Human Circulatory and Respiratory Systems: A Detailed Explanation

Blood flows from the left ventricle to the aorta - the largest artery in the body, and from there, blood vessels begin to continuously branch out into smaller and smaller vessels, reaching all parts of the body.

There are three protective barriers in the entire respiratory tract. First, nose hair blocks foreign objects such as bacteria, viruses, and dust from entering the respiratory tract. Second, the mucus secreted by the tracheal epithelial cells sticks to foreign objects and is carried out by the cilia movement of the mucosal epithelium. Third, there is a type of cell in the alveoli that can engulf foreign objects in the alveoli.