Cardiovascular System Flashcards

Cardiovascular System

  • Cardio refers to the heart, and vascular refers to blood vessels (arteries and veins).

Serous Membrane

  • A serous membrane is a serous fluid-filled sac lining cavities or organs.
  • It comprises two layers:
    • Parietal layer: The outer layer.
    • Visceral layer: The layer directly wrapping the organ.
  • Serous fluid exists between these layers.
  • Functions of Serous Fluid:
    • Protects organs.
    • Lubricates organ walls to reduce friction.
  • Serous Membrane Examples:
    • Lungs: Pleura.
    • Heart: Pericardium.
    • Abdominal Cavity: Peritoneum.

Pericardium

  • The serous membrane for the heart.
  • Composed of:
    • Visceral layer (directly covering the heart).
    • Parietal layer.
    • Pericardial fluid (filling the pericardial cavity).
  • Fibrous Pericardium: The outermost layer.

Heart Wall

  • Terminology: Use "cardium".
    • Endocardium: Innermost layer.
    • Myocardium: Muscle layer.
    • Epicardium: Outer layer.
  • Epicardium and the visceral layer of serous pericardium are the same thing (it depends on the perspective from which it is named).
  • Epicardium:
    • Outermost layer.
    • Made of simple squamous epithelium, areolar connective tissue, and adipose connective tissue.
  • Endocardium:
    • Innermost layer.
    • Made of endothelium (simple squamous epithelium) and areolar connective tissue (no fat cells).
    • Thinner compared to the epicardium.
  • Myocardium: Made of cardiac muscle.

Heart Wall Layers (Outside to Inside)

  • Fibrous Pericardium
  • Parietal Layer of Serous Pericardium
  • Pericardial Cavity (containing pericardial fluid)
  • Visceral Layer of Pericardium (Epicardium)
  • Myocardium
  • Endocardium

Blood Vessels

  • Types: Artery and Vein.
  • Artery: Thick smooth muscle layer.
  • Vein: Thin smooth muscle layer.
  • Histology Slide Identification:
    • Artery: Usually circular.
    • Vein: Usually collapsed.
  • Wall Structure: Three layers.
    • Tunica Intima: Innermost layer.
      • Made of endothelium (simple squamous epithelium), basement membrane, and sometimes loose areolar connective tissue.
    • Tunica Media: Middle layer.
      • Made of smooth muscles (thicker in arteries).
    • Tunica Externa: Outermost layer.
      • Made of simple squamous epithelium and loose areolar connective tissue.
  • Arteries:
    • Internal Elastic Lamina: Elastic connective tissue between tunica intima and tunica media.
    • External Elastic Lamina: Elastic connective tissue between tunica media and tunica externa.
  • Veins: Lack elastic connective tissue.
  • Arteries: Maintain circular shape due to connective tissue and thick smooth muscle.
  • Artery vs. Vein:
    • Lumen: Artery has narrower lumen; vein has a wider lumen.
    • Wall Thickness: Artery walls are typically thicker.
    • Shape: Artery is circular; vein is collapsed.
    • Tunica Media: Thickest in arteries.
    • Tunica Externa: Thickest in veins.
    • Elastic Fibers: More in arteries (internal and external elastic lamina).
    • Valves: Veins have valves to prevent backflow (arteries do not).

Blood Vessel Layers (Artery Specific Details)

  • Tunica Intima:
    • Endothelium (simple squamous epithelium).
    • Thin layer of loose areolar connective tissue.
  • Internal Elastic Lamina (between tunica intima and tunica media)
  • Tunica Media:
    • Smooth muscle cells.
  • External Elastic Lamina (between tunica media and tunica externa).
  • Tunica Externa:
    • Loose areolar connective tissue.

Identifying Artery vs. Vein

  • Artery: Maintains a circular shape.
  • Vein: Shows a collapsed shape.
  • Artery: Has a very thick tunica media.
  • Vein: Has a thin tunica media, thicker tunica externa.

Question Example

  • Feature present in arteries but not in veins: Elastic lamina.
  • Valves: Only in veins.
  • Both arteries and veins have tunica intima, tunica media and tunica externa
    • Tunica Intima: Endothelium (simple squamous epithelium) and thin, loose areolar connective tissue.
    • Tunica Media: Smooth muscles.
    • Tunica Externa: Loose areolar connective tissue (adventitia).

Erroneous Terminology Note

  • Endomysium, perimesium, and epimesium are terms used for skeletal muscle, NOT the heart. Use endocardium, myocardium, and epicardium for the heart.