The Respiratory System II Physiology

The major function of the respiratory system is to supply the body with oxygen and to dispose of carbon dioxide Events happening during respiration: 1.Pulmonary ventilation: Air must move into and out of the lungs; this process is commonly known as breathing 2.External respiration: Gas exchange between the pulmonary blood and alveoli must take place

Physiology 3.Respiratory gas transport: Oxygen and carbon dioxide must be transported to and from the lungs and tissue via the blood stream 4.Internal respiration: Gas exchange between the blood and tissue cells

Mechanics of Breathing Volume changes leads to pressure change, which leads to the flow of gases to equalize the pressure Inspiration: air is flowing into the lungs Expiration: air is leaving the lungs Inspiratory muscles: diaphragm and external intercostals

Inspiration At the end of a normal inspiration: -Chest is expanded -Rib cage is elevated -Diaphragm is depressed and flattened

Expiration At the end of a normal expiration: -Chest is depressed -Rib cage is descended -Diaphragm is elevated and dome- shaped

Forced expiration Forced expiration: the internal intercostal muscles are activated to help depress the rib cage, and the abdominal muscles contract -Asthma: the respiratory passageways are narrowed by spasms of the bronchioles -Pneumonia: the respiration passageways are clogged with fluid or mucus

Respiratory Volumes and Capacities Tidal volume (TV): the amount of air into and out of the lungs when breathing normally and quietly (approximately 500 ml of air) Inspiratory reserve volume (IRV): the amount of air that can be taken in forcibly over the tidal volume (approximately ml of air)

Respiratory Volumes and Capacities Expiratory reserve volume (ERV): The amount of air can be forcibly exhaled after a tidal expiration (approximately 1200 ml) Residual volume (RV): Even after the most strenuous expiration, about 1200 ml of air still remains in the lungs, and it can not be voluntarily expelled Vital Capacity (VC): the total amount of exchangeable air ( TV+IRV+EVR)

Dead Space Volume The amount of air remains in the conducting zone passageways and never reaches the alveoli

Respiratory Sounds Bronchial sounds: are produced by air rushing through the large respiratory passageways Vesicular sounds: occurs as air fills the alveoli

Respiration External Respiration: It is the actual exchange of gases between the alveoli and the blood Gas exchanges in the body occur according to the laws of diffusion Internal Respiration: It is the exchange of gases that takes place between the blood and the tissue cells

Oxygen Transport in the Blood Oxygen is transported in the blood in two ways: -Most attaches to hemoglobin molecules inside the red blood cells to form oxyhemoglobin -A very small amount of oxygen is carried dissolved in the plasma

Carbon Dioxide Transport in the Blood Most carbon dioxide is transported in plasma as the bicarbonate ion (HCO 3 - ) A smaller amount (between 20%-30%) is carried inside the red blood cells bound to hemoglobin -Carbon dioxide attaches to hemoglobin at a different site than oxygen does, so it does not interfere in any way with oxygen transport

Before carbon dioxide can diffuse out of the blood into the alveoli, it must: -Combine with hydrogen ions (H + ) to form carbonic acid (H 2 CO 3 ) -carbonic acid (H 2 CO 3 ) quickly splits to form water and carbon dioxide -Carbon dioxide then diffuses from the blood and enters the alveoli -HCO H +  H 2 CO 3  CO 2 + H 2 O Carbon Dioxide Transport in the Blood