6.2 Blood

• Lumens are a hole in a tube
• The blood pressure in arteries is high.
• The blood pressure in veins is very low.
• The blood pressure of capillaries is low.
• Arteries have a small lumen to wall ratio.
• Veins have a large lumen to wall ratio.
• Red blood cells are biconcave which increases their surface area.
• Red blood cells don't have a nucleus to save space.
• White blood cells have a nucleus.
• Capillaries are one cell thick and can let through one red blood cell at a time.
• Oxygen, nutrients, antibodies, hormones, heat, carbon dioxide and urea are transported in the blood.
• Plasma is the liquid the dissolves or carries all other components of the blood, nutrients and wastes.