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Circulatory System

Objective :

  • To learn the procedure for collection of different parts of cardiovascular system.
  • To learn the structure of the cardiovascular system of rat.

Theory :

  • The circulatory system transports oxygen and nutrients to metabolizing body tissues and removes carbon dioxide and other metabolic wastes for removal from the body. The rat has a closed circulatory system, i.e. blood remains within the vessels. A vessel that carries oxygenated blood away from the heart to a capillary bed is an "artery".
  • A vessel that carries deoxygenated blood in the reverse direction, i.e.from the capillaries back to the heart is a "vein". Note that the pulmonary artery and vein are exceptional in this regard. Heart is a four-chambered muscular pump that lies in the thoracic cavity within the pericardium. The right side supplies the pulmonary circulation and the left side the systemic circulation.
  • Each side of the heart has an atrium (the anterior chamber that receives blood) and a ventricle (a thicker walled chamber whose contractions drive the blood out of heart). The right atrium receives systemic venous blood (deoxygenated) from the cranial vena cava, caudal vena cava, azygos vein and the coronary sinus. The right atrium contracts and forces the blood into the right ventricle'.
  • The contraction of  right ventricle chamber pushes the blood into the 'pulmonary artery' and on to the lungs, where it receives oxygen. The oxygenated blood from the lungs enters the left atrium of the heart through the pulmonary vein.
  • Contraction of the left atrium pushes the blood into the left ventricle. The contraction of the left ventricle forces the oxygenated blood through the aorta to the rest of the body. The effectiveness of these contractions is increased by the presence of valves that prevent the backflow of blood. Between each atrium and its corresponding ventricle is a set of 'atrioventricular valves'.  
  • The  tricuspid valve is present between the right atrium and the ventricle. The bicuspid valve is present between the left atrium and the ventricle. Semilunar valves are present between the aorta and the left ventricle. A set of valves is found at the junction of the pulmonary artery and the right ventricle. These valves prevent blood from flowing back into the chamber. Chordae tendineae prevent the valves from flapping back into the atria.  The left and right coronary arteries, which arise from the aorta, provide the arterial supply to the heart.
  • The coronary veins follow the course of the arteries and open into the left atrium through the coronary sinus. The lymphatic vessels run in the epicardium and join into trunks and eventually drain into the tracheo-bronchial lymph nodes.

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