The body's most basic building block is a cell. The human body contains billions of cells. Clusters of cells form tissues. Specialized types of tissues form organs, such as the brain and the liver. An organ system (also called a body system) consists of tissues and organs that work together to perform a specialized function. The circulatory and respiratory systems are examples of organ systems.
Organ systems work together to maintain a state of homeostasis (balance). These systems need a constant internal environment to perform the required functions of the body.
In your role as an Emergency Medical Responder, it is important to know the terms used to describe body positions and directions. You must be able to use these terms correctly, so that you can describe the position in which a patient is found and transported. You will also need to know body positions so that you can place a patient in a specific position based on the patient's condition.
A body cavity is a hollow space in the body that contains internal organs. Knowing the body cavities and the organs found within each cavity will help you describe the location of the injury or the symptoms of a sick or injured patient.
The musculoskeletal system gives the human body its shape and ability to move, and it protects the major organs of the body. It consists of the skeletal system (bones) and the muscular system (muscles).
The respiratory system supplies oxygen from the air we breathe to the body's cells. It also removes carbon dioxide (a waste product of the body's cells) from the lungs when we breathe out. This system is made up of an upper and a lower airway. The upper airway includes the nose, the pharynx (throat), and the larynx (voice box). The lower airway consists of structures found mostly within the chest cavity, such as the trachea (windpipe) and the lungs.
The circulatory system is made up of the cardiovascular and lymphatic systems. This system has three main functions: (1) to deliver oxygen-rich blood and nutrients to body tissues, (2) to help maintain body temperature, and (3) to protect the body against infection. The cardiovascular system consists of the heart, blood, and blood vessels. The lymphatic system consists of lymph, lymph nodes, lymph vessels, tonsils, the spleen, and the thymus gland.
The nervous system is a collection of specialized cells that transfer information to and from the brain. The two main functions of the nervous system are to control the voluntary (conscious) and involuntary (unconscious) activities of the body and to provide for higher mental function (such as thought and emotion). The nervous system has two divisions: (1) the central nervous system (CNS) and (2) the peripheral nervous system (PNS).
The integumentary system is made up of the skin, hair, nails, sweat glands, and oil (sebaceous) glands. The skin is the largest organ of the body. It protects the body from the environment, bacteria, and other organisms.
