Flashcards in Histology of the CVS Deck (134)
What path does the blood take around the body?
Blood is pumped from the heart to the large elastic arteries, then to the medium muscular distributing arteries. It then goes to the arterioles, then metarterioles, the capillaries. From the capillaries, a small about of blood returns to the heart via the lymphatic system, but most goes to the post capillary venules, to the medium veins, to the large veins, then back to the heart.
At what rate does blood return to the heart via the lymphatic system?
Why does most blood return to the heart by going to post capillary venules?
Because of the pressure
When is blood flow fastest?
When total cross sectional area is least, and so in the aorta
What happens as the arteries branch?
The total cross sectional area of the vascular bed increases
Where is blood flow slowest?
Capillaries, as there are many divisons
Why is blood flow being slowest at the capillaries advantageous?
Because blood needs to hand around for gas exchange
What are arteries?
Blood vessels that carry blood away from the heart to the capillary beds
What is the major artery arising from the right ventricle?
The pulmonary trunk
What happens to the pulmonary trunk?
It bifurcates into the left and right pulmonary arteries
What do the pulmonary arteries do?
Supply the lungs with deoxygenated blood
What is the major artery arising from the left ventricle?
What does the aorta do?
It courses in a posteriorly oblique arch to descent into the thoracic cavity
What arises from the arch of the aorta?
Three major arterial trunks, the brachiocephalic artery, the common carotid artery, and the left subclavian artery
How does the aorta terminate?
In the abdominal cavity it bifurcates into left and right common iliac arteries in the pelvis, near the belly button
What happens in systole?
Left ventricular contraction causes blood pressure in the aorta to rise to approx. 120mm Hg- this is systolic pressure.
What happens to the aorta under systolic pressure?
The walls of the elastic aorta stretch
What happens in diastole?
The aortic semi-lunar valve closes, and the walls of the aorta recoil. Aortic pressure drops to 70-8mmHg- this is diastolic pressure.
Why do the aortic walls relax in diastole?
To maintain pressure on the blood, moving it forwards into the small vessels
What is the result of diastolic pressure?
It is stil high, so blood is moving the whole time, meaning that it doesn’t start and stop
What do elastic arteries acting do?
Conduct blood away from the heart
Act as pressure reservoirs
What do elastic arteries act as during diastole?
Axillary pumps, giving back the elastic energy stored during systole
What types are arteries classified into?
Elastic conducting arteries
Muscular distributing arteries
What layers do the walls of arteries and veins have?
Tunica intima (next to lumen)
Tunica adventitia (outside)
What does the tunica intima consist of?
Endothelium and subendothelial layer
What do some arteries have in addition to the three layers?
Internal elastic lamina between the tunica intima and media, and an external elastic lamina between tunica media and tunica adventitia
How are the arteries and veins connected?
How do the walls of the elastic arteries appear in the fresh state?
May be yellow
Why do the walls of elastic arteries look yellow in the fresh state?
Because of abundant elastin