advanced anatomy

• The Heart


  • Size of a person's fist
  • Beats 60-100 times/minute
  • About 100,000 times/day
  • Muscular pump made of fibers
  • Located in the center of the thoracic cavity, between the lungs
• Septum


  Wall that separates the heart into right and left sides
• Pericardium


  Outer double-walled sac to prevent friction
• Layers of the Heart

  Endocardium, myocardium, epicardium

  
• Chambers of the Heart

  • 2 Upper chambers = Atria
  • 2 Lower chambers = Ventricles

  
• Myocardium


  Composed of cardiac muscles
• Atria


  • Receive blood INTO the heart from the body
  • Right atrium fills with blood from superior and inferior vena cava
  • Left atrium fills with blood from the pulmonary vein
  • Contraction pushes blood into ventricles
  • Left and right atria separated by interatrial septum

  
• Ventricles


  • Receives blood from atria
  • Contraction pushes blood out of the heart
  • Right ventricle pushes blood through pulmonary artery
  • Left ventricle pushes blood through aorta
  • Left and right ventricles separated by interventricular septum
• Cardiac cycle


  The complete sequence of events in the heart from the beginning of one beat to the beginning of the following beat – includes systole and diastole
• Cardiac output


  The volume of blood ejected from the left ventricle of the heart in 1 minute (approximately 5 liters)
• Stroke volume


  The volume of blood pumped from the left ventricle of the heart in one beat
• Heart Valves


  Four valves; control direction of flow of blood
• Tricuspid valve


  Right atrioventricular valve, between right atrium and right ventricle
• Pulmonary valve


  Right semilunar valve, between right ventricle and pulmonary artery
• Mitral (bicuspid) valve


  Left atrioventricular valve, between left atrium and left ventricle
• Aortic valve


  Left semilunar valve, between left ventricle and aorta
• Blood Flow Through Heart

  Blood from body (superior/inferior vena cava) → R. atrium → R. ventricle (through tricuspid valve) → pulmonary artery (through pulmonary valve) → lungs for O2/CO2 exchange → L. & R. pulmonary veins (blood is now oxygenated) → L. atrium → L. ventricle (through mitral valve) → aorta (through aortic valve) → aorta → all parts of the body

  
• Sinoatrial (SA) node


  • Pacemaker, where the heartbeat begins
  • Causes wave of impulses through muscle of atria
  • Causes atria to contract
• Atrioventricular (AV) node


  • Simulated after SA node
  • Impulse goes down bundle of His → R. & L. bundle branches → Purkinje fibers → ventricles
• Conduction System of the Heart

  1. Ventricles contract simultaneously and force blood into lungs and body

  2. Atria and ventricles then relax briefly and a new cycle begins
• Systole


  • Contraction phase of cardiac cycle
  • Ventricles contract and push blood through pulmonary valve and aortic valve to distribute blood to lungs and body
• Diastole


  • Relaxation phase of cardiac cycle
  • Ventricles are filling with blood from atria
• Heart Rate


  • Controlled by the autonomic nervous system
  • Pulse is the measurement of the number of times the heart beats per minute
• Pulse


  • Occurs as a result of pressure when ventricles contract
  • Most common way of taking pulse is by palpating the radial artery on thumb side of wrist
• Normal resting heart rate

  60-100 beats/minute
• Bradycardia


  HR below 60
• Tachycardia


  HR above 100
• Cardiac Cycle


  The complete sequence of events in the heart from the beginning of one beat to the beginning of the next beat
• Cardiac Output


  The volume of blood ejected from the left side of the heart in one minute (approximately 5 liter)
• Stroke Volume


  The volume of blood pumped from the ventricle of the heart
• Pulse Sites


  • Radial = thumb side of wrist
  • Brachial = inner aspect of elbow where BP is taken
  • Carotid = between larynx and sternocleidomastoid (SCM) muscle on neck
  • Femoral = near groin
  • Popliteal = deep behind knee, felt when knee is slightly bent
  • Dorsalis pedis = top of foot slightly lateral to midline
• Arteries


  • Carry blood away from heart
  • Smallest branches are arterioles
• Veins


  • Smaller and thinner than arteries
  • Carry blood back to heart
  • Smallest branches are venules
  • Largest veins are superior/inferior vena cava
  • Major veins for phlebotomist: Cephalic, basilic, median cubital
• Capillaries


  • Smallest blood vessels, unicellular
  • Connect arteries to veins
  • So thin that blood flows slowly allowing time to exchange nutrients, O2, CO2, and waste materials
• Tunica adventitia


  • Thick outer layer, mostly connective tissue
  • Prevents rupture or bursting due to increased pressure
• Tunica media


  • Middle layer, smooth muscle and elastic fibers
  • Helps maintain normal blood pressure (BP); able to constrict
• Tunica intima


  • Inner layer, single layer of endothelial cells, connective tissue, and elastic fibers
  • Smoothness prevents abnormal blood clotting
• Functions of Blood


  • Transportation
  • Regulation
  • Hemostasis
  • Temperature regulation
• An average adult has about 4.5-5.5 liters of blood
• Whole blood is composed of approximately 2.8 liters (55%) of plasma and 1.9 liters (45%) of cells