The Human Body Cells Single vs Multicellular Organisms

The Human Body Cells Single vs. Multicellular Organisms How the human body is organized

Living Things: l l l Have cellular organization Contain similar chemicals Use energy Respond to their environments Grow, develop and reproduce

Cells: Cell Theory l l All organisms are made of one or more cells The cell is the basic unit of all living things

Single-celled organisms l l Uni-celled “one” cell Carries out all life functions in the one cell (feeding, reproducing, breathing) – Can produce own food or seek out prey – Reproduce rapidly

Multi-cellular Organisms l l More than one cell Often larger cells Have specialized “differentiated” cells Groups of cells work together to do certain tasks

Levels of Organization for the human body l l Cells Tissues Organ Systems

Cells l l The basic unit of structure and function in a living thing Structures within a cell: – Cell membrane – Nucleus – cytoplasm

Tissue l l A group of similar cells that perform the same function 4 basic types: – Muscle tissue – Nerve tissue – Connective tissue – Epithelial tissue

Muscle Tissue l l Makes parts of your body move, carries out movement Some moves blood through heart, food through digestive system or moves muscles

Connective Tissue l Provides support for body and connects all its parts l Bone, fat

Epithelial Tissue Covers surfaces of body, outside of internal organs l Protects structures l Includes Outermost layer of skin, lines the small intestine l

Nerve Tissue l l Carries messages back and forth between the brain and every other part of the body Brain, spinal cord, nerves

Organ l l l A structure that is composed of different kinds of tissue Performs a specific job Ex: heart, lungs

Organ System l A group of organs that work together to perform a major function

Organ Systems l l l Circulatory Digestive Endocrine Excretory Immune Muscular Nervous Reproductive Respiratory Skeletal Skin