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.

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

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.

The path air takes air enters through the nasal cavity It passes through the pharynx and larynx into 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

Lungs Structure spongy texture alveoli moist lining covered by cilia 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

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

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 O2 O2 O2 O2 CO2 CO2 CO2 CO2 External respiration: exchange of gases between alveoli and blood Internal respiration: exchange of gases between blood and cells blood lungs blood body

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)

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.

Breathing and Homeostasis ATP 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 CO2 O2

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