The Cardiovascular System

1. The Cardiovascular System

2. Objectives: • Describe the functions of the cardiovascular system • List and describe the structure of the types of blood vessels • Compare and contrast pulmonary and systemic circulation • Identify the external and internal structures of the heart and their functions • Describe how the heart beat is generated • Describe the events of a cardiac cycle • Describe blood pressure and how it is measured • Describe the composition of whole blood • Describe the composition of plasma • Describe the various formed elements and their functions • Describe the process of hemostasis • Identify and describe various disorders of the cardiovascular system • Identify risk factors associated with coronary disease

3. Functions: • A closed system of the heart and blood vessels • The heart pumps blood • Blood vessels allow blood to circulate to all parts of the body • to deliver oxygen and nutrients to and remove carbon dioxide and other waste products from the bodies tissues

4. Blood Vessels: Types • Taking blood to the tissues and back • Arteries - large, thickest walled, carry blood away from heart, blood is moved by the pumping of the heart • Arterioles - smaller, thinner walled, carry blood away from heart, blood is moved by pumping of the heart • Capillaries - smallest, thinnest vessels, one cell layer thick, site of exchange of materials between the blood and body tissues • Venules - thinner walled vessels, carry blood back towards heart • Veins - thin walled vessels, large lumen, have valves present which keep blood moving in one direction, blood is moved by “milking” action due to the contraction of skeletal muscles

5. Structure of Vessels • Three layers (tunics) • Tunic interna • Endothelium • Lines interior of vessels • Decreases friction from blood flow • Tunic media • Smooth muscle • Middle layer • Changes diameter of vessels • Controlled by sympathetic nervous system • Tunic externa • Mostly fibrous connective tissue • External layer • Supports and protects vessels

6. Structure of Vessels

7. Blood is squeezed forward through vein when skeletal muscles contract A valve opens allowing blood to fill chambers Valves close when backflow of blood occurs, preventing blood from going backwards Blood Movement Through Veins

8. Capillaries • Only one cell layer thick, just tunica interna • Due to thinness exchanges can be made across the membrane between the blood and tissues • Microcirculation – blood flow moves from arteries into capillaries where materials are exchanged, then into veins

9. Capillary Transport Mechanisms • 4 routes for materials to cross the capillary walls • Diffusion across the plasma membrane • Endocytosis/Exocytosis • Intercellular clefts – gaps in plasma membrane • Fenestrated capillaries – mainly areas of filtration and absorption (like intestines or kidneys) • Intercellular clefts and fenestrated capillaries depend on osmotic pressure in interstitial fluid surrounding capillaries

11. External Coverings of the Heart • Pericardium – a double serous membrane • Visceral pericardium • Next to heart • Parietal pericardium • Outside layer • Serous fluid fills the space between the layers of pericardium

12. External Coverings of the Heart

13. Muscular Tissue • Cardiac muscle: branched at the end with striations present, usually only one nucleus is present per cell • branches of each fiber come into contact at specialized junctions called intercalated discs • involuntarily controlled

14. External Structure of the Heart

15. Great Vessels of Heart • Aorta (largest blood vessel in the body) • Leaves left ventricle, carries oxygenated blood to all parts of the body • Pulmonary arteries • Leave right ventricle, carries deoxygenated blood to the lungs • Vena cava (Superior and Inferior) • Enters right atrium • superior vena cava brings deoxygenated blood from the upper part of the body • inferior vena cava brings deoxygenated blood from the lower part of the body • Pulmonary veins (four) • Enter left atrium, brings oxygenated blood from the lungs • Ligamentum Arteriosum – ligament between aorta and pulmonary trunk that holds the vessels in place

16. External Anatomy of the Heart • Heart is divided into four chambers • Atria • Receiving chambers • Right atrium • Left atrium • Ventricles • Discharging chambers • Right ventricle • Left ventricle

18. Blood Circulation • Pulmonary circulation – process of blood flow from right side of heart  lungs  back to left side of heart • Pulmonary trunk – heart pumps oxygen poor blood out of heart to lungs to get oxygen and release carbon dioxide; breaks into the pulmonary arteries • Systemic circulation – process of blood flow from the left side of heart  pump to body tissues  back to right side of heart

