unit 1 p6

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.the respiratory system starts at the nasal passage it brings the air in through the news then the nasal passage warms it and it becomes humidified. the hairs in the nose called cilia then filter the air then it passes through the




.trachea this filters the air we inspire and the branches into the bronchi






Gaseous exchange

In the lungs, oxygen and carbon dioxide are exchanged in the tiny air sacs called alveoli at the end of the bronchial tubes. The alveoli are surrounded by capillaries. When a person inhales, oxygen moves from the alveoli to the surrounding capillaries and into the bloodstream. At the same time, carbon dioxide moves from the bloodstream to the capillaries and into the alveoli. The carbon dioxide is removed from the lungs when a person exhales.

Mechanics of breathing

Inspiration: .The ribs expand via the external intercostal muscles they raise the rib cage

.This allows the lungs to increase in size

.Making room for oxygen

Expiration: the ribs relax so the lungs decrease in size

. This pushes the air out

. the internal intercostal muscles lower the rib cage

Tidal Volume: The amount of air which enters the lungs during normal inhalation at rest.

Vital capacity: is the maximum amount of air a person can breathe out from the lungs after a maximum inhalation.

Residual volume: the volume of air still remaining in the lungs after the most forcible expiration possible.

Controlling of breathing

Neural: There are two neural mechanisms that control respiration one for voluntary breathing and one for automatic breathing. The voluntary impulse originates in the cerebral cortex region of the brain and the automatic impulse originates in the medulla oblongata.

Chemical: the chemoreceptors in the brain and heart detect the amount of oxygen and other waste products that are in the body. As a result, they adjust the rate of breathing to compensate for any disruptions in balance of any of these chemicals. Too much carbon dioxide or acidity and too little oxygen cause the respiratory rate to increase. Carbon dioxide chemoreceptors are much more sensitive than oxygen chemoreceptors and, thus, exert an effect with smaller changes.