Hair and nails are special skin modifications. Skeletal system Supports and protects the body. Forms levers for movements. Muscle system Consists of muscles under conscious or unconscious control. Skeletal muscles are important in locomotion.
Smooth muscles are important in contraction of internal organs.
Cardiac muscle serves as the pumping tissue of the heart. Reproductive systems Consists of gonads and accessory tissues and organs that are necessary for producing the gametes and delivering the sperm to the oocytes. Organs are also present for nurturing the young, if internal fertilization and development are utilized. In mammals, mammary glands are present to provide nutrients for the infant. Sex organs also secrete hormones that are important in sexual development, behavior, and reproduction.