Anomalies of thoracic outlet in human fetuses: anatomical study.

BACKGROUND: Thoracic outlet syndrome (TOS) identifies the clinical condition determined by the mechanical compression and entrapment of the subclavian vessels and the brachial plexus cords within the space delineated by the scalene muscles, the clavicle, and the first rib. To date, there are no concluding explanations concerning the real causes of the appearance of TOS in children. This is the first study to investigate the existence, frequency, and type of thoracic outlet anomalies in the prenatal stage (human fetuses). METHODS: Eighty cervical dissections (40 consecutive spontaneously aborted human fetuses) were performed, and the musculoskeletal, vascular, and nervous elements that pass through the thoraco-cervico-axillary region were investigated. RESULTS: Overall, anatomical anomalies of the thoraco-cervico-axillary region were found in 60% of the 80 cervical dissections. Nine (22.5%) of the 40 fetuses had normal bilateral anatomy. In 6.3%, the scalene hiatus had an oval shape due to the common costal insertion of the anterior and middle scalene muscles. Fibromuscular bands were found in 15% of the fetuses. Hypertrophy of the anterior scalene muscle was seen in 12.5% of the dissections. In 28.7% of the cervical dissections, hypertrophy of the C7 transversal process was noted, bilateral in seven cases. There was one case of a "C-shaped" clavicle anomaly. The absence of the internal mammary artery was noted in one case. CONCLUSION: This study shows that the presence of TOS anomalies in fetuses is not a rare occurrence, emphasizing a pathological cervical background which can be harmful in situations of cervical trauma or inflammatory processes. Having knowledge of the types of anomalies which can lead to TOS is important for performing a complete surgical correction and avoiding the high failure rate of recurrent TOS.

Frequency, anatomical properties and innervation of axillary arch and its relation to the brachial plexus in human fetuses.

PURPOSE: "Axillary Arch" (AA) is the main musculotendinous variation of the axillary region. The aim of this study was to reveal the frequency, anatomical properties, and innervation of AA and its relation with brachial plexus in human fetuses. METHODS: In this study, 50 human fetuses (male: 20, female: 30), gestation age varied between 16 and 38 weeks (mean ± SD: 23.3 ± 5.3 week), were dissected at the anatomy laboratory of Mersin University, Faculty of Medicine. RESULTS: AA was found in 11 of the 50 fetuses, and in 3 of 11, it was bilateral. Among both sides, 6 of 14 AAs were on the right and 8 were on the left side. Seven of AA's (7% of the specimens) were in muscular and 7 (7%) of them were in musculotendinous structure. With regard to Testut's classification, six (6%) of them were of complete type, six (6%) were incomplete and two (2%) were concordant with both types. Three different types of AA were defined considering the shapes of the arches. According to our classification, seven of the AAs were of type 1, two of them were of type 2 and five of them were of type 3. Additionally, the incidence of the T2 spinal nerve joining the brachial plexus was significantly higher in the specimens with AA (p = 0.001). CONCLUSIONS: Each type of AA described in this study is thought to have individual clinical significance. Being aware of AA and its types can be important to determine a safe approach to the axillary region for surgeons. In addition, our results show the relation between the occurrence of AA and the variations in the formation of the proximal part of brachial plexus.

First data on the organization of the nervous system in juveniles of Novocrania anomala (Brachiopoda, Craniiformea).

