The lungs AS biology AQA

HideShow resource information
  • Created by: CHLOE
  • Created on: 06-01-14 18:15
Preview of The lungs AS biology AQA

First 339 words of the document:

3.1.4 The lungs of a mammal act as an interface with the environment. Lung
function may be affected by pathogens and by factors relating to lifestyle.
Lung function:
You breathe in and air enters the TRACHEA
This trachea then splits into two bronchi (one going into each lung)
Each bronchus will then split into many tubes called bronchioles
The bronchioles end in small air sacs called alveoli
The ribcage, intercostals muscles and diaphragm all play a role and work together to
move air in and out.
The essential features of the alveolar epithelium as a surface over which gas
exchange takes place.
Oxygen diffuses out of the alveoli across the alveolar epithelium and the capillary
Carbon dioxide diffuses into the alveoli from the blood and is breathed out.
Why will diffusion be very rapid?
As the red blood cells pass they slow down, more time for them to be diffused
There is a reduced distance between the alveolar air and the red blood cells as the
red blood cells are FLATTENED against the capillary walls.
The walls of the alveoli are very thin and so this allows for a short diffusion pathway
Have a very large surface area
The lungs are constantly being ventilated and blood is constantly moving through
the capillaries, this ensures that a steep concentration gradient is maintained
Inspiration (this is an active process and so requires energy)
The external intercostals muscles contract, whilst the internal intercostals muscles
The ribs are pulled UPWARDS and OUTWARDS, this increases the volume of the
thorax, the diaphragm muscles contract which causes it to flatten, also increasing
the volume of the thorax.
The increased volume of the thorax results in a decreased pressure in the lungs,
atmospheric pressure is now GREATER than pulmonary pressure which results in air
being forced into the lungs.

Other pages in this set

Page 2

Preview of page 2

Here's a taster:

This is a passive process and so does not require much energy
The internal intercostals muscles contract whilst the external intercostals muscles
The ribs move DOWN and IN and this decreases the volume in the thorax
The diaphragm muscles relax and so moves upwards
The decreased volume in the thorax increases the pressure in the lungs
The pulmonary pressure is now greater than the atmospheric pressure and so air is
forced out of the lungs
Pulmonary ventilation=tidal volume X ventilation rate
Pulmonary ventilation…read more

Page 3

Preview of page 3

Here's a taster:

Prevention and control: bcg vaccine makes people immune, better education,
better housing, improved health facilities better nutrition so immune system is not
Pulmonary Fibrosis
Formation of scar tissue in the lungs, the result of an infection such as TB or
exposure to substances such as asbestos and dust.…read more

Page 4

Preview of page 4

Here's a taster:

Elastin is elastic it helps the alveoli return to their normal shape after inspiration
and expiration.
Loss of elastin means the alveoli can't recoil to expel air as well, (it remains trapped
in the alveoli).
It also leads to destruction of the alveoli walls, which reduces the surface area of the
alveoli so the rate of gaseous exchange decreases.
Symptoms ­ shortness of breath, wheezing. Increased breathing rate to increase the
amount of air to the lungs.…read more


No comments have yet been made

Similar Biology resources:

See all Biology resources »See all resources »