Cardiovascular Histology

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mnm2186
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32605
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Cardiovascular Histology
Updated:
2010-09-14 14:40:05
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Histology
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Exam 3
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  1. Basic organization of CV components
    • ALL components of the CV system have 3 layers
    • 1. Tunica intima (inner, endocardium)
    • 2. Tunica media (middle, myocardium)
    • 3. Tunica adventitia (outer, epicardium)
  2. Tunica Intima
    • Lumenal (inner) layer
    • Endothelium (simple squam.) contacts blood
    • Subendothelium (loose CT / some smooth m. cells)
  3. How is the tunica intima oriented?
    Longitudinally!

    endothelium / subendothelial elements arranged on the axis of blood flow
  4. Functions of endothelium
    • 1. Maintains selective permeability barrier.
    • 2. Maintains non-thrombogenic barrier.
    • 3. Modulates blood flow and vascular resistance.
    • 4. Regulates cell growth.
    • 5. Regulates immune response.
    • 6. Maintains ECM.
    • 7. Involved in lipoprotein metabolism
  5. Tunica Media
    • Most prominent layer in arteries
    • - Smooth muscle / Elastic membranes (concentric / relative)
    • - Reticular fibers (type III collagen)
    • - Proteoglycans
  6. How are elements of the tunica media oriented
    • Elements of media are oriented concentrically (spiral)
    • (smooth muscle / elastic membranes)
  7. What synthesizes all the ECM in the tunica media?
    ECM made by smooth muscle cells
  8. Predominant feature of elastic arteries?
    Where is it found?
    What does it do?
    Elastic lamellae (type III reticular fibers / proteoglycans)

    Found in the tunica media

    Elastin rebound maintains BP in diastole (relaxation)
  9. What separates the t. intima and t. media?
    • Internal elastic lamina
    • (both; prominent in muscular arteries)
  10. What separates the t. media and t. adventitia?
    • External elastic lamina
    • (muscular arteries)
  11. Tunica Adventitia
    • Most prominent layers in veins
    • Connective tissue sheath
    • - mainly type I collagen
    • - elastic fibers
    • - smooth muscle
    • Vasomotor nervi vascularis
    • - innervated smooth m. of media

    large vessels may have vasa vasorum
  12. Where are vasa vasorum found? Be specific
    Vasa vasorum found in t. adventitia of large blood vessels
  13. How are elements of the tunica adventitia oriented
    t. adventitia is oriented longitudinally
  14. Basic organization of heart tissue
    • 1. Endocardium
    • 2. Myocardium
    • 3. Epicardium
    • 4. Conducting system of specialized cardiac m. cells
  15. Endocardium
    • Innermost heart layer (analog = t. intima)
    • Endothelial lining
    • Subendocardium
  16. Subendocardium
    Underlying layer of the endocardium

    • Composed of loose CT / elastic fibers / some smooth m. cells
    • Contains small veins / nerves

    In some locations, also contains Purkinje fibers
  17. Purkinje cells
    • Specialized cardiac muscle cells (subendocardium)
    • - larger than reg. cardiac m. cells
    • - fewer myofibrils (stains lighter)
    • - central nucleus (often binucleated) surrounded by glycogen (light area)
  18. Conduction system of the heart
    • - Impulse initiated at SA node (pacemaker)
    • - Travels to AV node
    • - AV bundle (of His) sends impulse to L/R bundle branches to apex of heart.
  19. Myocardium
    • Middle heart layer (analog = t. media)
    • - Thicker in ventricles (inner circular / outer spiral layers)
    • - Cardiac m. is anchored to cardiac skeleton (dense fibrous CT)
    • - Cardiac m is postmitotic
  20. Histological changes in myocardial infarcted tissue
    • - Lots of inflammatory cells
    • - Necrotic tissue

    With time, inflammatory cells increase in number / lots of scar tissue
  21. Epicardium
    • Outermost heart layer (analog = T. Adventitia)
    • - Thick layer of loose CT / adipose
    • - Contains neurovasculature
    • - Outermost layer = mesothelium (simple. squam)
    • - forms visceral serous pericardium
  22. Heart valves
    • 1. Right AV (tricuspid)
    • 2. Left AV (mitral)
    • 3. Pulmonic
    • 4. Aortic
  23. Elastic Arteries
    (conducting arteries)
    • Tunica Intima
    • - endothelial cells rest on thick subendothelium
    • - longitudinal oriented CT
    • - internal elastic lamina not clearly defined
    • Tunica Media
    • - concentric lamellae of elastin (40-70)
    • - some smooth muscle
    • Tunica Adventitia
    • - thin, compared to vessel
    • - vasa vasorum, extend into t. media
  24. Muscular Arteries
    (distributing arteries)
    • Tunica Intima
    • - endothelial cells rest on subendothelium (some smooth m.)
    • - longitudinal orientation
    • - internal elastic lamina, prominent identifying feature
    • Tunica Media
    • - concentric smooth muscle (3-40)
    • - some elastin (special stain required)
    • Tunica Adventitia
    • - external elastic lamina
    • - longitudinal oriented fibroblasts / collagen / elastic fibers
    • - vasa vasorum / lymphatics
  25. Arterioles
    • Tunica Intima
    • - endothelial cells rest on thin subendothelium
    • - internal elastic lamina not usually visible
    • Tunica Media
    • - concentric smooth muscle (< 3)
    • Tunica Adventitia
    • - very thin
  26. Continuous Capillaries
    (somatic capillaries)
    • - Continuous endothelium resting on basal lamina
    • - Cells joined by tight junctions (zonula occludens)
    • - Found in CNS / PNS, muscle, CT, exocine glands
  27. What is special about CNS capillaries?
    • Surrounding basal lamina of continuous capillaries is layer of astrocytic endfeet. Endfeet induce formation of blood-brain barrier
    • - endothelial tight junctions
    • - paucity of pinocytotic vesicles
  28. Fenestrated Capillaries
    (visceral capillaries)
    • - Continuous endothelium interrupted by pores (fenestrae)
    • - Pores may have thin diaphragm over them (except renal glomeruli)
  29. Endocrine vs. Exocrine capillaries
    • Endocrine = fenestrated
    • Exocrine = continuous
  30. Sinusoidal Capillaries
    (discontinuous capillaries)
    • - Specialized w/ relatively large lumens
    • - Many open fenestrations
    • - Absence of continuous basal lamina
    • - Macrophages present along walls

    Found in liver / lymphoid / hematopoietic organs
  31. Venules
    • - small, postcapillary vessels
    • - paired w/ arterioles
    • - very thin walls
    • - functional characteristics of capillaries (exchange vessels)
  32. Veins
    • Tunica Intima
    • - very thin
    • - valves formed by subendothelial CT (not in large veins)
    • - valves have covering of endothelium

    • Tunica Media = poorly developed
    • Tunica Adventitia = very well developed
  33. What are the prominent layers in arteries vs. veins?
    • Artery = prominent media
    • Vein = prominent adventitia
  34. Large arteries vs. Large veins
    • Large Artery
    • - thick intima
    • - thick media
    • - underdeveloped adventitia

    • Large Vein
    • - thick intima
    • - thin media
    • - well developed adventitia w/ longitudinal bundles of smooth m.
  35. Lymphatic vessels
    • - very thin-walled vessels
    • - large irregular lumens (some valves)
    • - larger lymphatics similar to veins w/o well defined tunics

    Should not see RBC's in lymphatics

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