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The Respiratory System Day 2 Notes – Process of Breathing Inhalation vs. Exhalation Muscles of the Respiratory System Diaphragm: dome-shaped muscle separating thoracic and abdominal cavities External intercostals: pulls ribs to elevate rib cage; inspiratory muscles Internal intercostals: depresses rib cage Inspiratio n Diaphragm contracts & flattens External intercostals lifts rib cage Lungs stretched to larger size Volume in thoracic cavity increases Air pressure inside lungs decrease Air sucked into lungs Expiratio n Inspiratory muscles relax Internal intercostals depress ribcage Rib cage descends, lungs recoil Volume in thoracic cavity decreases. Pressure in thoracic cavity increases Gases forced out Air Content Inspiration Content Exhalation 21% Oxygen 17% 0.04% Carbon Dioxide 4.04% 78% Nitrogen 78% 0.96% Inert Gases 0.96% Vital Capacity (VC): total exchangeable air VC = TV + IRV + ERV Tidal Volume (TV): amount of air in/out during normal, relaxed breathing (~500ml) Inspiratory Reserve Volume (IRV): additional air that can be forcibly inhaled breathing in a normal tidal volume (~3100) Expiratory Reserve Volume (ERV): additional air that can be forcibly exhaled after the expiration of a normal tidal volume(~1200) Residual Volume (RV): air still left in lungs (~1200) allows gas exchange to continue between breaths Respiratory capacity Factors that affect capacity: size, age, sex, physical condition spirometer Used to measure respiratory capacities Gas transport in blood Oxygen: attaches to hemoglobin molecules inside RBC’s Hemoglobin: respiratory pigment, contains 4 heme groups with iron (Fe) Gas transport in blood Carbon dioxide: Transported as bicarbonate ions (70%) Bound to hemoglobin (23%) Dissolved in plasma (7%) Controlling Respiration Control center = medulla oblongata Responds to pH changes in blood High CO2 carbonic acid forms lowers pH O2 sensors in the aorta and carotid arteries External Respiration Ventilation – exchange of air between lungs and atmosphere Physical process during which oxygen is taken up by capillaries of lung alveoli and carbon dioxide is released from blood. Gas Exchange in pulmonary capillaries Breathing is largely an involuntary activity Internal Respiration • Tissue respiration/cellular respiration • Refers to a metabolic process in which oxygen is released to tissues or living cells and carbon dioxide is absorbed by the blood. • Once inside the cell the oxygen is used for producing energy in the form of ATP • All cells require oxygen for metabolism • All cells require means to remove carbon dioxide • Gas exchange at cellular level