B3: Health and risk

Explain how mammalian lungs are adapted to efficient gas exchange (4)

• Many alveoli » provide large S.A

• Alveoli have thin walls / one-cell think » provides SHORT diffusion distancce

• Ventilation » maintains HIGH conc. gradient of gases

• Extensive / large capillary network covering alveoli » provides large S.A

• Ficks law Rate of diffusion (e.g if conc. diff or s.a increase, rate of diffusion increases + vice versa for diffusion distance)

Describe formation of atheroma which leads to atherosclerosis

1 - High blood pressure causes damage to ENDOTHELIAL lining of artery

2 - Triggers inflammatory response in artery

3 - Cholesterol + WBC accumulate on top of e/o » forming ATHEROMA

4 - Atherosclerosis occurs when Calcium SALTS + Fibrous tissue build up on top of plaque » hardening it

5 - Causes narrowing of LUMEN of artery

++ If question is applied to CVD / CHD, must say CORONARY artery not just artery.

How does Atherosclerosis act as a risk factor of CVD

• Atherosclerosis causes narrowing of LUMEN of CORONARY ARTERY

• Reducing ability of (O₂) blood flow freely from coronary artery → cardiac MUSCLE

• Less O₂ blood supplied to CARDIAC MUSCLE for aerobic resp.

• Less aerobic resp » less energy released for MUSCLE CONTRACTION to pump blood efficiently around all 4 chambers of heart MUSCLE.

+ Atherosclerosis can trigger thrombosis

Describe formation of a blood clot

1 - Damage to wall of blood vessel » collagen = exposed

2 - Collagen attracts Platelets → accumulate + cause release of thromboplastin + calcium ions

3 - Thromboplastin = enzyme catalyses conversion of prothrombin → thrombin

4 - Thrombin = enzyme catalyses conversion of soluble fibrinogen → INsoluble fibrin

5 - Fibrin forms a mesh / network of fibres (+ platelets) » TRAP RBCs + form a platelet scab

++ If smth not present e.g an enzyme like thrombin » lead to EXCESSIVE BLEEDING

++ can be reduced by taking warfarin