Abstract
Purpose
The minute details of the structure of the anal canal are still not well understood. The complex structural configuration of the muscles, ligaments and raphes remains unclarified. This study was undertaken to determine the precise structure of the posterior part of the anal canal and to facilitate an understanding of previous studies.
Methods
For macroscopic examination, 14 right pelvic halves from 14 Japanese cadavers were used. Observation and dissection were performed from the median plane. In the histological examination, six left pelvic halves were used. The sections of the posterior parts of the anal canal were stained with hematoxylin and eosin, Elastic van Gieson, anti-smooth actin antibody and anti-skeletal myosin antibody.
Results
We identified the following muscles arranged from the internal side to the external side: internal anal sphincter, longitudinal muscle (LM), external anal sphincter (EAS) and levator ani muscle (LAM). Two different types of conformation of the posterior part of the anal canal were found, each bearing a different shape of EAS. In both types, LM penetrated the inferior part of EAS. After penetrating EAS, some fibers of LM ran posterosuperiorly and attached to the “the posterior fibers” which reach the dorsal side of the coccyx.
Conclusions
We defined and labeled the connective tissues between the anal canal and coccyx on the basis of their relative position to LAM. Based on a comparison of the two types of the posterior part of the anal canal, we propose that there are two phases due to constriction and relaxation of LM.
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References
Ayoub SF (1979) Anatomy of the external anal sphincter in man. Acta Anat (Basel) 105:25–36
Borley N (2008) Gray’s anatomy, 40th edn. London
Brachet D, Lermite E, Arnaud J-P (2012) Tratamiento quirúrgico de la enfermedad hemorroidal. EMC —Técnicas Quirúrgicas-Aparato Digestivo 28:1–16
Courtney H (1948) Posterior levator space abscess. Am J Surg 75:405–412
Courtney H (1949) The posterior subsphincteric space; its relation to posterior horseshoe fistula. Surg Gynecol Obstet 89:222–226
Foye PM (2010) Anal nerve risks with paracoccygeal lumbosacral fixation. Surg Radiol Anat 32:805. doi:10.1007/s00276-010-0688-3
Goligher J (1980) Surgery of the anus, rectum and colon, 4th edn. London
Joguet E, Robert R, Labat JJ, Riant T, Guerineau M, Hamel O, Louppe JM (2011) Anatomical basis of digital rectal examination. Surg Radiol Anat 34:73–79. doi:10.1007/s00276-011-0832-8
Kinugasa Y, Arakawa T, Abe H, Abe S, Cho BH, Murakami G, Sugihara K (2012) Anococcygeal raphe revisited: a histological study using mid-term human fetuses and elderly cadavers. Yonsei Med J 53:849–855. doi:10.3349/ymj.2012.53.4.849
Kinugasa Y, Arakawa T, Abe S, Ohtsuka A, Suzuki D, Murakami G, Fujimiya M, Sugihara K (2011) Anatomical reevaluation of the anococcygeal ligament and its surgical relevance. Dis Colon Rectum 54:232–237. doi:10.1007/DCR.0b013e318202388f
Kurihara H, Kanai T, Ishikawa T, Ozawa K, Kanatake Y, Kanai S, Hashiguchi Y (2006) A new concept for the surgical anatomy of posterior deep complex fistulas: the posterior deep space and the septum of the ischiorectal fossa. Dis Colon Rectum 49(10 Suppl):S37–S44. doi:10.1007/s10350-006-0736-6
Milligan E, Morgan C (1934) Surgical anatomy of the anal canal with special reference to anorectal fistule. Lancet 2:1150–1156
Nivatvongs S, Gordon P (2007) Principles and practice of surgery for the colon, rectum, 3rd edn. New York
Oh C, Kark AE (1972) Anatomy of the external anal sphincter. Br J Surg 59:717–723
Parks AG (1954) A note on the anatomy of the anal canal. Proc R Soc Med 47:997–998
Parks AG (1961) Pathogenesis and treatment of fistuila-in-ano. Br Med J 1:463–469
Shafik A (1975) New concept of the anatomy of the anal sphincter mechanism and the physiology of defecation. II. Anatomy of the levator ani muscle with special reference to puborectalis. Invest Urol 13:175–182
Shafik A (1975) A new concept of the anatomy of the anal sphincter mechanism and the physiology of defecation. The external anal sphincter: a triple-loop system. Invest Urol 12:412–419
Shafik A (1976) A new concept of the anatomy of the anal sphincter mechanism and the physiology of defecation. III. The longitudinal anal muscle: anatomy and role in anal sphincter mechanism. Invest Urol 13:271–277
Shafik A (1999) Levator ani muscle: new physioanatomical aspects and role in the micturition mechanism. World J Urol 17:266–273. doi:http://www.ncbi.nlm.nih.gov/pubmed/10552142
Stefanski L, Lampe P, Aleksandrowicz R (2008) The probability of finding nerve branches to the external anal sphincter. Surg Radiol Anat 30:675–678. doi:10.1007/s00276-008-0379-5
International federation of associations of anatomists (1998) Terminologia anatomica: international anatomical terminology. Thieme Medical Publishers, New York
Toldt B (1903) Anatomischer atlas fur studierende und arzte. 4. Berlin, pp 526–538
Acknowledgments
This work is supported by Grant-in-Aid for Scientific Research C (23590216) from the Ministry of Education, Culture, Sports, Science, and Technology, Japan.
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The authors declare that they have no conflict of interest.
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Muro, S., Yamaguchi, K., Nakajima, Y. et al. Dynamic intersection of the longitudinal muscle and external anal sphincter in the layered structure of the anal canal posterior wall. Surg Radiol Anat 36, 551–559 (2014). https://doi.org/10.1007/s00276-013-1228-8
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DOI: https://doi.org/10.1007/s00276-013-1228-8