Ultrastructural study of synovial membrane from the antebrachiocarpal joint of calves.
The synovial intima from the antebrachiocarpal joint of 4-month-old calves was between 1 and 3 cells in thickness and did not have a basal lamina. Numerous areas of the intimal matrix were in direct contact with the joint lumen. The synovial membrane was comprised mainly of A-type synoviocytes usually located adjacent to the joint lumen. These cells were characterized by numerous filopodia (or lamellipodia), large, empty-appearing vacuoles, numerous lysosomes, large vacuoles containing granular material separated from the vacuolar membrane by a radiolucent band, and coated micropinocytotic vesicles. Smooth micropinocytotic vesicles were seen only rarely in these cells. In contrast, B-type cells had few filopodia, numerous smooth micropinocytotic vesicles, few coated micropinocytotic vesicles, a well-developed Golgi apparatus and rough endoplasmic reticulum, mitochondria that were longer and had a denser matrix than that of A cell mitochondria, and surprisingly, only few maturing or fully formed secretory granules. A distinct intermediate (C or AB) type synoviocyte could not be unequivocally identified. Desmosome-like structures were present between synoviocytes, although it was considered questionable if these were true intercellular junctions. No other junctions were present.
Leach
D H
DH
Department of Veterinary Anatomy, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Canada.
Caldwell
S J
SJ
Ferguson
J G
JG
D000818:Animals; D002350:Carpus, Animal / Q000033:anatomy & histology* / Q000166:cytology; D002417:Cattle; D005552:Forelimb / Q000033:anatomy & histology*; D007596:Joints / Q000166:cytology / Q000648:ultrastructure*; D008297:Male; D008854:Microscopy, Electron; D008855:Microscopy, Electron, Scanning; D013583:Synovial Membrane / Q000166:cytology / Q000648:ultrastructure*