General overview (exchange and transport in animals)

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