EMG of the digastric muscle in gibbon and orangutan: Functional consequences of the loss of the anterior digastric in orangutans

Unlike all other primates, the digastric muscle of the orangutan lacks an anterior belly; the posterior belly, while present, inserts directly onto the mandible. To understand the functional consequences of this morphologic novelty, the EMG activity patterns of the digastric muscle and other potential mandibular depressors were studied in a gibbon and an orangutan. The results suggest a significant degree of functional differentiation between the two digastric bellies. In the gibbon, the recruitment pattern of the posterior digastric during mastication is typically biphasic. It is an important mandibular depressor, active in this role during mastication and wide opening. It also acts with the anterior suprahyoid muscles to move the hyoid prior to jaw opening during mastication. The recruitment patterns of the anterior digastric suggest that it is functionally allied to the geniohyoid and mylohyoid. For example, although it transmits the force of the posterior digastric during mandibular depression, it functions independent of the posterior digastric during swallowing. Of the muscles studied, the posterior digastric was the only muscle to exhibit major differences in recruitment pattern between the two species. The posterior digastric retains its function as a mandibular depressor in orangutans, but is never recruited biphasically, and is not active prior to opening. The unique anatomy of the digastric muscle in orangutans results in decoupling of the mechanisms for hyoid movement and mandibular depression, and during unilateral activity it potentially contributes to substantial transverse movements of the mandible. Hypotheses to explain the loss of the anterior digastric should incorporate these functional conclusions. © 1994 Wiley-Liss, Inc.     

Vagal communicating branches between the facial and glossopharyngeal nerves, with references to their occurrence from the embryological point of view.

A rare and hitherto not reported case in which a branch of the vagal nerve communicated simultaneously with the facial and the glossopharyngeal nerves was encountered in the body of a Japanese male cadaver in an anatomy class. This vagofacial-vagoglossopharyngeal (X.VII-X.IX) communicating branch was found to issue from the vagal nerve truck in close association with the pharyngeal branches (rami pharyngei nervi vagi), bifurcating soon into a vagofacial (X.VII) and a vagoglossopharyngeal division (X.IX). The X.VII division coursed forward and reached the posterior belly of the digastric muscle; after entering this muscle, this division broke up into filaments to communicate with the ramus digastricus of the facial nerve which was found to play an equivalent role in making the vagofacial ansa. The X.IX division, in contrast, took its course medially to reach the stylopharyngeal muscle. After entering this muscle, the X.IX division communicated with the stylopharyngeal branch of the glossopharyngeal nerve, which was found to be the equivalent to the X.IX division; these two form together the vagoglossopharyngeal ansa. Therefore, it could be concluded that the X.VII-X.IX communicating branch constitutes the vagal moieties of the vagofacial as well as the vagoglossopharyngeal ansae. The background of the appearance of the communicating branches observed in this report is discussed in the text from the developmental viewpoint on the basis of the findings obtained in chick embryos stained in whole mounts with anti-neurofilament protein antibody.     

Neuromechanisms of reciprocal interrelation between jaw-opening and jaw-closing muscles in the cat (author's transl)]

Neural controlling mechanisms between the digastric (jaw-opening) and masseter (jaw-closing) muscles were studied in the cat. High threshold afferent impulses from the anterior belly of the digastric muscle to masseteric montoneurons in the trigeminal motor nucleus induced an EPSP-IPSP sequence of potentials with long latency, and high threshold afferent impulses from the masseter muscle also exerted a similar effect on digastric motoneurons in the same nucleus innervating the anterior belly of the digastric muscle. These results suggest that reciprocal inhibition via Ia interneurons as observed between the flexor and extensor muscles in the spinal cord does not exist between the digastric and masseter muscles in the cat. However, the respective motoneurons innervating the masseter and digastric muscles receive inputs of early excitation-late inhibition via high threshold afferent nerve fibers from each antagonistic muscle. As such, since EPSPs preceding IPSPs are recognized, these high threshold afferent impulses may exert not only a reciprocal inhibitory effect, but also a synchronous excitatory or inhibitory effect on the antagonistic motoneurons.     

