CIRCULATORY SYSTEM

• Circulatory System


  Pumps and directs blood cells and substances carried in blood to all tissues of the body
• Functions of the Circulatory System

  • Transport: For transport of nutrients, hormones, oxygen and other needed substances in the cell
  • Excretory: It also moves waste, carbon dioxide and secretory products to their disposal areas / organs
  • Protection: Aids in fighting off pathogenic microorganism by providing and/or transporting the cells and substances needed for this purpose
• Division of Circulatory System

  • Cardiovascular System
  • Lymph vascular System
• Components of the Cardiovascular System

  • Blood vessels: Forms closed circuit to and from the heart
  • Walls of all blood vessels except capillaries contain smooth muscle and connective tissue in addition to the endothelial lining
• Layers of Blood Vessels

  • Tunica intima
  • Tunica media
  • Internal elastic lamina
  • Tunica adventitia
• Types of Blood Vessels

  • Capillaries
  • Arteries
  • Veins
• Cells in the Capillaries

  • Endothelial cells
  • Pericytes / cells of Rouget / Mural cells
• Types of Capillaries according to size

  • Continuous Capillaries
  • Fenestrated Capillaries
  • Discontinuous Capillaries / Sinusoids
• Heart


  • Hollow muscular organ, about a size of a clenched fist, located in the central mediastinum of thoracic cavity
  • Modified artery that has a pumping capacity that propels blood to the arteries of both the systemic and pulmonary circulations
• Layers of the Heart

  • Endocardium / Tunica intima
  • Myocardium / Tunica media
  • Epicardium / Tunica serosa / Visceral pericardium
• Cardiac Skeleton


  • Septum
  • Annuli fibrosi
  • Trigona fibrosa
• Composition of Blood


  • Serum
  • Plasma
  • Blood cells
• White Blood Cells / Leukocytes


  • Functions for immunity and defence
  • Become active outside the circulation, specifically leaving the microvasculature in a process involving cytokines, selective adhesion, changes in the endothelium, and transendothelial migration or diapedesis
• Types of Leukocytes


  • Granulocytes
  • Agranulocytes
• Types of Granulocytes


  • Neutrophil
  • Eosinophil
  • Basophil
• Types of Agranulocytes


  • Monocyte
  • Lymphocyte
• Red Blood Cells / Erythrocytes

  • Approximately 7.5 μm in diameter, 2.6 μm thick at the rim, but only 0.75 μm thick in the center which gives them the biconcave shape
  • Terminally differentiated structures lacking nuclei and completely filled with the O2-carrying protein hemoglobin
  • Normally quite flexible, which permits them to bend and adapt to the irregular turns and small diameters of capillaries

  
• RBCs are the only blood cells whose function does not require them to leave the vasculature
• Blood is a specialized connective tissue consisting of cells and fluid extracellular material called plasma
• Blood is a distributing vehicle, transporting O2, CO2, metabolites, hormones, and other substances to cells throughout the body. It participates in heat distribution, the regulation of body temperature, and the maintenance of acid-base and osmotic balance.
• Propelled mainly by rhythmic contractions of the heart, about 5 L of blood in an average adult moves unidirectionally within the closed circulatory system.
• The so-called formed elements circulating in the plasma

  • Erythrocytes (red blood cells)
  • Leukocytes (white blood cells)
  • Platelets

  
• Leukocytes or white blood cells are classified into

  • Granulocytes
  • Agranulocytes

  
• Granulocytes


  • Neutrophils
  • Eosinophils
  • Basophils
• Agranulocytes


  • Lymphocytes
  • Monocytes
• Blood cells can be studied histologically in smears prepared by spreading a drop of blood in a thin layer on a microscope slide
• Red blood cell (Erythrocyte)

  Biconcave shape, 6-8 μm size, red or salmon pink color

  
• Eosinophil

  Bilobed nucleus, reddish orange granules, 1-2 weeks life span
• Basophil

  Bilobed or S-shaped nucleus, dark blue/purple granules, several months life span
• Lymphocyte

  Round nucleus, no granules, hours to years life span

  
• Monocyte (Agranulocyte)


  Indented or C-shaped nucleus, no granules, hours to years life span
• Platelets (Thrombocytes)


  Round or discoid shape, blue or purple color, 8-11 days life span
• Neutrophil


  3-5 lobes, faint/light pink in color, 1-4 days