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.
As the ventricle contracts, blood leaves the heart through the pulmonic valve, into the pulmonary artery and to the lungs, where it is oxygenated. The oxygenated blood then returns to the heart through the pulmonary veins. Left side of the heart. The pulmonary veins empty oxygen-rich blood from the lungs into the left atrium.