Talk:HM Practical - Blood Vessel Histology

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HM Practical - Blood Vessel Histology


Starting at the Heart:

  • Elastic arteries (conducting) - large arteries
    • examples - aorta, brachiocephalic, common carotid, subclavian, vertebral, common iliac arteries.
    • thin wall compared to diameter.
    • tunica media more elastic fibres, less smooth muscle.
    • pressure reservoir.
  • Muscular arteries (distributing) - medium sized arteries
    • examples - axillary, brachial, radial, intercostal, splenic, mesenteric, femoral, popliteal, tibial.
    • capable of greater vasoconstriction/vasodilation.
    • adjust blood flow rate.
  • Arterioles - small arteries deliver blood to capillaries.
    • tunica interna, media (smooth muscle few elastic fibres), externa (elastic and collagen fibres)
    • regulate blod flow into capillaries.
  • Capillaries - smallest vessels.
    • endothelium and basement membrane.
    • main site of exchange (nutrients, waste).
    • connect arterioles and venules.
  • Venules - smallest veins.
    • uniting capillaries drain into veins.
    • further from capillary bed tunica media increases.
  • Veins - same 3 coats as arteries.
    • tunica interna and tunica media thinner than companion artery, tunica externa thicker.
    • many veins contain valves to prevent back flow.

Aorta (elastic artery)

(2 virtual slides) Showing layers of the wall: tunica intima, tunica media and tunica adventitia. The media is extensive with multiple layers of smooth muscle mixed with elastic laminae, some of which are fenestrated. Vasa vasorum and nervi vasorum in the tunica adventitia; capillaries in adipose tissue surrounding the artery. (Note: capillaries are roughly 8 micrometers in diameter, enough to see 1 or 2 red blood cells inside the lumen).

Tunica intima

  • delimits the vessel wall towards the lumen of the vessel and comprises its endothelial lining (typically simple, squamous) and associated connective tissue.
  • Endothelium - simple squamous epithelium, cells organised longitudinally, joined by tight and gap junctions.
  • Internal elastic lamina (layer, membrane) not obvious due to may elastic layers.
  • the tunica intima of elastic arteries is thicker than in other arteries.

Tunica media

layer of circumferential smooth muscle and variable amounts of connective tissue. A second layer of elastic fibers, the external elastic lamina, is located beneath the smooth muscle.

  • Elastin - fenestrated sheets or lamellae between muscle layers.
  • Smooth Muscle Cells - arranged in layers.
  • Collagen fibre and ground substance.

Tunica adventitia

mainly of connective tissue fibres. The tunica adventitia blends with the connective tissue surrounding the vessel, and the definition of the outer limit of the tunica adventitia is therefore somewhat arbitrary.

  • Thin - collagen fibres, elastic fibres (not lamellae), fibroblasts, macrophages.

vasa vasorum - (Latin, "vessels of the vessels") the network of small blood vessels that supply large blood vessels.

Other Features

  • Thoracic duct (lower left) - largest lymphatic vessel in the body.
  • Adipose tissue - brown and white adipose.
  • Neurovascular bundle.

Masson's Trichrome

(Although called a trichrome, four dyes (hematoxylin, Biebrich scarlet, acid fuchsin, and analine blue) are utilized.

  • Stains nuclei deep blue, skeletal and smooth muscles red, collagen and mucin blue.
  • Stains brain and spinal cord parenchymal tissue dusky pink to red.
  • Used to evaluate fibrosis
  • Striations in skeletal muscles also shows up much better in Masson’s trichrome than in hematoxylin and eosin stain.

Muscular Artery

  • Medium sized (muscular) artery and vein - (2 virtual slides)
  • Distinct layers of wall of an artery: tunica intima, internal elastic lamina, tunica media (many layers of smooth muscle), external elastic lamina (multiple layers) extending into tunica adventitia;
  • In the vein, the same 3 tunics can be seen but the tunica media is reduced, and the tunica adventitia is wider compared to the artery.

nervi vasorum - (nervi vascularorum) vascular nerves that innervate both arteries and veins and control vessel vasodilation and vasoconstriction.

Neurovascular bundle

The toluidine blue stains nucleic acids blue and polysaccharides purple and also increases the sharpness of histology slide images.

  • Veins - tunica interna and tunica media thinner than companion artery, tunica externa thicker.

Vena Cava

Valves are absent.

  • tunica intima - contains some subendothelial connective tissue.
  • tunica media - comparatively thin with collagen and elastic fibres.
  • tunica adventitia - very wide, contains bundles of longitudinal smooth muscle and the transition to the surrounding connective tissue is gradual.