Lungs And Lung Disease

Respiratory System - Mouth Trachea - flexible airway Bronchi - two divisions in the trachea Bronchioles - series of branching subdivisions of the bronchi Alveoli - minute air sacs

Inhalation - When the air pressure of the atmosphere is greater than the pulmonary pressure inside the lungs, air is forced into the alveoli Diaphragm muscles contract, flattening, increasing volume of thorax Ribs pulled upwards and outwards External intercostal muscles contract

Expiration - When the pulmonary pressure in the lungs is greater than that of the atmosphere, air is forced out of the lungs Diaphragm relaxes, domed shape, decreasing the volume of the thorax Ribs move downwards and inwards The intercostal muscles contract

Pulmonary ventilation = tidal volume x ventilation rate

Tidal volume - normal volume of air taken in at each breath during rest Ventilation rate - breathing rate Essential Features of Exchange surfaces -

Large surface area to volume ration - speed ups the rate of exchange Very thin - keeps diffusion pathway short Partially permeable - Allow selected materials to diffuse easily Movement of the environmental medium - e.g. air - to maintain a diffusion gradient Movement of the internal medium - e.g. blood - to maintain a diffusion gradient

Fick's law - Diffusion = Surface area x difference in concentration Length of diffusion path

Role of Alveoli in Gas Exchange - Diffusion of gases between red blood cells and the alveoli will be quick because :

Red blood cells are slowed as they pass, allowing more time for diffusion The distance of diffusion is reduced as the red blood cells are flattened against the walls The walls of both alveoli and capillaries are very thing and therefore reduce diffusion distance Have large Surface area Breathing movements constantly ventilate the lungs , and the heart constantly circulates the blood Blood flow maintains a concentration gradient

Pulmonary Tuberculosis -

Causes - Mycobacterium bovis Symptoms- Persistent cough, loss of appetite, tiredness, fever, bloody sputum Transmission - Air droplets, close contact Cause of Infection - Bacteria grow and divide in the upper lungs White blood cells ingest the bacteria, leading to inflammation of the lymph nodes and drain that area of the lungs Some bacteria usually remain for years and re-emerge later when your immune system is week It destroys the lung tissue, resulting in cavities and scar tissue Prevention - Vaccination is risky, but if someone doesn't have immunity they are given the vaccine Better education about TB Better Housing Improved Health facilities Better nutrition to keep the immune system strong

Asthma A localised allergic reaction Causes- Inflamed airways, Large amounts of mucus , fluid enters airways, Bronchiole contract Symptoms - Difficulty in breathing - due to constriction of the airway Wheezy sound breathing - air passing the constricted airway Tight feeling in the chest - consequence of not being able to ventilate the lungs Coughing - reflex response to the obstructed bronchi