| System | Key facts |
|---|
| Digestive | Digestion starts in the mouth (salivary amylase); stomach HCl and pepsin; most digestion and absorption in the small intestine (villi); liver makes bile (no enzyme); pancreas — insulin and digestive juice |
| Circulatory | Heart has 4 chambers; William Harvey discovered circulation; normal BP 120/80; pulse 72/min; arteries carry blood away from the heart (except pulmonary artery — deoxygenated) |
| Blood | RBC (haemoglobin, 120 days, made in bone marrow), WBC (immunity), platelets (clotting); blood groups A, B, AB, O (Landsteiner); Rh factor; O− universal donor, AB+ universal recipient |
| Respiratory | Gas exchange in alveoli; breathing rate 12–18/min |
| Excretory | Kidneys — nephron is the unit; urea formed in liver; dialysis for kidney failure |
| Nervous | Neuron unit; cerebrum (thinking), cerebellum (balance), medulla (involuntary actions); reflex via spinal cord |
| Endocrine | Pituitary (master gland), thyroid (thyroxine, iodine), adrenal (adrenaline — fight or flight), pancreas (insulin, glucagon) |
| Skeletal | 206 bones; femur longest; stapes smallest; 32 teeth in adults |