Sample Answer

Evaluation Statement

• The respiratory and circulatory systems work together highly effectively to deliver oxygen during exercise.
• Evaluation based on structural efficiency and functional coordination.

Structural Efficiency

• The systems demonstrate optimal structural design for oxygen delivery.
• Alveoli provide extensive surface area with walls only one cell thick.
• Capillary networks create minimal diffusion distances in muscles.
• Heart chambers and valves maintain unidirectional flow despite rapid rates.
• Evidence indicates these structures strongly meet oxygen delivery requirements.
• The thin barriers and vast surface areas ensure rapid gas exchange.
• This criterion shows superior structural adaptation for exercise demands.

Functional Coordination

• Both systems synchronise responses to match oxygen supply with demand.
• Breathing rate increases significantly during exercise to maximise oxygen intake.
• Cardiac output rises dramatically through heart rate and stroke volume changes.
• Blood flow redistribution prioritises active muscles over non-essential organs.
• The evidence demonstrates highly effective functional integration.
• Systems adjust proportionally to exercise intensity without lag time.
• This coordination strongly fulfils oxygen delivery requirements.

Final Evaluation

• Weighing both criteria confirms highly effective oxygen delivery during exercise.
• Structural features enable maximum diffusion while functional coordination ensures precise matching.
• Minor limitations exist only at extreme exercise intensities.
• The systems’ integrated design optimally supports human movement performance.

Sample Answer

Overview Statement

• Blood vessels demonstrate perfect structure-function relationships throughout the cardiovascular system.
• Components include arteries, arterioles, capillaries, and veins, each with unique structural adaptations.
• These adaptations enable specific functions from high-pressure transport to efficient gas exchange.

Arteries and High-Pressure Transport

• Arterial walls contain three thick layers with elastic tissue and smooth muscle, which enables high-pressure blood transport.
• Elastic recoil maintains blood pressure between heartbeats, ensuring continuous flow to tissues.
• Thick walls resist the force of blood pumped from the heart at high pressure.
• Such structural strength prevents arterial damage while maintaining efficient circulation.

Arterioles and Flow Control

• Arterioles possess pronounced smooth muscle layers, allowing precise blood flow control.
• Constriction and dilation redirect blood based on tissue metabolic demands.
• During exercise, arterioles to muscles dilate while others constrict, optimising oxygen delivery.
• Flow regulation demonstrates how structure enables dynamic circulatory responses.

Capillaries and Exchange Efficiency

• Single-cell endothelial walls maximise diffusion efficiency between blood and tissues.
• Minimal thickness combined with slow blood flow creates optimal exchange conditions.
• Extensive branching provides enormous surface area for gas and nutrient transfer.
• Exchange effectiveness depends on the interplay between wall structure and flow rate.

Veins and Blood Return

• Thinner walls with larger lumens accommodate low-pressure blood storage and return.
• One-way valves compensate for reduced wall strength by preventing backflow.
• Wall flexibility allows expansion to store blood when needed.
• Valve placement ensures upward blood flow against gravity.

• Nasal hairs and mucus in the nasal cavity trap large particles and pathogens, which prevents them from entering the lungs.
• The reason for this is the sticky mucus captures debris while hairs act as a physical barrier.
• Blood vessels in the nasal cavity warm incoming air, therefore protecting delicate lung tissue from cold shock.
• The pharynx contains tonsils with lymphoid tissue that identify and destroy pathogens, consequently reducing infection risk.
• These structures work by white blood cells within tonsils actively attacking bacteria and viruses before they reach lower airways.
• The trachea and bronchi contain cilia and mucus-producing cells that function together to move trapped particles upward.
• This mechanism operates via rhythmic ciliary beating, which ensures particles are expelled before reaching alveoli.
• As a result, multiple protective structures create a comprehensive defence system for the lungs.

Sample Answer

• The heart has four chambers: two upper atria that receive blood and two lower ventricles that pump blood.
• The right atrium receives deoxygenated blood from the body via the vena cavae.
• The right ventricle pumps deoxygenated blood to the lungs via the pulmonary artery.
• The left atrium receives oxygenated blood from the lungs via the pulmonary veins.
• The left ventricle pumps oxygenated blood to the body via the aorta.
• Four one-way valves prevent backflow: atrioventricular valves between atria and ventricles, and arterial valves at vessel exits.

Sample Answer

• Alveoli are tiny air sacs located at the end of bronchioles in the lungs.
• They have extremely thin walls (one cell thick) that enable gases to diffuse easily.
• They are surrounded by an extensive network of capillaries, which creates a large surface area for gas exchange.
• The close proximity between alveoli and capillaries results in a short diffusion distance for gases, allowing rapid oxygen and carbon dioxide exchange.

\(D\)

\(B\)