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Cardiovascular System

Cardiovascular System. Honors Anatomy & Physiology. Introduction Placement Mediastinum – slightly to the left Size Heart – fist covered by second hand Aorta – diameter of dominant thumb. II. Protection and Layers of the Heart A. Protection - Pericardial Sac

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Cardiovascular System

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  1. Cardiovascular System Honors Anatomy & Physiology

  2. Introduction Placement Mediastinum – slightly to the left Size Heart – fist covered by second hand Aorta – diameter of dominant thumb

  3. II. Protection and Layers of the Heart A. Protection - Pericardial Sac 1. Pericardial Membrane a) Double layered sac with slick pericardial fluid in between tissue layers b) Purpose: absorb and reduce friction

  4. 2. Parietal Pericardium a) Tough layer of connective tissue b) Has connective tissue extending from the outside of itself to anchor it to other tissues 3. Visceral Pericardium a) Covers the outside of the heart b) Also referred to as “epicardium” c) Simple squamous epithelium (1) Surface of heart is slick and smooth

  5. 4. Pericardial fluid a) Secreted by visceral layer b) 10-20 mLof pericardial fluid c) Lubrication

  6. B. Layers of the Heart 1. Epicardium a) Slick layer of simple squamous cells = visceral layer of pericardial sac 2. Myocardium a) Heart muscle b) Characteristics of myocardial cells (1) Short and branched

  7. (2) Join each other with Gap Junctions = intercalated discs (a) Ensures that when one cardiac cell contracts, its partners will contract with it (b) Sets up teamwork = All or None Contraction (c) Chamber of heart made up of these cells contracts completely or not at all

  8. (3) Have sarcomeres with visible A and I bands = striated

  9. (4) Have automaticity - Self-stimulating and are rhythmic (a) Do not need nervous system to stimulate them to contract (b) Nervous system can INFLUENCE these cardiac cells to speed up (release of epinephrine) or slow down (vagus nerve releasing acetylcholine) (5) Use free fatty acids for fuel instead of glucose

  10. Are life-long cells and in permanent Go (a) If these cells die, they are replaced with scar tissue (i) Tough patch (ii) Decreases heart chamber’s ability to contract Have a single nucleus, centrally located

  11. Myocardial cells

  12. 3. Endocardium a) Lines the inside of the heart chambers b) Same tissue called “endothelium” as it continues into entering and exiting blood vessels c) Made of simple squamous epithelial tissue d) Provides a slick surface for blood to pass over and through heart

  13. Heart Chambers Atria – Receiving Chambers 2 upper chambers of the heart Thin walls; smooth inner surface Right atrium receives deoxygenated blood from body Superior vena cava – brings blood from upper body Inferior vena cava – brings blood from legs and lower body Left atrium receives oxygenated blood from lungs Left and right pulmonary veins (2 each)

  14. Ventricles – Pumping Chambers 2 lower chambers Thicker walls; irregular inner surface Contain papillary muscles and chordaetendinae to prevent heart valves from turning inside out during ventricular contraction Right ventricle pumps blood to lungs through pulmonary artery Left ventricle pumps blood to body through aorta Wall is 3x’s thicker than right

  15. Heart Chambers

  16. IV. Valves of the Heart and Heart Sounds Tough, fibrous tissue between heart chambers and major blood vessels of heart Gate-like structures – One-way valves Blood should always travel from the Atria  Ventricle major artery (Pulmonary or Aorta)

  17. A. Atrioventricular valves 1. Characteristics a) Located between atria and ventricle b) Made of leaflets, known as “cusps” c) Have a strong cord of connective tissue anchoring the leaflet = chordaetendinae (1) Keeps cusps from flopping back into atria during ventricular contraction (2) If too long or have been damaged, cusp will go past its stopping point and “flop” up into the atria (a) Causes heart to have to re-pump the same blood (b) Causes congestion as new blood is trying to come into atria (c) Known as “murmur” (leaky valve) d) Chordaetendinae anchored to ventricular wall by papillary muscles

