Anatomy and Physiology - The Lungs

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The Lungs

The Larynx:

  • Part of the vocal cords and is located between the pharynx and the trachea.
  • It is made up of cartilage.

The Lungs:

  • There are two and they are surrounded by the plural membrane.
  • The lungs are divided up into lobes; two on the left and three on the right.

The Trachea:

  • Connects the larynx with the bronchus and progressively into the smaller dimensions called the bronchiole.
  • It is a flexible fibro elastic and muscular structure which allows the neck to move.
  • Allows the transport of oxygen from the atmosphere to the lungs and carbon dioxide from the lungs into the atmosphere.
  • It is strengthened by rings of cartilage to prevent it come collapsing.
  • Contains cilia and mucus, which are hair like structures which traps dust and bacteria which is within the air, as it passes down the trachea.

Ciliated Lining:

  • A collection of fine hairs that cover the inside of the trachea.
  • They help to trap small particle and foreign bodies. 
  • Move in waves in one direction back up towards the head.
  • Goblet cells / mucus moving, wafting.

The Bronchus:

  • It splits into two tubes and so enables air to pass into both lungs.
  • Cells in the bronchi contain cilia to trap pathogens and prevent disease.
  • It splits into smaller divisions called the bronchioles.

The Bronchioles:

  • They are tiny tubes within the lungs.
  • They are connections of the bronchus.
  • The bronchioles are attached to tiny air sacs called the alveoli, where gas exchange takes place by the use of diffusion into the pulmonary capillaries. 

The Alveoli:

  • They are very thin – only one cell thick (epithelium).
  • They have a large surface area to volume ratio.
  • They are moist to assist with the diffusion of gases.
  • Their function is gas exchange.
  • Small air sacs that allow the diffusion of oxygen across their membrane into red blood cells in the surrounding capillaries.
  • They also allow the diffusion of carbon dioxide from the blood plasma to diffuse back into the alveoli.
  • Elasticised tissue to allow expansion.

Pleural Membranes:

  • They are lubricated and surround the whole lungs to keep them moist.
  • Without the pleural membranes, the lungs would face resistance and friction from the chest wall while they are expanding and contracting, which may cause shortness of breath ect.

The Diaphragm:

  • It is a sheet of internal muscle.
  • It is dome shaped when relaxed.
  • Extends across the bottom of the rib cage.
  • Divides the lungs and hearth from the stomach, kidney, liver etc.
  • Helps with the mechanism of breathing.
  • The intercostal muscles help bring enlargement of the thorax.
  • A large dome shaped muscle that contracts and relaxes causing the chest cavity to increase and decrease in volume allowing the lungs to expand and contract (breathing).
  • Changes pressure / maintains pressure within the lungs. 

Mechanisms of Breathing

This is done by two processes:

  • Inspiration - breathing in.
  • Expiration - breathing out.

These processes rely on pressure changes within the lungs, these are controlled by two sets of muscles:

  • The diaphragm:
  • A


Sam Morran


A nice resource with the correct amount of detail you would be required to know.  I also like the fact that you have to test yourself - try doing it before reading the work!

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