8.2 - Blood Vessels

Question 1

State and describe the 3 components of blood vessels.

Answer 1

Elastic fibres: composed of elastin, can stretch and recoil, providing vessel walls with flexibility Smooth muscle: contracts or relaxes, changing the lumen size Collagen: structural support for vessels (maintains shape

Question 2

Describe the functions of arteries.

Answer 2

• Carries bloody away from heart to body tissues - Usually carries oxygenated tissue (except pulmonary artery) AWAY from the heart umbilical artery carries fetus’s deoxygenated blood to placenta for gas exchange with mothers blood - Pressure in arteries > veins

Question 3

Describe the structure and related functions of arteries.

Answer 3

Has elastic fibres, smooth muscle, collagen - Elastic fibres enable arteries to withstand force of blood pumped from heart & stretch to take large volumes of blood - Between heart contractions - elastic fibres recoil - helps even out blood surges giving a continous flow - Artery lined with endothelium, smooth and doesn’t interrupt blood flow

Question 4

Describe the function and structure of arterioles.

Answer 4

Arterioles have more smooth muscle and less elastin than arteries - due to less pulse surge from heart - Arterioles constrict or dilate to control blood flow to organs

Question 5

Define vasoconstriction and vasodilation.

Answer 5

Vasoconstriction - when arteriole smooth muscle constricts, blood vessels constrict, stopping blood flow to capillary bed (stops heat loss) Vasodilation - when smooth muscle in arterioles relax, blood flows into the capillary bed (increasing heat loss)

Question 6

What are the structures of capillaries?

Answer 6

• Microscopic blood vessels linking arterioles to venules - Form a network through all body tissue - Small lumen - diameter of an erythrocyte - Substances exchanged through capillary walls between tissue cells and blood.

Question 7

What are the functions of capillaries?

Answer 7

• Gaps between endothelial cells (fenestrations) are large in the capillary cell wall - this is where substances pass out of the capillary wall –except in CNS where there are tight junctions within cells

Question 8

What are the adaptations of blood capillaries?

Answer 8

• Large SA for diffusion of substances into and out of the blood - Total cross-sectional area of capillaries is greater than arterioles, blood flow rate falls - Slower blood movement allows more time for diffusion - Walls are single endothelial cell thick - this shortens diffusion distance.

Question 9

What are the structures of veins and venules?

Answer 9

• Veins have no pulse as the surges are lost in capillaries –hold a large blood reservoir (60% of blood in volume at veins and venule) - Lots of collagen, little elastin, larger lumen - Have valves to stop backflow of that is blood flowing against gravity

Question 10

Explain the functions of veins and venules.

Answer 10

• Carry blood away from cells towards heart - Usually deoxygenated, except the pulmonary vein and umbilical vein (takes oxygenated blood from placenta to fetus) - Skeletal muscle contraction helps push blood back against gravity

Question 11

Give vein adaptations for blood flow back to heart.

Answer 11

When veins go back to the heart, blood pressure is too low and it is against gravity 1. Veins have 1 way valves 2. Larger veins run between big, active muscles in body When muscles contract, they give blood extra push in vein 3. Breathing movements in the chest act as pump Pressure in chest changes, squeezing actions move blood into veins of chest of abdomen towards heart