Breathing

• Most animals and plants consist of different types of cells organised as tissues, organs and systems.
• The human respiratory system is a body system adapted for efficient gas exchange.
• Breathing is the process of moving air into and out of the lungs, as it is carried to and from the exchange surfaces of the alveoli.
• Alveoli are tiny air sacs in the lungs, where gas is exchanged during breathing.
• The diaphragm is a large sheet of muscle that separates the lungs from the abdominal cavity.
• The rib cage is the arrangement of bones in the thorax, formed by the ribs, vertebral column and sternum, that encloses the lungs and heart.
• The rib cage moves to create a lower air pressure in the lungs than that of the air outside the body.
• Air then rushes into the lungs when the rib cage moves to create a lower air pressure.
• The diaphragm is the most important muscle when we inhale.
• The external intercostal muscles are the second most important muscles when we inhale.
• Breathing is a passive process resulting from pressure changes in the lungs.
• When we inhale and exhale more forcibly, other muscles are also used.
• Exhalation is the result of the diaphragm and external intercostal muscles relaxing.
• The respiratory system consists of the structures and organs involved in breathing, including the airways, lungs, and chest wall.
• The human gas exchange system consists of the structures and organs involved in breathing, including the airways, lungs, and chest wall.
• Breathing in involves moving air into the lungs, as it is carried to and from the exchange surfaces of the alveoli.
• Breathing out involves exhaling air from the lungs, which is the result of the diaphragm and external intercostal muscles relaxing.
• The structure of the respiratory system includes the airways, lungs, and chest wall.
• The human gas exchange system includes the structures and organs involved in breathing, including the airways, lungs, and chest wall.
• Each gill filament has a network of blood capillaries.
• Gas exchange in fish is more difficult than in animals that live on land due to the lower concentration of oxygen in water.
• The concentration of oxygen in water is around 1% at 15°C, compared to 21% in the air at any temperature.
• The exchange of oxygen and carbon dioxide is more efficient in fish due to the large surface area of the gills, the large surface area of the blood capillaries in each gill filament, the short distance required for diffusion, and the efficient ventilation of the gills with water.
• Fish gills allow water to be taken in through the mouth, pass over the gills, and then out under the operculum.
• Fish gills extract 70 to 80% of the available oxygen from the water.
• Water that flows over the gills flows in the opposite direction to the blood, a process known as counter current flow.