1. Respiratory Physiology
Chapter 13
Respiratory Physiology

2. Respiration Pulmonary ventilation (breathing) External respiration
Air moving in and out of lungs so gas exchange can occur
External respiration
Gas exchange between pulmonary blood and alveoli
Respiratory gas transport
Gas transported to and from lungs and tissue cells in body
Internal respiration
At systemic capillaries, gas exchange between blood and tissue cells (cellular respiration)

3. Mechanics of Breathing
Mechanical process (pulmonary ventilation)
Inspiration- air flowing into lungs
Expiration- air leaving lungs

4. Inspiration Diaphragm contracts (moves downward)
Inspiratory muscles contract
external intercostals contract lifting rib cage
Both cause size of thoracic cavity to increase
Since lungs adhere tightly to thorax walls due to the surface tension between pleural membranes, lungs expand
Decrease in gas pressure causes air to be sucked into lungs

5. Expiration Muscles relax, rib cage descends, lungs recoil
Thoracic volume decreases, causing an increase in pressure
Air flows out of lungs

6. Respiratory Volumes & Capacities
Tidal volume- normal amount of air take in and out during a breath (~500 ml)
Inspiratory reserve volume (IRV)- amount of air that can be forcible taken in above the tidal volume (~2100 – 3200 ml)

7. Vital capacity (VC)- total amount of exchangeable air
Expiratory reserve volume (ERV)- amount of air that can be exhaled above the tidal volume (~1200 ml)
Residual volume- air that cannot be expelled, needed for gas exchange to continue in lungs in between breaths
Vital capacity (VC)- total amount of exchangeable air
= TV + IRV + ERV

8. Respiratory Sounds Bronchial sounds Vesicular breathing sounds
Air rushing through large respiratory passageways (trachea & bronchi)
Vesicular breathing sounds
Occurs as air fills alveoli
Soft and resemble muffled breeze

9. External Respiration Exchange of gas between lungs and blood
Gas exchange always diffuses from area of high concentration to low concentration
Oxygen concentration
high in lungs, low in capillaries
Carbon dioxide concentration
high in blood, low in lungs

10. Internal Respiration Exchange of gases between blood and cells
Oxygen concentration
High in capillaries, low in cells
Carbon dioxide concentration
High in cells, low in blood