The organization and development of the nervous system are traditionally used for phylogenetic analysis and may be useful for clarification of evolution and phylogeny of some poor studied groups. One of these groups is brachiopods: most data on their nervous system organization were obtained in 19th century. In this research, antibody staining and confocal laser scanning microscopy were used to study the nervous system of early ontogenetic stages of the brachiopod Novocrania anomala. Although N. anomala adults are thought to lack a supraenteric ganglion, a large supraenteric ganglion exists in N. anomala juveniles with either a trocholophe or a schizolophe. During ontogenesis, the supraenteric ganglion in the juvenile changes its shape: the commissure between the two lobes of the ganglion extends. This commissure possibly gives rise to the main brachial nerve in adults. The supraenteric ganglion gives rise to the cross (transversal) nerves that extend to the accessory brachial nerve, which gives rise to the tentacular nerves. In juveniles with a trocholophe, the accessory brachial nerve gives rise to the frontal and intertentacular nerves of tentacles that form a single row. When the trocholophe transforms into the schizolophe, the second row of tentacles appears and the innervation of the tentacles changes. The intertentacular nerves disappear and the second accessory nerve forms and gives rise to the laterofrontal tentacular nerves of the inner and outer tentacles and to the abfrontal nerves of the inner tentacles. The so-called subenteric ganglion, which was described as a ganglion in N. anomala adults, is represented by a large circumvisceral nerve in N. anomala juveniles.The results suggest that 'phoronid-like' non-specialized tentacles may be regarded as the ancestral type of tentacles for brachiopods and probably for all lophophorates. The presence of intertentacular nerves is the ancestral feature of all lophophorates. The transformation of the juvenile supraenteric ganglion into the main brachial nerve of N. anomala adults suggests that research is needed on the development and organization of the supraenteric ganglion and the main brachial nerve in other brachiopods, whose adults have a prominent supraenteric ganglion.

Establishing Myelinating Cocultures Using Human iPSC-Derived Sensory Neurons to Investigate Axonal Degeneration and Demyelination.

Complex signaling between Schwann cells and axons are vital for peripheral neuron development, myelination, and repair. The interaction between these two cell types can be modeled in vitro by coculturing rodent Schwann cells and neurons together. These have in the past been used with great success to help unravel the bidirectional signaling mechanisms that lead to Schwann cell proliferation and myelination. To provide more translatable potential, we have developed myelinating cocultures using human, induced pluripotent stem cell (iPSC)-derived neurons. Under the right conditions, the human neurons are efficiently myelinated by rat Schwann cells, demonstrating successful cross-species signaling. This chapter describes all the necessary steps to generate these myelinating cocultures and methods to investigate and quantify various aspects of myelination. The myelinating cocultures can be maintained in excellent health for over 1 year, facilitating their use to study developmental or chronic disease processes. With this in mind, we have used the cocultures to model a sensory neuropathy which displays clinically with both axonal and demyelinating features. In the cocultures, we found evidence of extensive axonal degeneration and demyelination demonstrated by axonal swelling and fragmentation, and myelin disintegration. The myelinating cocultures can therefore be used to study complex, human disease processes that result in both axonal and myelin-associated degenerative processes.

Distinct roles for secreted semaphorin signaling in spinal motor axon guidance.

Neuropilins, secreted semaphorin coreceptors, are expressed in discrete populations of spinal motor neurons, suggesting they provide critical guidance information for the establishment of functional motor circuitry. We show here that motor axon growth and guidance are impaired in the absence of Sema3A-Npn-1 signaling. Motor axons enter the limb precociously, showing that Sema3A controls the timing of motor axon in-growth to the limb. Lateral motor column (LMC) motor axons within spinal nerves are defasciculated as they grow toward the limb and converge in the plexus region. Medial and lateral LMC motor axons show dorso-ventral guidance defects in the forelimb. In contrast, Sema3F-Npn-2 signaling guides the axons of a medial subset of LMC neurons to the ventral limb, but plays no major role in regulating their fasciculation. Thus, Sema3A-Npn-1 and Sema3F-Npn-2 signaling control distinct steps of motor axon growth and guidance during the formation of spinal motor connections.

Innervation of pulmonary veins: morphologic pattern and pathways of nerves in the human fetus.

The aim of the study was to determine the anatomy of intrinsic nerves supplying human pulmonary veins (PVs). Twenty-two hearts of human fetuses with full sets of PVs were examined using a histochemical method for acetylcholinesterase in order to stain transmurally intrinsic neural structures on non-sectioned PVs for subsequent stereomicroscopic examination. Findings of the study demonstrate that epicardiac nerve extensions from both the dorsal right atrial and the middle dorsal subplexuses reached the right superior as well as the right inferior PVs, whereas the left superior PV was supplied by nerve extensions from the left dorsal subplexus. The left and middle dorsal subplexuses contributed nerves to the left inferior PV. The ganglia related topographically to PVs were patchy in distribution. On the left and right superior PVs, 38+/-6 and 31+/-3 ganglia were found, respectively, whereas 46+/-7 and 38+/-7 ganglia were identified on the left and right inferior PVs. The size of ganglia was similar for all four veins, ranging in area from 0.004+/-0.0003 to 0.007+/-0.0004 mm(2). The total area of ganglia distributed on a given PV was similar, ranging from 0.15+/-0.0003 to 0.25+/-0.0004 mm(2). The present findings demonstrate that the richest ganglion sites supplying intrinsic nerves to the human PVs are located on the posterior sides of both inferior and the left superior PVs and, therefore, these sites may be considered primary targets for focal pulmonary vein ablation in catheter-based therapy of atrial fibrillation.

