1. The Cardiovascular System Chapter 15

2. Heart is two pumps in one: Right side – pulmonary circulation Left side – systemic circulation Heart → Arteries → Arterioles → Capillaries → Venules→ Veins → Heart Artery – any vessels that carries blood away from the heart. Vein – any vessels that carries blood toward the heart

6. Parietal pericardium: outer fibrous layer inner serous layer Pericardial cavity Visceral pericardium (epicardium) Pericarditis Cardiac Tamponade

7. Heart Wall 3 Layers: Epicardium – serous membrane Myocardium – muscle layer Endocardium – continuous throughout circulatory system

9. Cardiac Muscle : involuntary, striated Intercalated discs: gap junctions functional syncytium desmosomes – “spot welds”

18. Anastomoses – collateral circulation Ischemia – reduced blood flow Hypoxia – reduced oxygen supply Angina pectoris – “strangled chest” Myocardial infarction – death of an area of tissue due to interrupted blood flow

21. Cardiac cycle One complete heart beat: systole (contraction) and diastole (relaxation) of both atria and systole and diastole of both ventricles

23. Heart Murmurs – abnormal sounds caused by the flow of blood. Mitral stenosis Mitral valve prolapse

25. Conduction system of the heart Sinoatrial (SA) node – “pacemaker’ → Atrioventricular (AV) node → Atrioventricular (AV) Bundle - Bundle of His → Purkinje fibers – conduction myofibers Ectopic pacemaker

33. Regulation of Heart Rate Sympathetic N.S. increases heart rate and force of contraction – secrete epinephrine –accelerator nerves Parasympathetic N.S. decrease heart rate and force of contraction through the vagus nerve. Sends continuous impulses. Secretes acetylcholine

35. Other factors that influence heart rate Temperature Ions – K+ and Ca++ Hormones Hypoxia, acidosis and alkalosis slow heart Age gender Physical fitness

36. Anatomy of blood vessels Arteries carry blood away from the heart Hole is called the lumen Three layers or tunics: –Tunica interna (intima) –Tunica media –Tunica externa (adventitia)

37. Tunica interna Simple squamous epithelium called endothelium Secretes biochemicals that inhibit platelet aggregation Also substances that dilate or constrict vessels

38. Tunica media Bulk of vessel wall Smooth muscle fibers Innervated by the sympathetic N.S. – vasoconstriction; decreased impulses = vasodilation Thick layer of elastic connective tissue

39. Tunica externa Thin layer Connective tissue Attaches artery to surrounding tissue Contains tiny vessels – vasa vasorum that form capillaries and provide blood to external cells of the vessel

40. Arteries Large arteries are elastic (conducting) arteries – pressure reservoirs Medium arteries are muscular (distributing) arteries – more smooth muscle

43. Arterioles Have all three layers, but thin as they divide Branches called metarterioles join capillaries Arteriovenous shunts

45. Capillaries Only a single layer of endothelium and a basement membrane Connect arterioles and venules Microcirculation Functional part of system for exchange of gases, wastes and nutrients True capillaries begin at a precapillary sphincter

48. Types of capillaries Continuous - intercellular clefts, but otherwise uninterrupted

51. Types of capillaries Continuous - intercellular clefts, but otherwise uninterrupted Fenestrated capillaries – have “windows” or pores – act in filtration Sinusoids or discontinuous capillaries have spaces between cells, and basement membrane is incomplete or absent Tight junctions – form a barrier

52. Venules Small vessels that join capillaries and veins Add layers

53. Veins Have same three tunics as arteries, but have a thinner tunica media Contain valves Act as blood reservoirs

59. Hemodynamics: Physiology of Circulation Velocity of blood flow is inversely related to the cross-sectional area of the blood vessels (total area). Slow flow through capillaries allows for exchange. The circulation time – right atrium to foot and back – is about one minute in a resting person.

60. Blood pressure Pressure on walls of a vessel Arterial pressure rises and falls as the left ventricle contracts Highest during systole – Systolic pressure Lowest during diastole – Diastolic pressure Mean arterial pressure is about 93 mm Hg

62. Factors that influence arterial blood pressure Cardiac Output: SV (ml/beat) X HR (beats/min) = CO(ml/min.) 70 ml X 75 = 5250 ml or 5.25 liters Within limits, the greater the stretching of the muscle fibers, the greater the force of contraction – Starling’s Law

64. Hormonal Regulation of B. P. Epinephrine and norepinephrine Renin-angiotensin system ADH – antidiuretic hormone - vasopressin ANP – atrial natriuretic peptide Others

66. Hepatic Portal Circulation Drains spleen, stomach, pancreas, gallbladder and small and large intestines 2 nd capillary bed in liver Glucose is removed, and stored as glycogen Blood is detoxified Leaves through hepatic vein → inferior vena cava

68. Fetal Circulation Obtains oxygen and nutrients from maternal circulation Two arteries off internal iliac arteries run through umbilical cord Umbilical vein returns oxygenated blood Several shunts in fetal circulation:

69. Ductus venosus – bypasses fetal liver and dumps blood from umbilical vein into inferior vena cava. Foramen ovale – hole in atrial septum, blood passes from right atrium to left atrium, bypassing the developing lungs Ductus arteriosus – connects pulmonary artery with aorta If does not close – patent ductus arteriosus – get mixing of venous and arterial blood.

71. Circle of Willis