Explain the mechanism involved in external respiration.
Respiration is the process of gas exchange involving oxygen, carbon dioxide, and specialized organs such as lungs or gills, between animals and the environment and within the animal body. It is of 2 types: internal (within the body) and external (between animal and environment) respirations.
External Respiration
External Respiration or breathing is the process of exchange of gases between the external environment and bloodstream of an animal. Different organisms follow different mechanisms of external respiration. They are of 5 types:
• Direct diffusion: primitive method sponges, jelly fishes, and flatworms; direct diffusion of oxygen to surface cells and then to cells inside the body.
• Diffusion into blood: e.g. annelids and amphibians; diffusion of oxygen from moist surface layer to capillary walls and then to bloodstream.
• Tracheae: air moves into surface openings called spiracles and then to specialized tubes called tracheae, which divides into small braches in contact with organs and muscles (seen in insects and arthropods).
• Gills: specialized infoldings with a layer of cells and capillaries, which take up dissolved oxygen from water and exchange carbon dioxide by countercurrent mechanism (seen in fishes and aquatic animals).
• Lungs: the most advanced form of respiration seen in the terrestrial vertebrates. Lungs are specialized organs with several small chambers impregnated with blood capillaries, e.g. humans, other mammals, and birds.
Mechanism
Diffusion is the main mechanism of gaseous exchange, which involves movement of a substance from high- to low-concentrated areas. The basic 3 components of external respiration are surface area of alveolar membrane, partial pressure gradient of gases, and ventilation and perfusion matching. Human respiratory system comprises nose, air passages (pharynx, trachea, bronchus, and bronchioles), and lungs (alveoli surrounded by blood capillaries). Inspiration (breathing in) and expiration (breathing out) are the 2 main stages of respiration, in addition to gaseous exchange within the body.
External air is drawn into the body to increase oxygen supply and internal air exhaled out to release carbon dioxide from the body.
• Inspiration: contraction of intercostal muscles, movement of sternum and, in turn, ribs in upward and outward directions, flattening of diaphragm, volume increase in thoracic cavity, reduction in pressure, and air rushes in.
• Expiration: relaxing of intercostal muscles, movement of sternum and, in turn, ribs in inward and downward directions, relaxing of diaphragm, volume decrease in thoracic cavity, increase in pressure, and air expelled out.
Respiration is the process of gas exchange involving oxygen, carbon dioxide, and specialized organs such as lungs or gills, between animals and the environment and within the animal body. It is of 2 types: internal (within the body) and external (between animal and environment) respirations.
External Respiration
External Respiration or breathing is the process of exchange of gases between the external environment and bloodstream of an animal. Different organisms follow different mechanisms of external respiration. They are of 5 types:
• Direct diffusion: primitive method sponges, jelly fishes, and flatworms; direct diffusion of oxygen to surface cells and then to cells inside the body.
• Diffusion into blood: e.g. annelids and amphibians; diffusion of oxygen from moist surface layer to capillary walls and then to bloodstream.
• Tracheae: air moves into surface openings called spiracles and then to specialized tubes called tracheae, which divides into small braches in contact with organs and muscles (seen in insects and arthropods).
• Gills: specialized infoldings with a layer of cells and capillaries, which take up dissolved oxygen from water and exchange carbon dioxide by countercurrent mechanism (seen in fishes and aquatic animals).
• Lungs: the most advanced form of respiration seen in the terrestrial vertebrates. Lungs are specialized organs with several small chambers impregnated with blood capillaries, e.g. humans, other mammals, and birds.
Mechanism
Diffusion is the main mechanism of gaseous exchange, which involves movement of a substance from high- to low-concentrated areas. The basic 3 components of external respiration are surface area of alveolar membrane, partial pressure gradient of gases, and ventilation and perfusion matching. Human respiratory system comprises nose, air passages (pharynx, trachea, bronchus, and bronchioles), and lungs (alveoli surrounded by blood capillaries). Inspiration (breathing in) and expiration (breathing out) are the 2 main stages of respiration, in addition to gaseous exchange within the body.
External air is drawn into the body to increase oxygen supply and internal air exhaled out to release carbon dioxide from the body.
• Inspiration: contraction of intercostal muscles, movement of sternum and, in turn, ribs in upward and outward directions, flattening of diaphragm, volume increase in thoracic cavity, reduction in pressure, and air rushes in.
• Expiration: relaxing of intercostal muscles, movement of sternum and, in turn, ribs in inward and downward directions, relaxing of diaphragm, volume decrease in thoracic cavity, increase in pressure, and air expelled out.
