blood vessels Flashcards
what are arteries
vessels that carry blood away from the heart
what are arterioles
small blood vessels that distribute blood from an artery to the capillaries
what is a closed circulatory system
blood is held in vessels
what is an open circulatory system
blood is not held in vessels
what are veins
vessels that carry blood back to the heart
what are venules
small blood vessels that collect blood from capillaries and lead into the veins
what are blood vessels a part of
closed circulatory systems
what does tissue fluid do
bathes the tissues and cells
what can a higher pressure in blood vessels do
allow blood to flow more quickly
what is the function of blood vessels
allow more rapid delivery of oxygen and nutrients and more rapid removal of carbon dioxide and other wastes
what is transport independant of
body movements
describe the movement of blood from the heart through the different vessels and back to the heart
heart —> arteries —> arterioles —–> capillaries –> venules —> veins –> heart
where does blood flow through
a series of vessels
what is each vessel adapted for
its particular role in relation to its distance from the heart
what is the inner lining in all types of blood vessels made up of
the inner lining is made of a simple layer of cells called the endothelium
why is the endothelium smooth
to reduce friction with the flowing blood
what do arteries and arterioles carry
oxygenated blood from the heart to the body cells
which artery is the only artery that carry deoxygenated blood
the pulmonary artery carries deoxygenated blood to the lungs
what do veins and venules carry
deoxygenated blood from the bodys cell to the heart and the lungs
which vein is the only vein that carries oxygenated blood
pulmonary vein
where does gas exchange occur
capillaries
what are the main components of blood vessels
elastic fibres
collagen
lumen
smooth muscle
what is the function of the elastic fibres
made of elastin. they stretch and recoil providing the vessel with flexibility
what is the function of the smooth muscle
contracts and relaxes changing the shape of the lumen
what is the function of the collagen
provides structural support to maintain shape and volume of the blood vessel
what is the function of the arteries
carry blood away from the heart to the tissues of the body. they carry deoxygenated blood except in the pulmonary artery
what is the function of the pulmonary artery
carries dexoygenated blood from the heart to the lungs and during pregnancy
what does the umbilical artery carry
carries deoxygenated blood from the fetus to the placenta
what is blood in the arteries carried under
higher pressure than blood in veins
what do artery walls contain
elastic fibres, smooth muscle and collagen
what do the elastic fibres enable artery walls to do
withstand the force of the blood pumped out of the heart and stretch (within limits maintained by collagen) to take the larger blood volume
what happens to the artery walls in between contractions
the elastic fibres recoil and return to their original length which helps to even out the surges of blood pumped from the heart to give a continuous flow
what can you still feel when the heart contracts
a surge of blood
why is the lining of the artery smooth
so the blood easily flows over it
what is the function of the arterioles
distribute blood from an artery to the capillaries
what do the walls of the arterioles contain
a layer of smooth muscle
why do arteriole walls have more smooth muscle and elastin than arteries
they have little pulse surges
why can arterioles do to control the flow of blood into individual organs
constrict or dilate
what is vasoconstriction
when smooth muscle in the arteriole contracts, it constricts the vessel and prevents blood from flowing into a capillary bed
what is vasodilation
when the smooth muscle in the arteriole relaxes, blood flows through into the capillary bed
what can constriction of arteriole walls be useful
to divert the flow of blood to areas demanding more oxygen
what do capillaries form
an extensive network through all the tissues of the body
what is the size of the lumen of a capillary
really small that red blood cells (with a diameter of 7μm to 8μm) have to travel through in single fule
where are substances exchanged
through the capillary walls between the tissue cells and the blood
what is the size of the gaps between the endothelial cells making up the capillary walls
really large
what happens in the gaps between the endothelial walls
this is where many substances pass out of the capillaries into the fluid surrounding the cells
what is the blood entering the capillaries from the arterioles
oxygenated
what happens to the blood in teh capillaries by the time it reaches venules
it has less oxygen and more carbon dioxide (it becomes deoxygenated)
what happens to the blood in the lung and placenta capillaries
deoxygenated blood enters the capillaries and oxygenated blood leaves the capillaries
what is the size of the lumen of a capillary
5-10μm
the capillaries have a very large surface area and a very thin layer for…
.. the diffusion of substances into and out of the blood
why does the rate of blood flow fall in capillaries
total cross sectional area of the capillaries is always greater than the arteriole supplying them
what does the relatively slow movement of blood through the capillaries do
gives more time for the exchange of materials by diffusion between the blood and the cells
how thick is the capillary wall
a single endothelial cell thick
what is the function of the veins
carry blood away from the cells of the body towards the heart and carry deoxygenated blood
what is the function of the pulmonary vein and umbilical vein
the pulmonary vein carries oxygenated blood from the lungs to the heart
the umbilical vein carries oxygenated blood from the placenta to the fetus
where does deoxygenated blood flow into from the capillaries
into small veins called venules and then larger veins. it then reaches the main vessels carrying the deoxygenated blood back to the heart
what are the main vessels carrying deoxygenated blood back to the heart
the inferior vena cava from the lower parts of the body and the superior vena cava from the head and upper body
why dont veins have a pulse
the surges from the heart pumping are lost as the blood passes through the narrow capillaries
how much of your blood volume is in your veins at any one time
60%
what is the blood pressure in the veins
lower compared to the pressure in the arteries
what do medium sized veins have to prevent the back flow of blood back to the heart and prevent it flowing in the opposite direction
valves
describe the structure of veins
the walls contain a lot of collagen and little elastic fibre and the vessels have a wide lumen and a smooth thin endothelium so the blood flows easily
describe the structure of the venules
they have no elastic fibres or smooth muscle. several venules join up to one vein. they link the capillaries with the veins
why must deoxygenated blood in the veins be returned to the heart
to be pumped to the lungs and be oxygenated again
what is the functions of the valves
they act as a one way blood flow system. these are flaps or infoldings of the inner lining of the vein. when blood flows in the direction of the heart, the valves open so that blood can pass through. they close to prevent the backflow of blood`
where do many of the bigger veins run between
the big active muscles in the body
what happens when the active muscles contract
they squeeze the veins forcing the blood towards the heart
what happens as skeletal muscles relax
blood rushes back against the valves causing them to close and prevent the blood from being forced away from the heart
what happens as skeletal muscles contract
blood beyond the site of contraction is forced towards the heart opening the valves
what do valves behind the site contractions prevent
blood from being forced away from the heart
how do the breathing movements of the chest act as a pump
the pressure changes and the squeezing actions move blood in the veins of the chest and the abdomen towards the heart
how do varicose veins form
if a vein wall becomes weakened, valves may no longer close properly. this allows backflow of blood, causing the vein to become enlarged and bumpy
where do varicose veins usually occur
in superficial veins near the skin surface in the lower legs as opposed to deep veins which lie underneath muscles.
how to get rid of varicose veins
they can be surgically removed without affecting blood flow as most blood is returned to the heart by deep veins
what is blood pressure
the main force that drives blood from the heart around the body
what is systole and diastole
systole - heart contraction
diastole - heart relaxation
what happens to the blood pressure during systole
blood is pumped through the aorta and other arteries at high pressure. the elastic fibres of arteries enable them to expand and allow blood through
what happens to blood pressure during diastole
blood pressure in the arteries drops. the elastic recoil of the artery walls help force the blood on
what happens as blood moves through the different vessels
its velocity and pressure drops continuously
