Unit 1: Section 4: RESIPRATORY SYSTEM
- Created by: Amy Burgess
- Created on: 06-01-16 09:33
Lung structure
Air enters the trachea
The trachea splits into 2 bronchi - one bronchus to each lung
Each bronchus branches into smaller tubes called bronchioles
The bronchioles end in small air sacs called the alveoli
Gases are exchanged in the alveoli
The diaphragm ruin cage and intercostal muscles all work together to force air out
Ventilation
Inspiration-
Intercostal and diaphragm muscles CONTRACT
this causes the rib cage to move upwards and outwards , and the diaphragm to FLATTEN = INCREASINGLY the volume of the thorax
As the volume of the thorax increase, the lung pressure DECREASES
thus causes air to flow into the lungs
(Active process - requires energy)
Expiration-
Intercostal and diaphragm muscles RELAX
the ribcage moves downwards and inwards , the diaphragm becomes CURVED again
The thread volume DECREASES, causing the air pressure to INCREASE
Air is forced out of the lungs
(Passive process- doesn't require energy)
Alveoli structure
Single layer of thin flat cells - alveoli epithelium
Walls of capillaries are capillary endothelium
Walls of alveoli made from elastin (a protein)
Gas exchange in the alveoli
O2 diffuse out of the alveoli, across the alveoli epithelium and the capillary endothelium
O2 is bound to haemoglobin
CO2 diffuses into the alveoli , from the blood
CO2 is breathed out
Factors affecting diffusion&alveoli adaptations
A thin exchange surface - alveolar epithelium one cell thick
A large surface area - Large number of alveoli
A steep concentration gradient - a high concentration of O2 and CO2 between alveoli and capillaries = diffusion across . Steep concentration gradient maintained by blood flow and ventilation
Pulmonary ventilation
PV is a measure of lung function
PV is the volume of air taken into the lungs in one minute
Measured in dm3min-1
PV = tidal volume x ventilation rate
Tidal volume is = volume of air in each breathe
Ventilation is = number of breathes per minute
You can use spirometer traces to calculate PV
Explain the infection stage of TB
When infected with TB bacteria , immune system cells build a wall around the bacteria in the lungs - this forms small hard lumps called tubercles
Infected tissue in the tubercles dies and the gaseous exchange surface is damaged, so the tidal volume is decreased
TB causes fibrosis, which reduces the tidal volume further
If bacteria enter the bloodstream they can spread to other parts of the body
What are the symptoms of TB
Persistent cough, coughing blood and mucus , chest pains , fatigue
Many people with TB are asymptomatic as the infection is inactive - they means they are unable to pass it on
If they become weak from another disease/illness, it will become active- symptoms will be displayed and it can be passed on
How is TB transmitted
Droplet infection- infected person coughs or sneezes , tiny droplets of saliva and mucus containing the bacteria are released = infection transmission
TB is more common in areas where where hygiene levels are poor and where people live in crowded conditions
Vaccine available and can be treated with antibiotics
Fibrosis
Formation of scar tissue on the lungs
Result of infection or exposure to asbestos or dust
Scar tissue is thicker and less elastic than Normal lung tissue
The alveoli are less able to expand so can't hold as much air - tidal volume is decreased
Harder to force air out of the lungs due to lost elasticity
Effect on gas exchange -
Reduces the rate of gas exchange
Diffusion slower across a thicker scarred membrane
Less O2 diffuses = aerobic Respiration is reduced
Symptoms - fatigue, dry cough, chest pain, increased breathing rate
Asthma
Airways become inflamed and irritated - allergic reaction usually
In asthma attack, muscle lining the bronchioles contracts and lots of mucus is made - causes constriction of airways, making it difficult to breathe
Air flow severely reduced - less O2 in alveoli so less in blood = reduced rate of aerobic respiration
Symptoms - wheezing , tight chest, sudden onset of symptoms
Medicated with inhaler that relaxes bronchioles muscles
Emphysema
Caused by smoking or long term exposure to air pollution
Particles trapped in alveoli, which causes inflammation, which attracts phagocytes
Phagocytes produce an enzyme that breaks down the protein elastin
Loss of elastin means that alveoli can't recoil to expel air as well
Also, destruction of alveoli walls, which reduces surface area, which reduces gas exchange
Lack of O2 reaching cells
Symptoms - shortness of breathe , wheezing, increased breathing rate
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