  18. 2. Tricuspid valve a) Located between right atrium and right ventricle b) Has three leaflets 3. Bicuspid/Mitral valve a) Located between left atrium and left ventricle b) Has 2 leaflets – thicker and tougher than tricuspid valve 4. Sound – When AV valves close, make a “LUB” sound – loudest of the two heart sounds

  19. B. Semilunar valves 1. Characteristics a) Built differently from AV valves b) Leaflets, or cusps, are made of a half- moon shaped piece of connective tissue c) They have no chordaetendinae or papillary muscles d) Both semilunar valves consist of three leaflets

  20. 2. Pulmonary semilunar valve a) Found in the Pulmonary Artery (trunk) b) Prevent blood from going back into right ventricle 3. Aortic semilunar valve a) Found in the Aorta (just as the aorta leaves the heart) b) Prevents blood from going back into the left ventricle

  21. 4. Action a) Opposite of AV valves in their action b) Closed most of the time c) Only time they open is when the ventricles are pumping or ejecting blood out d) When ventricles relax, blood close to valve falls back toward ventricle e) Valves “catch” the blood by closing and prevent backflow 5. Sound – When semilunar valves fill and close, they make a soft “dup” sound **Heart sounds w/ flow of pumping

  22. Circulation Pulmonary Circulation Heart → Lungs →Heart Coronary Circulation Heart → Heart → Heart Systemic Circulation Heart → Body → Heart

  23. VI. Electrical System of the Heart A. Understanding the Electrical System of the Heart 1. SA node (Sinoatrial node) a) Located in upper right atrium b) Pacemaker (1) Begins the cycle of the heart firing (2) When it fires (depolarizes), the atria contract and electrical stimulation goes to the AV node

  24. (3) Has it own pace (4) Contraction of atria is from top to bottom (5) Can be influenced by autonomic nervous system (a) Sympathetic NS can speed it up (b) Parasympathetic NS can slow it down – Vagus nerve (Cranial nerve X)

  25. 2. AV node (Atrioventricular node) a) Located at the base of right atrium, close to AV valve and atrial septum b) Will send the depolarization (electrical stimulus) to the Bundle of HIS 3. Bundle of HIS a) These fibers go through the ventricular septum b) Split into left and right bundle c) No contraction of heart muscle occurs 4. Purkinje fibers a) Bundles connect up with Purkinje fibers at the apex b) Embedded in the myocardium of the ventricles c) Contraction of ventricles is from bottom to top

  26. B. Acting out the electrical system 1. SAAV, Bundle, PurkinjeBOOM! 2. Pause that occurs between atrial contraction and ventricular contraction allows the ventricles to fill with blood

  27. VII. ECG (EKG) A. Understanding the parts of the ECG 1. P wave a) Represents the SA node firing and the atria contracting b) Depolarization of atria

  28. 2. QRS complex a) Records the depolarization of the AV, Bundle, and Purkinje fibers as they cause the big ventricles to contract b) Atria are repolarizing, but big ventricular depolarization covers this up

  29. 3. T wave a) Repolarization of ventricles B. Acting Out the ECG

  30. Application Using the ECG First ECG Strip SA node is not firing “Ectopic Pacemaker” – AV node takes over the job of being the pacemaker Second ECG Strip AV node isn’t firing consistently Known as “partial AV block” – if not corrected, person could die Correcting the problem of ectopic pacemaker and partial AV block Can both be corrected by inserting a pacemaker

  31. Third ECG Strip Ventricular Tachycardia Ventricles are pumping so fast that very little blood fills the ventricles and goes out to their loops 6 – 10 minutes of this activity becomes life threatening Sympathetic NS out of control!! Parasympathetic NS must be activated to help slow the heart down Causes Heart attack may make heart cells oversensitive and they get out of rhythm Illegal stimulants – cocaine, methamphetamine, heroine

  32. Fourth ECG Strip Fibrillation Atria and ventricles are all out of rhythm and not pumping any blood External defibrillation device – shot of electricity helps heart to start over – resets SA node Causes Heart attack Household accidental electrocution

