respiratory system

Inspiration: diaphragm contracts, extending chest cavity downwards intercostal muscles contract, extending rib cage upwards and outwards chest cavity volume increases pressure decreases air flows from higher pressure to lower pressure in lungs

expiration: diaphragm relaxes, pushing up into chest cavity rib cage moves down and inwards chest cavity volume increases air flows from higher pressure in lungs to lower pressure outside

hundreds of millions of alveoli give lungs huge internal surface area for large amounts of gas exchange

each alveolus well supplied with BV, so as much blood as possible is close to the air in alveolus and continuous flow of blood maintain concentration gradient of oxygen and carbon dioxide between blood and air in lungs

alveoli membrane is very thin so gas molecules do not have far to travel- increase efficiency of gas exchange

lungs are positioned deep inside body to prevent excessive evaporation of fluid that covers respiratory surfaces.

Important for alveoli membrane to be covered in thin film of moisture so gases can dissolve and hence diffuse into and out of the blood

respiratory muscles can move to change lung volume so we constantly inspire and expire, which maintains concentration gradient of oxygen and carbon dioxide between air and blood

blood in capillaries surrounding alveoli is brought to lungs by pulmonary artery

blood is deoxygenated (low concentration of oxygen, lower than concentration in the air in alveolus)

oxygen dissolves in moisture on inside of alveolus and diffuses through membrane on walls of capillaries and into blood

blood arriving at capillaries of alveoli has come from body circulation where it has picked up CO2 produced by respiration in cells

concentration of CO2 is higher in alveolar capillaries than in air in alveolus

so CO2 diffuses out of blood and into air in alveolus

<p>constant flow of blood through capillaries -blood in capillaries is constantly replaced by new blood which is low in oxygen and high in carbon dioxide</p> <p>movement of air into and out of alveoli as we breathe in and out the air that has picked up CO2 from and lost O2 to is replaced by new air with each breath, the new air is low in CO2 and high in O2</p> Signup and view all the answers

<p>-disease caused by LT exposure to irritating particles in air taken into lungs -e.g. smokers inhale irritants in tobacco smoke -irritating particles cause damage to alveoli -they lose their elasticity, often replaced with fibrous tissue, and may break down, reducing internal SA of lungs -lost elasticity of lung tissue = constantly inflated, so breathing out requires voluntary effort</p> <p>two problems of emphysema sufferers: -inadequate SA for gas exchange -difficulty ventilating in the lungs</p> Signup and view all the answers

<p>-usually begins in walls of bronchi -inhaled smoke particles constantly irritate mucous membrane that lines air passages -results in excess production mucus -cells at base of membrane begin to divide more rapidly and accumulating mucus cannot be removed -results in smoker's cough -trapped mucus causes rupture of alveoli -emphysema has them developed -cancerous growth developed -may spread to other parts of body</p> Signup and view all the answers

<p>-difficulty breathing due to narrowing of airways, due to: *smooth muscles contracting, narrowing airway *inflammation causing lining of airways to thicken, narrowing its diameter *mucus filling the airway, narrowing tube</p> <p>During asthma attack: -muscles surround bronchioles spasm -sudden involuntary contractions -cause narrowing of air passages and hence difficulty in breathing -irritation of membranes usually cause secretion of excess mucus, restricting movement of air -reduce volume of air going into and out of lungs means exchange of gases is impaired and blood carries lower levels of oxygen and normal</p> Signup and view all the answers

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