Fusion of the neural arches was studied in 6 serially sectioned human foetuses
aged 9 and 10 weeks. In foetuses of 9 weeks, the completion of arches was
observed in the cervical, upper thoracic, and middle thoracic regions of the
vertebral column. During the 10th week of development, fusion of neural processes
progresses in the lower thoracic and upper three lumbar vertebrae.
(Folia Morphol 2010; 69, 3: 177-179

Grzymisławska, M.

Woźniak, W.

English

Via Medica Journals

Folia Morphol. Vol. 69, No. 3, pp. 177–179Copyright © 2010 Via MedicaISSN 0015–5659www.fm.viamedica.plO R I G I N A L   A R T I C L E177Address for correspondence: Dr M. Grzymisławska, Department of Anatomy, University of Medical Sciences, Święcickiego 6,60–781 Poznań, Poland, tel: +48 61 854 65 64, e-mail: margaretg@o2.plFormation of the vertebral archesof the cervical, thoracic and lumbarvertebrae in early human foetusesM. Grzymisławska, W. WoźniakDepartment of Anatomy, University of Medical Sciences, Poznań, PolandFusion of the neural arches was studied in 6 serially sectioned human foetusesaged 9 and 10 weeks. In foetuses of 9 weeks, the completion of arches wasobserved in the cervical, upper thoracic, and middle thoracic regions of thevertebral column. During the 10th week of development, fusion of neural pro-cesses progresses in the lower thoracic and upper three lumbar vertebrae.(Folia Morphol 2010; 69, 3: 177–179)Key words: human embryology, vertebral column, vertebral archesINTRODUCTIONThe embryonic development of the vertebral co-lumn has been widely investigated [7–11] and hasbeen summarised by O’Rahilly and Meyer [12].Detailed, well illustrated studies of the vertebralcolumn, as a whole and particular regions of thecolumn, at the end of the embryonic period havebeen performed by O’Rahilly et al. [13–16].Bagnal et al. [1–5] studied the foetal vertebralcolumn by radiography, with particular attentionpaid to longitudinal growth and ossification centresin the vertebral column.The aim of the present study is the examinationof fusion of the neural arches in the cervical, thora-cic, and lumbar regions of the vertebral column infoetuses aged 9 and 10 weeks.MATERIAL AND METHODSSerial sections of six human foetuses aged 9 (threefoetuses) and 10 (three foetuses) weeks were stud-ied. The foetuses belong to the Collection of theDepartment of Anatomy of the University of Medi-cal Sciences in Poznań. Sections of thickness 5 and10 mm were made in the horizontal plane. The stainsemployed included haematoxylin and eosin, andcresyl violet (according to Nissl), according to Mal-lory method, and Bodian’s protargol.RESULTSIn all investigated foetuses, the vertebrae formthe cartilaginous column and ossification was notdetectable.In the nine-week-old foetuses the neural pro-cesses of the vertebrae extended dorsally on eachside of the neural tube and they united to com-plete the neural arches which formed the vertebralarches. This completion of the arches was observedin the cervical, upper thoracic, and middle thoracicregions of the vertebral column (Figs. 1–3).Fusion of the neural processes appeared first ontheir surface facing the dorsal part of the spinalcord. The ends of these processes were still sepa-rated and acquired a bifurcated shape (Figs. 1, 2).This was particularly evident in the cervical andupper thoracic vertebrae. In the lower thoracic andlumbar regions of the spinal cord the neural pro-cesses were close to each other but they were stillseparated (Fig. 4).In foetuses aged 10 weeks, fusion of the neu-ral processes was observed in all thoracic and up-178Folia Morphol., 2010, Vol. 69, No. 3per three lumbar vertebrae (Figs. 5, 6). In lower 2lumbar vertebrae the neural processes were close tothe median plane but were not fused yet. The neuralprocesses in this region were completed by the mem-brana reuniens dorsalis, which closed the vertebral ca-nal from surface epithelium and subjacent mesenchyme.The shape of the fused ends of the neural pro-cesses resembled that of the foetuses aged 9 weeks.DISCUSSIONCondensation of the sclerotomal mesenchymearound the notochord is the earliest primordium ofthe skeleton and is frequently referred to as the bla-stema stage. This stage is followed by the cartilagi-nous stage which begins early in the 6th week. Thisblastema anlage forms the centrum which lies ven-Figure 1. Horizontal section of cervical region in foetus of9 weeks. Stained with cresyl violet; ¥ 40; a — neural process,b — spinal cord.Figure 2. Horizontal section of upper thoracic region in foetus of9 weeks. Stained with cresyl violet; ¥ 40; a — body of vertebra,b — rib, c — neural process, d — spinal cord, e — transverseprocess.Figure 3. Horizontal section of middle thoracic