Hand fasciae innervation: The palmar aponeurosis.

There are few data in the scientific literature about the innervation of fasciae of the hand. The present study first elucidates the density and location of nervous structures in the palmar aponeurosis and, for comparison, in the flexor retinaculum (both can be considered specializations of the deep fascia of the upper limbs). Second, it compares nonpathological with pathological palmar aponeurosis. Samples of nonpathological fascia were taken from the flexor retinaculum and palmar aponeurosis of 16 upper limbs of unembalmed cadavers. Samples of pathological palmar aponeurosis were taken from seven patients with Dupuytren's disease. All samples were stained immunohistochemically with anti-S100 and anti-tubulin antibodies, and analyzed quantitatively and qualitatively by microscopy. The palmar aponeurosis showed higher median density than the retinacula of free nerve endings (22 and 20 elements/cm2 , respectively), Pacinian corpuscles (2 and 0 elements/cm2 ) and Golgi-Mazzoni corpuscles (1.0 and 0.5 element/cm2 ). Some corpuscles were located at the intersections of the fibers in the three directions. Free nerve endings were denser in pathological palmar aponeurosis (38 elements/cm2 ). The results indicate that the palmar aponeurosis is central to proprioception of the hand and that surgery should therefore avoid injuring it. The higher density of free nerve endings in pathological samples indicates that the nervous structures are implicated in the amplified fibrosis of Dupuytren's disease. Clin. Anat. 31:677-683, 2018. © 2018 Wiley Periodicals, Inc.

Autonomic and sensitive somatic innervation of the ostrich elbow and knee joints articular capsule.

The present research was carried out on the fibrous layer of the ostrich's elbow and knee joints articular capsule, employing opportunely modified gold chloride Ruffini's method, to study the autonomic and sensitive somatic nerve components. The distribution of both nerve components followed frequently the vascular networks. The autonomic innervation was represented by isolated or grouped ganglion cells, frequently placed along the course of nerve trunks, close to the epineurium or located within the perineural connective tissue. The sensitive somatic innervation was constituted by free and encapsulated corpuscles. The last one, morphologically classified as Pacini, Pacini-like and Golgi-Mazzoni's corpuscles, were found isolated or grouped to constitute simple and complex flower sprays, "opposito-polar corpuscles" and "poichilomorphous fibres". The very few Golgi-Mazzoni's corpuscles were found only in the knee joint articular capsule. The two nerve components, found in the considered districts, did not shown significant quanti-qualitative and topographic differences. This datum, at least in appearance, seems to conflict with the ostrich functional aptitudes. In fact, the ostrich is a bird unable to fly but very able to run.

Morphological characteristics and distribution of the autonomic and sensitive innervation of the prostate in some animal species.

The sensitive and autonomic innervation of the prostate was studied in some mammals (rat, rabbit, horse, donkey and bull) using gold chloride impregnation. In all the species considered the gland was supplied with conspicuous innervation located in the thickness of the capsule and in trabeculae. The autonomic innervation was constituted by ganglion cells of different sizes (small, medium and large), isolated or in groups of large ganglia also, always located along the course of nerve bundles. The sensitive nervous component, placed more frequently in the most superficial layer of the capsule, consisted of delicate networks originating by more fibres and, above all, of capsulated receptors such as Pacini and Golgi-Mazzoni corpuscles. A characteristic finding, but only present in the horse, donkey and bull, was the helicoidal disposition of thin collagen fibres around thin nervous bundles that ended up to the point where the nerve trunk divided.

Periarticular neural elements in the shoulder joint.

Due to its unconstrained nature, the glenohumeral joint must necessarily have several mechanisms to regulate its position in space. The neural mechanisms associated with this positioning have not been fully evaluated anatomically. In this study, three fresh-frozen human cadaveric adult shoulders were dissected. Specimens were excised from the proximal biceps insertion, the superior, middle, and inferior glenohumeral ligaments, and the capsule superior to the glenohumeral ligaments. In two specimens, a portion of glenoid labrum was analyzed using a modified gold chloride staining method and light microscopy. A portion of mid-biceps tendon was used as a control. In the superior glenohumeral ligament, 45% of sections contained neural elements consisting of Golgi's, Ruffini's, and Pacini's corpuscles as well as free nerve endings. The predominant types were Ruffini's and Golgi's. The middle glenohumeral ligament sections revealed all four receptor types in 42%, with the most common elements being Pacini's and Ruffini's receptors. The inferior glenohumeral ligament specimens contained the four receptor types in 48% of sections, with Ruffini's, Pacini's, and Golgi's types equally distributed. The shoulder capsule specimens revealed Ruffini's and Pacini's receptors in 47.5% of sections. Only free nerve endings were identified in the biceps tendon and glenoid labral tissue. These findings suggest that the pattern of neural elements does not appear to be random in nature and may have some correlation with the specific functions of some of the glenohumeral ligaments.

