Cardiovascular System

1. Cardiovascular System Ms. Harborth Anatomy & Physiology II

2. Location and Size of Heart • About the size of a person’s fist • Cone-shaped, weighs less than a pound • Base – pointed towards right shoulder • Apex – pointed at the left hip • Located in thoracic cavity in mediastinum

3. Covering and Wall • Pericardium (visceral and parietal) • Heart wall has 3 layers: • Epicardium (visceral pericardium) • Myocardium – thick bundles of cardiac muscle. Layer that actually contracts. • Endocardium – reinforces the myocardium. Thin, glistening sheet of endothelium.

5. Chambers and Great Vessels • 2 Atria, 2 Ventricles • Right side – Receives O2-poor blood from superior and inferior venae cavae. Pumps through pulmonary trunk to pulmonary arteries which carries blood to the lungs. • PULMONARY CIRCUIT • Left side – receives O2-rich blood from pulmonary veins. Pumped out through aorta to all body tissues. • Walls of left side are much thicker and more powerful. Why? • SYSTEMIC CIRCUIT

7. Valves • Atrioventricular (AV) valves. Open during relaxation, closed during contraction • Left – called bicuspid or mitral valve • Right – called tricuspid valve • Semilunar valves. Open during contraction, closed during relaxation • Pulmonary and Aortic

9. Blood flow Through Heart

10. Cardiac Circulation • Coronary arteries branch from aorta and encircle heart in atrioventricular groove. • Coronary veins empty into coronary sinus on backside of heart. Coronary sinus empties into right atrium.

11. Heart Attacks • When heart beats rapidly, myocardium may receive inadequate blood. • Angina pectoris – “warning pain” • Myocardial infarction – myocardium stops contracting due to heart cell death.

12. Conduction • Autonomic NS and Intrinsic Conduction System control heartbeat. • Intrinsic Conduction System – Made up of unique tissue • Sinoatrial Node “pacemaker” • Atrioventricular node • Atrioventricular bundle • Bundle branches • Purkinje fibers

13. Cardiac Cycle • Systole (contraction) & Diastole (relaxation) • Cardiac cycle – events in one complete heartbeat. About .8 sec.

14. Heart Sounds • “Lub” – closing of AV valves • “Dub” – closing of semilunar valves at end of systole

15. Cardiac Output • Amount of blood pumped out by each side in 1 min • CO = HR x SV • AVERAGE: • 75 beats/min x 70 ml/beat = 5250 ml/min • (That’s more than the entire blood volume in one minute!) • What is stroke volume, and how do we regulate it? • What is heart rate, and how do we regulate it?

16. Blood Vessels • Arteries -> arterioles -> capillary beds -> venules -> veins • Only capillaries serve the needs of body cells • Tunics: • tunica interna(thin layer of endothelium. Cells form slick layer to decrease friction) • tunica media (mostly smooth muscle and elastic tissue) • tunica externa(fibrous connective tissue. Support and protect)

17. Comparing Arteries, Veins and Capillaries

18. Venous Return

19. Capillary Beds • Walls are only 1 cell layer thick, allowing blood to go in and out of tissues. • Microcirculation

20. Major Arteries

21. Major Veins

22. Brain Circulation“Circle of Willis”

23. Hepatic Portal System

24. Fetal Circulation

25. Circulation Physiology • Arterial Pulse + Blood Pressure = Vital Signs • Arterial Pulse: normally equals the heart rate

26. Pressure Gradient

27. Measuring Blood Pressure • Systolic Pressure: • Pressure in arteries at the peak of ventricular contraction • Diastolic Pressure: • Pressure in arteries when the ventricles are relaxing • Systolic/Diastolic (120/80 mm Hg average)

28. Measuring Blood Pressure

29. Factors Affecting Blood Pressure • Neural factors (ANS) • Renal factors (kidneys) • Temperature • Chemicals • Diet • Hypertension • Hypotension