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1. The Cardiovascular System Chapter 11

2. The Cardiovascular System • Cardiovascular system is a closed system • Consists of • Heart: The heart pumps blood • Blood vessels : Blood vessels allow blood to circulate to all parts of the body • Function: • To deliver oxygen and nutrients and to remove carbon dioxide and other waste products

3. Heart • Heart is transport system pump for the blood • Heart is two pumps in one • Pulmonary Circulation: • R side of heart receives blood from body, pumps blood to lungs and returns to L heart • Systemic Circulation: • L side of heart pumps blood to tissues of the body & return to R heart • Heart of healthy person pumps approx. 7200 L of blood each day at the rate of 5L/min.

4. Anatomy of the Heart • Location, size and shape of Heart • Size: size of a closed fist • Shape • Apex: Blunt rounded cone • Base: larger flat part • Location: • Located in thoracic cavity in left of mediastinum (midline) between the two lungs • Superior surface of diaphragm • Important clinically when using a stethoscope, performing an ECG, or performing CPR

5. Anatomy of the Heart • Heart is enclosed by a double-walled sac called Pericardium • Composed of: • A superficial fibrous pericardium • A deep two-layer serous pericardium • Parietal pericardium lines the internal surface of the fibrous pericardium • The visceral pericardium or epicardium lines the surface of the heart • & separated by fluid-filled pericardial cavity • Helps in reducing friction as heart moves within the pericardial sac

6. Anatomy of the Heart • Heart Wall: composed of 3 layers of tissues: • Epicardium – visceral layer of the serous pericardium, lines the surface of the heart • Myocardium – Middle layer, cardiac muscle layer forming the bulk of the heart, responsible for heart contraction • Endocardium – Lines inner surface of heart chambers

7. Heart Chambers and Vessels • Heart consists of 4 chambers: • Two atria, two ventricle • Atria: Thin walled, forms the superior part of heart • Ventricle: Thick-walled, forms the inferior part of heart • Large veins: carry blood to the heart: • Superior and inferior venae cavae • carry blood from body to R atrium • 4 pulmonary veins carry blood from lungs to L. atrium • Arteries: conveying blood away from heart: • Aorta carries blood from L. ventricle to the body • Pulmonary trunk carries blood from R. ventricle to lungs

8. Heart Chambers and Valves • Atria • Right atrium: three major openings to receive blood returning from the body (superior vena cava, inferior vena cava, coronary sinus) • Left atrium: four openings that receive blood from 4 pulmonary veins from lungs • Two atria are separated from each other byInteratrial septum

9. Heart Chambers and Valves • Ventricles • Atrioventricular valves: openings between atria and ventricles • Right ventricle opens to pulmonary trunk • Left ventricle opens to aorta • Interventricular septum between the two ventricle

10. Heart Valves • Heart valves ensure unidirectional blood flow through the heart • Atrioventricular (AV) valves: lie between the atria and the ventricles • AV valves allow blood flow from atria to ventricle • But prevent backflow into the atria when ventricles contract • AV valve between L atrium & L ventricle has 2 cusps – Bicuspid Valve • AV valve between R atrium & R ventricle has 3 cusps – Tricuspid Valve

11. Heart Valves • Semilunar Valves: • Aortic semilunar valve: lies between the left ventricle and the aorta • Pulmonary semilunar valve: lies between the right ventricle and pulmonary trunk • Semilunar valves prevent backflow of blood into the ventricles

12. Blood Flow Through the Heart • Superior and inferior vena cava dump blood into the right atrium • From right atrium, through the tricuspid valve, blood travels to the right ventricle • From the right ventricle, blood leaves the heart as it passes through the pulmonary semilunar valve into the pulmonary trunk • Pulmonary trunk splits into right and left pulmonary arteries that carry blood to the lungs

13. Blood Flow Through the Heart • Oxygen is picked up and carbon dioxide is dropped off by blood in the lungs • Oxygen-rich blood returns to the heart through the four pulmonary veins from lungs • Blood enters the left atrium and travels through the bicuspid valve into the left ventricle • From the left ventricle, blood leaves the heart via the aortic semilunar valve and aorta • From aorta, supply blood to all body parts

14. Blood Flow Through the Heart

15. Cardiac Circulation • Blood in the heart chambers does not nourish the heart muscles • Coronary arteries in heart supply blood to heart muscles • Coronary arteries branch from the aorta to supply the heart muscle with oxygenated blood • Cardiac veins from heart drain blood into a large venous cavity called Coronary sinus • Coronary sinus thenempties into the right atrium

16. Physiology of Heart • Heart muscle cells contract, without nerve impulses, in a regular, continuous way • Heart is autorhythmic • Initiate, conduct and impulse • Heart contains special tissue that produces & sends electrical impulses to the heart muscle to contract

