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MORPHOMETRY OF THE ULTRASTRUCTURE OF THE BLOOD‐JOINT BARRIER IN THE RABBIT KNEE
Author(s) -
Knight A. D.,
Levick J. R.
Publication year - 1984
Publication title -
quarterly journal of experimental physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.925
H-Index - 101
eISSN - 1469-445X
pISSN - 0144-8757
DOI - 10.1113/expphysiol.1984.sp002805
Subject(s) - ultrastructure , anatomy , chemistry , synovial membrane , endothelium , synovial joint , basement membrane , synovial fluid , biophysics , pathology , biology , medicine , articular cartilage , alternative medicine , arthritis , immunology , osteoarthritis , endocrinology
The ultrastructure of the barrier to water and solute exchange between blood and a synovial cavity was studied morphometrically in five rabbit knees. The synovial surface consisted of 80% synoviocytes and 20% interstitium in direct contact with synovial fluid. The surface intercellular gaps were wide (0·1–5·5 µm). A rich network of capillaries lay just beneath the surface, the commonest (modal) depth of the capillary perimeter being 5 µm at its nearest point. Of these capillaries, 91% were fenestrated in adipose synovium, 44% in areolar synovium and 21% in posterior synovium; the remainder were continuous capillaries. The number of fenestrae per fenestrated capillary was low (∼0·5 µm –1 , circumference: ∼6 µm −2 ). The fenestrae (width 52 nm; membrane thickness 3–4 nm) occupied ∼1% of the fenestrated endothelial surface‐area. Nuclear segments and intercellular junctions were roughly twice as frequent in continuous capillaries as in fenestrated capillaries of the same circumference, indicating that continuous endothelial cells are of smaller surface area than fenestrated cells. The basement membranes of continuous and fenestrated synovial capillaries were relatively thick (98 and 110 nm respectively), perhaps supporting the synovial endothelium during joint motion. In both fenestrated and continuous capillaries the nuclei were preferentially oriented away from the synovial surface (92 and 67% respectively), which presumably facilitates exchange with the surface.