RT Journal Article T1 Morphogenesis of Human Scalene Muscles Between Weeks 6 and 13 of Development: Anatomical Aspects and Clinical-Functional Relevance A1 Martínez Sanz, Elena A1 Barrio Asensio, María Del Carmen A1 Maldonado Bautista, Estela A1 Palomar-Gallego, María Angustias A1 Catón Vázquez, Francisco Javier A1 Arráez Aybar, Luis Alfonso A1 Murillo González, Jorge Alfonso A1 Mérida Velasco, José Ramón AB The scalene muscles represent a crucial muscle group in cervical anatomy, with significant clinical and functional implications. Despite their importance, studies on their embryonic and fetal development remain scarce. This study examined the morphogenesis of the scalene muscles bilaterally in 33 developing human specimens [66 sides from 12 embryos (Weeks 6-8) and 21 fetuses (Weeks 9-13)] using serial histological sections and conventional light microscopy. The scalene blastema appeared during Week 6 of development, comprising myoblasts, mesenchymal cells, and collagen fibers, and was surrounded by fibroblast-like cells and collagen fibers. The ventral rami of spinal nerves forming the brachial plexus, along with the subclavian artery, divided this blastema into two components: a medial portion (scalenus anterior muscle primordium), pierced by the phrenic nerve, and a lateral portion (scalenus medius muscle primordium), pierced by the dorsal scapular nerve and the branches forming the long thoracic nerve. The scalene triangle, through which these neurovascular elements pass, formed between the scalenus anterior and medius primordia. The scalenus minimus muscle was identified in 7 of 66 sides (10.6%). Our findings suggest that the scalene blastema originates from both hypaxial myotomes and sclerotomes of the cervical somites. The developmental relationship between the scalene blastema and adjacent neurovascular structures may help explain anatomical variations in this region with clinical significance. Furthermore, the insertion of the scalenus anterior muscle into the parietal pleura via the suprapleural membrane primordium provides new insight into its functional role in respiratory mechanics. PB WILEY SN 1098-2353 YR 2025 FD 2025 LK https://hdl.handle.net/20.500.14352/129003 UL https://hdl.handle.net/20.500.14352/129003 LA eng NO Martínez-Sanz E, Barrio-Asensio MC, Maldonado E, Palomar-Gallego MA, Catón J, Arráez-Aybar LA, Murillo-González JA, Mérida-Velasco JR. Morphogenesis of Human Scalene Muscles Between Weeks 6 and 13 of Development: Anatomical Aspects and Clinical-Functional Relevance. Clin Anat. 2025 Nov 9. doi: 10.1002/ca.70046. Epub ahead of print. PMID: 41208303. NO Banco Santander/Universidad Complutense de Madrid research project (PR108/20\u201018) NO Complutense Research Group 920202 (GRFN32/23) DS Docta Complutense RD 1 ene 2026