17. Physiology of Heart • The heart's conducting system consists of: • Sinoatrial (SA) node • Atrioventricular (AV)node • Bundle of His • Bundle branches • Purkinje fibers

18. Physiology of Heart • Sinoatrial (SA) Node • Mass of autorhythmic cells • Electrical impulse that causes rhythmic contraction of heart muscles arises in the SA node • Pacemaker of the heart • Located in R. atrium • Send impulse 70 to 80 times a minute

19. Physiology of Heart • AV Node: • The electrical impulse from the SA node spreads over the right and left atria • causes atrial contraction • Then impulses are conducted to the atrioventicular (AV) node

20. Physiology of Heart • Bundle of His (AV bundle) • Then electrical impulse is relayed down to Bundle of HIS • Conducts impulse to right and left bundle branches • Bundle Branches • Right and left branches • Branch into purkinje fibers • Purkinje Fibers • Enter myocardium of ventricle walls • Carry impulse to ventricles • Ventricular contraction

21. CARDIAC CONDUCTION SYSTEM SUMMARY Sinoatrial Node AV Node AV Bundle Bundle Branches Purkinje Fibers

22. Cardiac Cycle • Cardiac cycle: Is the sequence of events in one heartbeat • It is the repetitive pumping process that begins with onset of cardiac muscle contraction and ends with beginning of next contraction • Cardiac muscle contraction is responsible for pressure and blood movement. How? • Blood moves from high pressure to low pressure

23. Cardiac Cycle • The length of cardiac cycle is about 0.8 sec • Interval from end of one contraction to the following contraction • Consists of Two Phases: • Systole phase • Diastole phase

24. CARDIAC CYCLE • Systole Phase • Contraction phase • Atrial Systole (0.1 sec.) • After passive filling with blood • Atrial pressure rises above ventricular pressure • And AV valves open • Blood is ejected from atria to ventricle • semilunar valves closed • Ventricles fill with blood

25. CARDIAC CYCLE • Ventricular Systole (0.3 sec.) • AV and semilunar valves closed until Ventricle pressure rises above aorta and pulmonary trunk pressure • opens semilunar valves • Blood pushed into pulmonary trunk and Aorta • 120 mm Hg pressure • Atria in diastole

26. CARDIAC CYCLE • Diastole Phase • Relaxation phase • Ventricular Diastole • Follows ventricular systole • AV valves reopen and filling begins • 80 mm Hg pressure

27. Electrocardiogram: ECG • When impulse pass through the heart, electric currents are generated • Electric current that can be measured at the surface of the • body - ECG • P wave: Atrial depolarization • QRS complex: Ventricular • depolarization • T wave: Ventricular • repolarization

28. Heart Contractions • Tachycardia—rapid heart rate over 100 beats per minute • Bradycardia—slow heart rate less than 60 beats per minutes

29. Heart Sounds • First heart sound or “lubb” • Atrioventricular valves vibrations as valves close at beginning of ventricular systole • Second heart sound or “dupp” • Results from closure of aortic and pulmonary semilunar valves at beginning of ventricular diastole, lasts longer

30. Cardiac Output • Cardiac output (CO) • Amount of blood pumped by heart in one minute • Stroke volume (SV) • Volume of blood pumped by each heartbeat • Usually remains relatively constant • About 70 mL of blood is pumped out of the left ventricle with each heartbeat • Heart rate (HR) • Typically 75 beats per minute

31. Cardiac Output • CO = HR  SV • CO = HR (75 beats/min)  SV (70 mL/beat) • CO = 5250 mL/min • Starling’s law of the heart— the more the cardiac muscle is stretched, the stronger the contraction • Important factor for stretching the heart muscle is venous return • The greater the volume of blood returned to the heart by the veins, the greater the volume of blood the heart will pump

32. Regulation of the Heart • To maintain homeostasis, amount of blood pumped by heart must vary: • Eg. Cardiac output increases more during exercise than resting • Intrinsic regulation: Results from normal functional characteristics of heart, not depend on neural or hormonal regulation

33. Regulation of the Heart • Extrinsic regulation: Involves neural and hormonal control • Neural Control • Parasympathetic stimulation • Supplied by vagus nerve, acetylcholine is secreted, • decreases heart rate, maintain • heart beat average of 70 beats/min. • Sympathetic stimulation • Supplied by cardiac nerves • Increases heart rate and force of contraction. • Epinephrine and norepinephrine released. • Increased heart beat causes increased cardiac output

34. Regulation of the Heart • Hormonal Control • Epinephrine and norepinephrine from the adrenal medulla • Increases rate and force of heart contraction • Occurs in response to increased physical activity, emotional excitement, stress

