The Respiratory System: PART 2 Physiology

Physiology The major function of the respiratory system is to supply body with oxygen and dispose of carbon dioxide Events happening during respiration: Pulmonary ventilation: Air moves into & out of the lungs -- commonly known as breathing External respiration: Gas exchange between the pulmonary capillaries & alveoli must take place

respiration Events Cont. Respiratory gas transport: Oxygen & carbon dioxide must be transported to and from the lungs & tissue via the blood stream Internal respiration: Gas exchange between the blood and tissue cells Gas exchange in the body occurs by ________________________

Mechanics of Breathing Volume changes leads to pressure changes  gases flow to equalize the pressure Inspiration: air flows into the lungs Expiration: air leaves 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/ 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 depress the rib cage, abdominal muscles contract Asthma: the respiratory passageways are narrowed by spasms of the bronchioles (use inhalers) Pneumonia: the respiration passageways are clogged with fluid or mucus

Respiratory Volumes and Capacities Tidal volume (TV): amount of air into/out of lungs when breathing normally & quietly (approximately 500 mL of air) Inspiratory reserve volume (IRV): amount of air that can be taken in forcibly over the tidal volume (approx. 2100-3200 mL of air)

Respiratory Volumes AND Capacities Expiratory reserve volume (ERV): amount of air that can be forcibly exhaled after a tidal expiration (approx. 1200 mL) Residual volume (RV): Even after the most strenuous expiration, about 1200 mL of air still remains in the lungs & it cannot be voluntarily expelled Vital Capacity (VC): the total amount of exchangeable air ( TV+IRV+EVR)

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

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

Respiration Internal Respiration: External Respiration: The exchange of gases between the alveoli and the blood Gas exchanges in the body occurs by process 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: 1) Most attaches to hemoglobin molecules inside the red blood cells to form oxyhemoglobin 2) A very small amount of oxygen is carried dissolved in the plasma (clear yellow fluid of blood after RBC, WBC, platelets are removed)

Carbon Dioxide -- CO2 Transport in the Blood Most carbon dioxide is transported in plasma as the bicarbonate ion (HCO3-) [balances acids in body – buffer] 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

Carbon Dioxide Transport in the Blood Before carbon dioxide can diffuse out of the blood into the alveoli, it must: 1) Combine with hydrogen ions (H+) to form carbonic acid (H2CO3) 2) carbonic acid (H2CO3) quickly splits to form water and carbon dioxide 3) Carbon dioxide then diffuses from the blood and enters the alveoli HCO3- + H+  H2CO3  CO2 + H2O