Anatomy Atlases: Illustrated Encyclopedia of Human Anatomic Variation: Opus I: Muscular System: Alphabetical Listing of Muscles: P: Pyramidalis

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Illustrated Encyclopedia of Human Anatomic Variation: Opus I: Muscular System: Alphabetical Listing of Muscles: P

Pyramidalis

Ronald A. Bergman, PhD
Adel K. Afifi, MD, MS
Ryosuke Miyauchi, MD
Peer Review Status: Internally Peer Reviewed

The first anatomist to refer to the pyramidalis was Nocolai Massa (1538) who assumed that this muscle assisted in the erection of the penis while Vesalius (1543) thought that it had the function of expressing urine from the penis, "pene urieversum efformans musculum". Riolan (1649) noted that the muscle is occasionally absent, as did Crooke (1650), and Rolfinck (1656). Rolfinck also noted that occasionally only one of the two muscles was present, almost invariably on the right side. Diemerbroek (1672) repeated these observations Ruysch (1704) reported that on one side the muscle was doubled. A similar description of three pyramidales was cited by Winslow (1749). Additional reports of variations in this muscle were given by Verheyen (1706), Santorini (1724), Hammer (1765), Sabatier (1781) (who described the presence of two pyramidales on each side, or four in each body) and Lieutaud (1782). Horner (1826) reported three and sometimes four muscles on each side and Hallett (1848) said he saw two pyramidales on each side in several cases. The muscle is a constant feature of man and other primates and may be related to the assumption of the upright posture in man. Vallois (1926) referred to this association in humans. An expanded version of this history can be found in the article by Ashley-Montague, (1939).

This muscle varies greatly in length (20-138mm) and size. It is often absent on one or both sides, in which case the size of the lower part of the rectus is often increased. It is rarely symmetrical bilaterally. It is absent in about 8% of all individuals studied, more frequently in males and more often on the right side. The muscle is present in ~82% of the white population, ~90% of Blacks, ~95% of Japanese, and ~"always" present in Chinese. Loth's data, combined with that of Mori, give us the following table:

Population	Authors	Observations	%Present
French	Ancel (1902)	146	71
French	LeDouble (1897	243	89
Berber	Leblanc, Curtillet (1930)	43	72
English	Thomson (1897)	270	74
Irish	Knott (18)	160	76
Japanese	Mori (1964)	567	94.5
American	Dwight (1895)	673	79
Polish	Loth (1924)	200	79
Alsatian	Schwalbe, Pfitzner (1894)	393	87
Chinese	Nakano (1923)	23	100
Chinese	Wagenseil (1927)	80	99
Black	Loth (1912), streblow (1915)	105	87
Black	Vallois (1926)	2266	82

In some instances, the muscle has been found doubled and may extend upward as far as the umbilicus. It is usually supplied by the subcostal nerve (T12) and occasionally by the iliohypogastric (L1).

The pyramidalis muscle is supplied by the muscular branches of the inferior epigastric artery and veins.

Syn.: m. pyramidalis abdominis.

Varieties of Pyramidalis.
from Anson, Beaton, and McVay.

References

Adachi, B. (1910) Beitrage zur Anatomie der Japaner. XII. Die Statistik der Muskelvarietäten. Z. Morph. & Anthrop.12:261-312.

Ancel, P. (1901-02) Documents receuillies à la salle de dissection de la Fac. de Médecine de Nancy. Bibliographie Anatomique, IX & X:133-160.

Ando, T. (1938) On the rectus abdominis and the pyramidalis. Sotai taijino kaibogakuteki kenkyu. 2:1-30. In Japanese.

Anson, B.J., Beaton, L.E. and C.B. McVay. (1938) The pyramidalis muscle. Anat. Rec. 72:405-411.

Ashley-Montagu, M.F. (1939) Anthropological significance of the musculus pyramidalis and its variability in man. Am. J. Phy. Anthropol. 25:435-490.

Beaton, L.E. and B.J. Anson. (1939) The pyramidalis muscle: Its occurrence and size in American Whites and Negroes. Am. J. Phys. Anthropol. 25:261-269.

Bryce, T.H. (1923) Myology. Quain's Elements of Anatomy, Longmans, Green and Co., London.

Crooke, H. (1650) Myographia. London.

Cruvielheir, J. (1880) Traité d'Anatomie descriptive. II, Paris. van Diemerbroek, I. (1672) Anatome corporis humani. Ultrajecti.

Dwight, T. (1893) Observations on the psoas parvus and pyramidalis. A study on variation. Proc. Am. Phil. Soc. 31:117-123.

Fallopius, G. (1562) Observationes Anatomicae. Venetiis. Gegenbaur, C. (1895) Lehrbuch der Anatomie des Menschen. Leipzig.

Hallett, C.H. (1848) An account of the anomalies of the muscular system, met with in the dissecting-room of the University during the years 1846-47; with general remarks. Edinburg. Med. Surg. J. 69:1-32.

Hallett, C.H. (1849) An account of the anomalies of the muscular system, met with in the dissecting room of the University during the years 1847-1848; with general remarkes. Edinburg. Med. Surg. J. 70:1-20.

Hammer, W.C. (1765) De musculorum Varietate. Dissertation, Erlangen.

