Secretions from endocrine organs reach their target cells via the blood because the endocrine organs are ductless glands. Some tissues that are not organs also secrete local or tissue hormones. Skin This is the largest organ of the body. Skin helps protect the organism from the external environment and water loss. Many sense organs are associated with the skin.
Skin is important in heat exchange and body temperature regulation.
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.