Cardiovascular system

Transcription

1 Cardiovascular system 1

2 Essential Question: How does the structure of the heart allow it to function in pumping blood? 2

3 Function? 3

4 Location of Heart 4

5 Heart coverings double sac of serous membrane pericardium visceral pericardium (epicardium) hugs external heart surface part of heart wall parietal pericardium anchors heart to surrounding structures filled with serous fluid why? pericarditis inflammation of pericardium decrease in serous fluid layers stick together painful 5

6 Walls of heart epicardium outer most layer visceral pericardium connective tissue myocardium middle layer mostly cardiac muscle endocardium lines heart cavities epithelial tissue 6

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8 Chambers of the heart atria receiving chambers ventricles pumping chambers interventricular septum divides right side from left side 8

9 Heart external structure 9

10 Pulmonary circulation from right side of heart (right ventricle), to pulmonary arteries, to lungs, to pulmonary veins and then back to left side of heart (left atrium) function gas exchange get rid of carbon dioxide pick up oxygen 10

11 systemic circulation from left ventricle, to aorta, to arteries, to body tissues (capillaries), to veins, to inferior and superior vena cavas, to right atrium function: brings oxygen to tissues picks up wastes 11

12 Heart Valves function one way flow of blood Atrioventricular valves: tricuspid valve between right atrium and right ventricle Mitral (bicuspid valve) between left atrium and left ventricle pulmonary semilunar valve between right ventricle and pulmonary trunk aortic semilunar valve between left ventricle and aorta 12

13 Chordinae tendinae "heart strings that anchor the valves each set of valves works at different times. Incompetent valve valve does not close properly, blood back flows valvular stenosis valve flap becomes stiff can be due to repeated bacterial infections forces heart to contract more vigorously Treatment: Valve replacement 13

14 Cardiac Circulation coronary arteries feed heart muscle with nutrients cardiac veins drain heart muscle coronary sinus vein that empties into right atrium 14

15 Problems with blood flow to heart muscle angina pectoris chest pain due to lack of oxygen to cardiac muscle Myocardial infarction = heart attack or coronary 15

16 Conduction System of Heart pumps 6 quarts of blood/ 1000 times per day cardiac muscle can contract spontaneously, not needing a nerve impulse contraction occur regularly atrial cells beat 60 times/minute ventricular cells beat times/minute So how do they beat at the same time? 16

17 two controlling systems: 1. nerves from autonomic nervous system accelerate or slow heart rate 2. Intrinsic conduction system (nodal system) built in heart tissue regulates at ~75 beats/minute 17

18 Intrinsic conduction system 18

19 sinoatrial node (SA) located in right atrium= Pacemaker atrioventricular node (AV) located at junction of right atrium and right ventricle atrioventricular bundle (bundle of His) bundle branches located in interventricular septum Purkinje fibers muscle of ventricle walls 19

20 Problems with heart conduction: 1. heart block damage to AV node, causes ventricles to beat at own rate (slower) 2. damage to SA node slower heart rate install artificial pacemaker inserted 3. ischemia lack of blood supply to heart muscle leads to fibrillation rapid uncoordinated contractions (looks like a bag of worms) heart cannot pump treatment defibrillator 20

21 4. tachycardia rapid heart rate, over 100 beats/min prolonged could lead to fibrillation 5. bradycardia slower than normal heart rate <60 beats/min 21

22 Cardiac cycle and heart sounds Systole heart contraction diastole heart relaxation cardiac cycle = one complete heartbeat when both atria and ventricles contract and relax 0.8 seconds/ cycle based on 75 beats/min heart sounds: "lub dup" lub = AV valves closing dup = semilunar valves closing Heart murmur = abnormal sounds, caused by valve problem 22

23 Cardiac events 23

24 Cardiac output = amount of blood pumped out by each side of the heart in 1 minute = heart rate X stroke volume stroke volume = volume of blood pumped out by a ventricle per heartbeat ex. cardiac output = 75 beats/min X 70 ml/beat = 5250 ml/min therefore: the entire amount of blood in your body passes through your body per minute 24

25 regulation of stroke volume normally pump 60% of blood in ventricles regulated by: 1. the stretching ability of the heart muscle before contraction more stretched = stronger contraction 2. amount of venous return to heart more blood = more stretching if volume or speed increased = higher stroke volume 25

26 regulation of heart rate regulated by autonomic nervous system sympathetic division increases heart rate parasympathetic = decreases heart rate epinephrine, thyroxine hormones that increase heart rate also affected by age, gender, exercise, body temp females beats/min males beats/min 26

27 regulation of cardiac output 27

28 congestive heart failure heart is "worn out" heart is weak progressive condition cause atherosclerosis, high blood pressure, myocardial infarcts treatment = digitalis slows and steadies the heart rhythm Pulmonary congestion if left heart fails, right side still pumps blood to lungs blood vessels in lungs swell fluid leaks into lung air spaces pulmonary edema if untreated suffocation Peripheral congestion right side fails edema in distal parts of body puts strain on heart heart fails 28

