How are enzymes needed for the body to function?

Enzymes are like catalysts and they helo in body's chemical reactions and thus are important . Example you can take of lipase , or amylase , and there are many

blood enters the heart through two large veins, the inferior and superior vena cava, emptying oxygen-poor blood from the body into the right atrium of the heart. as the ventricle contracts, blood leaves the heart through the pulmonic valve, into the pulmonary artery and to the lungs where it is oxygenated.