Submandibular gland I: an anatomic evaluation and surgical approach to submandibular gland resection for facial rejuvenation

Submandibular gland resection for aesthetic reasons has been hotly debated. Detractors maintain that the procedure is dangerous because it puts too many important structures at risk, notably motor nerves. The present study was undertaken to elucidate the neurovascular and soft-tissue anatomy of the digastric triangle via cadaver dissections so that a surgical approach to achieve safe aesthetic submandibular resection could be performed. Fifteen digastric triangles dissections were performed in fixed and fresh cadaver specimens. The dissection focus was to understand the submandibular neurovascular relationships, capsule as well as fascial layers, and measurements to known structures. The marginal mandibular nerve is located external to the submandibular capsule, approximately 3.7 cm cephalad to the inferior margin of the gland. The hypoglossal nerve is posterior to the digastric sling in a position that is protected deep within the visceral layer of the neck. The lingual nerve is located underneath the mandibular border, crossing anterior to the submandibular duct. The vascular supply is variant, but with an average of one and a half vessels entering medially to the superficial lobe of the gland, one intermediate vessel entering medially to supply the superficial and deep lobes, and one deep perforator that runs from the central portion of the deep lobe to the superficial lobe. Appreciation of this anatomy is critical in the submental approach for partial resection. Although it can be technically challenging, the anatomy is straightforward and partial submandibular gland resection can be executed via a consistent, safe approach to optimize facial rejuvenation in certain patients.     

Comparative myology of the hominoid cranial base. I. The muscular relationships and bony attachments of the digastric muscle

This paper aims to document accurately the soft tissue anatomy and bony attachments of the posterior belly of the digastric muscle and other closely related muscles in the mastoid region of extant hominoids and fossil hominids. Five wet specimens including individuals of Pan, Gorilla and Pongo were dissected and described. Eight casts of fossil hominid cranial bases were also studied along with measurements and notes made from the same original fossil hominid specimens to assess their soft tissue markings in the light of the findings for the three great apes. The results indicate that whereas the attachment of the posterior belly of the digastric muscle in Homo sapiens is associated with a deep groove or fossa, it originates from a widened area and leaves no bony markings on the cranial base of the three great apes. Following a change in the position of the foramen magnum and the occipital condyles in hominids and H. sapiens the insertion of the posterior belly of the digastric has remained posteriorly positioned but has become compressed into a deep groove. It is likely that this has come about by the displacement of the more medial soft tissue structures which have been moved laterally away from the occipital condyles.     

Microelectrophysiological analysis of the fiber components of the rat digastric muscle

Membrane potential at rest (MP), action potential (AP), critical level of depolarization (CLD) and latent period (LP) of different muscle fibers were studied in two bellies of digastric muscle. Even and chaotic distribution of different muscle fibers was observed in the anterior and posterior belly, respectively. It is believed that electrophysiological data correspond to the results of histological analysis of muscle fibers in digastric muscle.     

Change of digastric muscle length in feeding rabbits

An experiment was undertaken to measure directly the changing length of a jaw muscle during feeding in four intact, unanesthetized New Zealand White rabbits. Metal markers were implanted to define the anterior and posterior ends of the single belly of the digastric muscle and fluroscopic images were recorded on videotape while the animals fed on pelleted chow and carrot. Graphs of muscle length versus incisor separation were obtained by making measurements of single frames of the videotape record. The graphs revealed that when pelleted chow was being chewed the length of the diagastric muscle changed by no more than 9% of its greatest length; during the latter part of the closing stroke it changed very little. Incising and chewing carrot caused the digastric muscle to change in length continuously throughout the chewing cycle; incising carrot resulted in a 13% change in the length of the digastric muscle. The velocity of shortening is slightly less than one muscle length per second.     

An anomalous muscle (accessory subscapularis-teres-latissimus muscle) in the axilla penetrating the brachial plexus in man.

