Human Body I

human body, the physical substance of the human organism, composed of living cells and extracellular materials and organized into tissues, organs, and systems.
Human anatomy and physiology are treated in many different articles. For detailed discussions of specific tissues, organs, and systems, see human blood; cardiovascular system; digestive system, human; endocrine system, human; renal system; skin; human muscle system; nervous system; reproductive system, human; respiration, human; sensory reception, human; skeletal system, human. For a description of how the body develops, from conception through old age, see aging; growth; prenatal development; human development.