Respiration & Circulation of oxygen Respiration in polar bears also takes place in a similar way to most mammals. The bear's closed circulatory system has a complex system of arteries and veins carrying blood cells and oxygen to the body systems. The main function of the circulatory system is to carry oxygen to the body systems and to get carbon dioxide out of the body. The respiratory system is the main source of oxygen for circulation. Within the respiratory system, the bear inhales air from it's environment through negative pressure breathing, where lung volume increases as the rib muscles and diaphragm contract. The air enters through the polar bear's nasal cavities, then goes down the larynx. The oxygen divides into the two bronchi located in the polar bear's chest, and then divides again into the bronchioles. The oxygen locates itself in the alveoli within the lungs, where it exchanges oxygen for carbon dioxide within the blood capillaries, and travels through veins back to the heart. When the oxygenated blood reaches the heart, it is pumped through arteries to other areas of the body, bringing oxygen needed for cell respiration and function to the cells that needs it most. The blood is deoxygenated by exchange with capillaries in the muscle and other body cells before traveling back to the heart and then lungs, repeating its cycle. This function allows the animal to interact with its environment for its necessary functioning, as well as producing carbon dioxide that may beneficial to other organisms in its environment.
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ENergy from FoodPolar bears, like most mammals, get their energy and mass from the food they eat. Their food, such as meat from seals or other arctic animals, goes into the digestive system through ingestion, where it is broken down to its simplest sugars and proteins. When the glucose from the food is broken down, it is cycled around the body to cells where its is to be processed. When glucose enters the body's cells such as muscle or nervous cells where it is constantly needed to power functions, it is sent to the mitochondria organelle. Within the mitochondria, cellular respiration occurs, in which glucose, water, and oxygen are used to produce ATP, the molecule uses as cellular energy in the body.
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