An anomalous muscle passing through the brachial plexus was found in 10 cases out of 380 sides of 190 human cadavers in the dissection course. The muscle was designated as 'accessory subscapularis-teres-latissimus muscle'. This muscle arose near the lateral margin of the scapula, either from the surface of the subscapularis muscle or from the border of the quadrangular terminal tendon of the latissimus dorsi or from both of those sources when the muscle was divided into two heads. It ran obliquely upward to fuse with the insertion of the subscapularis. The largest anomaly was 2.5 cm in width and 7 cm in length. This muscle could be classified into three types on the basis of its nerve supply and its relation to the brachial plexus. The type I muscle crossed over the axillary and lower subscapular nerves, behind the radial nerve and was innervated by the lower subscapular nerves. The type II musclepenetrated the brachial plexus separating the radial nerve into two roots; the upper from the posterior division of the upper trunk and the lower from the posterior divisions of the middle and lower trunks. The type II muscle was supplied by a branch of the radial nerve, which originated always at the same level as the origin of the thoracodorsal nerve. The type III muscle passed through the further more ventrocaudal level of the plexus; in one case it divided the radial nerve into an upper root from the posterior divisions of the upper and middle trunks and a lower root from the lower trunk, and, in another case, into an upper main root from all the three trunks and a lower slender root from the lower trunk. The type III muscle was supplied by branches from the radial and in addition from the thoracodorsal nerve in one case. In four out of ten cases, the subscapular or thoracodorsal artery also passed posterior to the anomalous muscle. A discussion was made on the nature of the anomalous muscle.     

Insect visceral muscle. Excitation and conduction in the proctodeal muscles

Bioelectrical potentials were studied from longitudinal muscle fibres of the cockroach proctodeum. The muscle bundle receives a polyaxonal innervation from both anterior and posterior branches of the anterior proctodeal nerve. Evoked post-synaptic potentials consisted of two independent, but similar components generated through the two branches. An action potential in the muscle fibre could be generated with single branch stimulation, and more readily by co-operation of excitation in the two nerve branches.Any part of the muscle was capable of acting as a pacemaker for myogenic rhythmic action potential, and the pacemaker region fluctuated with time. Excitation of the muscle could spread in two ways, directly myogenic and indirectly through nerve tracts. Myogenic conduction (2 cm/sec) was observed to be slower than neural conduction (35–38 cm/sec) in the muscle bundle.     

Organization of the larval pre-ecdysis motor pattern in the tobacco hornworm,Manduca sexta

The tobacco hornworm, Manduca sexta, undergoes several larval molts before transforming into a pupa and then an adult moth. Each molt culminates in ecdysis, when the old cuticle is shed. Prior to each larval ecdysis, the old cuticle is loosened by pre-ecdysis behavior, which consists of rhythmic compressions that are synchronous along the abdomen and on both body sides, and rhythmic retractions of the abdominal prolegs. Both pre-ecdysis and ecdysis behaviors are triggered by a peptide, eclosion hormone. The aim of the present study was to investigate the neural circuitry underlying larval preecdysis behavior. The pre-ecdysis motor pattern was recorded in isolated nerve cords from eclosion hormone-treated larvae, and the effects of connective transections and ionic manipulations were tested. Our results suggest that the larval pre-ecdysis compression motor pattern is coordinated and maintained by interneurons in the terminal abdominal ganglion that ascend the nerve cord without chemical synaptic relays; these interneurons make bilateral, probably monosynaptic, excitatory connections with identified pre-ecdysis motor neurons throughout the abdominal nerve cord. This model of the organization of the larval pre-ecdysis motor pattern should facilitate identification of the relevant interneurons, allowing future investigation of the neural basis of the developmental weakening of the pre-ecdysis motor pattern that accompanies the larval-pupal transformation.Abbreviations A3, A4... abdominal ganglia 3, 4... - AT terminal abdominal ganglion - ALE anterior lateral external muscle - DN dorsal nerve - DN_A anterior branch of the dorsal nerve - DN_L lateral branch of the dorsal nerve - DN_P posterior branch of the dorsal nerve - EH eclosion hormone - TP tergopleural muscle - VN ventral nerve - VN_A anterior branch of the ventral nerve - VN_L lateral branch of the ventral nerve - VN_P posterior branch of the ventral nerve     