Chicken wings and the brachial plexus.

OBJECTIVES: Some stages of limb development can now be described in terms of gene sequences and functions. This paper reports on the development of the brachial plexus (BP) in the chick. It also presents a short review on the principles of the peripheral nerve outgrowth. METHODS: The early development of the brachial plexus of chicken embryos is mapped using immunohistochemistry. This is then analysed in relation to the expression pattern of an axonal guidance gene, Semaphorin3a, by in situ hybridization studies. RESULTS: The motor axons that innervate the chick wing emerge from the spinal cord in spinal nerves 12-17. These axons grow towards the developing limb and then congregate at its base to form the plexus. In response to unknown cues, these axons rearrange, before emerging in the defined nerve trunks that innervate the limb. The developmental stages of BP morphogenesis described here closely correlate with previous reports with a significant difference of a shorter 'waiting period'. DISCUSSION: The development of the brachial plexus is now better understood. The waiting period, with more modern techniques, is observed to be shorter than previously reported. The significance of this and the role of the guidance molecule, Semaphorin3a, in this process, are being investigated and the results may have important implications on the management of brachial plexus palsy and other peripheral nerve lesions.

Coracobrachialis muscle and the musculocutaneous nerve: a study using human embryonic sections.

In comparative anatomy, the musculocutaneous nerve is hypothesized to pass between the superficial and deep muscle bellies of the coracobrachialis muscle. The superficial belly is supplied by nerve branches of the lateral cord of the brachial plexus, while the deep belly by the musculocutaneous nerve. Observations of longitudinal sections of ten human embryonic arms (7 weeks; crown-rump length 26-32 mm) demonstrated that the coracobrachialis muscle was always continuous with the short head of the biceps muscle. If the aforementioned hypothesis was applied, the deep belly behind the musculocutaneous nerve course was continuous with the biceps. However, such a close relation between the coracobrachialis and biceps was not known in supplying nerves in adults. A further study using embryos of some apes without the deep belly of the coracobrachialis would be necessary for the comparison between a pattern of the embryonic muscle division and the muscle classification in comparative anatomy.

The growth of segmental nerves from the brachial myotomes into the proximal muscles of the chick forelimb during development.

A study has been made of the growth of segmental nerves 13 to 16 (SN13 to SN16) into the chick limb bud, from the time when they have just reached the ends to the brachial myotomes (stage 21: Hamburger and Hamilton, '51), until they enter the newly formed ventral (stage 24) and dorsal (stage 25) pre-muscle cell masses in the limb bud. At stage 22 axon bundles of SN13 to SN16 have grown off the ends of their respective myotomes, and converge towards the most densely packed mesenchyme in the limb bud at segmental level 15. As a consequence, the first axon bundles of SN14 and SN16 have almost joined those of SN15, whereas the further removed SN13 axon bundles have not yet reached the level of SN15. By stage 23 the first axon bundles from SN14 to SN16 have joined at segmental level 15 to form a nerve which grows toward the ventral pre-muscle cell mass. At stage 24 axon bundles from SN13 have joined those from SN14 to SN16 to form the brachialis longus inferior nerve, which enters the densest region of the ventral pre-muscle. Other axons from SN13 to SN15 grow along the pathways provided by the early arriving axon bundles towards the ventral pre-muscle, but diverge from those at segmental level 14 to grow to the dorsal pre-muscle. By stage 25 axon bundles from SN13 to SN15 have joined to form the brachialis longus superior nerve which enters the densest region of the dorsal pre-muscle. At stage 26 a plexus has formed due to this pattern of growth of the segmental nerves between stages 22 and 25. It is suggested that pre-muscle cells synthesize a nerve growth factor which directs the growth of axons into the limb bud.

