Respiratory Physiology Chapter 13 Respiratory Physiology

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)

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

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

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

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)

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

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

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

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