The model on test is the 'Sprinter Stick which according to the website is designed to be a 'segmental stretching device' and is the most rigid of the smaller models. The rigidity is still allows some flex without too much pressure and the stick certainly feels strong enough to take a hard rub if needs be.
In most vertebrates oxygen enters the bloodstream  via diffusion at the alveoli of the lungs. This diffusion (a  passive thing) is accomplished because oxygen concentration â¦ in the  lungs is much higher than that of the blood, even than that of   oxygenated blood.es, in a sense the respiratory system removes oxygen from the air and replaces it with carbon dioxide. When the respiratory system takes in air, it reduces the concentration â¦ of oxygen from 21% to 16%. The air is inhaled by the diaphragm into the trachea, which leads into the lungs via the bronchi.
Small blood vessels called capillaries surround the alveoli. Oxygen passes through the thin walls of the alveoli and into the blood in the capillaries. A protein in the red blood cells called hemoglobin helps to transport the oxygen. At the same time, carbon dioxide passes from the blood into the alveoli. When air is breathed out, or exhaled, the air contained in the alveoli, which is rich in carbon dioxide, is forced out of the lungs and exits the body through the nose and mouth.