Pattern of development of ascending and descending fibers in embryonic spinal cord of chick: II. A correlation with behavioral studies.

Studies on the embryonic spinal cord were extended to include the development of the ascending and descending fibers from the brachial level. This study was designed to correlate morphological development of the intersegmental system with physiological and behavioral observations of early embryonic behavior. Chick embryos were analyzed prior to day 6 of incubation, which is before closure of the reflex arc and arrival of supraspinal inputs to the embryonic spinal cord. Injections of 3H-proline were made in the upper brachial level of chick embryos of stages 27--29 (5--6 days). The location of radioactive label in the marginal zone was analyzed autoradiographically to show the projection of labeled axonal flow from the site of injection. The majority of the labeled axons in the marginal zone was in the first 2--3 segments in both ascending and descending directions from the site of injection. By stage 27 (day 5), ascending labeled axons extended to the upper cervical level and labeled descending axons extended only about 4--5 segments to the upper thoracic level. By stage 29 (day 6) labeled ascending axons extended into the medulla oblongata, and labeled descending axons still extended only 4--5 segments caudally. These studies (Parts I and II) show that at stage 27 (day 5) there was considerable axoplasmic flow of radioactive label in the marginal zone from the lumbar to the brachial plexus but not in the opposite direction from the brachial to the lumbar plexus. Also, axoplasmic flow of label initially extended from the brachial plexus to the medulla oblongata sometime between stages 27--29. It was concluded that the intersegmental system of the embryonic spinal cord is well developed by day 6 of incubation and provides the neuro-anatomical substrate for early embryonic behavior.

Innervation of avian latissimus dorsi muscles and axonal outgrowth pattern in the posterior latissimus dorsi motor nerve during embryonic development.

The distribution of the innervation to the anterior latissimus dorsi (ALD) and posterior latissimus dorsi (PLD) muscles of the chicken are described on the day of hatching and 6 weeks later using electron microscopy. In the ALD muscle, there are 5,000 muscle fibres and 374,000 endplates supplied by about 169 skeletomotor axons; in the PLD muscle, there are 12,000 focally innervated muscle fibers supplied by about 20 skeletomotor axons. On the cell surface of the muscle fibers the mean total subsynaptic area contacted by each motor axon is comparable in the ALD and PLD muscles. The growth pattern of the axons in the PLD motor nerve was described from the ninth day in ovo up to 6 weeks after hatching. The axons arrive in the PLD muscle in two successive waves: first, the large somatic axons which are already present before the ninth day in ovo and second, the small autonomic axons which continue to accumulate until hatching. The total number of somatic axons decreases from the ninth day until the hatching day when it reaches its definitive value. This decrease takes place during a period when the numbers of myofibers and of endplates dramatically increase, and it coincides with the axonal segregation by the Schwann cells. The myelination of the axons starts on the 15th day in ovo and is essentially complete upon hatching. Despite the decreasing number of somatic axons in the PLD nerve, the decrease in number of nerve endings per PLD endplate and the increasing number of PLD endplates per PLD muscle, it was found that between the 16th day in ovo and 6 weeks after hatching the mean number of axonal branches per PLD motor axon does not decrease.

Polysialylated NCAM expression during motor axon outgrowth and myogenesis in the fetal rat.

