L.8, 12 Blood vessels histology

Question 1

What is vein valve structure and purpose

Answer 1

The valves are bicuspid folds of tunica intima. Thus not robust but are used to prevent backflow. When walking, the venous valves break the column of blood into short segments and skeletal muscle around the veins compress them and propels blood back to the heart.

Question 2

How do you test for venous thrombosis

Answer 2

compression test on ultrasound: If there is no blood in the lumen of a vein due to a blockage, then lumen will collapse during compression.

Question 3

How do varicose veins happen

Answer 3

Superficial veins stretch and their valve cusps no longer meet, so they become incompetent. The veins become dilated, swollen and tortuous. Stasis can result in venous ulcers

Question 4

How does blood pressure change across the blood vessels

Answer 4

Starts off mean 95 and only goes down 10 in the muscular arteries then biggest drop in the arterioles to 35.
In the capillaries go to 15 then goes down to 0-2 in the right atrium.

Question 5

How does blood vessel structure relate to how much blood it contains?

Answer 5

While the diameter of each type decreases individually down the vessels, the cross sectional area is getting bigger. There is also more blood in the venous system due to low pressures and distensible vessels.

Question 6

What is dissecting aneurysm - commonly in carotid or aorta

Answer 6

Due to a focal weakness in the vessel wall, blood under pressure accumulates in between the intima and the media, forming a false channel. This channel is extended due to low resistance and can lead to rupture.

Question 7

What is the relationship between blood velocity and cross sectional area

Answer 7

There is an inverse relationship: eg. in the capillaries there is maximal cross sectional area and minimal flow rate