Anatomy & Physiology of Cardiovascular System. Chapter 18 & 19

Transcription

1 Anatomy & Physiology of Cardiovascular System Chapter 18 & 19

2 Objectives..cont 1. Discuss the physiological stages of cardiac muscle contraction. 2. Trace a typical ECG and label each wave or complex 3. Define the terms systole and diastole. 4. Outline the phases of the cardiac cycle. 5. Discuss heart sounds in terms of what they represent. 6. Define the terms cardiac output (CO), heart rate (HR), and stroke volume (SV). 7. Discuss the factors the regulate heart rate.

3 Objectives 1. List the organs that compose the cardiovascular system and discuss the general functions of this system. 2. Describe the location, size, and orientation of the human heart. 3. Define the term cardiology. 4. Describe the structure of the heart in terms of its coverings, layers, chambers, valves, and blood vessels. 5. Explain why the atria are passive chambers, while the ventricles are active. 6. Name the function of heart valves. 7. Distinguish between AV and SL valves in terms of location, structure.

4 INTRODUCTION The major function of the cardiovascular systems is to circulate substances throughout the body. In other words, its organs function to supply cells & tissues with oxygen & nutrients and also to remove wastes (CO2 & urea) from cells and tissues. If cells do not receive O2 & nutrients and wastes accumulate, cells will die! Cardiology is the study of the heart and the diseases associated with it.

5 Functions Assist in gas transport. Deliver nutrients, hormones Remove waste products from the cells Assist in temperature regulation Assist in balancing body fluids and helps prevent dehydration

6 Major Components Pump (heart) Continuously circulates blood Network of tubes Arteries- blood away from heart Veins- blood back to the heart Blood Fluid that fills the circulatory system

7 Specific parts Pulmonary arteries- transport blood to lungs Pulmonary veins- transport oxygenated blood to hear Aortic arch and trunk- main arteries from heart Common carotid artery- carries blood to brain Renal vein and artery- connects to kidneys Mesenteric veins- connects to intestine

8

9 Accessory Organs Lungs- organ where oxygen is taken up and CO 2 is released Kidneys- organ where wastes are removed from blood; critical in regulating fluids in the body Small intestine- digestion Large intestine- water absorption

10 The Heart The human heart has four chambers Left and right ventricle Left and right atrium The left side of the heart pumps oxygenated blood to the body. the right side of the heart pumps deoxygenated blood to the lungs where oxygen can be absorbed by the hemoglobin.

11 The heart functions to contract and propel blood through the two blood transport systems. 1. Pulmonary system 2. Systemic system

12

13 LOCATION/SIZE OF HEART A. Location = within mediastinum behind the body of the sternum between the points of attachment of ribs 2 through 6. B. Size = closed fist; 300g (adult). C. Base = wide superior border; D. Apex = inferior point.

14 LOCATION OF HEART

15 Surface Anatomy of the Heart (anterior view)

16 Structure of the heart Wall of the heart made up of three distinct layers pericardium : parietal layer lies inside fibrous, and visceral layer (epicardium) adheres to outside of the heart; pericardial space with pericardial fluid separates the two layers. Epicardium: visceral layer Myocardium: thick, contractile middle layer of heart wall; compresses the heart cavities, and the blood within them, with great force Endocardium: delicate inner layer of endothelial tissue

17 Wall of the heart

18 Cardiac muscle Each cardiac muscle contians two types of intracellular contractile protiens, actin & myosin. The myosin appears thick where as actin appears thin and connected to Z band on end.

19 Cardiac Muscle

20 Chambers of the heart divided into four cavities with the right and left chambers separated by the septum 1. Atria Two superior chambers, known as receiving chambers, because they receive blood from veins Atria alternately contract and relax to receive blood and then push it into ventricles Myocardial wall of each atrium is not very thick, because little pressure is needed to move blood such a small distance Auricle earlike flap protruding from each atrium

21 Chambers of the heart..cont Ventricles Two lower chambers, known as pumping chambers, because they push blood into the large network of vessels Ventricular myocardium is thicker than myocardium of the atria, because great force must be generated to pump blood a large distance; myocardium of left ventricle is thicker than the right, because it must push blood much further

22

23 Valves of the heart mechanical devices that permit the flow of blood in one direction only. Atrioventricular (AV) valves prevent blood from flowing back into the atria from the ventricles when the ventricles contract 1.Tricuspid valve guards the right atrioventricular orifice; free edges of three flaps of endocardium are attached to papillary muscles by chordae tendineae 2. Bicuspid, or mitral, valve similar in structure to tricuspid valve except only two flaps present