Polysialylation of the neural cell adhesion molecule (NCAM) converts it into an anti-adhesive molecule, attenuating intercellular adhesion and repelling apposed membranes. Previous studies have demonstrated that interaxonal repulsion, or defasciculation, induced by polysialylated NCAM (PSA-NCAM) expressed along outgrowing chick motor axons promotes intramuscular branching and facilitates differential guidance of segregating axonal populations. In the present study, we have examined the expression of PSA-NCAM in a developing mammalian motor system during axonal outgrowth, separation of distinct axonal populations, and intramuscular branching. Furthermore, we provide the first clear demonstration of the spatiotemporal modulation of PSA-NCAM expression on myotubes during each stage of myogenesis. Immunohistochemical labelling was used to compare the spatiotemporal pattern of PSA-NCAM expression with those of total-NCAM, the cell adhesion molecule L1, and growth associated protein (GAP-43) during development of the phrenic nerve and diaphragm of fetal rats (embryonic days, E11-E19). During segregation of phrenic and brachial axonal populations at the brachial plexus (E12.5-E13), PSA-NCAM expression was restricted to phrenics, being absent from brachial motoneurons. Both populations labelled equivalently for NCAM, L1, and GAP-43. We postulate that PSA-NCAM may be a component of the molecular machinery that specifically guides phrenic motoneuron growth at the brachial plexus. During diaphragmatic morphogenesis, PSA-NCAM expression: (i) remained high within the phrenic nerve throughout intramuscular branching; (ii) was transiently up-regulated on myotubes during myotube separation associated with primary and secondary myogenesis; (iii) was restricted to those regions of primary and secondary myotube membranes, which were juxtaposed and about to separate. These data suggest a role for PSA-NCAM in the guidance of specific subsets of mammalian motoneurons and in intramuscular branching, and demonstrate an intimate correlation between PSA-NCAM expression and myotube separation.

Expression of cytochrome P4501b1 (Cyp1b1) during early murine development.

PURPOSE: To examine the embryonic expression of cytochrome P4501b1 (Cyp1b1) gene by whole mount in situ hybridization. METHODS: FVB/NcrlBR mouse embryos staged at 9.5, 10.5, and 11.5 dpc were obtained by timed breeding experiments. Antisense and sense RNA probes labeled with digoxigenin UTP were generated by in vitro transcription of an 848 bp Cyp1b1 cDNA fragment that was subcloned into transcription vector pCRII-TOPO. The digoxigenin labeled RNA was localized using an alkaline phosphatase conjugated anti-digoxigenin Fab fragment. Colorimetric detection of the digoxigenin labeled probe was performed with substrate solution containing 4-nitro-blue tetrazolium chloride (NBT) and 5-bromo-4-chloro-3-indolyl phosphate (BCIP). RESULTS: During early stages of murine development Cyp1b1 mRNA was detected in the developing eye, hindbrain, branchial arches, forelimb bud, ligaments supporting the liver primordium and developing kidney. In the eye and forelimb bud Cyp1b1 displayed restricted expression along the axes of development. In the developing eye Cyp1b1 exhibited dorsal expression with respect to the dorso-distal/proximo-ventral axis and anterior expression with respect to the anterior-nasal/posterior-temporal axis. In the forelimb bud Cyp1b1 expression was localized posteriorly. The polarity of Cyp1b1 expression was lost at 11.5 dpc, at which time expression was additionally seen in ventral (eye) and anterior (forelimb bud) areas. CONCLUSIONS: The spatio-temporal expression patterns observed in this study suggest that during early stages of murine development, Cyp1b1 participates in establishment and/or maintenance of polarity along the axes of embryonic development. Expression of Cyp1b1 in the dorso-distal end of the optic cup, from which the ciliary body and iris are derived, correlates with the expression patterns seen in adult tissues and the abnormal development of these structures as part of the glaucoma phenotypes resulting from Cyp1b1 mutations.

Chromosome 18 aneuploidy: anatomical variations observed in cases of full and mosaic trisomy 18 and a case of deletion of the short arm of chromosome 18.

Cases of full and mosaic trisomy 18 and a body of an infant with the 18p-syndrome were dissected in detail to compare the anatomical variations associated with these 3 chromosome imbalances involving autosome 18. The types and numbers of morphologic variations present in both the full and mosaic trisomy 18 bodies were similar to the types and numbers of variations seen in all other cases of full trisomy 18 that have been studied by gross dissection. Apart from an atrial septal defect, the body of the infant with the 18p- imbalance showed only 2 striking defects: 1) deficiencies of the levator palpebrae superioris muscle of the upper eyelid, and 2) absence of the ligament of the head of the femur. The first variation provides a morphologic basis to explain the ptosis which is observed frequently in affected individuals. Absence of the ligament of the head of the femur may be a factor contributing to congenital dislocation of the hip, which is reported occasionally in affected individuals. In addition to providing more detailed information about the phenotype of individual aneuploidy syndromes, studies of cases of different imbalances of single autosomes may provide additional insights about the genotype/phenotype relationships of specific chromosome segments.

