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The Respiratory System
The Respiratory System
The respiratory system includes the organs and tissues in the body that maintain gas exchange between the internal and external environment. Many species can exchange gases directly through cells that are in contact with the environment.
Frogs can exchange gases through the skin.
Frogs can exchange gases through the skin.
Fish exchange gases as water passes
through the gills.
Fish exchange gases as water passes
through the gills.
Many animals, including humans, have a more complex process for gas exchange. Our cells need oxygen for survival and we need to be able to get rid of carbon dioxide.
The respiratory system can be divided into 2 sections:
Upper respiratory system (nasal passages, pharynx, and larynx).
Lower respiratory system (trachea, lungs, and diaphragm).
These organs work together to bring oxygen into the body and get rid of the carbon dioxide in the lungs.
During gas exchange, oxygen is inhaled into the mouth and nose and travels through the upper respiratory system into the lungs. Once the air is in the lungs, it moves into smaller structures called alveoli, which are surrounded by tiny bloood vessels called capillaries.
Two important exchanges take place in the alveoli.
Carbon dioxide molecules in the blood diffuse into the alveoli to be exhaled from the lungs.
The oxygen molecules in the lungs diffuse across the surface of the alveoli into the blood vessels to enter the circulatory system.
Once the carbon dioxide reaches the lungs, it will be pushed out of the body each time you exhale.
The oxygen in the blood is carried by specialized red blood cells (the disc- shaped structures in this image) that contain the protein hemoglobin.
If carbon dioxide builds up in the blood, the pH of the blood lowers and becomes acidic, causing a disruption to homeostasis. When sensors in the body detect a change in the pH, a signal is sent to speed up the breathing rate to get rid of carbon dioxide and increase oxygen intake.
Following a threat, breathing rate slows down as the pH returns to neutral.
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