An Introduction to Types of Respiration
Respiration is the process in which organisms exchange gases between their body cells and the environment. From prokaryotic bacteria and archaeans to eukaryotic protists, fungi, plants, and animals, all living organisms undergo respiration. Respiration may refer to any of the three elements of the process.
First, respiration may refer to external respiration or the process of breathing (inhalation and exhalation), also called ventilation. Secondly, respiration may refer to internal respiration, which is the diffusionof gases between body fluids (blood and interstitial fluid) and tissues. Finally, respiration may refer to the metabolic processes of converting the energy stored in biological molecules to usable energy in the form of ATP. This process may involve the consumption of oxygen and production of carbon dioxide, as seen in aerobic cellular respiration, or may not involve the consumption of oxygen, as in the case of anaerobic respiration.
Key Takeaways: Types of Respiration
- Respiration is the process of gas exchange between the air and an organism's cells.
- Three types of respiration include internal, external, and cellular respiration.
- External respiration is the breathing process. It involves inhalation and exhalation of gases.
- Internal respiration involves gas exchange between the blood and body cells.
- Cellular respiration involves the conversion of food to energy. Aerobic respiration requires oxygen while anaerobic respiration does not.
Types of Respiration: External and Internal
![Breathing Diagram](https://www.thoughtco.com/thmb/GcQ1pRVytuc0vlV-PRYJnkC9hR0=/1500x1000/filters:no_upscale():max_bytes(150000):strip_icc():format(webp)/breathing_diagram-5c37af15c9e77c00013abdbd.jpg)
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External Respiration
One method for obtaining oxygen from the environment is through external respiration or breathing. In animal organisms, the process of external respiration is performed in a number of different ways. Animals that lack specialized organs for respiration rely on diffusion across external tissue surfaces to obtain oxygen. Others either have organs specialized for gas exchange or have a complete respiratory system. In organisms, such as nematodes (roundworms), gases and nutrients are exchanged with the external environment by diffusion across the surface of the animals body. Insects and spiders have respiratory organs called tracheae, while fish have gills as sites for gas exchange.
Humans and other mammals have a respiratory system with specialized respiratory organs (lungs) and tissues. In the human body, oxygen is taken into the lungs by inhalation and carbon dioxide is expelled from the lungs by exhalation. External respiration in mammals encompasses the mechanical processes related to breathing. This includes contraction and relaxation of the diaphragm and accessory muscles, as well as breathing rate.
Internal Respiration
External respiratory processes explain how oxygen is obtained, but how does oxygen get to body cells? Internal respiration involves the transportation of gases between the blood and body tissues. Oxygen within the lungs diffuses across the thin epithelium of lung alveoli (air sacs) into surrounding capillaries containing oxygen depleted blood. At the same time, carbon dioxide diffuses in the opposite direction (from the blood to lung alveoli) and is expelled. Oxygen rich blood is transported by the circulatory system from lung capillaries to body cells and tissues. While oxygen is being dropped off at cells, carbon dioxide is being picked up and transported from tissue cells to the lungs.
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