19. Blood Circulation: Pulmonary and Systemic Pathways CO2 is given off by the blood into the lungs and O2 is picked up by the blood from the lungs. O2 is given off by the blood and and CO2 is picked up by the blood from the body’s tissue. Animation video

20. Coronary Blood Supply • Blood in the heart chambers does not nourish the myocardium • The heart has its own nourishing circulatory system • Coronary arteries • Cardiac veins • Blood empties into the right atrium via the coronary sinus

21. Internal Structures of the Heart: Heart Wall • Three layers • Epicardium • Outside layer • This layer is the parietal pericardium • Connective tissue layer • Myocardium • Middle layer • Mostly cardiac muscle • Endocardium • Inner layer • Endothelium

22. Internal Structures of Heart • Right and left side act as separate pumps • Four chambers • Atria • Receiving chambers • Right atrium • Left atrium • Ventricles • Discharging chambers • Right ventricle • Left ventricle • The valves allow blood to flow in only one direction • Four valves • Atrioventricular valves – between atria and ventricles • Bicuspid valve (left) • Tricuspid valve (right) • Semilunar valves between ventricle and artery • Pulmonary semilunar valve • Aortic semilunar valve

23. Internal Structures of the Heart

24. The Heart’s Pace Maker: Regulation of Heartbeat Special tissue sets the pace • Sinoatrial node • Pacemaker • Atrioventricular node • Atrioventricular bundle • Bundle branches • Purkinje fibers • Contraction is initiated by the sinoatrial node • Sequential stimulation occurs at other autorhythmic cells Fibrillation results when SA node is not working properly.

25. ECG: Electrocardiagram • This graph shows the electrical changes which occur when the muscles of the heart wall depolarize and repolarize.

26. ECG: Electrocardiogram • The first little upward notch of the ECG tracing is called the "P wave." The P wave indicates that the atria (the two upper chambers of the heart) are contracting to pump out blood. • The next part of the tracing is a short downward section connected to a tall upward section. This next part is called the "QRS complex." This part indicates that the ventricles (the two lower chambers of the heart) are contracting to pump out blood to the body.

27. ECG: Electrocardiogram • The next short upward segment is called the "ST segment." The ST segment indicates the amount of time from the end of the contraction of the ventricles to the beginning of the rest period before the ventricles begin to contract for the next beat. • The next upward curve is called the "T wave." The T wave indicates the resting period of the ventricles.

28. Cardiac Cycle • Atria contract simultaneously • Atria relax, then ventricles contract • Systole = contraction • Diastole = relaxation • Cardiac cycle – events of one complete heart beat • Mid-to-late diastole – blood flows into ventricles • Ventricular systole – blood pressure builds before ventricle contracts, pushing out blood • Early diastole – atria finish re-filling, ventricular pressure is low

29. Cardiac Cycle

30. Cardiac Cycle: Valves

31. The Heart’s Pace Maker: Regulation of Heartbeat

32. Cardiac Output • The amount of blood pumped out by each side of the heart in 1 minute. • Stroke volume – the volume of blood pumped out by a ventricle with each heartbeat. • Heart rate – the number of heart beats per minute • CO = HR x SV

33. Cardiac Output • Example: • Resting values • HR = 75 beats/min • SV = 70 ml/min • CO = HR (75 beats/min) x SV (70 ml/beat) • CO = 5250 ml/min

34. Pulse • Pulse – pressure wave of blood as it passes through an artery • Monitored at “pressure points” where pulse is easily palpated

35. Blood Pressure • Measurements by health professionals are made on the pressure in large arteries • Systolic – pressure at the peak of ventricular contraction • Diastolic – pressure when ventricles relax • Pressure in blood vessels decreases as the distance away from the heart increases • Human normal range is variable • Normal • 140–110 mm Hg systolic • 80–75 mm Hg diastolic • Hypotension • Low systolic (below 110 mm HG) • Often associated with illness • Hypertension • High systolic (above 140 mm HG) • Can be dangerous if it is chronic