The development of vestibulocochlear efferents and cochlear afferents in mice.

We have reinvestigated the embryonic development of the vestibulocochlear system in mice using anterograde and retrograde tracing techniques. Our studies reveal that rhombomeres 4 and 5 include five motor neuron populations. One of these, the abducens nucleus, will not be dealt with here. Rhombomere 4 gives rise to three of the remaining populations: the facial branchial motor neurons; the vestibular efferents; and the cochlear efferents. The migration of the facial branchial motor neurons away from the otic efferents is completed by 13.5 days post coitum (dpc). Subsequently the otic efferents separate into the vestibular and cochlear efferents, and complete their migration by 14.5 dpc. In addition to their common origin, all three populations have perikarya that migrate via translocation through secondary processes, form a continuous column upon completion of their migrations, and form axonal tracts that run in the internal facial genu. Some otic efferent axons travel with the facial branchial motor nerve from the internal facial genu and exit the brain with that nerve. These data suggest that facial branchial motor neurons and otic efferents are derived from a common precursor population and use similar cues for pathway recognition within the brain. In contrast, rhombomere 5 gives rise to the fourth population to be considered here, the superior salivatory nucleus, a visceral motor neuron group. Other differences between this group and those derived from rhombomere 4 include perikaryal migration as a result of translocation first through primary processes and only then through secondary processes, a final location lateral to the branchial motor/otic efferent column, and axonal tracts that are completely segregated from those of the facial branchial and otic efferents throughout their course inside the brain. Analysis of the peripheral distribution of the cochlear efferents and afferents show that efferents reach the spiral ganglion at 12.5 dpc when postmitotic ganglion cells are migrating away from the cochlear anlage. The efferents begin to form the intraganglionic spiral bundle by 14.5 dpc and the inner spiral bundle by 16.5 dpc in the basal turn. They have extensive collaterals among supporting cells of the greater epithelial ridge from 16.5 dpc onwards. Afferents and efferents in the basal turn of the cochlea extend through all three rows of outer hair cells by 18.5 dpc. Selective labeling of afferent fibers at 20.5 dpc (postnatal day 1) shows that although some afferents are still in early developmental stages, some type II spiral ganglion cells already extend for long distances along the outer hair cells, and some type I spiral ganglion cells end on a single inner hair cell. These data support previous evidence that in mice the early outgrowth of afferent and efferent fibers is essentially achieved by birth.

Brachial plexus variations in human fetuses.

OBJECTIVE: We examined the anatomic variations of the brachial plexus (BP) in human fetuses. METHODS: This study was performed with 200 BPs from spontaneously aborted fetuses without detectable malformations. The plexuses were dissected, and the normal position and/or morphological variations of the BP were determined and photographed. RESULTS: There were no variations in 93 plexuses, and 107 plexuses were observed to have different variations. Morphological variations were observed more frequently among female fetuses and right sides. The BPs were composed mostly of the C5, C6, C7, and C8 nerves and the T1 nerve (71.5%). A prefixed plexus was observed in 25.5% of cases, and a postfixed plexus was observed in 2.5% of cases. In one case (0.5%), the C4 and T2 nerves joined the formation. The inferior trunk was not formed in 9% of cases. The superior trunk was not formed in 1% of cases. In one plexus, the superior trunk was formed by the ventral rami of the C4 and C5 nerves. In one case, the inferior trunk was formed by the ventral rami of the T1 and T2 nerves. Division variations were observed most frequently. There were also variations in the terminal branches, such as the roots of the median nerve joining in the distal part of the arm (8.5%), the axillary nerve being separate from the posterior division of the superior trunk (2.5%), and a connection existing between the median and musculocutaneous nerves (1%). CONCLUSION: Knowledge of BP variations is important for surgeons who perform surgical procedures in the cervical and axillary regions.

Morphogenesis of the primary arterial trunks of the forelimb in the rat embryos: the trunks originate from the lateral surface of the dorsal aorta independently of the intersegmental arteries.