Henle, J. (1871) Handbuch der Muskellehre des Menschen, in Handbuch der systematischen Anatomie. Verlag von Friedrich Vieweg und Sohn, Braunschweig.

Hibi, M. (1931) Über den M. pyramidalis bei den Hokuriku-Japanern, Kanazawa Kaibô. Gyoseki 9:18-19.

Igarashi, N. and M. Hoshiba. (1936) The M. pyramidalis. Kanazawa Ikadaigaku Kaibogakukyoshitsu Gyosekishu 22:62-79. In Japanese.

Kaneno, T. and K. Wajima. (1955) A study on the M. rectus abdominis. Nihon Daigaku Zasshi 14:1511-1525. In Japanese.

Kawaai, M. (1936) On the M. pyramidalis, especially in its area, of adults and fetus. Kaibogaku Zasshi 9:182-197. In Japanese.

Knott, J.F. (1881) Muscular anomalies. Proc. Roy. Irish Acad. Sci. Ser. 2, 3:627-641.

Knott, J.F. (1881), Horner, W.E. (1826) A Treatise on Special and General Anatomy. Philadelphia. Muscular anomalies. Proc. Roy. Irish Acad. Sci. Ser. 2, 3:627-641.

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LeDouble, A.F. (1897) Traité des Variations du Système Musculaire de l'Homme et Leur Signification au Point de vue de l'Anthropologie Zoologique. Libraire C. Reinwald, Scheicher Freres, Paris.

Lieutaud, J. (1782) Zergleiderungskunst, nach der neuesten mit ... Bemerkungen von Hrn. Portal; vermehrten Ausgäbe, übersetzt. Leipzig.

Loth, E. (1912) Beiträge zur Anthropologie die Negerweichteile (Muskelsystem). Stuttgart. 98-99.

Loth, E. (1919) Anthropmorphfologia des Muscles. Bull. Mém. Soc. Anthrop. Paris. 10:116-133.

Loth, E. (1921) Antropomorfologia miésni. Arch. Nauk. Antropologicznich (Warsaw) 1:129-134.

Loth, E. (1931) Anthropolgie des parties molles. Paris. 143-147. von Luschka, H. (1870) Der M. pubotransversalis des Menschen. Arch. Anat. Physiol. Wissen. Med. 1870:227-231.

Macalister, A. (1875) Observations on muscular anomalies in the human anatomy. Third series with a catalogue of the principal anomalies hitherto published. Trans. Roy. Irish Acad. Sci. 25:1-130.

Massa, N. (1536) Liber introductorius Anatomiae, sive dissectionis corporis humani. Venetiis. Cap.21:37-38.

Meckel, J.F. (1828) System der vergleichenden Anatomie. Halle. 3:392-670.

Mori, M. (1964) Statistics on the musculature of the Japanese. Okajimas' Fol. Anat. Jap. 40:195-300.

Morita, M. (1940) On the M. pyramidalis of man and mammals. Igaku Kenkyu 14:151-157. In Japanese.

Morita, M. (1947) On the M. rectus abdominis, appendix, the length of the M. pyramidalis. Kaibogaku Zasshi 23:50-55. In Japanese.

Nakamura, S. (1935) Ueber den M. rectus abdominis und den M. pyramidalis der Japaner (aus Kyushu). J. Kumamoto Med. Soc. 11:1251-1261)

Nakano, T. (1923) Beiträge zue Anatomie die Chinesen. Die Statistik des Muskelvarietäten.Okajimas' Folia Anat. Jap. (Tokyo) 1:273-282.

Obata, T. and A. Sugiyama. (1943) The M. rectus abdominis and M. pyramidalis. Sotaitaiji no Kaibogakuteki Kenkyu 4:155-185. In Japanese.

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Riolan (Filii), J. (1649) Opera Anatomica. Paris. 83.

Rolfinck, W. (1656) Dissertationes Anatomicae. Noribergae, 579-580.

Ruysch, F. (1704) Thesaurus Anatomicus quartus. 37, no. 83.

Sabatier, R.B. (1781) Traité complet d'Anatomie. Paris. 1:262-264.

Santorini, G.D. (1724) Observationes Anatomicae. Venetiis. Cap. 9:160.

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Schwalbe, G. and W. Pffitzner. (1889) Variet Statistik und Anthropologie. Anat. Anz. 4:705-714.

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Schwalbe, G. and W. Pfitzner. (1893-94) Morphologische Arbeiten. Jena 3:459-490.

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Testut, L. (1884) Les anomalies musculaires chez les Negros et chez les Blancs. Internat. Monatschrift Anat. et Histol. 1:285-291.

Tomita, A. (1937-39) Study on the pyramidalis. Kyushu Igakusenmongakko Igakkai Zasshi 2:43-58. In Japanese.

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Vallois, H.V. (1925b) La signification des variations musculaires dans les races humaines. Rev. Anthrop. 35:11-24.

Vallois, H.V. (1926) Valeur et signification du muscle pyramidal de l'abdomen. Arch. Anat., Histol. & Embryol. 5:497-525.

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Wagenseil, F. (1927) Muskelbefunde bei Chinesen. Verh. Ges. Phys. Anthrop. (Stuttgart) 2:42-50.

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