36. Blood Pressure

37. Diseases and Disorders of the Cardiovascular System Myocardial infarction: heart attack • blockage of coronary artery which supplies the myocardium • cardiac muscle dies causing the heart not to function properly • can be due to formation of deposits of cholesterol and lipids called plaques, blood clots called thrombus, or an embolism which is a blood clot that forms somewhere else in the body, breaks free and lodges in a coronary artery stopping the flow of blood Angina pectoralis: sharp pain radiating into the left arm and /or neck accompanied by a feeling of pressure within the chest - a classic symptom of problems with blood flow to the heart muscle itself

38. Diseases and Disorders of the Cardiovascular System • Congestive Heart Failure: Cardiac decompensation causes blood circulation to become inadequate  tissues don’t get the support needed to supply oxygen and carry out wastes • Ectopic Focus – the sinoatrial node doesn’t work properly causing abnormal pacing • Fibrillation – condition in which the heart becomes uncoordinated and can no longer function as a pump • Heart Block – the atrioventricular nodes are damaged • Incompetent valve – one or more valves in the heart become damaged causing blood to leak back through (no longer one way flow) • Pulmonary congestion – initial condition when the left side of the heart fails (blood still pumping through right side, but gets backed up when left side stops pumping.)

39. Diseases and Disorders of the Cardiovascular System • Atherosclerosis: commonly called “hardening of the arteries” • arteries began to loose elasticity due to aging and formation of plaques in their walls • They narrow and reduce blood supply to regions of the body particularly the brain and heart

40. Diseases and Disorders of the Cardiovascular System • Aneurysm: a weakened area within the wall of an artery or arteriole • Because of the high pressure, the vessel wall balloons out and can rupture when the wall becomes stretched too thin  leads to a serious internal hemorrhage (internal bleeding)

41. Diseases and Disorders of the Cardiovascular System • Arrhythmia: due to the irregular beat of the heart • may be due to damage to the SA or AV node, or the myocardium • commonly treated with medications or by the implantation of an artificial pace-maker Bradycardia: the heart is beating too slow • Tachycardia: the heart is beating too fast

42. Blood • The only fluid tissue in the human body • Classified as a connective tissue • Living cells = formed elements • Non-living matrix = plasma • Color range • Oxygen-rich blood is scarlet red • Oxygen-poor blood is dull red • pH must remain between 7.35–7.45 • Blood temperature is slightly higher than body temperature

43. Blood: Plasma • Composed of approximately 90 percent water • Includes many dissolved substances • Nutrients • Salts (metal ions) • Respiratory gases • Hormones • Proteins : Albumin – regulates osmotic pressure, Clotting proteins – help to stem blood loss when a blood vessel is injured, Antibodies (globulins) – help protect the body from antigens • Waste products

44. Blood: Formed Elements • Erythrocytes = red blood cells • Leukocytes = white blood cells • Thrombocytes or Platelets = cell fragments • Formed in red bone marrow (hematopoiesis)

45. Whole Blood Composition

46. Blood: Formed Elements p. 313

47. Blood: Formed Elements

48. Red Blood Cells • Anucleate – no nucleus (unable to grow and divide) • Live about 100-120 days – remains eliminated by spleen and liver • Developing RBCs divide many times and begin hemoglobin synthesis • After enough hemoglobin produced, the cell ejects the nucleus and organelles causing the cell to collapes inward (concave shape) (takes 3-5 days) • RBC production controlled by hormone erythropoietin • Production not based on number of RBCs, based on amount of oxygen in blood

49. Blood: Formed elements Red Blood Cells Platelets Lymphocyte Basophil Eosinophil Monocyte Neutrophil

50. Blood Mini-Lab • Obtain prepared slide of blood • Identify and sketch at least 5 different formed elements (use color pencils) • You’ll sketch 1 picture – please see me to get approval for your drawing BEFORE you draw! • Analysis: • Explain the differences between the various white blood cells you saw in your slide.