NEET PG DENTAL EXAM

Detailed explanation-1: -When muscles contract and relax during the inspiration and expiration process, pressure changes occur in the thoracic and abdominal cavities. These pressure changes compress the nearby veins and assist blood return to the heart. Valves prevent the backflow of blood.

Detailed explanation-2: -Positive pressure breathing increases pressure throughout the thorax, decreasing the blood volume contained in the vascular structures within it. The volume of the heart and pulmonary veins as well as the blood vessels of the lungs all decrease during positive pressure breathing.

Detailed explanation-3: -Venous return is facilitated by a number of factors, including inspiration, increased total blood volume, increased venomotor tone, the cardiac suction effect, the presence of venous valves and the skeletal muscle pump.