blood vessels Flashcards
how many liters of blood is in each human
5 litres
what happens when the heart beats
150 millitres of blood is pumped out of it and carried to different parts of the body by means of the blood vessels
how many types of blood vessels are there
3 types
name the three types of blood vessels
arteries ,veins , capillaries
how are arterioles formed
as the artery goes further away from the heart ,it branches again and again ,the muscle becomes thinner and thinner and the blood vessels become narrower and narrower the narrow branches of artery are called arterioles
how are capillaries formed
arterioles branch again until they form very tiny vessels called capillaries
can capillaries be seen with the naked eye
no, the are microscopic
what are capillaries made up of
a single layer of endothelial cells
what is the function of capillaries
allows oxygen and nutrients such as glucose to diffuse from the blood into the tissues ,carbon dioxide and other excretory wastes can diffuse from the tissues into the blood in the capillaries
how are venules formed
the capillaries join to form venules
how are veins formed
venules join to form veins
why is the middle muscular layer of veins much thinner than those found in arteries
the blood within the arteries are in great pressure .in the veins the blood is no longer under pressure since it lost its pressure at the capillaries
why is it a problem that the blood in the veins are not under pressure
there is not enough pressure to take the blood back to the heart and blood may flow back to the capillaries
what solution is there for the blood in the veins that are not under pressure
muscular movement (walking and running ) cause the blood in the veins to be squeezed towards the heart .
semi lunar valves like those found in the heart are found in intervals along the veins to prevent the blood from flowing back into the capillaries
