Biology

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Catharine Cox

• Biology
• The development of internal gas exchange
  surfaces in larger organisms to maintain adequate
  rates of exchange. Mammals (alveoli, bronchioles,
  bronchi, trachea, lungs), including the
  ventilation system.

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How Organisms are adapted to gas exchange

• To enable efficient gas exchange organisms
  have to be adapted. In this case the walls of
  the alveoli are made up of a layer of epithelial
  cells which are flattened. The capillaries are
  also made up from this way. This allows gases to
  diffuse through two membranes only. To keep the
  alveoli moist water constantly diffuses through
  it.

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Respiratory System in Mammals

• The respiratory system is the gas exchange
  organ in mammals. It contains the following
• Alveoli
• bronchioles
• bronchi
• Trachea
• lungs

This can be seen on the following diagram
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Diagram of the Breathing System
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Ventilation System

• The concentration gradient across the
  respiratory system is maintained by
• Blood flow on one side
• Air flow on the other side

This allows oxygen to diffuse down its own
gradient from air to blood, while carbon dioxide
can diffuse down its own concentration gradient
from blood to air.
The flow of air into and out of the alveoli is
known as Ventilation, and has two stages
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Two Stages of Ventilation

• Inspiration
• How it works-
• Diaphragm flattens and contracts
• Intercostal muscles contract making the ribs come
  up and out
• This increases the volume of the the thorax which
  in turn increases the lung and alveoli volume
• Pressure of air is decreased and so air flows IN
  to equalise this.

• Expiration
• How it works
• Diaphragm relaxes and curves upwards
• Ribs fall as intercostal muscles relax
• This decreases volume of thorax which in turn
  decreases lung and alveoli volume.
• This increases the pressure of air and so air
  flows OUT to equalise this.

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Diagram
The following diagram helps explain this
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Gas In the Alveoli
Table to show what happens to the composition of
air when it reaches the alveoli

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The End!