By Sasha Fenimore, Max Leal, Will Fyfe

 An organ is something that has many kinds of tissue that all function together to perform a specific task in an organism.  Organs don’t usually function alone. Most of the time there are a group of organs called an organ system working together to carry out an important function.

 Like we stated earlier organs are made up of several different tissues.  One of these tissues is muscle tissue. Muscle tissue is composed of cells that can contract. ▪ The human body contains three kinds of muscle tissue. ▪ Skeletal muscle- moves bones in your trunk, limbs, and face. ▪ Smooth muscle- handles body functions that you cannot control consciously. ▪ Cardiac muscle- pumps blood through your body.  Another of these tissues is nervous tissue. Nervous tissue contains cells that receive and transmit messages in the form of electrical impulses.

▪ These cells called neurons are specialized to send and receive messages from muscles, glands, and other neurons throughout the body.  Epithelial tissue consists of layers of cells that line or cover all internal and external body surfaces. ▪ Each epithelial layer is formed from cells that are tightly bound together, providing a protective barrier for these surfaces.  Connective tissue binds, supports, and protects structures in the body. ▪ Connective tissues are the most abundant and diverse of the four types of tissue, and include bone, cartilage, tendons, fat, blood, and lymph.

 Here is a list of organ systems, their major structures, and their functions.  Skeletal system: ▪ Major structures are bones. ▪ Its functions are that it provides structure and supports and protects internal organs.  Muscular system: ▪ Major structures are muscles (skeletal, cardiac, and smooth). ▪ Its functions are the they provide structure; supports and moves trunk and limbs; moves substances through the body.

 Integumentary system: ▪ Major structures are skin, hair, and nails. ▪ Its functions are to protect against pathogens and help regulate body temperature.  Circulatory system: ▪ Major structures include the heart, blood vessels, and blood. ▪ Its function is to transport nutrients and wastes to and from all body tissues.

 Respiratory system: ▪ Major structures are air passages and lungs. ▪ Its function is to carry air in and out of the lungs, where gases such as oxygen and carbon dioxide are exchanged.  Immune system: ▪ Its major structures are lymph nodes and vessels and white blood cells. ▪ Its function is to provide protection against infection and disease.  Digestive system: ▪ Major structures include the mouth, esophagus, stomach, liver, pancreas, small and large intestines. ▪ Its functions are to store and digest food, absorb nutrients, and eliminate waste.

 Excretory system: ▪ Major structures include kidneys, ureters, bladder, urethra, skin, and lungs. ▪ Its functions are maintaining water and chemical balances and eliminating waste.  Nervous system: ▪ Major structures are the brain, spinal cord, nerves, sense organs, and receptors. ▪ Its proposes are to control and coordinate body movements and sense, control consciousness and creativity, and to help monitor and maintain other body systems.

 Endocrine system: ▪ Major structures include the adrenal gland, thyroid gland, pancreas, and hypothalamus. ▪ Its main proposes are to maintain homeostasis, regulate metabolism, regulate water and mineral balance, regulate growth, and regulate sexual development and reproduction.  Reproductive system: ▪ Major structures are in females the ovaries, uterus, and mammary glands. In males are the testes. ▪ The function of this system is to produce offspring.

 Many organs and organ systems in the human body are housed in separate compartments called body cavities.  These cavities protect delicate internal organs from injuries and from the daily wear and tear of walking, jumping, and running.  They also allow for organs to expand and contract while remaining supported.

 The human body has four main cavities that house one or more internal organs.  The cranial cavity encases the brain.  The spinal cavity surrounds the spinal cord.  The thoracic cavity contains the heart, the esophagus, the lungs, trachea, and bronchi.  The abdominal cavity contains organs of the digestive, reproductive, and excretory systems.

 Each organ system has organs associated with it according to the organs primary function.  Its sometimes hard to tell which organ belongs to which organ system because organs sometimes perform different function vital to different systems.  Each organ carries out its own specific function, but for an organism to survive, the organ systems must work together.

 For example nutrients from the digestive system are distributed throughout the body by the circulatory system. And the efficiency of the circulatory all depends on collecting nutrients from the digestive system and from obtaining oxygen by way of the respiratory system.