8c – The circulatory system

Question 1

circulatory system

Answer 1

• an organ system that allows blood to circulate and transport nutrients, oxygen, CO2, hormones and blood cells around the body.
• consists of the heart, arteries, veins, capillaries and blood.

Question 2

arteries

Answer 2

• Carries blood away from the heart to the rest of the body.
  Every beat, the heart squirts high pressure blood into arteries.
• They are adapted by having thick walls to withstand the sudden high pressures. A wave of stretching then passes along the walls, called a pulse.
• Thick cell walls, narrow lumen.

Question 3

veins

Answer 3

• Carries blood back to the heart from the rest of the body.
• Thin walls and wide lumen since the blood is flowing under much less pressure.
• Muscles in skeleton help move blood along veins.
• Valves prevent blood from flowing the wrong direction.

Question 4

capillaries

Answer 4

• Arteries divide into narrow capillaries, connects arteries and veins.
• Cell wall is very thin (one cell) to allow faster diffusion of substances.

Question 5

capillaries

*A mixture of RBC’s, WBC’s, plasma and platelets.

Answer 5

• Erythrocytes (RBC’s) are hollow, disc shaped cells with no nucleus that contain haemoglobin, which binds to oxygen in the lungs and releases it into tissues. Lots of oxygen = bright red, less oxygen = dark red.
• White blood cells (WBC’s) are a wide range of cells, part of the immune system that help fight pathogens from the body.
• Platelets are tiny fragments of cells with no nucleus that produce substances needed to clot blood at the site of an injury (E.g. cut skin).
• Plasma is a pale yellow coloured liquid which suspends all cells and dissolved substances.