It has been believed that the primary arterial trunk of the mammalian forelimb is derived from the 7th intersegmental artery. Here we examined the early morphogenesis of the arteries and nerves in the forelimb region by adopting a method that combined intravascular dye-injection with nerve staining to whole mounted rat embryos. The study was carried out on greater numbers of specimens at smaller intervals of embryonic stages and from earlier stages than those in previous reports. We report that: (1) The multiple primary arterial trunks in the forelimb region (primary subclavians) originate directly from the lateral surface of the dorsal aorta independently of the intersegmental arteries, previous to the formation of limb buds. (2) The tips of the 8th (and the 9th) primary subclavians that originate from the aorta near the origin of the 8th (or the 9th) intersegmental artery bend cranially and/or caudally. With the formation of limb bud, they extend to form the longitudinal trunks in the presumptive axillary region. The primary arteries in the free arm region branch off from this longitudinal trunk, and one of them develops into the axial artery. (3) The origins of the primary subclavians shift their positions on the surface of the dorsal aorta and approach the origins of the neighboring intersegmental arteries to join them, and then replace the latter. Consequently, the primary subclavians appear to be "the lateral branches of the in tersegmental arteries." (4) The 8th primary subclavian is dominant at first, but is replaced by the 7th primary subclavian, which develops into the definitive subclavian artery. (5) With the brachial nerve plexus formation, the axillary arterial plexus derived from the longitudinal trunk develops to form two stems of the axillary artery.

Some aspects of the communicating branch between the musculocutaneous and median nerves in man.

Fascicular arrangement of the human brachial plexus is examined on 2 common cases and 3 peculiar cases in which a communicating branch was observed between the median and the musculocutaneous nerve. The musculocutaneous nerve consitss of spinal nerves from C.5, 6 and 7. The branch to the coracobrachialis receives its fibers from C.7 before it leaves the musculocutaneous nerve in 3 cases and after it leaves the musculocutaneous nerve in one case. In one case, C.7 does not send a branch to the coracobrachialis. The median nerve arises by two roots, one from the lateral cord, and the other from the medial cord of the brachial plexus. In a case in which a communicating branch was observed from the median nerve to the musculocutaneous, the fibers from C.7 join to the median nerve via the medial cord. Thus the median nerve involved all elements of the spinal nerve from C.5 to T.1. The elements of the median and the musculocutaneous nerves, therefore, are not affected by appearance of the communicating branch. The communicating branch between the median and the musculocutaneous nerves, consists of the fibers arose from C.5 and C.6, in all examined cases.

Mathematical models of brachial plexus development during the fetal period: clinical aspects.

BACKGROUND: The brachial plexus is an important anatomical structure. It can be damaged in both the perinatal and postnatal periods as a result of injury. The available literature does not provide much discussion of the development of the brachial plexus in human fetuses. OBJECTIVES: The goal of the study was a mathematical analysis of fetal brachial plexus growth and geometry. MATERIAL AND METHODS: The study examined 220 human brachial plexuses, derived from 110 fetuses (including 50 females - 45.45%) aged 14-32 weeks of fetal life, with a crown-rump length (CRL) ranging from 80 to 233 mm. Anthropological methods, preparation, digital image acquisition, the Image J measurement tool, the Scion Image for Windows program and statistical methods were applied. In each fetus, somatic as well as linear parameters were observed: lengths, diameters and distances between the nerves making up the brachial plexus geometry. RESULTS: In the majority of the linear parameters analyzed, no sexual dimorphism or asymmetry were observed. The following asymmetries and sexual dimorphisms appear to be significant from the clinical point of view: asymmetry in the length of the C7 and Th1 nerve left radix, asymmetry in the diameters of the musculocutaneous nerve on the left and the median and ulnar nerves on the right; as well as an increased distance between nerves roots in female fetuses. The weekly growth of individual parts of the plexus varied, as did the correlation ratios among them. The most rapid growth was observed between the 14th and 18th weeks, and the slowest between the 24th and 28th weeks. Four formulae were used in the mathematical growth model: linear regression, logarithmic function, the von Bertalanffy growth model and the Gompertz curve. CONCLUSIONS: The prenatal development of the brachial plexus is not constant. The applied mathematical functions proved useful in describing its growth rate.