On the vegetative and sensitive innervation of the Retractor clitoridis muscle in some domestic animals.

The retractor clitoridis muscle originates from the coccygeal vertebrae in the cow, ewe, goat and mare, and from the anal musculature in the sow. It terminates at the base of the clitoris. In all the species considered, a vegetative innervation was found. This was represented by isolated or grouped ganglion cells. Nervous sensitive supply was also present. This was represented by Pacinian, Pacinian-like and Golgi-Mazzoni's corpuscles, and by Krauses's end bulbs. A notable difference was found in the amount and type of these receptors. They were numerous in the sow, ewe and goat, and rare in the cow and mare. Additionally, in the sow, ewe and goat, all the above mentioned receptors were found, while, in the cow and mare, only Pacinian and Pacinian-like corpuscles occurred. The morphology of these receptors was described and hypotheses were made concerning their probable functional role.

The nerve endings of the acetabular labrum.

The nerve endings of the human acetabular labrum were investigated. Twenty-three acetabular labra were obtained from 24 fresh human cadavers, stained with Suzuki's silver impregnation and an immunohistochemical technique for neurogenic specific protein S-100, and examined by light and electron microscopy. Ramified free nerve endings were seen in all specimens by silver staining, and also were observed by the immunohistochemical technique for S-100 protein. Sensory nerve end organs, such as a Vater-Pacini corpuscle, Golgi-Mazzoni corpuscle, Ruffini corpuscle, and articular corpuscle (Krause corpuscle), were observed by silver staining. Collagen fibers were scattered sparsely in the superficial layer of the labrum, and nerve endings were observed mostly in this region. Collagen fibers were sparse, and nerve endings also were observed in some regions among the collagen fiber bundles in the inner layer. Innervation of the acetabular labrum was confirmed in this study, suggesting that nerve endings in the labrum may be involved in nociceptive and proprioceptive mechanisms.

Mechanoreceptors in human myotendinous junction.

The sensory-nerve-ending system of 40 myotendinous junctions of human palmaris longus and plantaris muscles was studied histologically. All the known four types of nerve endings were identified. The Ruffini corpuscles could be found in equally small numbers (one to five) in both the muscular and tendineal sites of the junction. Also the free nerve endings were distributed equally on both sites. The Pacini corpuscles were frequent in the tendineal site (six to 14), but rare in the muscular site (one to three). The Golgi tendon organs were, in turn, frequent in the muscular site (nine to 12) but rare in the tendineal site (one to four), respectively. Within the muscle and tendon parts of the junction, the distance between two mechanoreceptors was always more than 250 microns and the receptor distribution was homogeneous. Further studies are needed to give functional explanation for these anatomic findings.

Neural elements in the human temporomandibular articular disc.

The purpose of this study was to determine the presence and describe the location of neural elements in the articular disc of the human temporomandibular joint. Six articular discs were obtained from three adult human subjects at autopsy. Four discs were cut into segments of known anterior-posterior orientation. The remaining two were processed intact. All tissues were stained in bulk with gold chloride, and frozen, sectioned on a sliding microtome at 70 to 100 microns, mounted on slides, dehydrated, and coverslipped. Nerve fibers were seen penetrating the discs from the pericapsular connective tissue. Structures resembling Ruffini endings, Pacinian corpuscles, and Golgi tendon organs were identified in the pericapsular connective tissue and within the disc. The population density of neural elements was the greatest at the periphery of the disc and progressively decreased towards the center, which was essentially devoid of them. The concentration of neural elements appeared to be greater at the anterior and posterior margins of the disc, with the greatest concentration being posteriorly. These findings support the theory that afferent nerves may arise from neural elements within the disc.

Neural elements in human cervical intervertebral discs.