A vagal nerve branch controls swallowing directly in the seawater eel

By developing a new in vivo method to evaluate the esophageal closure, which reflects inhibition of swallowing, we demonstrate that the vagal X1 branch projected from the glossopharyngeal-vagal motor complex (GVC) controls the upper esophageal sphincter (UES) muscle directly. Although eel vagal nerve consisted of five branches, other branches (X2, X3, X4 and X5) did not influence the esophageal pressure. When the X1 nerve branch was stimulated electrically, the balloon pressure in the UES area increased with optimum frequency of 20 Hz. Since similar optimum frequency was observed both in the pithed eel and in the isolated UES preparation, such characteristic of X1 nerve is not due to anesthetic used during experiment. As the isolated UES preparation consists of muscle cells and nerve terminals, and as the optimum frequency of the nerve terminal is identical with that of the X1 branch, it is most likely that the X1 nerve branch is identical with the nerve terminals within the UES preparation. On the other hand, since the GVC neurons fire spontaneously at around 20 Hz, the optimum frequency of 20 Hz means that the eel UES is usually closed vigorously and relaxed only when the GVC neuron is inactivated. The effect of X1 stimulation was inhibited by curare, but not by atropine, indicating that the X1 nerve branch releases acetylcholine, which acts on the nicotinic receptor on the UES striated muscle. Beside vagal nerve X1 branch, spinal nerve SN2, SN3 and SN4 also contributed to the UES closure, but SN1 did not influence the UES movement. However, since the efficacy of these spinal nerve stimulations is about 1/10 of that by vagal X1 branch, the eel UES may be controlled primarily by a vagal nerve X1 branch, and secondarily by spinal nerves (SN2, SN3 and SN4).     

The Mm. levatores costarum longi in some catarrhine monkeys

In this paper, the authors mentioned that the M. levator costae longus is present, even if very rarely, in two species of macaque; that the nerve supply is not by the ramus anterior but by the ramus posterior of the spinal nerve which is the same branch for the M. levator costae brevis; that this is monosegmental muscle and is a thickening, separation, and elongation of one part of the fasciculi of the M. levator costae brevis; and that moreover this muscle may be classified into two different types.     

组织透明化三维显示全包埋耳皮肤神经血管网（英文）

目的 结合组织学染色技术和组织透明化策略研究耳部皮肤中神经纤维和血管的空间对应关系。方法 将耳廓前面和后面的皮肤从其中间软骨仔细剥离，然后直接分别用蛋白基因产物9.5 (PGP 9.5)和鬼笔环肽对耳部皮肤的神经纤维和血管进行免疫荧光染色并进行组织透明化处理。随后，以全包埋方式将耳皮肤组织裱贴在载玻片上用于荧光显微镜和共聚焦显微镜观察。结果 本研究显示PGP 9.5阳性神经纤维伴随鬼笔环肽标记的血管一道从耳廓的基部走行到其外围区域形成耳廓的神经血管网。在传统的免疫荧光染色技术基础上，后续的组织透明化技术可以更好地展示耳部皮肤中神经纤维和血管的形态学细节。结论 从方法学的角度来看，组织透明化技术增进了耳部皮肤中免疫荧光标记的可视性，它可能成为有效的技术手段用于解析正常和病理状态下耳部神经血管网的空间结构。     

Differential delay of reinnervating axons alters specificity in the rat serratus anterior muscle

