Circulatory system and blood

• 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
• Types of blood vessels

  1. Capillaries
  2. Arteries
  3. Vein
• Types of Capillaries

  1. Continuous Capillaries
  2. Fenestrated Capillaries
  3. Discontinued Capillaries or Sinusoid
• Continuous Capillaries are the most common type of capillary. It is found in the muscles, connective tissues, lungs, exocrine glands, and nervous tissue. It has a well developed occluding junctions that allows cellular exchange.
• Circulatory System

  • Pumps and directs blood cells and substances carried in blood to all tissues of the body
  • Transports nutrients, hormones, oxygen and other needed substances in the cell
  • Moves waste, carbon dioxide and secretory products to their disposal areas / organs
  • 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

  • Heart
  • Blood Vessels
  • Blood

  
• Structure of Blood Vessels

  • Inner lining (tunica intima) - single layer of extremely flattened epithelial cells called endothelial cells
  • Intermediate predominantly muscular layer (tunica media) - alternating layers of smooth muscle and collagen or elastic lamellae
  • Outer supporting tissue layer (tunica adventitia) - connective tissue, small vessels and nerves and vasa vasorum

  
• Endothelium


  • Internal surface of all components of cardiovascular and lymphatic system
  • Simple squamous epithelium
  • Maintain a selectively permeable, antithrombogenic (inhibitory to clot formation) barrier
  • Determine when and where white blood cells leave the circulation for the interstitial space of tissues
  • Secrete a variety of paracrine factors - signals vessel dilation, constriction, and growth of adjacent cells
• Smooth Muscle


  • Occur in the walls of all vessels larger than capillaries and are arranged helically in layers
  • Permit regulated vasoconstriction and vasodilation
• Connective Tissue


  • Collagen: found in subendothelial layer
  • Elastic Fibers: provide resiliency to blood vessel

  
• 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 Conducting System

  • Sinoatrial Node (Pacemaker)
  • Atrioventricular Node
  • Atrioventricular Bundle of His
  • Purkinje Fibers

  
• Purkinje Fibers

  • Contractile Bundles
  • Abundant Glycogen
  • Sparse Bundles of Myofibrils
• Types of Blood vessels

  • Capillaries
  • Arteries
  • Veins

  
• Types of Capillaries

  • Continuous Capillaries
  • Fenestrated Capillaries
  • Discontinued Capillaries /Sinusoids
• Continuous Capillaries


  • Most common type, found in muscle, connective tissue, lungs, exocrine glands, and nervous tissue
  • With well-developed occluding junctions; allow cellular exchange
• Fenestrated Capillaries


  • Have a sieve-like structure that allows more extensive molecular exchange across the endothelium
  • Found in organs with rapid interchange of substances between tissues and the blood, such as the kidneys, intestine, choroid plexus, and endocrine glands
• Discontinued Capillaries /Sinusoids


  • Permit maximal exchange of macromolecules as well as allow easier movement of cells between tissues and blood
  • Have highly discontinuous basement membranes and much larger diameters, often 30-40 μm, which slows blood flow
  • Found in the liver, spleen, some endocrine organs, and bone marrow
• Veins


  • Carry blood back to the heart from microvasculature all over the body
  • Most veins are classified as small or medium veins that are usually located close and parallel to corresponding muscular arteries
• Types of Arteries

  • Large Elastic Arteries
  • Muscular Arteries
  • Small Arteries
• Large Elastic Arteries

  • Also called Conducting Arteries
  • With fenestrated elastic laminae in the thick tunica media
  • Contains Vasa Vasorum
• Muscular Arteries


  • Less elastic material than Elastic Artery
  • Distribute blood to all organs and maintain steady blood pressure and flow with vasodilation and constriction
• Small Arteries


  • No vasa vasourm
  • Distribute blood to arterioles, adjusting flow with vasodilation and constriction
• Blood


  • Specialized connective tissue consisting of cells and fluid extracellular material called plasma
  • 5L is unidirectionally moving within closed circulatory system
  • Liquid Portion of Blood is Plasma
  • When removed off clotting factors, the liquid portion is called Serum
• Formed elements in Blood

  • Leukocytes
  • Erythrocytes
  • Thrombocytes
• Composition of Plasma

  • Albumin
  • Alpha and Beta Globulins
  • Complement Proteins
  • Fibrinogen
  • Immunoglobulins
• Erythrocytes (Red Blood Cell)


  • Make up hematocrit portion (44%)
  • Enucleated, biconcave discs
  • Normal lifespan is 120 days
  • Completely filled with the O2 -carrying protein hemoglobin
  • The only blood cells whose function does not require them to leave the vasculature
• Leukocytes (White blood cells)


  • Granulocytes (neutrophils, eosinophils, basophils)
  • Agranulocytes (lymphocytes, monocytes)
• Granulocytes

  • Possess two major types of abundant cytoplasmic granules: lysosomes/azurophilic granules and specific granules
  • All leukocytes become active outside the circulation
• Granulocyte Types

  • Neutrophils
  • Eosinophils
  • Basophils
• Neutrophils


  • Most abundant type of leukocyte
  • Polymorphic, multilobed nuclei
  • Faint pink cytoplasmic granules
  • Phagolysosomal killing and removal of bacteria
• Eosinophils


  • Bilobed nuclei
  • Eosinophilic specific granules
  • Destruction of helminthic parasites and for modulating inflammation
• Basophils


  • Rarest type of circulating leukocyte
  • Irregular bilobed nuclei
  • Strongly basophilic specific granules
  • Important in allergies and chronic inflammatory conditions, including histamine, heparin and various hydrolases
• Agranulocyte Types

  • Lymphocytes
  • Monocytes
• Lymphocytes


  • Range widely in size
  • Have roughly spherical nuclei
  • T- and B-cell subtypes in the immune system
  • Little cytoplasm and few organelles
  • Effector and regulatory cells for adaptive immunity
• Monocytes


  • Distinctly indented or C-shaped nuclei
  • Precursors of macrophages and other cells of the mononuclear phagocyte system
• Platelets


  • Small cell fragments (2-4 μm) derived from megakaryocytes in bone marrow
  • Triggers blood clotting
  • Contents: Actin filaments, Alpha granules, Delta granules, Open canalicular system
• Hematopoiesis is the production of mature blood cells from hematopoetic stem cells/progenitor cells