RESUMEN
BACKGROUND: The anatomy and function of the long thoracic nerve are not fully understood. The purposes of this study were to clarify the anatomy of the long thoracic nerve and to propose a clinical test to assess the function of the upper division of the long thoracic nerve. METHODS: The long thoracic nerve and the serratus anterior muscle were studied in fifteen fresh cadavera. Six patients had an operation to treat a brachial plexus injury, and the long thoracic nerve was electrically stimulated. The resulting shoulder motion was then observed. RESULTS: The long thoracic nerve was formed by branches arising from the C5, C6, and C7 nerve roots. The C5 and C6 branches joined beneath the scalenus medius muscle to form the upper division of the long thoracic nerve, which was located 1 cm posteriorly and superiorly to the upper trunk origin. The union of the upper division with the branch from C7 occurred caudally, in the axillary region. Two branches from the upper division of the long thoracic nerve to the upper portion of the serratus anterior muscle were consistently identified. After electrical stimulation of the upper division branches, shoulder protraction was observed. CONCLUSIONS AND CLINICAL RELEVANCE: In the supraclavicular region, the long thoracic nerve has a trajectory parallel to the brachial plexus, which is contrary to the schematic representation in most textbooks. The upper division of the long thoracic nerve can be assessed by the shoulder protraction test.
Asunto(s)
Neuropatías del Plexo Braquial/patología , Hombro/inervación , Nervios Torácicos/anatomía & histología , Nervios Torácicos/fisiología , Adulto , Neuropatías del Plexo Braquial/cirugía , Disección , Humanos , Músculo Esquelético/inervación , Raíces Nerviosas Espinales/anatomía & histologíaRESUMEN
The participation of neuroendocrine factors present within the central nervous system in the regulation of hemolymph free amino acid (FAA) concentrations was examined in the freshwater shrimp Macrobrachium olfersii. Test shrimps were injected intramuscularly with homogenates prepared from the eyestalks (ES), ventral nerve cord (VNC), supraesophageal (SEG), or thoracic ganglia (TG) of donor shrimps previously exposed for 6 hr to a high-salinity medium (HSM, 21% salinity). After injection of the homogenate, the shrimps were maintained for up to 6 hr in either freshwater (FW) or HSM. Hemolymph was sampled by cardiac puncture and prepared for reverse phase HPLC, derivatizing the FAA with phenylisothiocyanate. An FAA profile was determined and the [FAA]:[Cl-] ratios for the four FAA present in highest concentration (Gly, Arg, Ala, and Pro for ES and VNC experiments; Glu, Leu, Ala, and Val for SEG and TG experiments) were obtained. Nonparametric analyses revealed specific, notable effects resulting from homogenate injection, e.g., ES homogenate increased [Pro]/[Cl-] ratios in FW-exposed shrimps; SEG homogenate increased [Glu]/[Cl-] and [Val]/[Cl-] ratios in HSM-exposed shrimps; and TG homogenate increased [FAA]/[Cl-] ratios for Glu, Leu, Ala, and Val in HSM-exposed shrimps. Total FAA concentrations decreased after exposure of the shrimps to HSM but were increased by the injection of ES homogenate in FW-exposed shrimps and by TG homogenate in HSM-exposed shrimps. The total [FAA]/[Cl-] ratio was also increased by TG homogenate in HSM-exposed animals. There were no clear effects on [Cl-] alone.(ABSTRACT TRUNCATED AT 250 WORDS)
Asunto(s)
Aminoácidos/sangre , Hemolinfa/química , Sistemas Neurosecretores/fisiología , Palaemonidae/fisiología , Equilibrio Hidroelectrolítico/fisiología , Alanina/análisis , Alanina/sangre , Aminoácidos/análisis , Animales , Femenino , Ácido Glutámico/análisis , Ácido Glutámico/sangre , Leucina/análisis , Leucina/sangre , Nervio Óptico/fisiología , Palaemonidae/metabolismo , Nervios Torácicos/fisiología , Valina/análisis , Valina/sangreRESUMEN
Electrical stimulation of the XIII thoracic nerve (the 'mammary nerve') causes milk ejection and the release of prolactin and other hormones. We have analysed the route of the suckling stimulus at the level of different subgroups of fibres of the teat branch of the XIII thoracic nerve (TBTN), which innervates the nipple and surrounding skin, and assessed the micromorphology of the TBTN in relation to lactation. There were 844 +/- 63 and 868 +/- 141 (S.E.M.) nerve fibres in the TBTN (85% non-myelinated) in virgin and lactating rats respectively. Non-myelinated fibres were enlarged in lactating rats; the modal value being 0.3-0.4 micron 2 for virgin and 0.4-0.5 micron 2 for lactating rats (P greater than 0.001; Kolmogorov-Smirnov test). The modal value for myelinated fibres was 3-6 micron 2 in both groups. The compound action potential of the TBTN in response to electrical stimulation showed two early volleys produced by the A alpha- and A delta-subgroups of myelinated fibres (conduction velocity rate of 60 and 14 m/s respectively), and a late third volley originated in non-myelinated fibres ('C') group; conduction velocity rate 1.4 m/s). Before milk ejection the suckling pups caused 'double bursts' of fibre activity in the A delta fibres of the TBTN. Each 'double burst' consisted of low amplitude action potentials and comprised two multiple discharges (33-37 ms each) separated by a silent period of around 35 ms. The 'double bursts' occurred at a frequency of 3-4/s, were triggered by the stimulation of the nipple and were related to fast cheek movements visible only by watching the pups closely. In contrast, the A alpha fibres of the TBTN showed brief bursts of high amplitude potentials before milk ejection. These were triggered by the stimulation of cutaneous receptors during gross slow sucking motions of the pup (jaw movements). Immediately before the triggering of milk ejection the mother was always asleep and a low nerve activity was recorded in the TBTN at this time. When reflex milk ejection occurred, the mother woke and a brisk increase in nerve activity was detected; this decreased when milk ejection was accomplished. In conscious rats the double-burst type of discharges in A delta fibres was not observed, possibly because this activity cannot be detected by the recording methods currently employed in conscious animals.(ABSTRACT TRUNCATED AT 400 WORDS)