Objectives 33.3 The Respiratory System -Identify the structures of the respiratory system and describe their functions. -Describe gas exchange. -Describe how breathing is controlled. -Describe the effects of smoking on the respiratory system.

vocab Word Definition Pharynx Tube at the back of the mouth that serves as a passageway for both air and food, also called throat Trachea Tube that connects the larynx to the bronchi, also called the windpipe Larynx Structure in the throat that contains the vocal cords Bronchus One of two large tubes in the chest cavity that leads from the trachea to the lungs Alveolus One of many tiny air sacs at the end of a bronchiole in the lungs that provides surface area for gas exchange to occur diaphragm Large flat muscle at the bottom of the chest cavity that helps with breathing

Structures of the Respiratory System The respiratory system consists of the nose, pharynx, larynx, trachea, bronchi and lungs.

Nose To keep lung tissue healthy, air entering the respiratory system must be filtered, moistened, and warmed; this all happens in the nasal cavity or nose. Hairs lining the entrance to the nasal cavity filter and trap large particles.

Pharynx and Trachea Air moves through the nose to a cavity at the back of the mouth called the pharynx. Air moves from the pharynx into the trachea, or windpipe. A flap of tissue called the epiglottis covers the entrance to the trachea.

Larynx Between the pharynx and the trachea is the larynx, which contains two highly elastic folds of tissue known as the vocal cords.

Trachea Mucus produced in the trachea continues to trap inhaled particles. Cilia lining the trachea sweep both mucus and trapped particles away from the lungs toward the pharynx, where they can be swallowed or spit out.

Lungs From the trachea, air moves into two large tubes called bronchi. Each bronchus leads to one lung. Within each lung, the large bronchus divides into smaller passageways called bronchioles.

Lungs A network of capillaries surrounds each alveolus. The bronchioles continue to divide until they end at a series of tiny air sacs called alveoli. A network of capillaries surrounds each alveolus.

Gas Exchange Gas exchange happens at the alveoli in the lungs by diffusing across the thin capillary walls into the blood.

Smoking Three of the most dangerous substances in tobacco smoke are nicotine, carbon monoxide and tar. Nicotine is an addictive stimulant that increases heart rate and blood pressure. Carbon monoxide is a poisonous gas that blocks hemoglobin from binding with oxygen. Tar contains at least 60 compounds known to cause cancer.

Effects on the Respiratory System Tobacco smoke paralyzes cilia in the trachea, allowing inhaled particles to stick to enter the lungs.

Diseases Caused by Smoking Chronic Bronchitis ~ In chronic bronchitis, the bronchi become inflamed and clogged with mucus. Emphysema ~ Long-term smoking can lead to emphysema, the loss of elasticity and eventual breakdown of lung tissue. Lung Cancer ~ Lung cancer is particularly deadly because, by the time it is detected, it usually has spread to other areas of the body.