ISSN:
0002-9106
Keywords:
Life and Medical Sciences
;
Cell & Developmental Biology
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Medicine
Notes:
Morphogenesis and histogenesis of the facial muscles is described in human embryos and fetuses 4.2-360.0 mm (crown-rump length). The microscopic study was performed on 50 specimens that had been variously serially-sectioned and stained. Graphic or wax reconstructions were made from transverse serial sections at 11 representative ages. Three late fetuses and a term infant were studied grossly.Second branchial arch mesenchyme in early embryos (4.2-6.5 mm) becomes increasingly dense, but is not subdivided into distinct premuscle masses. By 8-20 mm, sheet-like collections (laminae) of premyoblasts and early myoblasts extend from the superficial part of the arch into the temporal, occipital, cervical and mandibular regions. Premuscle condensations deep in the arch become the stapedius, posterior digastric and stylohyoid muscles. The infraorbital lamina and the occipital platysma appear by 20-23 mm. The superficial muscles differentiate rapidly between 26 and 37 mm. Most are composed of myoblasts at 41 mm. By 80 mm, all the muscles contain myotubes and are in their definitive positions. At 80-140 mm, the myotubes become young muscle fibers. From 140 mm to 360 mm (term) the muscles increase in size and gain definitive attachments. Superficial muscles differentiate later than the deep and those in the cervicomandibular and occipital regions differentiate earlier than those in the frontal and midfacial regions. The muscle masses form pari passu with the muscular branches of the facial nerve which develop deep to them.
Additional Material:
11 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/aja.1001200207
