Fish

Gills
Breathing organ diagram GILLS Feathery lamellae absorb O₂ OPERCULUM Bony flap covers & protects gills MOUTH Water enters, flows over gills WATER FLOW Mouth in → operculum out NOSTRILS Air enters for lung breathing BUCCAL CAVITY Throat pumps air to lungs MOIST SKIN Cutaneous respiration LUNGS Simple sac-like lungs inside body MOIST SKIN Entire skin = breathing organ CLITELLUM Thickened band — landmark O₂ / CO₂ EXCHANGE Diffuses through mucus layer MUCUS LAYER Must stay moist to breathe SPIRACLES Tiny pores along abdomen sides TRACHEAL TUBES Air tubes reach every cell THORAX Also has spiracles for breathing NO LUNGS O₂ diffuses directly to cells TRACHEA Windpipe — air passage to lungs LEFT LUNG 2 lobes — slightly smaller RIGHT LUNG 3 lobes — slightly larger BRONCHI Branches into each lung NOSE / MOUTH Air entry — filtered & warmed DIAPHRAGM Muscle that drives breathing