[Experimental anatomical data on the structure of retrobulbar nervous plexus in man and various laboratory animals]. / Anatomo-éksperimental'nye dannye o stroenii retrobul'barnogo nervnogo spleteniia u cheloveka i nekotorykh laboratornykh zhivotnykh.

Retrobulbar nervous plexuses were studied in man, albino rat, guinea pig and rabbit by means of macro- and micropreparation with elective dyes use, histotopogrammes and in the experiment with sympathetic superior cervical node removal. It was established that models characteristic for mammals were present in this plexus structure. Branches of abducent nerve conducting sympathetic fibres to the eyeball are the part of the plexus in rodents and the rabbit. In all the cases sympathetic fibres to the eyeball pass without contact with ciliary ganglion, apart from guinea pig, in which portion of sympathetic fibres passes through additional ciliary ganglia. Only in man ciliary ganglion has sensory root although sympathetic fibres are not discovered in trigeminal nerve branches.

The sensorineural apparatus of the human eyelid.

The present study describes a complex array of sensory nerve terminals in the human eyelid. In many respects this pattern of innervation resembles that previously described in the rhesus monkey, but in other respects it is unique to man. The most prominent nerve terminals are a complex array of lanceolate and circular Ruffini and free nerve endings that envelop the eyelashes. In addition, Merkel cells have not been conclusively identified to date in other nonhuman primate nonsinus hairs. The external root sheath collar contains Merkel cells, and dermal Merkel cells have also been identified close to the collar. The anterior cutaneous surface of the eyelid contains small vellus hairs with typical lanceolate, Ruffini, and free nerve endings resembling those of primate facial skin. Scattered Meissner and scant simple corpuscles as well as scattered free nerve endings (FNEs) can be identified on the occlusal surface of the eyelid. Intraepithelial as well as dermal FNEs were most easily identified in this region in areas lacking other corpuscular receptors. Corpuscular receptors are especially common at the occlusal/conjunctival angle. The inner or conjunctival surface of the eyelid appears to be a glandular epithelium, whereas in the rhesus monkey it is stratified squamous epithelium. This epithelium needs additional study. In summary, the present study confirms the unique sensory neural status of the human eyelid and verifies the presence of Ruffini nerve terminals by light and electron microscopy and of free nerve ending terminals at least by light microscopy, as well as a unique pattern of innervation of the human eyelash.

The sensory innervation of primate eyelid.

The skin of primate eyelid contains three distinctive sensory nerve terminals. Small down hairs have a collar of lanceolate terminals that are formed by ramifications of the six to eight myelinated afferent fibers. Extensions of Schwann-cell cytoplasm form masses of cytoplasmic lamellae associated with these terminals. Every large hair or eyelash contains a large pilo-Ruffini as well as sparse lanceolate terminals. The eyelash Ruffini corpuscle resembles those of monkey facial guard hairs, sinus hairs, and joint capsules of the cat and pigeon. Sparse lanceolate terminals present between the Ruffini corpuscle and eyelash external root sheath resemble those of vellus hairs. On rare occasion Merkel cells are present in the hair follicle external root sheath above the sebaceous gland. Merkel touch spots, or Tastscheiben, are located between contiguous eyelashes as small rete pegs containing several Merkel cell-neurite complexes innervated by one or two myelinated afferent fibers. The function of this array of sensory terminals is presumed to represent an extensive mechanism of protection for the cornea and globe. On the basis of studies reported to date we can conclude that the Ruffini corpuscles (and related receptors) are the ubiquitous mechanoreceptors of cutaneous and musculoskeletal systems in birds as well as mammals.