title: Histogenesis and morphology of the flexor tendon pulley system in the human embryonic hand.
abstract: The number, position, structural and ultrastructural features of the flexor tendon pulley system in six human embryonic hands, aged from 6 to 12 weeks, were studied by light and electron microscope. The pulley system can be recognized from the ninth week; later, at 12 weeks, the structures are easily identified around the flexor tendon in positions closely correlated to those found during post-natal growth and in the adult hand. Structurally and ultrastructurally the pulleys are not simply thickened portions of the sheath. They are formed by three layers: an inner layer, one or two cells thick, probably representing a parietal synovial tendon sheath; a middle layer formed by collagen bundles and fibroblasts whose direction is mainly perpendicular to the underlying phalanx; and an outermost layer consisting of mesenchymal tissue with numerous vessels which extends dorsally in an identical layer, forming a ring that includes flexor and extensor tendons and the cartilaginous model of the phalanx. The pulley does not have a semicircular shape but a much more complicated one, owing to the middle layer which in part runs dorsally and in part ventrally, under the flexor tendons.
authors.affiliation: Department of Orthopaedics, University School of Medicine, Sassari, Italy. teren@tiscalinet.it
authors.forename: M C
authors.initials: MC
authors.lastname: Sbernardori
authors.forename: G
authors.initials: G
authors.lastname: Fenu
authors.forename: A
authors.initials: A
authors.lastname: Pirino
authors.forename: C
authors.initials: C
authors.lastname: Fabbriciani
authors.forename: A
authors.initials: A
authors.lastname: Montella
mesh_terms: D005865:Gestational Age; D006225:Hand / Q000196:embryology*; D006801:Humans; D013710:Tendons / Q000196:embryology*