region in foetus of9 weeks. Stained with cresyl violet; ¥ 40; a — neural process, b —spinal cord, c — body of vertebra, d — liver, e — thoracic aorta.Figure 4. Horizontal section of upper lumbar region in foetus of9 weeks. Stained with cresyl violet; ¥ 40; a — neural process,b — spinal cord, c — intervertebral disc, d — kidney,e — abdominal aorta.Figure 5. Oblique horizontal section of upper thoracic region infoetus of 10 weeks. Stained with cresyl violet; ¥ 40; a — neuralprocess, b — transverse process, c — ribs, d — spinal cord,e — spinal ganglion.179M. Grzymisławska, W. Woźniak, Formation of human foetal vertebral archestral to the neural tube and forms the primordium ofmost of the vertebral body.According to O’Rahilly and Müller [17], “In termsof adult anatomy, the body of a vertebra includesthe centrum and small part of the neural arch. Cor-respondingly, the vertebral arch is slightly less ex-tensive than the neural arch. A rib articulates withthe neural arch and not with the centrum.”From the dorsolateral angles of the centrum, theneural arch grows to enclose the spinal cord.By the end of the embryonic period, the verte-bral column presents a normal spina bifida totalis.The membrana reuniens dorsalis extends betweenthe neural processes.According to Bardeen [6], the neural arches fusein foetuses of 50 mm crown-rump length.In the present study it was found that the fu-sion of the neural arches progresses craniocaudal-ly. At 9 weeks the completion of neural arches wasobserved in the cervical, upper thoracic, and mid-dle thoracic regions. In foetuses aged 10 weeksthis fusion was found in all thoracic and upperlumbar vertebrae.REFERENCES1. Bagnal KM, Harris PF, Jones PRM (1977) A radio-graphic study of the human fetal spine. 1. The de-velopment of the secondary cervical curvature.J Anat, 123: 777–782.2. Bagnal KM, Harris PF, Jones PRM (1977) A radio-graphic study of the human fetal spine. 2. The se-quence of development of ossification centres inthe vertebral column. J Anat, 124: 791–802.3. Bagnal KM, Harris PF, Jones PRM (1979) A radio-graphic study of the human fetal spine. 3. Longitu-dinal development of the ossification centres. J Anat,128: 777–787.4. Bagnal KM, Harris PF, Jones PRM (1982) A radio-graphic study of the growth in width of the humanfetal vertebral column. Anat Rec, 204: 265–270.5. Bagnal KM, Harris PF, Jones PRM (1984) A radio-graphic study of variations of the human fetal spine.Anat Rec, 208: 265–270.6. Bardeen CR (1905) The development of the thora-cic vertebrae in man. Am J Anat, 4: 163–174.7. Götz W, Fischer G, Herken R (1991) Lectin bindingpattern in the embryonal and early fetal humanvertebral column. Anat Embryol, 184: 345–353.8. Götz W, Osmers R, Herken R (1995) Localisation ofextracellular matrix components in the embryonichuman notochord and axial mesenchyme. J Anat,186: 111–121.9. Müller F, O’Rahilly R (1986) Somitic-vertebral cor-relation and vertebral levels in the human embryo.Amer J Anat, 177: 3–19.10. Müller F, O’Rahilly R (1994) Occipitocervical seg-mentation in staged human embryos. J Anat, 185:251–258.11. Müller F, O’Rahilly R (2003) Segmentation in stagedhuman embryos: the occipitocervical region revisi-ted. J Anat, 203: 297–315.12. O’Rahilly R, Meyer DB (1979) The timing and se-quence of events in the development of the humanvertebral column during the embryonic period pro-per. Anat Embryol, 157: 167–176.13. O’Rahilly R, Müller F, Meyer DB (1980) The humanvertebral column at the end of the embryonic pe-riod proper. 1: The column as a whole. J Anat, 131:565–575.14. O’Rahilly R, Müller F, Meyer DB (1983) The humanvertebral column at the end of the embryonic pe-riod proper. 2: The occipitocervical region. J Anat,136: 181–195.15. O’Rahilly R, Müller F, Meyer DB (1990) The humanvertebral column at the end of the embryonic pe-riod proper. 3: The thoracicolumbar region. J Anat,168: 81–93.16. O’Rahilly R, Müller F, Meyer DB (1990)  The humanvertebral column at the end of the embryonic pe-riod proper. 4: The sacrococcygeal region. J Anat,168: 95–111.17. O’Rahilly R, Müller F (2001) Human embryology andteratology. 3rd Ed. Willey-Liss. New York, Chiches-ter, Weinheim, Brisbane, Singapore, Toronto.Figure 6. Horizontal section of lower thoracic region in foetus of10 weeks. Stained with cresyl violet; ¥ 40; a — neural process,b — spinal cord, c — body of vertebra, d — oesophagus, e —lung, f — rib.

Formation of the vertebral arches of the cervical, thoracic and lumbar vertebrae in early human foetuses

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Formation of the vertebral arches of the cervical, thoracic and lumbar vertebrae in early human foetuses

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