Cardiovascular System

• Blood is a uniquely specialized connective tissue in that it consists of two components: the formed elements of blood, or the blood cells, and the fluid part of blood or plasma

  
• Blood temperature


  About 38°C
• Blood viscosity


  Five times as viscous as water
• Blood pH

  Slightly alkaline, with a pH between 7.35 and 7.45
• Blood volume


  Adult males typically have more blood than do adult females, calculated as 7 percent of the body weight in kilograms
• Functions of the blood

  • Transporting Dissolved Gases, Nutrients, Hormones, and Metabolic Wastes
  • Regulating the pH and Ion Composition of Interstitial Fluids
  • Restricting Fluid Losses at Injury Sites
  • Defending against Toxins and Pathogens
  • Stabilizing Body Temperature
• Albumins


  Major contributors to plasma osmolarity and osmotic pressure; important for transporting fatty acids, thyroid hormones, some steroid hormones, and other substances
• Globulins


  Examples include antibodies (immunoglobulins) that aid in body defense and transport globulins that bind small ions, hormones, and substances
• Fibrinogen


  Functions in clotting, converted to fibrin (an insoluble protein) which removes the clotting proteins, leaving a fluid known as serum

  
• Classification of blood cells

  • Erythrocytes or red blood cells (RBCs)
  • Leukocytes or white blood cells (WBCs) - granular leukocytes (neutrophils, eosinophils, basophils) and agranulocytes (monocytes, lymphocytes)

  
• Hemoglobin


  Responsible for the red blood cell's ability to transport oxygen and carbon dioxide, with normal ranges of 14–18 g/dL in males and 12–16 g/dL in females

  
• Thrombocytes


  2 to 4 micrometers in diameter, 350,000 per microliter, prevent fluid loss when blood vessels are damaged by initiating a chain of reactions that result in blood clotting

  
• Substances influencing platelet formation

  • Thrombopoietin (TPO)
  • Interleukin-6 (IL-6)
  • Multi-CSF
• Types of white blood cells (abundance: 7000 per microliter)

  • Neutrophils (4150 per microliter)
  • Eosinophils
  • Basophils
  • Monocytes (456 per microliter)
  • Lymphocytes (2185 per microliter)
  • Natural killer (NK) cells

  
• Process of blood clotting

  1. Platelet activation

  2. Intrinsic pathway

  3. Extrinsic pathway

  4. Common pathway

  
• Antithrombin-III


  Inhibits several clotting factors, including thrombin
• Heparin


  A compound released by basophils and mast cells, is a cofactor that accelerates the activation of antithrombin-III
• Thrombomodulin


  Protein released by endothelial cells that binds to thrombin and converts it to an enzyme that activates protein C, which inactivates several clotting factors and stimulates the formation of plasmin

  
• Prostacyclin


  Released during the platelet phase, inhibits platelet aggregation and opposes the stimulatory action of thrombin, ADP, and other factors
• ABO blood group


  Determined by the presence or absence of two major antigens on the RBC membrane, antigen A and antigen B
• Rh blood group


  Anti-Rh antibodies do not develop spontaneously, they develop only in Rh-negative persons if an Rh-negative person receives a blood transfusion of Rh-positive blood

  
• Blood transfusion compatibility test

  1. Determination of blood type

  2. Crossmatch test

  
• Pulmonary circuit


  Carries blood to and from the gas exchange surfaces of the lungs
• Systemic circuit


  Transports blood to and from the rest of the body
• Arteries


  Carry blood away from the heart
• Veins


  Return blood to the heart
• Great vessels


  The largest veins and arteries in the body, those connected to the heart
• Capillaries


  Microscopic thin-walled vessels that interconnect the smallest arteries and the smallest veins, called exchange vessels because their thin walls permit the exchange of nutrients, dissolved gases, and wastes between the blood and surrounding tissues

  
• Right atrium


  Receives blood from the systemic circuit and passes it to the right ventricle which then pumps blood into the pulmonary circuit
• Left atrium


  Collects blood from the pulmonary circuit and empties it into the left ventricle, which pumps blood into the systemic circuit
• Heart position


  Located in the thoracic cavity near the anterior chest wall, directly posterior to the sternum, with the base at the level of the third costal cartilage and the inferior pointed tip (apex)
• Layers of the heart wall

  • Pericardium (fibrous pericardium and serous pericardium)
  • Myocardium (cardiac muscle tissue)
  • Endocardium (covers the inner surfaces of the heart, including the heart valves)
• Pericardial fluid


  15–50 mL of fluid secreted by the pericardial membranes, acting as a lubricant to reduce friction between the heart and surrounding structures

  
• Sternum


  Base sits posterior to the sternum at the level of the third costal cartilage
• Apex


  The inferior pointed tip of the heart
• Pericardium


  Surrounds the heart and consists of an outer fibrous pericardium and an inner serous pericardium; stabilize the position of the heart and associated vessels within the mediastinum
• Myocardium


  Cardiac muscle tissue that forms the atria and ventricles; contains cardiac muscle cells, connective tissues, blood vessels, and nerves
• Endocardium


  Covers the inner surfaces of the heart, including those of the heart valves
• Serous pericardium


  A two-layered membrane composed of an outer parietal layer and an inner visceral layer
• Pericardial cavity


  Normally contains 15–50 mL of pericardial fluid, secreted by the pericardial membranes acting as lubricant reducing friction between the opposing visceral and parietal surfaces as the heart beats