Circulatory System

• The Circulatory System is responsible for transporting throughout the body oxygenated blood from the heart and lungs via the arteries. Deoxygenated blood or oxygen-depleted blood is returned to its origin through the veins.
• Functions:

  1. Delivers oxygen and nutrients to all cells in the human body.
  2. Transports carbon dioxide and other wastes away from the cells.
  3. Helps in the coagulation process
  4. Regulates body temperature
  5. Assists in fighting diseases.
• Two Main Components

  1. Cardiovascular System - heart, blood vessels and blood
  2. Lymphatic System - lymph, lymph nodes and vessels
• Heart is a hollow muscular organ that has four chambers and is surrounded by a thin, fluid filled sac called pericardium. Size: same size of a person’s clenched fist.
• Epicardium: thin, watery membrane on the outer layer of the heart.

  Function: covers the heart and is attached to the pericardium.
• Pericardium: it is the membrane that encloses the heart and the roots of the major heart vessels.

  Function: protects the heart, prevents friction during heart contractions.
• Parietal pericardium: consists of dense connective tissue that protects the heart and maintains its position within the thoracic cavity.
• Visceral pericardium: envelopes the heart and forms epicardium which is the most superficial layer of the heart.
• Two layers of pericardium form the pericardial sac and this normally contains clear, straw colored fluid called pericardial fluid.
• Myocardium: thick layer of cardiac muscle in the middle layer of the heart. Function: pumps blood into the arteries by contracting.
• Endocardium: thin layer of epithelial cells in the inner layer of the heart. Function: lines the valves and interior chambers.
• Right Atrium: upper right chamber

  Function: receives deoxygenated blood from the body
• Right Ventricle: lower right chamber

  Function: receives the blood from the right atrium and pumps it into the pulmonary artery.
• Left Atrium: upper left chamber

  Function: receives oxygenated blood from the lungs and pumps it into the left ventricle.
• Left Ventricle: lower left chamber

  Function: receives blood from the left atrium and pumps it into the aorta.
• Right AV (atrioventricular) valve: tricuspid valve located between the RA and RV.

  Function: closes as the RV contracts preventing blood from flowing back to the RA.
• Left AV (atrioventricular) valve: bicuspid or mitral valve located between the LA and LV.

  Function: closes as the LV contracts preventing blood from flowing back to the LA.
• Interatrial Septum: partition that separates the RA from the LA.
• Interventricular Septum: separates the RV from the LV.
• Coronary Circulation receives blood supply thru the left and right coronary arteries, and coronary veins return the oxygen depleted blood from the heart muscle back to the heart. Coronary circulation supplies the blood and also provides drainage from the tissues. Composed of the left and right coronary arteries and coronary veins.
• Cardiac Cycle

  Systole (contraction) and diastole (relaxation) which lasts about 0.8 seconds
• Electrical Conduction System Sends electric impulses throughout the myocardium which is initiated by the sinoatrial (SA) node (pacemaker)
• ECG/electrocardiogram Provides the graphical representation of the cardiac cycle’s activity
• Origin of the Heart Sounds “Lubb” first sound produced as the ventricles contract or the AV valves close. “Dupp” second sound which is heard when the semilunar valves close and the ventricles relax
• The average heart rate is 72 bpm and the cardiac output refers to the volume of blood pumped per minute
• Pulse A rhythmic throbbing resulting from the alternating expansion and contraction of the artery
• Blood Pressure Force exerted by the blood on the walls of the vessel measured by the sphygmomanometer.
• Angina pectoris Chest pain resulting from reduced blood flow to the heart.
• Aortic stenosis A murmuring sound produced when the aortic leaflets fall to fully open during systole
• Bacterial endocarditis An infection that happens when a bacteria enters and resides in the heart lining or blood vessel.
• Congestive heart failure A chronic progressive condition that affects the pumping power of the heart muscles.
• Myocardial infarction Known as heart attack and caused by a decrease or full stoppage of blood flow that damages the heart muscle.
• Pericarditis Inflammation of the pericardial sac that may be due to viral infection.
• Vascular System - the loop which consists of a system of blood vessels through which blood is circulated to the rest of the body. Two Divisions: (1) pulmonary circulation and (2) systemic circulation
• Blood Vessel Structure A. Layers 1. Tunica adventitia (outer connective tissue) 2. Tunica media (middle muscle and elastic fiber) 3. Tunica intima (inner, endothelial cells) B. Lumen C. Valves
• Aneurysm: this is an enlargement of the artery due to the weakening of the artery wall.
• Arteriosclerosis: hardening of the artery wall due to aging.
• Atherosclerosis: formation of plaques in the inner walls.
• Embolism: clot or bubble which causes obstruction of an artery.
• Embolus: obstruction that is carried and lodged in a vessel.