The Organ Systems of the Human Body

Integumentary System

Principal Organs: Skin, hair, nails, cutaneous glands.

Principal Functions: Protection, water retention, thermoregulation, vitamin D synthesis, cutaneous sensation, electrolyte and acid-base balance.

Skeletal System

Principal Organs: Bones, cartilages, ligaments.

Principal Functions: Support, movement, protective enclosure of viscera, blood formation, mineral storage.

Muscular System

Principal Organs: Skeletal muscles.

Principal Functions: Movement, stability, communication (nonverbal), control of body openings, heat production.

Nervous System

Principal Organs: Brain, spinal cord, nerves, ganglia.

Principal Functions: Rapid internal communication, coordination, motor control, and sensation.

Endocrine System

Principal Organs: Pituitary gland, pineal gland, thyroid gland, parathyroid glands, thymus, adrenal glands, pancreas, testes, ovaries.

Principal Functions: Hormone production, internal chemical communication and coordination.

Circulatory System

Principal Organs: Heart, blood vessels.

Principal Functions: Distribution of nutrients, oxygen, wastes, hormones, electrolytes, heat, immune cells, and antibodies; internal fluid, electrolyte, and acid-base balance.

Immune System

Principal Organs: Lymph nodes, lymphatic vessels, thymus, spleen, tonsils.

Principal Functions: Recovery of excess tissue fluid, detection of pathogens, production of immune cells, defense against disease.

Respiratory System

Principal Organs: Nose, pharynx, larynx, trachea, bronchi, lungs.

Principal Functions: Absorption of oxygen, discharge of carbon dioxide, acid-base balance, speech.

Digestive System

Principal Organs: Teeth, tongue, salivary glands, esophagus, stomach, small and large intestines, liver, gallbladder, pancreas.

Principal Functions: Nutrient breakdown and absorption. The liver also functions in metabolism of carbohydrates, lipids, proteins, vitamins, and minerals; disposal of drugs and toxins; synthesis of plasma proteins; and cleansing of blood.

Urinary System

Principal Organs: Kidneys, ureters, urinary bladder, urethra.

Principal Functions: Elimination of wastes; regulation of blood volume and pressure; stimulation of red blood cell formation; control of fluid, electrolyte, and acid-base balance; detoxification.

Reproductive System

Male System:

Principal Organs: Testes, epididymides, spermatic ducts, seminal vesicles, prostate, bulbourethral glands, penis.

Principal Functions: Production and delivery of sperm; secretion of sex hormones.

Female System:

Principal Organs: Ovaries, uterine tubes, uterus, vagina, mammary glands.

Principal Functions: Production of eggs; site of fertilization and fetal development; fetal nourishment; birth; lactation; secretion of sehormones.