24 Valves of the heart..cont Semilunar (SL) valves half moon shaped flaps growing out from the lining of the pulmonary artery and aorta; prevent blood from flowing back into ventricles from aorta and pulmonary artery 1. Pulmonary valve at entrance of pulmonary artery 2. Aortic valve at entrance of aorta

25 Heart valves 1. Mitral valve 2. Tricuspid valve 3. Aortic valve 4. Pulmonary valve

26

27 Blood supply of heart tissue Coronary arteries: myocardial cells receive blood from right and left coronary arteries First branches to come off aorta Ventricles receive blood from branches of both right and left coronary arteries Each ventricle receives blood only from a small branch of corresponding coronary artery Most abundant blood supply goes to myocardium of left ventricle The right coronary artery is dominant in approximately 50% of all hearts. Few anastomoses exist between the larger branches of the coronary arteries

28 Blood supply of heart tissue (cont.) Veins of the coronary circulation As a rule, veins follow a course that closely parallels that of coronary arteries After going through cardiac veins, blood enters coronary sinus to drain into right atrium Several veins drain directly into right atrium

29 Coronary arteries:

30 Skeleton of the Heart

31 Conduction system of the heart 1. Sinoatrial (SA) node, 2. Atrioventricular (AV) node, 3. AV bundle 4. Purkinje fibers Sinoatrial node (SA node or pacemaker): in right atrial wall near opening of superior vena cava Atrioventricular node (AV node): small mass of special cardiac muscle in right atrium along lower part of interatrial septum Atrioventricular bundle (AV bundle or bundle of His) and Purkinje fibers extends by two branches down the two sides of the interventricular septum, and continues as Purkinje fibers Purkinje fibers extend out to papillary muscles and lateral walls of ventricles

32

33 Conduction system..cont Conduction system structures are more highly specialized than ordinary cardiac muscle tissue and permit only rapid conduction of an action potential through the heart SA node (pacemaker) Initiates each heartbeat and sets its pace Specialized pacemaker cells in the node possess an intrinsic rhythm

34 Sequence of cardiac stimulation After being generated by the SA node, each impulse travels throughout the muscle fibers of both atria, and the atria begin to contract As the action potential enters the AV node from the right atrium, its conduction slows to allow complete contraction of both atrial chambers before the impulse reaches the ventricles After the AV node, conduction velocity increases as the impulse is relayed through the AV bundle into the ventricles Right and left branches of the bundle fibers and Purkinje fibers conduct the impulses throughout the muscles of both ventricles, stimulating them to contract almost simultaneously

35 Conduction System

36 Electrocardiogram Normal ECG is composed of the following: P wave represents depolarization of the atria QRS complex represents depolarization of the ventricles and repolarization of the atria T wave represents repolarization of the ventricles; may also have a U wave that represents repolarization of the papillary muscle Measurement of the intervals between P, QRS, and T waves can provide information about the rate of conduction of an action potential through the heart P QRS T

37

38 Nerve supply of the heart Cardiac plexuses located near arch of aorta, made up of the combination of sympathetic and parasympathetic fibers Most fibers end in the SA node, but some end in the AV node and in the atrial myocardium Sympathetic nerves accelerator nerves Vagus fibers inhibitory, or depressor, nerves

39 Nerve supply of the heart

40 Nerve supply of the heart

41 Blood vessels Types of blood vessels Arteries Carry blood away from heart all arteries except pulmonary artery carry oxygenated blood Elastic arteries largest in body Examples: aorta and its major branches Able to stretch without injury Accommodate surge of blood when heart contracts and able to recoil when ventricles relax

42

43 Capillary Bed Arterioles Metarteriole Capallaries Venules

44 Capillaries primary exchange vessels Microscopic vessels Carry blood from arterioles to venules together, arterioles, capillaries and venules constitute the microcirculation Veins Carry blood toward the heart Act as collectors and as reservoir vessels; called capacitance vessels

45 Capillary Exchange

46 Venous valves

47 Layers of blood vessels Layers Tunica adventitia found in arteries and veins Tunica media found in arteries and veins Tunica intima found in all blood vessels; only layer present in capillaries

48

49

50 Structure of blood vessels 1. Endothelial cells Only lining found in capillary Line entire vascular tree Provide a smooth luminal surface protects against intravascular coagulation Intercellular clefts, cytoplasmic pores, and allow exchange to occur between blood and tissue fluid Capable of secreting a number of substances Capable of reproduction

51 Structure of blood vessels..cont 2. Collagen fibers Formed from protein molecules that aggregate into fibers Have only a limited ability to stretch Function to strengthen and keep lumen of vessel open 3. Elastic fibers Composed of insoluble protein called elastin Fibers can stretch over 100% under physiological conditions Play important role in creating passive tension to help regulate blood pressure throughout cardiac cycle 4. Smooth muscle fibers Present in all segments of vascular system except capillaries