This study attempted to characterize neural elements within the human cervical intervertebral disc. Cervical intervertebral discs were obtained from four adult human subjects at autopsy. Discs were stained in bulk with gold chloride, sectioned, and viewed with the light microscope. Nerve fibers appeared to enter the disc in the posterolateral direction and course both parallel and perpendicular to the bundles of the anulus fibrosus. Nerves were seen throughout the anulus but were most numerous in the middle third of the disc. Receptors resembling Pacinian corpuscles and Golgi tendon organs were seen in the posterolateral region of the upper third of the disc. These results provide further evidence that human cervical intervertebral discs are supplied with both nerve fibers and mechanoreceptors.

Intrinsic innervation of the rat knee joint articular capsule and ligaments.

In spite of the practical importance of having a detailed knowledge of knee joint innervation to understand the pathophysiologic aspects, little information is now available concerning the density and pattern of the nerve fibres which are distributed to it. The present study has been designed to investigate the density and distribution of nerve fibres and receptor corpuscles in the knee joint articular capsule, cruciate and collateral ligaments in the rat, using the acetylcholinesterase (AChE) histochemical in toto staining technique. The investigation was performed on male Wistar rats of 3 months of age, some of which had been treated with capsaicin to deplete their afferent 'C' fibres of their content of neuropeptides. AChE-positive nerve fibres and different types of receptor corpuscle endings were found within articular capsule and ligaments. The highest density of AChE-positive nerve fibres was noticeable in the fibular collateral ligament followed by the tibial collateral ligament, the posterior cruciate ligament, the anterior cruciate ligament and the articular capsule. In the articular capsule the number of type I endings was higher than in the ligaments. The opposite is true for the other type of receptor corpuscles found as well as for nerve endings. Capsaicin treatment significantly reduced the density of AChE-positive nerve fibres in knee joint ligaments but did not affect nerve fibres in the articular capsule. Moreover, it caused the disappearance of some kind of receptor corpuscles within the collateral and cruciate ligaments. The above data collectively suggest that the AChE in toto staining technique may represent a good method for investigating joint innervation and that a significant percentage of nerve fibres supplying knee joint ligaments is represented by C fibre afferents.

The occurrence and ultrastructure of a mechanoreceptor in the human cricopharyngeus muscle.

An encapsulated nerve structure resembling the Golgi tendon organ was found in a human cricopharyngeus muscle near the cricoid cartilage where muscle fibers terminate. The capsule consisted of lamellated flattened cells with a basal lamina. Capsular cells separated the lumen into small compartments which contained myelinated and/or nonmyelinated nerve fibers. Nonmyelinated nerve fibers were also found in the interlamellar spaces of the capsular cells. Some nonmyelinated nerve fibers were dilated and contained abundant mitochondria, being partly surrounded by a Schwann cell sheath and embedded in collagen bundles. These features indicate that the nerve structure is a mechanoreceptor similar to the Golgi tendon organ. Its location and structure indicate that it is placed to detect the tension of the cricopharyngeus muscle.

On the collateral sesamoidean (suspensory navicular) ligament of equines: topographic relations and sensitive innervation.

The origin and course of the collateral sesamoidean (suspensory navicular) ligament of the horse and ass and its attachment to the distal sesamoid bone were studied by means of dissection. Particular attention was given to the topographic relations between this ligament and the deep digital flexor tendon. Numerous sensitive nerve endings are present in this anatomical district. The free and encapsulated nerve endings, displayed by impregnating techniques, are mostly concentrated in the ligament tract connected to the above-named tendon and close to its attachment to the distal sesamoid angle. The nerve endings are identified as typical Pacini, Pacini-like and Golgi-Mazzoni corpuscles on account of their morphological features and are found isolated, grouped to form flower-sprays, lined up along the course of a single nerve fibre or grouped to originate poikilomorphous fibres.

Activation of Golgi tendon organs by asynchronous contractions of motor units in cat leg muscles.

Discharges from individual tendon organs of peroneus tertius muscle activated by the isometric contractions of single motor units were recorded in anaesthetized cats. Pairs of motor units acting on the same tendon organ were stimulated asynchronously at frequencies eliciting unfused contractions. Tendon organ responses to such contractions did not display a linear relation between discharge frequency and contractile force recorded at the muscle tendon. In several instances, one of the motor units exerted a predominant influence on the response of the tendon organ, even though this unit did not produce the strongest activation of the receptor when stimulated on its own.

