▶️ Answer/Explanation
(a)(i)
The correct identifications based on wall thickness and lumen size are:
• Row X: Vein (Thin wall, large lumen)
• Row Y: Capillary (Very thin wall, very narrow lumen)
• Row Z: Artery (Thick wall, narrow lumen)
(a)(ii)
• Name: Valves
• Function: To ensure the one-way flow of blood (prevent backflow). Veins carry blood at low pressure, often against gravity, so valves are necessary to keep blood moving towards the heart.
(b)
• organ A: Lungs (Blood flows from the heart to the lungs via the pulmonary artery and returns via the pulmonary vein).
• organ B: Heart (The central pump of the circulatory system).
• blood vessel C: Aorta (The main artery carrying oxygenated blood from the heart to the rest of the body).
• blood vessel D: Renal vein (The vessel carrying deoxygenated blood away from the kidney back towards the heart).
(c)
Any two of the following:
• Urea
• Excess water
• Excess ions (or salts)
(d)
Any two valid organ systems other than circulatory or digestive, such as:
• Nervous system
• Respiratory system (or gas exchange system)
• Reproductive system
• Excretory system
• Endocrine system