ULTRASTRUCTURE OF SENSORY NERVE-ENDINGS IN ARTICULAR CAPSULE OF KNEE-JOINT OF DOMESTIC CAT (RUFFINI-CORPUSCLES AND PACINIAN-CORPUSCLES)

Abstract

Two types of mechanoreceptor were found in the articular capsule of the knee joint [in Felis silvestris f. catus], Ruffini corpuscles and Pacinian corpuscles. Ruffini corpuscles are situated in the stratum fibrosum and consist of 2-6 cylinders. Each cylinder is made up of an afferent axon (.PHI. [diameter] = 3-4 .mu.m), its swellings and terminal processes, Schwann cells enveloping the nerve swellings and terminal processes, endoneural connective tissue and perineural capsule. The nerve swellings of a cylinder extend digitate processes into the endoneural connective tissue. Schwann cells form septa in the cylinders. The perineural capsule is incomplete in Ruffini corpuscles. The Pacinian corpuscles are 20-40 .mu.m wide and 150-250 .mu.m long. They are situated in groups of up to 5 at the boundary between the stratum synoviale and the stratum fibrosum. The afferent axon is myelinated (.PHI. = 3-5 .mu.m). Its terminal portion is inside the inner bulb which is formed of modified Schwann cells. Each corpuscle is enveloped by a perineural capsule (4-8 layers). The ultrastructure of the Pacinian corpuscles was compared with the ultrastructure of the skin receptors in the cat.