Levels of Organization in the Human Body

Organ Systems

A group of two or more organs working together for a specific job. ex. skeletal, muscular, circulatory, respiratory, excretory, nervous, digestive, reproductive

Cell

Basic unit of life that all organisms are made of.

Levels of Organization in the Human Body

Cells > Tissues > Organs > Organ Systems > Organism - you

Cell Specialization

Cells uniquely suited to perform a particular function. Ex. blood cells, heart cells, brain cells

Connective Tissue

Connects and holds together structures in the body, providing structure and support - ex. ligaments which connect bones, and bones themselves. Also fills in spaces - ex. cartilage in your ears and nose.

Organism

Entire living thing that carries out all the basic life functions - ex. humans. Highest level of organization: cells>tissues>organs>organ systems>organism.

Tissues

Groups of similar cells that perform a specific function in an organism. Several types of tissues come together to form organs. The 4 types are - epithelial, connective, muscular, nervous.

Epithelial Tissue

Outer layer of tissue on the body - ex. skin. Also lines some of the body's inner surfaces - ex. lining of the stomach.

Muscular Tissue

Tissues that contract and expand, creating movement. ex. skeletal muscles move the body, the stomach has muscles that expand when full and relax when empty.

Nervous Tissue

Tissues that relay messages throughout your body. Ex. nervous tissue in the stomach sends messages to the brain when the body is hungry.

Organs

Two or more tissues that work together to perform a specific job. ex. heart, lungs, stomach, intestine,