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## Cellular Respiration The oxygen-rich blood travels from the lungs to the heart. The heart pumps blood to the rest of the body through arteries. Arteries are divided into smaller arteries called arterioles, and finally to capillaries which carry oxygenated blood away from the heart to all other t...

## Cellular Respiration The oxygen-rich blood travels from the lungs to the heart. The heart pumps blood to the rest of the body through arteries. Arteries are divided into smaller arteries called arterioles, and finally to capillaries which carry oxygenated blood away from the heart to all other tissues and organs. In the presence of oxygen, glucose (food) is broken down into a form that the cell can use as energy. ### Mechanism of breathing Breathing is a continuous process and involves inhaling or taking in of oxygen-rich air and exhaling or giving out of carbon dioxide rich air. A breath involves one inhalation and one exhalation. The number of times a person breathes in a minute is called breathing rate. Breathing rate of a person varies during different activities. We breathe fast when we run but we breathe slowly when we are at rest. When we need extra energy during a physical exercise we breathe faster to supply more oxygen to our cells. This process uses up a large amount of food reserves within our body to provide more energy. That is why we also feel hungry after hard exercises. When we inhale air, ribs move up and outwards while the diaphragm moves down. Due to this, the space in the chest cavity increases and air enters into the lungs. When we exhale air, ribs move down and inwards while the diaphragm moves up. This movement reduces the space in the chest cavity and air is pushed out of the lungs. This enables the intake of oxygen and exhalation of carbon dioxide. ### The path of oxygen entering the human body during respiration is: - Nostrils - Nasal cavity - Pharynx - Trachea - Bronchi - Bronchioles - Alveoli - Blood - Cells