Circulatory System

• Components of the circulatory system

  • Heart
  • Artery
  • Capillary
  • Vein
  • Lymphatic capillary
  • Lymphatic vessel
  • Lymphatic duct
• Heart


  Pump blood, muscular organ that contracts rhythmically
• Artery


  Carry blood to tissues, away from the heart
• Vein


  Carry blood to the heart, convey blood to be pumped again
• Capillary


  Interchange between blood and tissue takes place, forms microvasculature
• Layers of the heart

  • Pericardium
  • Epicardium
  • Myocardium
  • Subendocardium
  • Endocardium
• Pericardium


  Fibrous, parietal layer of serous pericardium, pericardial fluid, visceral layer of serous pericardium
• Epicardium


  Visceral layer, simple squamous epithelium, adipose, thin layer of CT
• Myocardium


  Thickest tunic, cardiac muscle, contractile cardiac muscle fiber arranged spirally around each chamber
• Subendocardium


  Loose CT with Purkinje fibers
• Endocardium


  Simple squamous epithelium, elastic and collagen fibers, smooth muscle
• Heart chambers


  • Atria
  • Ventricles
• Atria


  Receive blood from veins, contraction forces blood to the ventricles
• Ventricles


  Thicker walls than atria, left is 3 times thicker than the right, ejects blood into arteries
• Heart valves


  • Atrioventricular
  • Semilunar
• Atrioventricular valves


  Dense regular CT with elastic and collagen fibers, supported by chordae tendineae
• Semilunar valves


  Dense regular CT with elastic and collagen fibers
• Fibrous skeleton


  Dense irregular CT, fibrous rings that anchor the base of the valves, site of origin and insertion of cardiac muscle
• Blood flow


  1. Sinoatrial node

  2. Atrioventricular node

  3. Atrioventricular bundle

  4. Purkinje fibers
• Sinoatrial node


  Pacemaker, sets the rhythm, sends excitation wave of electrical activity over the atrial walls causing them to contract
• Atrioventricular node


  Connect impulse between atria and ventricles
• Atrioventricular bundle


  Branch into right and left Purkinje fibers
• Purkinje fibers


  Deliver signal to ventricles
• Blood supply of heart walls

  • Coronary artery
  • Coronary vein
• Blood vessels


  • Microvasculature
  • Macrovasculature
• Microvasculature


  Visible with a microscope, arteriole, capillaries, venules
• Macrovasculature


  More than 0.1mm, large arterioles, muscular veins, muscular and elastic arteries
• Tissues of the vascular wall

  • Simple squamous endothelium
  • Smooth muscle
  • Connective tissue
• Simple squamous endothelium


  Weibel-palade bodies, semipermeable barrier between blood and interstitial fluid, anti-thrombogenic, secrete paracrine factors, synthesize collagen and proteoglycan, secrete and synthesize molecules that promote or minimize thrombus formation
• Smooth muscle


  Arranged helically in layers, occur in walls of larger vessels than capillaries, circular arrangement
• Connective tissue


  Collagen, elastic material, ground substance
• Layers of blood vessels

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


  Endothelium, basement membrane, IEL, subendothelial layer
• Tunica media


  Smooth muscle, elastic fibers, EEL
• Tunica adventitia


  Type 1 and type 3 collagen, fibroblast, continuous with the stromal connective tissue
• Arteries


  • Elastic
  • Muscular
  • Small
• Elastic arteries


  Largest, elastic recoil prevents falling of BP, contains vasa vasorum, 3 layers present, tunica media composed of elastic fibers, IEL less pronounced, adventitia is thinner than media
• Muscular arteries


  Medium sized, distributing arteries, 3 layers, tunica media contains more smooth muscles, 40 layers or more of smooth muscle, prominent IEL, EEL identifiable
• Small arteries


  Small diameter, thinner, adapted for vasoconstriction and vasodilation, 3 layers, 3-4 layers of smooth muscle
• Arterioles


  Delivers blood to capillaries, 3 layers, 1-2 layers of smooth muscle