the circulatory system Flashcards
(32 cards)
What does the circulatory system consist of?
The heart and blood vessels
What type of circulatory system is there in mammals?
Double circulatory system
What are the three different blood vessels?
Arteries, veins, capillaries
Which blood vessel carries blood under a high pressure?
Arteries
When does resistance to the flow increase?
As the blood flows into the arterioles and capillary beds
What does this cause?
Blood pressure and rate of flow to fall
Which blood vessel takes the blood into the heart at a low pressure?
Veins
Which is the main artery?
The aorta
What do the walls of arteries have?
A large amount of elastic tissue
What happens to the aorta when the left ventricle contracts?
It stretches
What happens to the aorta when the left ventricle relaxes?
It recoils
What do elastic tissues not do?
Contract and relax
Is the artery lumen bigger or smaller than the vein’s lumen?
Smaller
Is the artery wall thicker or thinner than a vein’s wall?
Thicker
Which are the only arteries to have valves?
Aorta and pulmonary artery
What type of blood do all arteries (except the pulmonary artery) carry?
Oxygenated blood
What do the arteries closer to the heart possess?
A higher ratio of elastic fibres to smooth muscle fibres
What do arterioles possess a higher proportion of?
Smooth muscle than elastic fibres
What can arterioles control?
The flow of blood to different tissues and organs
What is vasodilation?
Relaxation of the smooth muscle causes widening of the arteriole increasing blood flow
What is vasoconstriction?
Contraction of the smooth muscle causes narrowing of the arteriole reducing blood flow
How is venous return achieved?
Contraction of the skeletal muscles that surround veins, they compress the veins and push the blood along
What type of valves do veins have?
Semi-lunar
What is the role of these valves?
Prevent the backflow of blood
