The internal innervation and morphology of the human female levator ani muscle.

OBJECTIVE: The purpose of this study was to describe the microinnervation of the human the female levator ani muscle complex. STUDY DESIGN: Detailed microdissection of 10 fresh female levator ani muscles was performed. Specimens were processed by modified Sihler's staining technique. A composite drawing of the levator ani nerve (LAN) distribution was created. RESULTS: Six hemi-levator ani muscles were stained and digitally reconstructed. The LAN traveled perpendicular to major muscular bundles while progressively branching into finer nerves that eventually entered single muscle fascicles. The LAN continued its course through the iliococcygeous muscle to innervate the puborectalis, puboperinealis, and puboanalis muscles. There was no distinct separation between pubovisceralis and iliococcygeous fibers. There were muscle fibers that could be best described as coccygeoperinealis. CONCLUSION: The utilized staining technique enabled us to visualize the LAN microinnervation of the levator ani muscle that extends to puboperinealis and puboanalis muscles. A blueprint for LAN and levator ani morphology was created.

Evidence that some events of mammalian embryogenesis can result from differential growth, making migration unnecessary.

Three events during mammalian embryogenesis were reexamined that traditionally have been considered to be migratory. Using reconstructions of serially sectioned rat and human embryos and computer imaging, this descriptive study reexamined the following: sclerotome formation from the somite, spinal ganglion formation from the neural crest, and thyroid, parathyroid, and thymus gland formations from pharyngeal endoderm. The aim was to determine if the positional changes of the developing structures could be explained by differential growth (i.e., changes in the size and shape of the embryo and its parts) rather than migration (i.e., structures moving from one region of the embryo to another). Embryos and many of their internal structures, especially the neural tube, rapidly change in size and shape during the period when migration is described, but these phenomena were not considered in past studies. Surface reference points were used in past investigations that also move as the embryo and its internal structures enlarge. Computer imaging makes it feasible for the first time to keep magnifications identical for each series of reconstructions, rendering each one equivalent to one frame of a motion picture film. Using this technique together with more centralized, less mobile reference points, the study concludes that the positional changes that occur during the three events can be explained by differential growth. Anat Rec (Part B: New Anat) 289B:53-63, 2006. (c) 2006 Wiley-Liss, Inc.

Development of the sensory nerves to the dorsum of the tongue in staged human embryos.

To determine in selected, staged human embryos the time period and manner of formation of the sensory nerves to the mucosa on the dorsum of the tongue, cranial nerves V(3) and IX and their lingual branches were traced microscopically. These two cranial nerves along with cranial nerve VII are present in the dorsal part of their respective pharyngeal arch 1, 2, and 3 at Stage 13. All three nerves grow ventrally at Stage 16, and the lingual branches of V(3) and IX become closer to the developing tongue region. The lingual fibers begin to enter the tongue substance at Stage 17 when they appear as large short branches that terminate 100-400 microm from the dorsal mucosal basement membrane; of the fibers that are in the tissue deep to the surface mucosa, those in the posterior tongue segment terminate the closest and those in the anterior segment the farthest. Chorda tympani nerve fibers are joined with V(3) at Stage 20. At this stage nerve fibers reach the basement membrane in the posterior tongue segment and by Stage 23 they terminate at the basement membrane throughout the tongue, being sparsest in the anterior segment. Primordial papillae appear as small mucosal projections throughout the tongue at Stage 20 and are innervated by Stage 23. The study found that innervation to the dorsum of the tongue develops during the second month of prenatal life. During the 4-week period, Stages 13-23, an innervation pattern was observed based on the relative time fibers terminate at the basement membrane. The pattern begins caudally in the root, then moves rostrally lateral to the middle tongue segment, proceeding then to the tip of the tongue. The last area to become innervated is the medial part of the middle segment or central portion of the tongue.

The anatomy of midurethral slings and dynamics of neurovascular injury.

The aim of this study was to investigate the course of midurethral slings using tension-free vaginal tape. The TVT procedure was performed on six fresh pelves, measurements were obtained, and the structures were cross-referenced in 16 embalmed pelves. The midurethral sling enters the suburethral tissue 2.2-3 cm caudad to the internal urethral meatus, pierces the paraurethral musculature and vascular plexus, and exits 2+/-0.5 cm from the midline lateral to the point of insertion of the arcus tendineus fasciae pelvis. On the pubic tubercle the sling is 4+/-0.5 cm, 4+/-1 cm and 6+/-1 cm from the accessory obturator, the inferior epigastric and the external iliac vessels, respectively. The critical angle of error resulting in the external iliac vessel injury is 7-15 degrees. A current knowledge of pelvic anatomy may help the surgeon avoid the neural and vascular structures that are in the path of the sling.