Circulatory System and Blood

• Function of Circulatory System:

  1. Pumps and directs blood cells and substances
  2. Transport
  3. Excretory
  4. Protection
• Division of Circulatory System:

  1. Cardiovascular System
  2. Lymph circulatory System
• Components of the Cardiovascular System:

  • Heart
  • Blood vessels
  • Capillary
  • Artery
  • Vein
  • Blood
  • RBC
  • WBC
  • Platelets
• Circulatory System composed of three basic common structures:

  1. Tunica Intima
  2. Tunica media
  3. Tunica adventitia
• It is the innermost layer comprising a single layer of extremely flattened epithelial cells called endothelial cells supported by basement membrane and delicate collagenous tissue.


  tunica intima
• An intermediate predominantly muscular layer which contains alternating layers of smooth muscle and collagen or elastic lamellae.


  tunica media
• An outer supporting tissue layer that contains connective tissue, small vessels, nerves and vasa vasorum


  Tunica adventitia
• Tissues of the Vascular Walls:

  • Endothelium
  • Smooth Muscle
  • Connective Tissue
• Endothelium:

  • Internal surfaces of all components
  • Simple squamous epithelium
  • maintain selectively permeable
  • determine when and where WBC leaves
  • Secretes paracrine factors
• Smooth muscle:

  • occur in the walls of all vessels larger than capillaries
  • arranged helically layers
  • vasoconstriction and vasodilation
• Connective Tissue:

  • Collagen: found in subendothelial layer
  • Elastic fibers
• Tunica adventitia is composed of what?

  connective tissue
• Heart:

  • Hollow muscular organ, about the size of a clenched fist
  • located in the central mediastum of thoracic cavity
  • has pumping capacity that propels blood
• Structures of Heart:

  • Endocardium/Tunica Intima
  • Myocardium/Tunica Media
  • Epicardium/ Tunica Serosa/Visceral Epicardium
• Endothelium, fibroelastic tissue, smooth muscle fibres, and modified cardiac muscle fibers

  Endocardium/Tunica Intima
• What is the contractile cardiac muscle fibers that are arranged spirally around each heart chamber?

  Myocardium
• • It is simple squamous mesothelium supported by a layer of loose connective tissue
  • Corresponds to visceral layer of epicardium

  Epicardium
• • It is thicker than the endocardium and epicardium
  • Found on the walls of left ventricle


  Myocardium
• Cardiac Skeleton:

  • Forms base for all cardiac valves
  • Separates atria form ventricles
  • Provides points of insertion for cardiac muscle in the atria and ventricles
  • Dense irregular connective tissue
  • It acts as electrical insulation between atria and ventricles
• Specialized to generate and conduct waves of depolarization which stimulates rhythmic contractions

  Cardiac Conducting System
• Forms closed circuit to and from the heart

  Blood Vessels
• It permits and regulate metabolic exchange between blood and surrounding tissues.

  Capillary
• These smallest blood vessels always function in networks called?

  capillary beds
• Types of capillaries:

  • Continues capillaries
  • Fenestrated capillaries
  • Discontinued capillaries
• Continues capillaries:

  • Most common type of capillaries
  • Found in muscle, connective tissue, lungs, exocrine glands and nervous tissue
  • Allow cellular exchange
• Fenestrated capillaries:

  • sieve-like structure
  • found in organs with rapid interchange of substances between tissue and the blood such as kidney, intestine, choroid plexus and endocrine glands
• Discontinued capillaries:

  • permit maximal exchange of macromolecules which allows easier movement of cells
  • highly discontinues basement membranes
  • found in the liver, spleen, some endocrine organs and bone marrow
• Resist and control blood flow to capillaries, major determinant of systemic blood pressure

  arteriols
• Exchange metabolites by diffusion to and from cells

  capillaries
• It drains capillary beds; site of leukocyte exits from vasculature

  venules
• It carries blood back to the heart from microvasculature all over the body

  veins
• located close and parallel to corresponding muscular arteries

  veins
• collect blood from venules


  small veins
• carry blood to larger veins with no backflow

  medium veins
• return blood to heart

  large vein
• blood vessels that brings oxygen-rich blood from your heart to all of your body's cells

  arteries
• aka Conducting Arteries


  large elastic arteries
• With fenestrated elastic laminae in the thick tunica media it contains vasa vasorum

  large elastic artery
• Conducts blood from the heart with elastic recoil help move blood forward under steady pressure

  large elastic artery
• Less elastic material than elastic artery

  Muscular artery