Fig 1.
The architecture of the levator ani muscle.
Panel G shows the positions of the transverse sections in panels A-D and that of obliquely sectioned panel E (calculated from reconstruction). The sections show the bilayered make-up of the pubovisceral muscle (A-C) and its attachment to the rectococcygeal muscle (A,B), the extension of the pubovisceral and deep layer of the puborectal muscles to the pubic bone (B,C), the external anal sphincter, the superficial layer of the puborectal muscle, and the conjoint longitudinal muscle of the rectum (C-E), and the rectoperineal muscle (D). Panel E visualizes the successive layers of the anal-sphincter complex, while panel F, a calculated midsagittal section of this specimen, shows the muscles surrounding the anal canal. Panels G and H show reconstructions of the levator and sphincter ani muscles as seen from the left (G) and anterosuperior (H). The color code of the (outlined) structures is shown in S2 Fig and sections without outlines S5 Fig. Abbreviations: AL, anococcygeal ligament; Ant, anterior; B, bladder; Co, coccygeal muscle; EAS, external anal sphincter; GM, gluteus maximus muscle; Post, posterior; PR-D, puborectal muscle, deep portion; PR-S, puborectal muscle, superficial portion; PV, pubovisceral muscle with deep (purple) and superficial (orange) layers; RC, rectococcygeal muscle; U, urethra; R, rectum; V, vagina.
Fig 2.
The architecture of the anal sphincter complex and perineal body.
Panel D shows the positions of the sagittal sections of panels A-C. The sections show the position of muscles and the perineal body around the rectum (A: midsagittal; C: most lateral). Panels E and F show a left-lateral and left-anterior view of the muscles surrounding the rectum and vagina that have insertions on the perineal body. The rectococcygeal muscle and anococcygeal ligament are shown in panel E. The bulbospongious muscle is not shown in panel E so as not to hide the perineal body and deep perineal muscle. For the same reason, the vagina and uterus are not shown in panel F. The color code of the (outlined) structures is shown in S2 Fig and sections without outlines in S6 Fig. Abbreviations: AL, anococcygeal ligament; B, bladder; BS, bulbospongious muscle; DP, deep perineal muscle; EAS, external anal sphincter; LR, longitudinal smooth muscle of rectum; PB, perineal body; PR-D, puborectal muscle, deep portion; PR-S, puborectal muscle, superficial portion; Pub: pubic bone; RC, rectococcygeal muscle; RP, rectoperineal muscle; STP, superficial transverse perineal muscle; U, urethra; Ute, uterus; UVS, urethrovaginal sphincter; R, rectum; V, vagina.
Fig 3.
Shape and topographic relations of the mesorectum, rectal diaphragm, and perineal body in the male.
Panel J shows the positions of the transverse sections in panels A-D. The sections show the position of the rectococcygeal (A,B) and rectoperineal (C) muscles and perineal body (C,D). Panels E-I show anterior (E), left-lateral (F,G,I), and anterolateral (H) views of the mesorectum (E-I) and rectal diaphragm (H,I), and perineal body (G-I). Note anterior absence of mesorectum at Denonvilliers’ fascia (E), the rectoperineal and rectococcygeal muscles forming the inferior boundary of the mesorectum (E,F) and the connection of the pubovisceral muscle with the conjoint longitudinal muscle of the rectum (H,I). The color code of the (outlined) structures is shown in S2 Fig and sections without outlines in S7 Fig. Abbreviations: AL, anococcygeal ligament; Co, coccygeal bone, CL, conjoint longitudinal muscle of rectum; EAS, external anal sphincter; GM, gluteus maximus muscle; LR, longitudinal smooth muscle of rectum; M, mesorectum; P, prostate; PB, perineal body; PV, pubovisceral muscle with deep (purple) and superficial (orange) layers; RC, rectococcygeal muscle; RP, rectoperineal muscle; SV, seminal vesicles, U, urethra; R, rectum; *, Denonvilliers’ fascia.
Fig 4.
Shape and topographic relations of the perineal body and superficial perineal muscles.
Panel D shows the positions of the transverse sections in panels A-C. Panels E, F and H show magnifications of the boxes in panels A and B. Panel G shows an inferior view of the superficial perineal area, while panel H shows a section of the square in panel G. The empty area between the bulbospongious and ischiocavernous muscles is mostly occupied by fat. The asterisk in panel H identifies attachments of the superficial transverse perineal muscle to connective tissue septa in the ischioanal fat. Panels I-M show slightly left oblique view of perineal body as seen from superior (I; note basal and wing (asterisk) portions), with attachments of urethrovaginal sphincter and deep perineal muscle (J), rectoperineal, superficial transverse perineal and bulbospongious muscles (K), superficial portion of puborectal muscle (L; the internal anal sphincter and conjoint longitudinal muscle of the rectum were added to visualize the anorectal bend), and deep portion of puborectal muscle (M). The color code of the (outlined) structures is shown in S2 Fig and sections without outlines in S8 Fig. Abbreviations: AL, anococcygeal ligament; BS, bulbospongious muscle; CL, conjoint longitudinal muscle of rectum; DP, deep perineal muscle; EAS, external anal sphincter; IAS, internal anal sphincter; IC, ischiocavernosus muscle; PB, perineal body; PR-D, puborectal muscle, deep portion; PR-S, puborectal muscle, superficial portion; RP, rectoperineal muscle; STP, superficial transverse perineal muscle; U, urethra; UVS, urethrovaginal sphincter; R, rectum; V, vagina; Vv, veins.