Respiratory System 1

Human Respiratory System

Components of the Upper Respiratory Tract Functions: Passageway for respiration Receptors for smell Filters incoming air to filter larger foreign material Moistens and warms incoming air Resonating chambers for voice

Components of the Lower Respiratory Tract Functions: Larynx: maintains an open airway, routes food and air appropriately, assists in sound production Trachea: transports air to and from lungs Bronchi: branch into lungs Lungs: transport air to alveoli for gas exchange

Breathing (ventilation): air in to and out of lungs External respiration: gas exchange between air and blood Internal respiration: gas exchange between blood and tissues Cellular respiration: oxygen use to produce ATP, carbon dioxide as waste Four Respiration Processes

Inspiration/Expiration: air in/air out Cycle: Relaxed state: diaphragm and intercostal muscles relaxed Inspiration (Inhalation): diaphragm contracts, pulling muscle down, intercostal muscles contract elevating chest wall and expanding volume of chest, lowering pressure in lungs, pulling in air Expiration (Exhalation): muscles relax, diaphragm resumes dome shape, intercostal muscles allow chest to lower resulting in increase of pressure in chest and expulsion of air Process of Breathing: Pressure Gradient

Respiratory Cycle: Mechanism of Breathing

Gases diffuse according to their partial pressures External respiration: gases exchanged between air and blood Internal respiration: gases exchanged with tissue fluids Oxygen transport: bound to hemoglobin in red blood cells or dissolved in blood plasma Carbon dioxide transport: dissolved in blood plasma, bound to hemoglobin, or in the form of plasma bicarbonate Gas Exchange & Transport: A Passive Process

Gas Exchange Between the Blood and Alveoli

Oxygen transport – 1.5% dissolved in plasma – 98.5% bound to hemoglobin (Hb) Oxyhemoglobin Saturation Curve : – higher P O 2 results in greater Hb saturation Oxygen transport in Blood

Carbon dioxide transport: – ~9% dissolved in plasma – ~13% as carbamino compounds Most combined with Hb – ~78% converted to HC0 3 - CO 2 + H 2 O  H 2 CO 3  H + + HCO 3 - Haldane effect – Inverse relationship between amount of Hb-O 2 and CO 2 carrying capacity of blood Hb binds and transports more CO 2 than O 2 Hb buffers more H + than Hb-O 2 – Promotes conversion of CO 2 to HCO 3 - via carbonic anhydrase reaction CO 2 Transport

O 2 mostly transported in blood bound to hemoglobin CO 2 mostly transported in blood as HCO 3 - Lesser amounts of CO 2 are bound to Hb or dissolved in plasma Key Concept

As we exercise, the body needs to obtain more oxygen and remove more carbon dioxide (CO 2 ) This is done by increasing the rate and depth of breathing An increase in carbon dioxide in the blood is the main trigger that increases the rate and depth of breathing Regulation of Breathing

Chemoreceptors in the respiratory centre in the brain stem’s medulla detect an increase in blood CO 2 levels The intercostal and phrenic nerves increase the rate and depth of breathing Additional chemoreceptors on arteries near the heart monitor oxygen and blood acidity Regulation of Breathing

16 respiratory centres in medulla chemoreceptors on aorta and carotid artery heart brain intercostal nerve to external intercostal muscles phrenic nerve to diaphragm diaphragm ribs Regulation of Breathing