  33. VIII. Cardiac Cycle A. Steps 1. Passive Filling a) As blood coasts during diastolic pressure, atria fill b) AV valves are open and blood falls down to ventricles – which fill 70%

  34. 2. Atrial contraction (SA Node and P wave) a) Atria contract and send 30% of blood to ventricles 3. Ventricular Systole a) Contraction Phase: (LUB) (1) As ventricles begin to contract, blood is compressed (2) Semilunar valves are already closed so blood moves back toward atria, causing AV valves to close (3) Increased pressure causes semilunar valves to open

  35. b) Ventricular Ejection Phase: (QRS Complex) (1) Once SL valves open, ventricle walls contract and eject blood out into the arteries (2) Only 88% is ejected (3) Both ventricles pump same amount of blood (4) Right side pumps with 1/5 the force of left side

  36. 4. Relaxation (dup and T wave) a) Ventricles begin to repolarize and relax b) SL valves close due to backflow of blood, AV valves open, allowing passive filling – cycle repeats

  37. B. Cardiac Output 1. Amount of blood pumped out of the left ventricle in one minute 2. Heart rate = pulse a) Beats/min. b) 70-80 bpm average

  38. Stroke Volume Amount of blood out of the ventricle with each contraction 70 mL CO = HR x SV Cardiac Output = Heart Rate x Stroke Volume Cardiac Reserve As demands of body increase during exercise, CO must increase to meet demand In non-athletes, CR = 4 x CO In active or athletic people, CR = 7 x CO

  39. IX. Blood Pressure – Push or force of blood against blood vessel wall A. Having Your Heart in Your Hands for Blood Pressure 1. Push – Coast 2. Systolic – Diastolic 3. 120 – 80 4. Top number – Bottom number 5. First beat I hear – Last beat I hear

  40. B. Measured in mm of Hg BP = CO x PR Blood Pressure = Cardiac Output x Peripheral Resistance D. Normals 1. Systolic = 100 – 130 mm Hg 2. Diastolic = 60 – 90 mm Hg E. Hypotension = systolic < 90 mm Hg F. Hypertension = systolic > 140 mm Hg and/or diastolic > 90 mm Hg

  41. G. Factors affecting BP 1. Cardiac output (blood discharged by left ventricle/min.) 2. Peripheral resistance – resistance of wall against the blood as is rushes through the vessel 3. Blood volume – hemorrhage causes  BV  BP 4. Viscosity of blood -  in thickness =  BP

  42. X. Overview of Blood Vessels A. General Composition and Function 1. Allow for circulation of blood and other body fluids to all body cells 2. Three layers a) Tunica externa– outer layer of tough, fibrous tissue b) Tunica media – smooth muscle – allows vessels to constrict/dilate c) Tunica interna – smooth, inner layer; also known as “endothelium”

  43. B. Arteries 1. Carry blood AWAY from the heart 2. All but pulmonary arteries carry oxygenated blood 3. Aorta – largest, with thickest wall, ~ 1 in. in diameter 4. Arteries – large to medium sizes 5. Arterioles – smallest arteries

  44. C. Veins 1. Carry blood TOWARD the heart 2. All but pulmonary veins carry deoxygenated blood 3. Layers much thinner, less elastic 4. Series of internal valves – 1-way valves help move blood up to the heart 5. Superior and inferior vena cava – largest veins 6. Venules – smallest veins

  45. D. Capillaries – This is where the work is done! 1. Tiny, microscopic vessels 2. Red blood cells move through in single file 3. Walls are one cell layer thick 4. Function a) Gas exchange: Drop off O2 & pick up CO2 from body b) Nutrient drop-off c) Waste pick-up

  46. Fetal circulation Modifications required for fetus because fetus is not breathing, so oxygenated blood must be obtained in another fashion. Unique structures Placenta – connection and filter between mom & baby Umbilical arteries and vein Umbilical artery – carries deoxygenated blood from baby back to mom for processing and oxygenation Umbilical vein – carries oxygenated blood from mom to baby

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