35. Transport blood to the tissues and back Carry blood away from the heart Arteries Arterioles Exchanges between tissues and blood Capillary beds Return blood toward the heart Venules Veins Blood Vessels: The Vascular System

36. Generalized Structure of Blood Vessels • Arteries and veins are composed of three tunics (layers) – tunica intima, tunica media, and tunica externa • Lumen – central blood-containing space surrounded by tunics • Capillaries are composed of endothelium

37. Three layers (tunics) Tunic intima Endothelium Basement membrane Tunic media Smooth muscle Blood flow is regulated by smooth muscle of Tunica Media Vasoconstriction: smooth muscles contract, decrease in blood flow Vasodilation: smooth muscles relax, increase in blood flow Controlled by sympathetic nervous system Tunic externa Mostly fibrous connective tissue Thickness of each layer varies with type and diameter of blood vessel Blood Vessels: Microscopic Anatomy

38. Walls of arteries are the thicker than veins Lumens of veins are larger than arteries Because BP is low in veins and work against gravity Larger veins have valves to prevent backflow More valves in veins of lower extremities than in veins of upper extremities Walls of capillaries are only one cell layer thick to allow for exchanges between blood and tissue Differences Between Blood Vessels

39. Most arterial blood is pumped by the heart Veins use the milking action of muscles to help move blood Movement of Blood Through Vessels

40. Capillary beds consist of two types of vessels Vascular shunt— vessel directly connecting an arteriole to a venule True capillaries— exchange vessels Oxygen and nutrients cross to cells Carbon dioxide and metabolic waste products cross into blood Capillary Beds

41. Circulatory Pathways • The vascular system has two distinct circulations • Pulmonary circulation – short loop that runs from the heart to the lungs and back to the heart • Systemic circulation – routes blood through a long loop to all parts of the body and returns to the heart

42. Pulmonary Circulation • Heart pumps blood from right ventricle into pulmonary trunk • Pulmonary trunk divides into left and right pulmonary arteries, Transport blood to each lung • Two pulmonary veins exit each lung and enter left atrium

43. Systemic Circulation: Arteries • Oxygenated blood enter the heart from pulmonary veins through L. atrium • From L. atrium to L. ventricle • From L. ventricle to aorta • From aorta blood flows to all body parts

44. Systemic Circulation: Arteries • Aorta • All arteries are derived from aorta • Aorta is divided into 3 parts: • Ascending aorta • Aortic arch • Descending aorta • Ascending aorta: Passes superiorly to heart, has 2 branches • right and left coronary arteries, supply blood to cardiac muscles • Aortic arch: arching posteriorly and to the left and has 3 branches, carry blood to head and neck • Brachiocephalic artery • Left common carotid • Left subclavian artery

45. Systemic Circulation: Arteies • Aorta • Descending aorta: Longest part • Consists of: • Thoracic aorta: portion in thorax • Abdominal aorta: inferior to diaphragm: branches supply blood to abdominal wall and organs • Ends as two common iliac arteries: supply blood to pelvis & lower limbs • Coronary Arteries: - Only branches of ascending arteries, supply blood to heart

46. Return blood from body to right atrium Major veins Coronary sinus : returning blood from heart walls Superior vena cava: Returning blood from head, neck, thorax, upper limbs Inferior vena cava: Returning blood from abdomen, pelvis, lower limbs Types of veins Superficial, deep, sinuses (cranium & heart) Major veins of the Systemic Circulation

47. Arterial Supply of Brain Supply of blood to brain is crucial Lack of O2 kills the brain cells that cannot be revived The main arteries that supply blood to brain include Internal carotid artery Vertebral artery Internal carotid arteries divide into Anterior and middle cerebral arteries These arteries supply most of the cerebrum Vertebral arteries join once within the skull to form the basilar artery Basilar artery serves the brain stem and cerebellum Special Circulations

48. Arterial Supply of the Brain: Basilar artery divides to form Posterior cerebral arteries These arteries supply the posterior cerebrum Anterior and posterior blood supplies are united by small communicating arterial branches Result—complete circle of connecting blood vessels called cerebral arterial circle or circle of Willis around the pituitary gland Special Circulations

49. Hepatic Portal System • Nutrients and other substances absorbed by stomach and intestine are transported to liver by hepatic portal system • Hepatic portal system carries blood through veins from capillaries of stomach, intestine, spleen to liver • Largest vein of the system • From liver Hepatic veins join the Inferior vena cava

50. Pulse Pressure wave of blood Monitored at “pressure points” in arteries where pulse is easily palpated Pulse averages 70–76 beats per minute at rest Pulse

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