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Histology for Pathology Circulatory System. Theresa Kristopaitis , MD Associate Professor Director of Mechanisms of Human Disease Kelli A. Hutchens, MD, FCAP Assistant Professor Assistant Director of Mechanisms of Human Disease Loyola Stritch School of Medicine. OBJECTIVES.

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Histology for pathology circulatory system

Histology for PathologyCirculatory System

Theresa Kristopaitis, MD

Associate Professor

Director of Mechanisms of Human Disease

Kelli A. Hutchens, MD, FCAP

Assistant Professor

Assistant Director of Mechanisms of Human Disease

Loyola Stritch School of Medicine


1. Given a histologic section of a large or medium sized artery, identify the

a) tunica intima

b) tunica media

c) tunica adventitia

2. Identify the following structures in a histologic section of an artery

a) Endothelium

b) Internal elastic lamina

c) External elastic lamina

d) Vasovasorum

3. Distinguish the characteristics which separate large, medium and small arteries and arterioles.

4. In a tissue section, distinguish a medium sized artery from a medium sized vein

5. In a tissue section identify capillaries, describe their structure and function

6. Compare and contrast general structural features of the arterial vs venous system

7. Describe the structure and function of a lymphatic vessel

Vessel types
Vessel Types

  • Arteries

    • Large artery

    • Medium artery

    • Small artery

    • Arteriole

  • Veins

    • Large Vein

    • Medium Vein

    • Small Vein

    • Venule

  • Capillaries

    • Continuous

    • Fenestrated

    • Discontinuous

Overall structure of vessels
Overall Structure of Vessels

  • Three layers (tunica)

    • Tunica intima(inner most layer)

      • Endothelium

      • Subendothelium

      • Internal elastic lamina (IEL) in arteries

    • Tunica media

      • Smooth muscle layer

      • External elastic lamina (EEL) in arteries

    • Tunica adventitia (outer most layer)

      • Connective tissue and fibroblasts

      • Longitudinal smooth muscle in veins

      • Vasovasorum in large vessels

Large artery
Large Artery





Elastic fibers


Vasa vasorum

a = tunica intima - endothelial lining plus thin layer of underlying connective tissue called the subendothelium.

b = tunica media - alternating layers of elastic membranes (elastic lamina) and smooth muscle.

c = tunica adventitia - fairly dense connective tissue carrying small blood vessels,

the vasa vasorum


Endothelium: Composed of single layer of squamous cells, provides a permeable barrier, angiogenesis, release of single molecules.

Medium artery
Medium Artery

Also called muscular artery because the wall is dominated by smooth muscle.

Similar to large artery but internal and external elastic lamina are well defined and lack prominent vasovasorum.

Small artery arterioles
Small Artery & Arterioles


Small Arteries: Generally have same structure as medium artery but have a smaller diameter and no external elastic lamina. The tunica media also has fewer layers of smooth muscle cells.

Arterioles: The smallest arteries, lead blood flow into capillary beds. Only two layers of smooth muscle cells. Internal elastic lamina, external elastic lamina, and subendothelial layers usually absent.


  • Smallest vessels

  • Connect arterioles and venules

  • One layer of endothelial cells with a basal lamina


A capillary lying in the endomysium between skeletal muscle fibers. This one shows very dark endothelial nuclei and has 3 pink red blood cells* lined up in a row inside

Venules and small veins similar except
Venules and Small VeinsSimilar except

  • Small veins may have slightly larger lumen and more visible smooth muscle layer

  • Venules have small lumens, thin walls, and only single layer of endothelum. Have surrounding connective tissue


Medium-sized vein with a much less compact muscle layer than in arteries.

a - tunica media

b – tunica adventitia, which is at least as wide as the media, and often even wider.


(filled with


Medium vein
Medium Vein

Tunica intima

Tunica media

Tunica adventitia

Smooth muscle bundles

Quite similar to a large vein but smaller lumen, tunica adventitia contains fewer bundles of longitudinal smooth muscle and vasa vasorum is not prominent.


  • Folds in the intima seen in medium and larger veins

  • Number of valves increase with size of vessel

  • Prevent backflow of blood

  • Also present in the lymphatic vessels

Large veins
Large Veins

Vasa vasorum




Smooth muscle bundles

  • Tunica intima

  • Tunica media with a circular smooth muscle layer

  • Tunica adventitia: thickest layer with many longitudinal smooth muscle bundles and vasa vasorum.

Artery vs vein
Artery vs Vein



Lymphatic system
Lymphatic system

  • Composed of lymphatic capillaries, vessels, and ducts

  • Collect and drain interstitial fluid from tissue in the large veins

  • Have large lumens and relatively thin walls

  • Single layer of endothelium

  • Connective tissue outer layer with few smooth muscle cells

  • Also have valves



Thinned walled vessels with large lumens and valves. There are some fat cells and lymphocytes in the surrounding connective tissue.