Respiratory System Lungs Lungs are lateral to the

Respiratory System

Lungs • Lungs are lateral to the • • • heart Each is located in its own enclosed pleural cavity within the thoracic cavity Each lung is covered by a pleural membrane A pleural space lubricated with fluid also surrounds each lung

Pathway of Air to the Lungs • Pharynx - throat (extends to • • • larynx) Larynx - houses vocal chords leads to trachea Trachea - air passes through this tube on way to the lungs (windpipe) Bronchi - branches of trachea going to each lung Bronchioles - smaller branches of the bronchi Alveoli - air sacs surrounded by capillaries where oxygen is exchanged for CO 2 - (blood returns to heart from here)

Pathway of Air Into the Lungs Can be divided into 2 zones: • Conducting Zone • Respiratory Zone

Conducting Zone • Nose, nasal cavity, • • pharynx, larynx, trachea, bronchi Function: warm, filter and moisten inspired air Mucous traps airborne pathogens and cilia propel matter into the pharynx to be swallowed

Respiratory Zone • Bronchioles, alveoli • Function: gas exchange (CO 2 enters alveoli from blood and O 2 passes into blood from the alveoli) • Capillaries surround each alveolus for efficient gas exchange * In emphysema, the alveoli are damaged, reducing ability for gas exchange

Mechanics of Breathing • Diaphragm - muscle at the base of the lungs that regulates pressure within the pleural cavities by moving up and down

Inspiration & Expiration (see Figure 22. 13) Inspiration (breathing in) Expiration (breathing out) • Diaphragm contracts and • Diaphragm relaxes and moves down moves upwards • Intercostal muscles contract • Intercostal muscles relax and expand ribcage collapses • Volume of thoracic cavity increased as intrapulmonary decreases as (inside alveoli) pressure intrapulmonary pressure decreases increases • Air moves into lungs because • Air is forced out of lungs atmospheric pressure is because atmospheric greater than intrapulmonary pressure is less than pressure intrapulmonary pressure

Diaphragm movements

Regulation of Breathing • The medulla and pons • • contain respiratory centers that control breathing (figure 22. 24) The depth and rate of breathing are controlled by CO 2, O 2 and p. H (H+) concentrations in the blood CO 2 levels are the strongest stimulus for breathing Chemoreceptors in aorta and carotid arteries monitor blood and send signals to respiratory centers in pons and medulla