Pyramidalis

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.

Riferimenti dell’opera originale

Elenco riportato come compare nella fonte, senza normalizzazione dei formati bibliografici.

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