20.2: The Respiratory System: the exchange of gases

1. 20.2: The Respiratory System: the exchange of gases • Section Objectives: • Identify the structures involved in external respiration. • Contrast external and cellular respiration • Explain the mechanics of breathing.

2. food O2 ATP CO2 Why do we need a respiratory system? • Need O2 in • for cellular respiration • make ATP • Need CO2 out • waste product

3. Passageways and Lungs • respiratory system consists of a pair of lungs & a system of tubes that carry air to them • Breathing is just one of the functions that the respiratory system carries out.

4. The path air takes • air enters through the nasal cavity • It passes through the pharynx and larynxinto the trachea • The trachea forks to form two bronchi • Each bronchus branches into numerous bronchioles • The bronchioles end in clusters of tiny sacs called alveoli

5. Lungs • Structure spongy texture • high surface area • more absorption of O2 • alveoli • small air sacs • moist lining • mucus traps dust, pollen, particles • covered by cilia • hair-like extensions of cells • move mucus upward to clear out lungs

6. Moving gases into bloodstream • Inhale • O2 passes from alveoli to blood • by diffusion • Exhale • CO2 passes from blood to alveoli • by diffusion capillaries (circulatory system)

7. O2 O2 O2 O2 CO2 CO2 CO2 CO2 Gas exchange: Diffusion of gases • Gases move by diffusion from high to low concentration • capillaries are thin-walled tubes of circulatory system • alveoli are thin-walled sacs of respiratory system capillaries in lungs capillaries in muscle External respiration: exchange of gases between alveoli and blood Internal respiration: exchange of gases between blood and ce4lls blood lungs blood body

8. The Mechanics of Breathing • Breathing ventilates the lungs • The action of your diaphragm and the muscles between your ribs enable you to breathe in and breathe out. • Breathing is the alternation of inhalation(active) and exhalation (passive)

9. Control of Respiration • Breathing is usually an involuntary process. • partially controlled by an internal feedback mechanism that involves signals being sent to the medulla oblongata about the chemistry of your blood. • measure blood pH • CO2 = pH (acid) • coordinate breathing, heart rate & body’s need for energy • will send nerve signals to the rib muscles and diaphragm. • nerve signals cause these muscles to contract, and you inhale.

10. ATP CO2 O2 Breathing and Homeostasis • Homeostasis • keeping the internal environment of the body balanced • need to balance O2 in and CO2 out • need to balance energy (ATP) production • Exercise • breathe faster • need more ATP • bring in more O2 & remove more CO2 • Disease • poor lung or heart function = breathe faster • need to work harder to bring in O2 & remove CO2

11. Cleaning dirty air • To prevent foreign material from reaching the respiratory system is lined with ciliated cells that secrete mucus. • The cilia constantly beat upward in the direction of your throat, where foreign material can be swallowed or expelled by coughing or sneezing