29 Blood Vessels What are the differences? 29

30 Artery vs. Vein 30

31 Tunics 1. tunica interna lines the lumen (interior of vessel) endothelium on connective tissue helps decrease friction 2. tunica media middle coat smooth muscle, elastic tissue if constrict blood pressure increases if dilate blood pressure decreases 3. tunica externa outermost tunic fibrous connective tissue supports and protects vessels 31

32 Structural Differences between Arteries, Veins, and Capillaries Arteries thick tunica media smaller lumen no valves close to heart in terms of circulation high pressure Veins thin tunic media larger lumen has valves far from heart in terms of circulation low pressure 32

33 Ways blood gets back to heart against gravity 1. valves in veins 2. "milking" by skeletal muscles 3. larger lumen for more blood carrying capacity 4. pressure when we inhale fills veins near heart 33

34 Capillaries one cell thick tunica interna only form networks called capillary beds 34

35 Problems with blood vessels varicose veins cause standing for long periods, obese, pregnancy inefficient venous return blood pools valves do not work veins get twisted and dilated thrombophlebitis inflammation of a vein that results in clot pulmonary embolism clot that breaks and goes to lung 35

36 Arteries moves blood away from heart "most" carry oxygenated blood exceptions: pulmonary arteries umbilical arteries 36

37 Veins bring blood to the heart "most" carry deoxygenated blood exceptions: pulmonary veins umbilical vein 37

38 Special Circulations 1. The brain 38

39 Brain fed by carotids and vertebral arteries internal carotid arteries enter skull through temporal bone vertebral arteries enter back of brain and then becomes basilar artery Circle of Willis basilar and internal carotids connected by communicating arteries purpose protects brain provides alternate route for blood flow if clot or imparied blood flow 39

40 2. Hepatic Portal circulation circulation of digestive organs drains digestive organs, spleen, and pancreas and deliver to liver via hepatic portal vein liver processes nutrients from dig. system then goes to inf. vena cava 40

41 3. fetal circulation all nutrients, excretory and gas exchange through placenta umbilical vein blood rich with oxygen 2 umbilical arteries oxygen poor 41

42 ductus venosus vessel that bypasses liver foramen ovule hole between left and right atrium ductus arteriosus connects aorta and pulmonary trunk (bypasses lungs) ligmentum arteriosum collapsed ductus arteriosus after birth 42

43 Physiology of circulation pulse = alternating expansion and recoil of an artery pulse rate = heart rate pulse points are also pressure points points where put pressure to stop bleeding 43

44 Blood pressure = the pressure the blood exerts against the inner walls of the blood vessels keeps blood circulating = mean pressure within the large systemic arteries 44

45 Blood pressure in various areas of the cardiovascular system 45

46 measuring blood pressure 46

47 Effects of various factors on Blood pressure 1. peripheral resistance amount of friction by blood when it flows if vessel is narrow increase in resistance if blood is viscous increase if blood volume increases increase a. neural factors autonomic nervous system parasympathetic NS no effect sympathetic NS vasoconstricts blood vessels increases blood pressure ex. when getting up suddenly from lying down b.p. initially drops, get vasoconstriction to bring b.p. backup 47

48 b. renal factors: kidney alters blood volume to regulate arterial pressure If b.p. too high kidneys release more urine (water from the bloodstream) excreted if b.p. too low kidneys retain water if b.p. too low kidney releases renin that helps form angiotensin II vasoconstrictor c. temperature cold = vasoconstriction heat vasodilating 48

49 d. chemicals epinephrine increases heart rate and b.p. nicotine increases b.p. by vasoconstriction alcohol/ histamine vasodilation, decrease b.p. e. diet low salt, low saturated fats, low cholesterol prevents hypertension (high b.p.) 49

50 Problems with blood pressure normal blood pressure: systolic mm Hg diastolic mm Hg 1. Hypotension = low blood pressure systolic below 100 mm Hg athletes may have this, not a real problem orthostatic hypotension elderly condition dizziness when getting up from reclining or lying down chronic hypotension can indicate poor nutrition, low levels of blood proteins circulatory shock blood vessels are not filled with enough blood and cannot circulate normally, cause is blood loss 50

51 2. Hypertension high blood pressure "The Silent Killer" 140/90 or higher makes heart overwork can cause small tears in blood vessels (accelerate artherosclerosis) factors that affect blood pressure: diet, obesity, heredity, race, stress 51

52 Capillary exchange diffusion through interstitial fluid 4 methods of transport 52

53 bulk fluid exchange depends on hydrostatic pressure high pressure high on arterial end pressure low on venous end low 53

54 Artherosclerosis damaging process of blood vessel walls Steps: 1. damage to tunica interna 2. platelets initiate clotting 3. immune system and inflammatory process repair damage 4. repeated damage 5. increase in permeability to fats and cholesterol that sits under tunica interna 6. causes narrowing 7. arteriosclerosis end stage, lose elasticity, get scar tissue 54

55 What can be done? 1. balloon angioplasty 2. stent implantation 3. clot busting medicines 4. cholesterol lowering medications Lipitor, Crestor, etc. 55

56 Developmental Aspects fourth week heart is pumping 4th 7th week heart develops 4 chambers after birth bypass structures become blocked becomes more powerful and efficient if exercise as age get: varicose veins artherosclerosis hypertension 56

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