Respiration

04.14.2020
08:27:15
Biology/grade 9 - Today’s topic-Breathing movements- course book-pages 146 to 148.

Main points-
Inhaling:

the internal intercostal muscles relax and the external intercostal muscles contract, pulling the ribcage upwards and outwards
the diaphragm contracts, pulling downwards
the volume in the thorax gets bigger, forcing the lungs to expand, and the air pressure inside decreases
air is pushed into the lungs


Exhaling:

The external intercostal muscles relax and the internal intercostal muscles contract, pulling the ribcage downwards and inwards
the diaphragm relaxes, moving back upwards.
The lungs are elastic and shrink back to their relaxed volume and the air pressure inside increases
air is pushed out of the lungs.

Gaseous exchange refers to the exchange of oxygen and carbon dioxide, which takes place between the air and the blood vessels in the lungs.

Gas exchange in the lungs happens in the alveoli. Some of the features of alveoli include:

thin walls (just one cell thick)
large surface area
moist surface
many blood capillaries

Some of the oxygen is absorbed into the bloodstream when it enters the alveoli, resulting in a reduction of oxygen.
Cells of the body produce CO2 as a waste product during aerobic respiration. The bloodstream carries CO2 to the lungs for excretion and diffuses across the walls of the alveoli to be expired, resulting in a 100% increase of carbon dioxide breathed out.
The lining of the alveoli is coated with a firm of moisture in which oxygen dissolves. Some of this moisture evaporates into the alveoli and saturates the air with water vapour. The air you breathe out, therefore, always contains a great deal more water vapour than the air you breathe in.
















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