| Integumentary |
Skin (epidermis, dermis, hypodermis), hair, nails, glands |
Protection, temperature regulation, sensation, vitamin D synthesis |
| Skeletal |
206 bones, cartilage, ligaments, joints |
Support, movement (via levers), mineral storage, blood‑cell formation (hematopoiesis) |
| Muscular |
Skeletal, cardiac, smooth muscle fibers |
Voluntary & involuntary movement, posture, heat production |
| Nervous |
Brain, spinal cord, peripheral nerves, sensory receptors |
Rapid communication, integration of information, control of behavior |
| Endocrine |
Glands (pituitary, thyroid, adrenal, pancreas, gonads, etc.) |
Hormone secretion → long‑term regulation of metabolism, growth, reproduction |
| Cardiovascular |
Heart, blood vessels (arteries, veins, capillaries), blood |
Transport of nutrients, gases, wastes; immune defense; temperature control |
| Lymphatic/Immune |
Lymph nodes, vessels, spleen, thymus, tonsils, lymphoid tissue |
Fluid balance, immune surveillance, absorption of dietary fats |
| Respiratory |
Nasal cavity, pharynx, larynx, trachea, bronchi, lungs |
Gas exchange (O₂ ↔ CO₂), acid‑base balance, vocalization |
| Digestive |
Mouth, esophagus, stomach, small & large intestines, liver, pancreas, gallbladder |
Ingestion, digestion, absorption, elimination of waste |
| Urinary |
Kidneys, ureters, bladder, urethra |
Filtration of blood, excretion of waste, water‑electrolyte balance, acid‑base regulation |
| Reproductive |
Gonads (testes/ovaries), ducts, accessory glands, external genitalia |
Production of gametes, sex hormones, support of fetal development (in females) |