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Why do multi-cellular organisms need exchange surfaces and a transport system?
They have a small surface area to volume ratio, so diffusion is insufficient to provide all cells with the required oxygen and nutrients, and to remove all waste products. Exchange surfaces increase the rate of diffusion by shortening diffusion disctance
What substances need to be transported into and out of the body?
Oxygen, carbon dioxide, water, dissolved food molecules, urea
How are alveoli adapted for gas exchange?
Large surface area: increased rate of diffusion as more molecules can diffuse through
Good capillary network: provides a good blood supply for molecules to move into and out of, creating a high concentration gradient
Thin walls: short diffusion distance (1 cell thick)
Moisture: enables gases to dissolve
What factors affect the rate of diffusion?
Diffusion distance, concentration gradient, surface area
What is Fick’s Law?
Rate of diffusion=(surface areaxconcentration gradient)/thickness of membrane
What are the components of the blood?
Red blood cells, white blood cells, plasma, platelets
How are red blood cells adapted to their function?
Biconcave disk shape: creates a larger surface area, increasing rate of diffusion
No nucleus: allows more space for oxygen to be carried
Small and flexible shape: can squeeze through capillaries
Haemoglobin: a red pigment that binds to oxygen to allow the red blood cell to carry more oxygen
What is the function of white blood cells?
Providing immunological protection
How are white blood cells adapted to their function?
Phagocytes: engulf and digest pathogens by phagocytosis
Lymphocytes: produce antibodies and antitoxins
What is the function of platelets?
Forming blood clots
What is the function of the plasma?
Contains most of the blood’s components (proteins, waste products, hormones)
How is plasma adapted to its function?
Mainly made of water: acts as a solvent to transport materials around the body
What types of blood vessels are there?
Arteries, capillaries, veins
What is the role of the arteries?
Carry oxygenated blood away from the heart
How are the arteries adapted to their function?
Narrow lumen: maintains high pressure
Thick muscular wall: provides strength to withstand pressure
Elastic fibres: can stretch and recoil
No valves
Smooth inner lining: reduces friction
What is the function of veins?
Carry deoxygenated blood towards the heart
How are the veins adapted to their function?
Large lumen to create less pressure, thin walls and valves to prevent the back flow of blood
What is the function of capillaries?
Allows the exchange of materials at tissues
How are the capillaries adapted to their function?
Large network to create a greater surface area for diffusion, once cell thick so a shorter diffusion distance, and permeable walls to allow the exchange of substances
What are the two circuits making up the circulatory system?
Pulmonary and systemic
What is the pulmonary circuit?
Deoxygenated blood is transported to the lungs. Gas exchange happens, oxygenating the blood. Blood returns to the left side of the heart
What is the systemic circuit?
Oxygenated blood is pumped to tissues and organs. Exchange of materials occurs. Deoxygenated blood returns to the right side of the heart
Describe the pathway of blood around the body
Pulmonary vein, left atrium, left ventricle, aorta, body, vena cava, right atrium, right ventricle, pulmonary artery, lungs
Why is the left ventricle thicker than the right ventricle?
It pumps blood a further distance (to the whole body, not just the lungs) so a greater force and muscle mass is needed
