We need a respiratory system for gas exchange and to provide O2 for cellular respiration!

 Gas exchange is the physical method that organisms use to obtain oxygen from their surroundings and remove carbon dioxide.  The respiratory surface is the physical location of gas exchange in the organism.  Gas exchange helps maintain homeostasis in the body.

 1. Surface must be thin - Diffusion will occur faster.  2. Surface must be moist. O 2 and CO 2 must be dissolved in a liquid before they can diffuse.  3. Surface must be in contact with a supply of O 2 in the surroundings. The surroundings must have a supply of needed O 2 and be able to remove CO 2 for the organism.  4. Surface must be in contact with a transport system that carries dissolved materials to and from the cells.

 gas exchange organs in air- breathing vertebrates and some other animals.  made up of many small chambers (aveoli).  each chamber is surrounded by capillaries (where the exchange of O2 and CO2 occur).

 diaphragm - thin muscle which forms the floor of the chest cavity and is involved in breathing; separates lungs from abdominal cavity.  ribs -part of the skeletal system which protects the chest cavity which along with intercostal muscles are involved in breathing.

 pleura - two layered membrane which completely encloses the lung.  1. Visceral pleura: inner pleura which covers the lungs.  2. Parietal pleura – outer pleura is in contact with the diaphragm and other chest cavity organs.

air passage - pathway through which air flows to and from the environment and the respiratory surface during breathing.

 Nose: Air enters through 2 nostrils; Hair filter large particles from the air (dust, pollen).  Nasal cavity: (sinuses, nasal passages) - cilia and mucus help trap dust, bacteria, and other particles in the air. - capillaries present to warm the air as it flows through. This prevents damage to lung tissue by the cold air. ** Because the nose helps warm, moisten, and cleanse the air, breathing through the nose is better than mouth breathing.  Pharynx - connects mouth and nasal cavity to the larynx and esophagus.  Larynx – (Adam’s apple, voice box) - Contains vocal cords which stretch across the larynx and vibrate as air flows over them. - found at the top of the trachea. - Contain cartilage (largest is the thyroid cartilage: Adam’s apple).

 Epiglottis: flap-like structure at top of larynx that prevent food from entering the trachea.  trachea (windpipe) - connects the air to the lungs. - tube supported by “U” shaped cartilage rings. - ciliated mucous membrane moves mucus and trapped debris up into the nose and throat area where it can be removed by sneezing, swallowing, coughing, or spitting. - Tobacco smoke will stop cilia for 20 minutes and increase the amount of mucus present in the air passage, causing coughing and a greater risk of respiratory infection.

 bronchi – two short cartilage- ringed tubes that carry air from the trachea to the left and right lung. The bronchi are lined with a ciliated mucous membrane.  Bronchioles - Inside the lung, each bronchi divides into a tree- like network of smaller and thinner tubes called bronchioles which regulate the flow of air to the aveoli.  Alveoli – found at end of each bronchiole; grape-like cluster; Tiny air sacs surrounded by capillaries; function to exchange oxygen and carbon dioxide. This is the respiratory surface. (300 million with a surface area of 70 m 2 = size of classroom; 1/5 th the area of a basketball court).