The Respiratory System

The Respiratory System

The human body needs a constant supply of oxygen to enable energy to be released.

Breathing is the means by which this is done and the process is known as respiration.

The respiratory system brings air (with oxygen) into the body and removes carbon dioxide from the body.

Air passages

A series of air passages allow air and the oxygen it contains to be transferredto the blood stream and also remove waste products.

From the mouth and nose, air travels down the trachea into the trachea's two branches the bronchi that divide into bronchioles inside the lung.

The bronchioles sub-divide into small air sacs called alveoli.

The lungs

The lungs are sac-like with thin walls and are very flexible.

A plural membrane surrounding the lungs keeps them moist and lubricated.

The diaphragm

The diaphragm is a sheet of muscle that encloses the bottom of the thorax.

Contraction and relaxation of the diaphragm, combined with the intercostals muscles enables breathing.

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When breathing in (inspiration):

  1. Muscles across the ribs contract and pull the ribs upwards.
  2. The muscles of the diaphragm also contract and flatten out the floor of the rib cage.
  3. The lungs increase in size and so suck in air through the nose and mouth.

When breathing out (expiration):

  1. Muscles of the diaphragm and rib cage relax.
  2. The diaphragm pushes back into a domed position by the organs beneath it under pressure from the muscular abdominal wall.
  3. The ribs move down under their own weight. The space the lungs occupy is now smaller and so air is forced out again.