Structural Hierarchy/Body Systems

Structural Hierarchy /Chemical level, cellular level, tissue level, organ level, organ system level, organism level

Chemical Level /This level of the structural hierarchy includes atoms and molecules.

Cellular Level /Molecules are combined to form organelles and ultimately cells, which are the basic structural and functional units of organisms

Tissue Level /A tissue is a group of cells that work together to perform a common function. There are four basic tissue types that make up all organs of the adult human body: epithelial tissue (epithelium), connective tissue, muscle tissue, and nervous tissue

Organ Level /Different types of tissues join together to form organs, which are structures that are composed of two or more different tissues (four is most common); they have specific functions and usually have recognizable shapes

Organ System Level /Organs that work together to accomplish a common purpose. The various systems include: integumentary, skeletal, muscular, nervous, endocrine, reproductive, urinary, digestive, respiratory, lymphatic, cardiovascular

Organism Level /The highest level of structural hierarchy. It represents the sum total of all structural levels working together to promote life

Integumentary System /Forms the external body covering, and protects the deeper tissues from injury. Synthesizes vitamin D and houses the cutaneous (pain, pressure, etc.) receptors, sweat glands, and oil glands

Skeletal System /Protects and supports the body organs, and provides a framework the muscles use for movement

Muscular System /Consists of the muscles that provide body movement, maintain posture, and generate body heat

Lymphatic System /Picks up fluid leaked from the blood vessels and returns it to blood. Disposes of debris in the lymphatic stream. Houses white blood cells (lymphocytes) involved in immunity

Respiratory System /Takes in oxygen and gives off carbon dioxide

Digestive System /Makes food absorbable into the body

Nervous System /The body system of nervous tissues, organized into the brain,spinal cord, and nerves, that send and receive messages, and integrate the body's activities

Endocrine System /Glands that secrete hormones that regulate processes such as growth, reproduction, and nutrient use (metabolism) by body cells

Cardiovascular System /Circulates blood and lymph throughout the body. Also called the circulatory system. It consists of the heart, blood vessels, and blood.

Urinary System /Eliminates nitrogenous waste from the body

Reproductive System /Functions in creating offspring (organs include the penis and testes in males; ovaries, uterus, and vagina in females)

Homeostasis /The state of relatively stable, although dynamic, internal conditions