2. Specialized cells and tissues Single-celled organisms have only one cell Multicellular organisms are made up of many kinds of cells that have different functions. Tissues are specialized cells with similar structures and functions – There are four tissue types in the human body Epithelial tissue Connective tissue Muscle tissue Nerve tissue

3. Epithelial tissue Epithelial tissue contains cells that are packed tightly together. – Examples: outer layer of skin, lining of air passages, lining of internal organs

4. Connective tissue Connective tissue adds support and structure to the body, fills spaces, and stores fat. – Examples: blood, bone, cartilage, and fat cells

5. Muscle tissue Muscle tissue is like elastic. Its job is to contract and relax. There are three types of muscle tissue: – Skeletal muscle- moves the bones of the skeleton when directed by the brain – Smooth muscle does involuntary movements- like breathing – Cardiac muscle contracts to move blood around the body

8. Here are a few organs… – The brain is often compared to a computer – The heart works like a pump to send blood through your body – Blood vessels are like pipelines that transport blood – Lungs enable you to breathe to take oxygen your cells need. They supply oxygen and remove carbon dioxide from the blood – Sense organs help you react to your surroundings: ears, eyes, nose, tongue, and skin

10. The liver produces chemicals that flow into the small intestine to help in digestion. It also helps remove toxins from the blood The pancreas contains tissues that produce enzymes that aid digestion The stomach has smooth muscle tissue that contracts, squeezing the food to break it into smaller pieces.

11. Organ Systems A system is a group of organs that work together to perform a specific function. Many of these systems are easily recognized by their names…can you guess what they do?

17. Plants organ systems

19. *Images provided by Google and AltaVista