lines the arteries?
endothelium which is smooth so blood can flow over it easily
what links the arteries and the capillaries?
arterioles
how do the arterioles compare to the arteries?
they have more smooth muscle and less elastin in their wall as they have little pulse surge but can constrict or dilate to control amount of blood flow
what happens during vasoconstriction?
smooth muscle in the arterioles contract to constrict the vessel and prevent blood flow to the capillary bed
what happens during vasodilation?
smooth muscle in the wall of the arterioles relaxes so blood can flow through into the capillary bed
what are the capillaries?
microscopic blood vessels that link the arterioles to the venules
form an extensive network through all the tissues of the body
what is the diameter of the lumen of the capillary?
7.5 to 8 micrometers
red blood cell fits through in single file
how are substances exchanged?
through the capillary walls between the tissue cells and the blood
what makes up the capillaries?
endothelial cells
how are capillaries adapted for their role?
large surface area for the diffusion of substances
walls are a single endothelial cell thick
total cross-sectional area of the capillaries is always greater than the arterioles supplying them so the rate of blood flow falls making sure the blood runs through slowly to allow time for diffusion of substances
what do veins do?
carry blood away from the cells of the body towards the heart and apart from the pulmonary vein and the umbilical vein they carry deoxygenated blood
what is the direction of flow of deoxygenated blood?
capillaries to venules to veins to the vena cava
what are the two different vena cavas and what do they do?
inferior vena cava which carries blood from the lower parts of the body
superior vena cava which carries blood from the head and upper body
