The respiratory system and breathing rate

In a nutshell

The lungs are one of the main organs of the respiratory system. The alveoli are the site of gas exchange within the lungs. An individual's average breathing rate can be calculated using a simple equation.

The respiratory system

The lungs (6) are found in the thorax, which is the top part of the body. The thorax is separated from the lower part of the body by an organ called the diaphragm (8). There are two lungs in the thorax which are surrounded by the pleural membranes and protected by the rib cage.

When a person breathes in, the air flows from the mouth (1), through the trachea (4) and into the two bronchi (5). The bronchi go into each lung, where they split into smaller bronchioles (7). The bronchioles end at the alveoli (9) which are small air sacs. Gas exchange occurs at the alveoli.

Biology; Organisation; KS4 Year 10; The respiratory system and breathing rate

Alveoli

The alveoli are small air sacs surrounded by a network of blood capillaries and are the site of gas exchange in the lungs. The lungs contain hundreds of millions of alveoli.

Blood from the body passes alongside the alveoli in the capillaries, containing little oxygen and lots of carbon dioxide. The carbon dioxide diffuses from the blood out into the alveolus to be breathed out. Oxygen diffuses from the alveoli into the blood to be transported to the body’s cells. When near the body’s cells, the red blood cells release oxygen for use in respiration.

Breathing rate

A person’s breathing rate can be calculated using a simple equation.

$breaths\space per \space minute = {number\space of\space breaths\over number\space of\space minutes}$

Example

Henry takes $135\space breaths$ in $9\space minutes$ . Calculate his average breathing rate in $breaths\space per \space minute$ .

$={135\over 9}$

$= \underline1\underline5\space breaths\space per\space minute$

$\underline{Henry's\ breathing\ rate\ is\ 15\ breaths\ per\ minute.}$