concept 3: respiratory system

• major function: gas exchange, supply body with O2 and dispose of CO2
• conducting zone (most irritated/inflamed): warms, humidifies, filters air as travels to respiratory zone; air enters nose through nostrils and is moistened as passes through nasal cavity. air moves through pharynx, which connects nasal cavity and mouth to larynx and esophagus
• epiglottis: piece of cartilage that blocks larynx when swallow food
• air travels through trachea which splits into right and left primary bronchi that enters lungs. lungs surrounded by pleurae (serous membranes that line thoracic wall and diaphragm)
• bronchioles: smallest passageways (less than 1mm)
• respiratory zone: where gas exchange occurs in bronchioles, alveolar ducts and alveoli; bronchioles empty into alveolar ducts, which dead end in tiny alveolar sacs that contain alveoli (bulk of gas exchange occurs)
• gas exchange: diffusion of O2 and CO2 between alveoli and blood in lungs and then later the blood and body tissues; arteries and veins feed into each alveolar sac with capillaries connecting to each alveoli: CO2 move out of blood and into alveoli, O2 moves into blood and out of alveoli
• diaphragm: muscle that moves lungs, separates thoracic cavity from abdominal cavity. volume changes in lungs -> pressure changes, which causes air to move
• inspiration: when air moves into lungs, lungs expand -> air flows in
• expiration: when air exits out of lungs, lungs recoil -> air flows out