Multicellular means made of many cells. Based on your vocabulary reference sheet, what does the prefix multi- mean? Multi- means many Multicellular means made of many cells. 2

Multicellular organisms contain many different forms of specialized cells that work together to meet the needs of the entire organism. Groups of these specialized cells are called tissues. 3

These tissues join together inside of animals to form organs These tissues join together inside of animals to form organs. Every organ is made up of more than one type of tissue. Caution: The image of a dissected rat you are about to see may be disturbing to some students. Photo by Allen Lew 4

Organs work together to perform complex tasks Organs work together to perform complex tasks. A group of organs that works together to complete a task is referred to as a body system or an organ system (These are two ways of saying the same thing.) 5

To digest and absorb nutrients from food Organ System: Digestive System Primary Function To digest and absorb nutrients from food Major Organs Esophagus Stomach Small Intestine Large Intestine Nutrients travel from the digestive system directly into the circulatory system.

To absorb oxygen and expel carbon dioxide Organ System: Respiratory System Primary Function To absorb oxygen and expel carbon dioxide Major Organs Lungs Trachea Bronchi Diaphragm Oxygen travels from the respiratory system directly into the circulatory system.

Organ System: Circulatory System Primary Function To distribute oxygen and nutrients throughout the body Major Organs Heart Blood vessels Major Tissue Blood White blood cells are also part of the immune system.

To remove waste products from the body Organ System: Excretory System Primary Function To remove waste products from the body Major Organs Kidneys Bladder Colon The colon is also the final section of the digestive system and helps absorb water and salt.

Organ System: Skeletal System Primary Function Provides shape, structure and protection for internal organs Major Organs Bones Major Tissue Marrow Ligaments Marrow inside bones creates new blood cells!

Organ System: Muscular System Primary Function Allows for movement of the skeleton and other tissues in the body Major Organs Muscles Major Tissues Tendons Muscles always PULL on bones to make them move.

Organ System: Nervous System Primary Function Transmits signals and stores information Major Organs Brain Spinal cord Major Tissue Nerves All 5 senses are a part of the nervous system!

Organ System: Endocrine System Primary Function Produce hormones to maintain homeostasis Major Organs Endocrine Glands Major Molecule Hormones Male and female reproductive organs both produce hormones!

Organ System: Immune System Primary Function Defend the body from germs and parasites Major Cells White Blood Cells Major Molecules Antibodies Antibody White blood cells and antibodies travel through the circulatory system! White blood cell engulfing anthrax bacteria (The micrograph was taken by Volker Brinkmann with a Leo 1550 scanning electron microscope.)

Removes fluid from around cells and filters it for bacteria Organ System: Lymphatic System Primary Function Removes fluid from around cells and filters it for bacteria Major Organs Lymph nodes Lymphatic vessels Spleen Lymph is the fluid from between body cells that has been absorbed by the lymphatic system.

Organ System: Integumentary System Primary Function Protection from damage and dehydration Major Organs Skin Hair follicles Skin helps keep the body from overheating by sweating.

Produces gamete cells needed for Organ System: Reproductive System Primary Function Produces gamete cells needed for sexual reproduction Major Organs Testes (male) Ovaries (female) The male gamete cell is called a sperm and female gamete cell is called an ovum or egg.

Can organs belong to more than one organ system? Yes! Almost all major organs belong to more than one system. Heart: Muscular and Circulatory Lungs: Respiratory and Excretory Brain: Nervous and Endocrine