Previous studies have shown remarkable rostrocaudal selectivity by regenerating motoneurons to the rat serratus anterior (SA) muscle after freezing, crushing, or sectioning the long thoracic (LT) nerve. The LT nerve contains motoneurons from both the sixth and seventh cervical spinal nerves (C6 and C7), with C6 motoneurons as the major source of innervation throughout the muscle, and with C7 motoneurons innervating a larger percentage of muscle fibers caudally than rostrally. To determine if synaptic competition can play a role in neuromuscular topography, both the LT nerve and the branch carrying C6 (rostral) motoneurons to the LT nerve were crushed in newborn rats. This approach provides a temporal advantage to regenerating C7 (caudal) motoneurons. After an initial period during which C7 motoneurons reinnervated a larger proportion of muscle fibers than normal in all SA muscle sectors, C6 motoneurons regained their original proportion of rostral muscle fibers. Caudally, however, C7 motoneurons maintained an expanded territory. With this two-site crush method, the number of C6 motoneurons that reinnervate the SA muscle was significantly decreased from normal, whereas the number of C7 motoneurons remained the same. It is concluded that when C7 motoneurons are given a temporal advantage, synaptic specificity can be altered transiently in rostral muscle sectors and permanently in caudal sectors, and this is correlated with a disproportionate loss of C6 motoneurons. Moreover, this may be an important model for studies of synaptic competition, where terminals destined to be eliminated can be identified beforehand. © 1995 John Wiley & Sons, Inc.     

Patterned regeneration of internal femoral structures in the cockroach, Periplaneta americana L

The morphology of the nerve and tracheal supply to the extensor tibiae muscle in normal legs was compared to that in regenerate legs. In normal femurs, the extensor nerve and trachea extend along the posterior surface of the extensor muscle. The nerve and trachea are closely associated and branch coincidently at regular intervals. In regenerate femurs, the nerve and trachea are not closely associated with each other, and both structures differ from normals in their branching patterns. The results suggest that tissue level interactions during regeneration differ from those during embryogenesis.     

Innervation pattern of the deep extensor abdominal muscle in the crayfish species Astacus astacus

The deep extensor abdominal muscle consisting of one medial and two lateral muscle bundles together with the nerve innervating the muscles of crayfish species Astacus astacus, was prepared. Light microscopic investigations of methylene blue stained preparations showed that the nerve innervating the deep extensor abdominal muscle consists of five distinct axons. The five axons were stained separately with lucifer yellow and the innervation pattern of the axons was determined. To confirm the histological results the axons were also stimulated with a suction electrode to elicit excitatory postsynaptic currents on the muscle membrane which were detected using a macro patch electrode. The muscle is innervated by a common excitatory and a common inhibitory axon branching over all three muscle bundles and sending additionally a branch to the L1-bundle of the next posterior segment, and by two axons specific for the two lateral muscle bundles. The axon specific for the innervation of the L1-bundle sends also a branch to the L1-bundle of the next posterior segment. In addition there is one excitatory axon which directly innervates the medial muscle bundle of the next posterior segment branching in most of the cases also to the medial bundle of the segment where it originates.Abbreviations DEAM deep extensor abdominal muscle - EPSC excitatory postsynaptic current - IPSC inhibitory postsynaptic current - L lateral - M medial - GABA -aminobutyric acid     

Arterial supply of the anterior ear.

Twenty cadaver auricles were injected with a latex solution to define the arterial supply of the anteroauricular surface. Two arterial networks exist, the network of the triangular fossa-scapha and the network of the concha. Both eventually communicate on the anthelix. The triangular fossa-scapha network originates from one subbranch of the upper auricular branch of the superficial temporal artery and from branches of the posterior auricular artery that come through the earlobe and triangular fossa and over the helical margin. The conchal network is provided by two to four perforators that come from the posterior auricular artery, piercing the conchal floor. Auricular branches of the superficial temporal artery in the preauricular region and their communications with the posterior auricular artery also were confirmed. We believe that a greater understanding of the detailed arterial anatomy in this area allows one to develop safely a variety of surgical techniques for reconstruction of the ear.     

Anatomical anomaly of human digastric muscles

In the submandibular region an anatomical anomaly of muscle arrangement was found. Between the left and right digastric muscles, asymmetric accessory digastric muscles were detected, which all arose from the mandible and were attached to the hyoid bone. Furthermore, the right anterior digastric muscle had an accessory belly. These anomalies of digastric muscles may be anatomical manifestations of a functional support of the mylohyoid muscle.