The Respiratory System a simple system designed to get oxygen into the body, and to get rid of carbon dioxide and water. Made up of Respiratory tract and lungs.

Cellular Respiration: (enzymes) Glucose (C 6 H 12 O 6 )+ oxygen (O 2 ) → energy + CO 2 + H 2 O (fuel) CO 2 = carbon dioxide  O 2 is carried into our body every time we breath in (inhale).  CO 2 is carried out of our body every time we breathe out (exhale).  our nervous system monitors the amount of CO 2 in our body (not the amount of O 2 ).

Respiratory Tract Air is drawn in through the nose or the mouth. Behind the nose is the nasal cavity. It is here that the air is warmed, filtered and moistened before continuing to the lungs. From the nasal cavity air enters the pharynx and moves into the trachea/wind pipe. The trachea is lined with little hair-like structures called cilia. These cilia sweep any tiny particles out of the air and prevent them from entering the lungs. There are also mucous glands that secrete mucous to catch particles (dust, smoke, bacteria) in their sticky film. Cilia move mucous upwards towards nasal cavity. Fiter: our airways (trachea, nose, lungs, bronchi) are lined with cilia and mucus cells.

At the top of the trachea is a space that contains the vocal chords; it is called the larynx. Air passing through the larynx vibrates the vocal chords and makes sounds. The trachea splits into two tubes called bronchi. They take the air toward each of the lungs. Each bronchus divides again and again, making smaller and smaller tubes. The smaller tubes are called bronchioles. THE LUNGS spongy, saclike respiratory organs where gas exchange occurs made of tiny hollow sacs called alveoli (~700 million of them) the diaphragm (a muscle) and intercostal muscles, controlling the ribs, are responsible for inhalation (breathing in). Each bronchiole ends in a single air sac called an alveolus.

Gases in Air InhaledExhaled CO 2 → 0.04% → 5% O2O2 → 20%→ 15% Other → 0.96% → 1% N→ 79% (N → nitrogen)

Air in Our Lungs Total volume→5.5 liters (l) Vital capacity→4.0 l Normal breath→0.5 l Residual air→1.5 l

Respiration Is due to diffusion and pressure Air is a compressible fluid that is a mixture of gases. Variations in the volume of a compressible fluid produces changes in pressure. They are inversely proportional: If volume of the lungs increases, the pressure decreases and vice versa. Fluids move from area of high pressure to an area of low pressure. – Higher pressure in lungs than outside (atmospheric pressure) causes air to exit: Exhalation. – Lower pressure inside lungs than outside causes air to come into lungs: Inhalation. Diaphragm and intercostal muscles of the rib cage allow for the change in volume of the lungs.

Gas Exchange O 2 passes through the walls of the alveoli into blood vessel (capillaries) by diffusion. O 2 binds to hemoglobin in the red blood cells (RBC) O 2 is carried away to our cells. CO 2 produced by our cells as a waste product of cellular respiration carried to the lungs by the RBC in our blood enters our lungs by diffusion then we breathe the CO 2 out.