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• Component Structures of Cardiovascular System

  • Heart
  • Blood vessel
  • Arteries
  • Capillaries
  • Veins
• Functions of Circulatory system

  • Brings nutrients, oxygen, hormones and other vital substances to the cells of the body from varying points of origin
  • Helps maintains the body's homeostasis and aids in fighting off pathogenic organisms by providing and transporting the cells and substances needed for these purposes
  • Includes cardiovascular (blood) and lymphatic system (lymph)
• Heart


  A hollow muscular organ about the size of a clenched fist located in the mediastinum of the thoracic cavity
• Layers of the Heart

  • Endocardium
  • Myocardium
  • Epicardium
• Heart Chambers


  • Right and left ventricles
  • Right and left atria
  • Left ventricle: pump of the systemic circulation
  • Right ventricle: pump of the pulmonary circulation
  • Left atrium: drains and receives oxygenated blood from the pulmonary veins
  • Right atrium: drains and receives deoxygenated blood from the systemic circulation
• Heart Structures


  • Interatrial septum: separates right from left atrium
  • Interventricular septum: separates right from left ventricle
  • Mitral valve: prevents backflow of blood from the left ventricle to the left atrium
  • Tricuspid valve
  • Semilunar valves: guards the semilunar orifices (pulmonary and aortic)
  • Superior vena cava - drains the upper portion of the body
  • Inferior vena cava - drains the lower portion of the body
  • Coronary sinus - drains the cardiac veins
• Histologic Layers of the Heart

  • Myocardium
  • Epicardium
  • Endocardium
• Myocardium


  • Middle layer composed of cardiac muscle cell and responsible for heart contractions
  • The muscle fibers originate and inserts in the cardiac skeleton
• Epicardium


  • Outermost histologic layer of the heart
  • Simple squamous mesothelium
• Endocardium


  • Surrounds the numbers of modified cardiac muscle fibers that comprise the heart's impulse conducting system
  • Thinnest layer, lines the internal surface of the heart
  • Consists of four sublayers: endothelium, subendothelial layer, dense connective tissue layer, subendocardium
• Cardiac Skeleton


  • Refers to the dense fibrous connective tissue that forms the central support of the heart into which the cardiac muscles and valves are attached
  • Three main components: septum membranaceum, annuli fibrosi, trigona fibrosa
• Conducting System of the Heart

  • Specialized to generate and conduct waves of depolarization
  • Triggered by a population of modified cardiac muscle fibers called Purkinje fibers that are noncontractile but are specialized to initiate and conduct electrical impulses
  • Components: Sinoatrial node (SA), Three internodal tracts, Atrioventricular node (AV), AV bundle of His, Two bundle branches, Purkinje fibers
• Gap Junctions


  Impulses are passed on to individual cardiac fibers via the gap junctions that exist in the intercalated disks
• Cardiac Musculature


  • Does not need neural stimulation to contract but is controlled by the efferent fibers of the autonomic nervous system
  • Vagal fibers: inhibit heart action
  • Sympathetic fibers: stimulate heart action
• Tissues of Vascular Wall

  • Endothelium
  • Smooth muscle
  • Connective tissue
• Endothelium


  • Specialized epithelium that acts as a semipermeable barrier between two major internal compartments
  • Squamous, polygonal, and elongated with the long axis
  • Functions: Presents a Nonthrombogenic layer, Regulate blood flow, Local immune response, Secretes growth factors
• Cardiac Muscle


  • Elongated, branching cells containing 1-2 centrally located nuclei
  • Contains actin and myosin myofilaments
  • Intercalated disks: Specialized cell-cell contacts
  • Electrically, cardiac muscle behaves as single unit
• Smooth Muscle


  • Occurs at wall of all vessels larger than capillaries
  • Helically arranged
• Connective Tissue


  • Collagen fibers are found in the subendothelial layer
  • Elastic fibers provide the resiliency required for the vascular wall to expand under pressure
  • Has three concentric layers: Intima, media and adventitia
• Types of Capillaries


  • Continuous
  • Fenestrated
  • Sinusoidal
• Histologic Layers of Arteries and Veins

  • Tunica intima
  • Tunica media
  • Tunica adventitia
• Tunica Intima


  • Innermost histologic layer of arteries and veins
  • Consist of endothelium and subendothelial layer made up of loose connective tissue
• Tunica Media


  • Middle histologic coat of arteries and veins
  • In arteries with relatively large caliber, an additional layer, external elastic membrane, is present
• Tunica Adventitia


  Outermost histologic coat of arteries and veins
• Types of Arteries


  • Arterioles
  • Muscular Arteries
  • Elastic Arteries; Conducting Arteries
• Arterioles


  Diameter ranges from 40-400 um
• Muscular Arteries


  • They distribute blood from different parts of the body
  • Consists most of the named arteries
• Elastic Arteries; Conducting Arteries

  • Tunica intima consists only of endothelium and/or internal elastic membrane. There is practically no subendothelial tissue
  • Tunica media is thickest layer, consist mainly of sheets of elastin called elastic lamellae arranged concentrically
  • Tunica adventitia is relatively thin and merges with the surrounding connective tissue. It contains vasa vasorum
• Sensory Organs Associated with Arteries

  • Carotid bodies
  • Aortic bodies
  • Carotid sinus
• Carotid Bodies


  • Sensitive to changes in oxygen and carbon dioxide tension in the blood
  • Afferent nerve endings in the carotid bodies come from glossopharyngeal nerve
• Aortic Bodies


  • Sensitive to changes in oxygen and carbon dioxide tension in the blood
  • Afferent nerve endings in the aortic bodies come from vagus nerve
• Carotid Sinus


  • Contains baroreceptors
  • Afferent nerve endings in the carotid bodies come from glossopharyngeal nerve
• Veins


  • Compared to the arteries that they accompany, veins have bigger calibers, more irregular lumens, and thinner and less elastic walls
  • Classified into small (venules), medium and large veins
  • Many medium-sized veins are provided with valves that ensure unidirectional flow of blood
• Types of Veins


  • Venules
  • Medium Veins
  • Large Veins
• Venules


  Diameter ranges from 1mm or less
• Medium Veins


  • Diameter ranges from 1-9 mm
  • Includes almost all the named veins and their principal tributaries
• Large Veins


  • Diameter ranges from >10 mm
  • Includes almost all the named veins and their principal tributaries
• Histologic Layers of Veins

  • Tunica intima
  • Tunica media
  • Tunica adventitia
• Tunica Intima of Veins

  Consist of endothelium and thin subendothelial layer with minimal amounts of connective tissue
• Tunica Media of Veins


  Composed of small bundles of circularly arranged smooth muscles and is thinner than arteries of the same caliber