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Human Respiratory System

Components of the Upper Respiratory TractFunctions: 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

Gas Exchange Between the Blood and Alveoli

• Oxygen transport– 1.5% dissolved in

plasma– 98.5% bound to

hemoglobin (Hb)• Oxyhemoglobin

Saturation Curve :– higher PO2

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 HC03-

• CO2 + H2O H2CO3 H+ + HCO3-

• Haldane effect– Inverse relationship between amount of Hb-O2 and

CO2 carrying capacity of blood• Hb binds and transports more CO2 than O2

• Hb buffers more H+ than Hb-O2

– Promotes conversion of CO2 to HCO3- via carbonic anhydrase

reaction

CO2 Transport

• O2 mostly transported in blood bound to hemoglobin

• CO2 mostly transported in blood as HCO3-

• Lesser amounts of CO2 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 (CO2)This is done by increasing the rate and depth of breathingAn 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 CO2 levelsThe intercostal and phrenic nerves increase the rate and depth of breathingAdditional chemoreceptors on arteries near the heart monitor oxygen and blood acidity

Regulation of Breathing

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respiratorycentres in medulla

chemoreceptorson aorta and carotid artery

heart

brain

intercostal nerve to externalintercostal muscles

phrenic nerve to

diaphragm

diaphragm

ribs

Regulation of Breathing