[Functional properties of the Golgi tendon organs]. / Propriétés fonctionnelles des organes tendineux de Golgi.

Golgi tendon organs are encapsulated mechanoreceptors present at the myo-tendinous and myo-aponeurotic junctions of mammalian skeletal muscles. Within the tendon organ capsule, the terminal branches of a large diameter afferent fibre, called Ib fibre, are intertwined with collagen bundles in continuity with tendon or aponeurosis at one end. The other end is connected with a fascicle of 5-25 muscle fibres, contributed by several motor units. The contraction of these fibres, exerting strain on the collagenous bundle and causing deformation of sensory terminals, is the adequate stimulus of the tendon organ. For this stimulus, the tendon organ has a very low threshold, so that a single fibre twitch can elicit a discharge from the receptor. A tendon organ can thus signal the contraction of a single one of the 10-15 motor units which contribute fibres to the fascicle connected with the receptor. The number of tendon organs present in a muscle, taken together with the fact that a given motor unit can activate several tendon organs, strongly suggests that the contraction of every motor unit in this muscle is monitored by at least one tendon organ. The exact nature of the information provided by tendon organs to the central nervous system remains an open question because no simple relation could be established between the discharge frequency of a receptor and the contractile forces of its activating motor units. It is known, however, that, due to their dynamic sensitivity, tendon organs are efficient in signaling rapid variations of contractile force. The dynamic parameters of muscle contraction prevail in the information carried by afferent discharges from tendons organs.

Stretch sensitivity of Golgi tendon organs in fatigued gastrocnemius muscle.

Alterations in Golgi tendon organs' (Ib afferent receptors) stretch sensitivity were assessed in fatigued gastrocnemius muscle of cats. Muscle fatigue to 60-50% peak tension was induced in 13 cats by electrical stimulation of L7 and S1 ventral roots. Forty-three group Ib afferent fibers were recorded in L7 or S1 dorsal root filaments before and during fatigue. Fiber activity was assessed by applying to the Achilles tendon a 5-mm ramp stretch at 5 or 25-30 mm X s-1. Group Ib afferent responses to both velocities of stretch were either completely abolished or depressed over several seconds compared to pre-fatigue firing frequencies. When responding, longer latencies (measured at 5 mm X s-1 only) to firing onset occurred during fatigue. Increasing the rate of stretch (250 mm X s-1) to produce a 5-mm stretch approximately equivalent to twitch tension time revealed a depression more selective to static stretch sensitivity. Post-excitation depression of the Ib receptor potential appears to be one possible mechanism. These acute adaptations in Ib afferent discharge to muscle stretch were opposite in direction to those recently reported in fatigued muscle for group Ia and group II muscle spindle afferents. Functional implications of these results are discussed.

Therapeutic traction: a review of neurological principles and clinical applications.

A brief review of traction and its application as a therapeutic tool is outlined. The preliminary results obtained indicate that traction, as used in this study, along with isokinetic exercises and chiropractic manipulation, have a very positive effect on tension headaches originating from the posterior muscles in conjunction with pathomechanics of the cervical spine. A brief but pertinent review of the literature dealing with the anatomy and physiology of the muscle spindle, the muscles, the joints, the neural connections in the spinal cord and the central nervous system is presented, to provide the basic principles of the possible mechanisms underlying the therapeutic result obtained. This framework also provides the basis of a second paper, which will explore the neural control mechanisms that are intrinsic in the control of the head, eyes and cervical spine movement, with the view of utilizing these to facilitate manipulation of this region.

Force-sensitive interneurons in the spinal cord of the cat.

The input-output properties of interneurons mediating spinal reflexes were investigated by extracellularly recording the response of interneurons to excitation from muscle receptors in the ankle extensor muscles of decerebrated, spinal cats. A population ofinterneurons in the intermediate region ofthe spinal cord is potently excited by increases in muscle force. Unlike the discharge of Golgi tendon organs, which accurately encodes moment-to-moment variations in the force of a single muscle, the discharge of these interneurons depends in a dynamic and usually nonlinear way on the force in several muscles. Powerful input from unidentified mechanoreceptors in muscle, presumably free nerve endings, is at least partly responsible for these properties. These force-sensitive interneurons are more likely to mediate clasp knife-type inhibition than simple negative force feedback.