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Development of the Epaxial Muscles in the Human Embryo
Author(s) -
Mekonen Hayelom Kebede,
Hikspoors Jill P.J.M,
Mommen Greet,
Köhler S Eleonore,
Lamers Wouter H
Publication year - 2016
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.30.1_supplement.1035.1
Subject(s) - anatomy , vertebral column , spinal column , lumbar , longissimus , biology , column (typography) , compartment (ship) , medicine , geology , geometry , surgery , oceanography , mathematics , connection (principal bundle)
Background The appearance of the true muscles of the back is dominated by three muscle columns, but a division into a lateral sacrospinal compartment with longissimus (medial) and iliocostal (lateral) divisions, and a medial compartment with transversospinal muscles is presently more often used. Although back muscles are defined by their embryological origin and innervation pattern, no detailed study on their development is available. Methods Human embryos (5–10 weeks development) were studied, using Amira® and Cinema4D® remodeling software for visualization. Results At Carnegie Stage (CS)15, the epaxial portions of the myotomes became identifiable laterally to the developing vertebrae. At CS16, these portions fused to form a longitudinal muscle column, which became innervated by the dorsal branch of the spinal nerve. At CS17, the longitudinal muscle mass segregated into medial and lateral columns (completed at CS18). At CS18, the medial column segregated again into intermediate and medial columns (completed at CS20). Between CS20 and CS23, the cervical portions of the three columns segregated again form lateral to medial resulting ventrolaterally in rod‐like continuations of the caudal portions of the columns and dorsomedially in spade‐like portions. The lateral and intermediate columns did not separate in the lower lumbar and sacral region. The observed topography identifies the iliocostalis and splenius as belonging to the lateral column, the longissimus to the intermediate column, and the multifidus and (semi‐)spinalis to the medial column. The medial group acquired its transverso‐spinal course during closure of the vertebral arches in the early fetal period. Conclusion Epaxial muscle growth is characterized by cranio‐caudal and latero‐medial gradients in development. Our ontogenetic approach shows that all back muscles can be classified as components of the erector spinae. Support or Funding Information NFP (Netherlands Fellowship Programmes)