8.2 Blood Vessels

Question 1

Different components used in blood vessels

Answer 1

Elastic fibres - composed of elastin, can stretch and recoil and provide vessel walls with flexibility
Smooth muscle - contracts or relaxes to change size of the lumen
Collagen - provides structural support to maintain shape and volume of the vessel

Question 2

Artery

Answer 2

Carry blood away from the heart at high pressure

Question 3

What type of blood do arteries usually carry?

Answer 3

Oxygenated blood, except the pulmonary artery and during pregnancy, umbilical artery

Question 4

Artery walls

Answer 4

Tunica externa - made of collagen, tough to resist pressure, fibrous
Tunica medica - smooth muscle and elastic fibres, allow stretch and recoil of vessel, to absorb pressure changes and push blood along
Tunica intima - endothelium, smooth & flat cells (squamous epithelium) to reduce friction
Narrow lumen - maintain pressure

Question 5

Arterioles

Answer 5

Link arteries and capillaries
More smooth muscle and less elastin in wall than arteries
Can constrict or dilate to control blood flow to specific organs

Question 6

How do arterioles alter blood flow to certain organs?

Answer 6

Smooth muscle in arteriole contracts, to constrict the vessel, prevent blood flow to capillary bed (vasoconstriction)
When smooth muscle relaxes, blood flows through the capillary bed - vasodilation

Question 7

What is an aneurysm?

Answer 7

A bulge or weakness in a blood vessel

Question 8

Capillaries

Answer 8

Blood vessels that link arterioles with venules and form an extensive network through all the tissues of the body

Question 9

Capillaries adaptations for job

Answer 9

Provide a large surface area for diffusion of substances into and out of the blood
Total cross sectional area of the capillaries is always greater than the arteriole supplying them, so rate of blood flow falls. Slower movement of blood means there is more time for materials to be exchanged by diffusion.
The walls are a single endothelial cell thick, giving a very thin layer for diffusion.

Question 10

Veins

Answer 10

Carry blood towards the heart at a lower pressure and have semi lunar valves to keep blood flowing in one direction

Question 11

What type of blood do veins carry?

Answer 11

Usually deoxygenated blood, apart from the pulmonary vein and in pregnancy the umbilical vein

Question 12

How does blood reach the veins?

Answer 12

Deoxygenated blood flows from the capillaries into venules and then larger veins. Finally, it reaches the two main vessels heading towards the heart (inferior and superior vena cava)

Question 13

Vein walls

Answer 13

Tunica externa - made of collagen, fibrous and tough
Tunica media - less smooth muscle and elastic fibres, as they don’t need to withstand high pressure and fluctuations
Tunica intima - endothelium, with smooth and flat cells
Wider lumen - eases blood flow back to the heart at low pressure

Question 14

Venules

Answer 14

Link capillaries with veins
They have very thin walls and little smooth muscle
Many venules join to form a vein

Question 15

Adaptations to move blood against the force of gravity

Answer 15

Majority of veins have one way valves - when flowing towards the heart, the valve opens, so blood flows through, if in the opposite direction, it closes
Bigger veins run between big, active muscles in the body. When muscles contract, they squeeze the veins, forcing blood towards the heart
Breathing movements of the chest act as a pump. Pressure changes and the squeezing actions move blood in the veins of the chest and the abdomen towards the heart