52 Types Circulation Systemic circulation blood flows from the left ventricle of the heart through blood vessels to all parts of the body (except gas exchange tissues of lungs) and back to right atrium Pulmonary circulation: venous blood moves from right atrium to right ventricle to pulmonary artery to lung arterioles and capillaries where gases are exchanged; oxygenated blood returns to left atrium via pulmonary veins; from left atrium, blood enters left ventricle

53

54 The Heart As a Pump Cardiac cycle a complete heartbeat consisting of contraction (systole) and relaxation (diastole) of both atria and both ventricles; the cycle is often divided into time intervals Atrial systole Contraction of atria completes emptying blood out of the atria into the ventricles AV valves are open; semilunar (SL) valves are closed Ventricles are relaxed and filling with blood This cycle begins with the P wave of the ECG

55 Cardiac cycle (cont.) ventricular contraction Occurs between the start of ventricular systole and the opening of the SL valves Ventricular volume remains constant as the pressure increases rapidly Onset of ventricular systole coincides with the R wave of the ECG and the appearance of the first heart sound

56 Ejection SL valves open and blood is ejected from the heart when the pressure gradient in the ventricles exceeds the pressure in the pulmonary artery and aorta Rapid ejection initial, short phase is characterized by a marked increase in ventricular and aortic pressure and in aortic blood flow

57 Cardiac cycle (cont.) ventricular relaxation Ventricular diastole begins with this phase Occurs between closure of the SL valves and opening of the AV valves A dramatic fall in intraventricular pressure but no change in volume The second heart sound is heard during this period

58

59 Contraction: systole Relaxation: Diastole The heart sounds Heart sound lub closing of AV valves dub closing of semilunar valves Heart sounds have clinical significance because they give information about the functioning of the valves of the heart

60 Cardiac out put Cardiac Output - the amount of blood pumped by a ventricle per minute. Units may be in milliliters or Liters per minute. Heart Rate - number of cardiac cycles per minute. Average Stroke Volume - amount of blood pumped out of a ventricle each beat. Average resting stroke volume = 70 ml.

61 COP Determined by: Cardiac output = Stroke Volume x Rate 5040ml = 70ml x 72 bpm Peripheral resistance Diameter of blood vessels Viscosity of blood Peripheral resistance resistance to blood flow Factors that influence peripheral resistance Blood viscosity Diameter of arterioles

62 Frank Starling Law of the Heart = Increased blood volume = increased stretch of myocardium Increased force to pump blood out.

63

64 Factors that affect heart rate 1. SA node normally initiates each heartbeat. 2. Anxiety, fear, and anger often increase heart rate 3. Grief tends to decrease heart rate 4. Emotions 5. Exercise 6. Increased blood temperature 7. Decreased blood temperature

65 Venous Return to Heart Venous return: amount of blood returned to the heart by the veins 1. Stress-relaxation effect : occurs when a change in blood pressure causes a change in vessel diameter 2. Gravity: the pull of gravity on venous blood while sitting or standing 3. Venous pumps: Respirations Skeletal muscle contractions Semilunar valves in veins

66 Blood pressure Systolic blood pressure : while ventricles are contracting Diastolic blood pressure: when ventricles are relaxed Pulse pressure: difference between systolic and diastolic Relation to arterial and venous bleeding 1. Arterial bleeding: blood escapes from artery 2. Venous bleeding: blood flows slowly and steadily due to low, practically constant pressure

67 Blood pressure

68 Factors influencing blood pressure Blood Pressure = Blood Volume Peripheral Resistance Blood volume loss due to injuries, hemorrhages, use of diuretics, etc. = BP Blood volume increases due to increased water retention from increased ADH production, IVs or transfusions = BP

69 Factors influencing blood pressure Blood Pressure = Blood Volume Peripheral Resistance Peripheral Resistance affected by: blood viscosity (thickness) (Polycythemia) diameter of vessels (vasoconstriction/vasodilation) Vasoconstriction = diameter = resistance = BP Vasodilation = diameter = resistance = BP elasticity of arterial walls Elastic Arterial Walls = BP

70 Blood pressure Hypotension: abnormal low blood pressure. Sustained systolic blood pressure of below 100 mm Hg. Hypertension : High blood pressure arterial blood pressure of 140/90 mm Hg or above

71 Pulse Pulse: alternate expansion and recoil of an artery Alternating increase and decrease of pressure in the vessel Elasticity of arterial walls allows walls to expand with increased pressure and recoil with decreased pressure Pulse site: Temporal radial carotid apical brachial posterior tibial Dorsal spedis pulse. Popliteal Femoral

72 Any Question??? Good luck Dr. Yassin Abobaker Abdulghani