NEET Biology-05 Breathing, Blood and the Kidney

Imagine being able to sort every “breathing–blood–kidney” question by logic instead of memorizing random facts. This guide walks you through the human body systems that NEET loves to test—complete with the classic traps students fall into. Start with breathing across animals: every respiratory surface must be thin, moist, and richly supplied for diffusion. Then connect the sequence from simple diffusion in sponges and flatworms to earthworm cuticle, insect tracheae (oxygen straight to tissues—no blood pigment), gills in many aquatic groups (not just fishes), and lungs in reptiles, birds, and mammals. You’ll also see why amphibians use skin and buccal lining as accessory surfaces, while humans depend on lungs alone. Next, trace air through the human tract to the alveoli, separate conducting vs exchange parts, and learn how pleura and the airtight thorax link volume to lung expansion. Breathing mechanics, spirometry values, and pressure changes become straightforward. Gas exchange is explained using partial pressures, along with hemoglobin’s oxygen dissociation curve (including the Bohr effect) and carbon dioxide transport via bicarbonate and carbonic anhydrase. You’ll also cover blood and lymph (plasma proteins, cells, clotting, ABO/Rh), heart structure and ECG basics, circulation, plus kidney function from nephron structure to countercurrent concentration, hormones (RAAS, ADH, ANF), dialysis, and key disorders—so you can answer with clarity and confidence.