There are 4 main types of tissues in the human body: epithelial, connective, muscle, and nervous tissue. Epithelial tissue forms boundaries between environments and performs functions like secretion and absorption. Connective tissue is the most abundant and has many varieties that accomplish support, protection, and transport functions throughout the body. Muscle tissue contains 3 main types - skeletal, cardiac, and smooth muscle - that enable body movement. Nervous tissue transmits electrical signals within the central and peripheral nervous systems.