4.4 Circulation

Question 1

Describe the function and structure of arteries

Answer 1

carry oxygenated blood away from the heart towards cells except:
- pulmonary artery = carry deox blood from heart to lungs
- umbilical artery = carries deox blood from fetus to placenta

+ external layer of tough tissue

+ middle layers contain elastic fibers and smooth muscle

+ smooth lining allows easiest blood flow

+ small lumen when unstretched by blood flow

Question 2

Describe the function and structure of veins

Answer 2

carry deoxygenated blood back towards heart except:
- pulmonary vein = carry ox blood from lungs back to heart for circulation
- umbilical vein = carry ox blood from placenta to fetus

+ outer tough layer - made of collagen fibres
+ relatively thin layer of smooth muscle with few elastic fibres
+ smooth inner surface
+ relatively large lumen

Question 3

Describe the function and structure of capillaries

Answer 3

minute vessels (no smaller than a red blood cell) that spread throughout tissues of the body
branch between cells so substances can diffuse between cells and the blood quickly

+ very thin walls, no elastic fibres, smooth muscles or collagen

+ oxygen and food molecules quickly diffuse out of blood in the capillaries into nearby body cells

+ carbon dioxide and waste molecules diffuse in

Question 4

Describe the structure of the heart

Answer 4

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