Raphe perinei

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The raphe perinei ( gr. - lat. , Ῥαφή rhaphe "seam" = Verwachsungsnaht ) is to the rear (from the front anteroposterior ) extending compound of the embryonal applied genital folding, more precisely of the temporarily formed urogenital sinus , in the median plane . The raphe forms during the development of the genitals in the embryo as a merging line of the two urogenital folds or scrotal bulges and is later, however, differently visible: from a clearly visible elevation to almost inconspicuous and only as a slight discoloration of the skin.

Embryogenesis and development of the raphe perinei

Sex development in the embryonic phase from the 4th to the 12th week, taking into account equality up to the 7th week. From the 9th week, the scheme for a male and female individual is divided.

The origin of the formation of raphe in both sexes starts with the development of the external genitalia. In both the female and the male embryo, it begins with a sexually undefined ( indifferent ) phase. Later, from the 12th week of pregnancy (SSW), the clear definition ( differentiation ) for the two sexes ends . In the indifferent phase, the following anatomical structures are first created:

  • Genital or urethral folds: they are on both sides of the cloaca membrane ( cloaca )
  • Genital cusps : they lie ventrally ( ventrally ) from the cloacal membrane
  • Genital bulges or labioscrotal bulges: they unfold laterally ( lateral ) of the genital folds

The urogenital membrane is formed between the genital folds and initially closes the urogenital ostium . After the urorectal septum has grown together with the cloacal membrane, the membrane tears and releases the ostium .

A strong increase in cells (overgrowth) of the mesenchyme on the head and abdomen ( cranioventral ) of the cloacal membrane creates the genital tubercle ( tuberculum genitale ), which is the original and common attachment of the clitoris and penis to both sexes . The genital hump elongates into a protophallus , which is initially the same length in both sexes.

In male embryos, under the influence of androgens, the protophallus elongates to the penis ( phallus ) and the urogenital groove ( sulcus urogenitalis ) then closes to the pars spongiosa of the urethra . It also forms the urethral erectile tissue.

In female embryos, the protophallus remains short and develops into the clitoris. The urogenital groove, which is delimited by the two urogenital folds ( plicae urogenitales ), arises on the underside of the changing protophallus . These urogenital folds, which remain separate, ultimately form the inner, small labia ( labia minora ).

On the side of the genital protuberance, the aforementioned sexual bulges and thus the attachment of the outer, large labia ( labia majora ) and the scrotum (scrotum) arise . The genital folds then merge in the rear section to form the frenulum labiorum pudendi . In the female embryo, the labia minora later emerge from them. The tissues of the genital bulges unite from the front and back ( anterioposterior ), where they form the commissura labiorum anterior and commissura labiorum posterior and thus also the later pubic mound ( mons pubis ).

Raphe perinei in men

Penis of a man from below. The raphe (seam)

The raphe penis is the line of adhesion remaining on the underside of the penis in males . Beginning with the frenulum ( frenulum ). It continues over the underside of the penis to the scrotum, where it then extends as a scrotum suture ( raphe scroti ) to the perineum ( perineum ) or anus . To the front, in an anterior direction, it continues on the foreskin ligament and on the foreskin as a foreskin suture ( raphe praeputii ).

Raphe perinei in the female

In female individuals, the raphe perinei is more or less pronounced at the lower end of the vulva , the fourchette ( commissura labiorum posterior ), up to the anus .

Raphe perinei and obstetrics

If an incision in the perineum ( episiotomy ) is required during obstetrics, a distinction is made between three types of incision:

  • midline ( median ) episiotomy
  • medium to lateral ( mediolateral ) episiotomy
  • lateral ( lateral ) episiotomy

In the median episiotomy, the perineum ( perineum s) is split in the connective tissue raphe perinei from the posterior commissure ( commissura labiorum posterior ) in the course of the midline.

Raphe perinei in animals

  • Perineal region, i.e. perineal suture, raphe perinei in a female horse ( mare )

  • Raphe penis on the underside of the penis of an Asian elephant ( Elephas maximus )

literature

  • Walther Graumann u. a .: Compact textbook anatomy in four volumes . tape 3 . Schattauer, Stuttgart a. a. 2004, ISBN 3-7945-2063-7 , pp. 223 .
  • Keith L. Moore, Arthur F. Dalley, AMR Agur: Clinically Oriented Anatomy . 7th edition. Wolters Kluwer / Lippincott Williams & Wilkins, Philadelphia 2014, ISBN 978-1-4511-1945-9 , pp. 420 .
  • Alfred Sigel, RH Ringert: Pediatric urology. 2nd, completely revised edition, Springer, Berlin / Heidelberg a. a. 2001 ISBN 978-3-540-64764-5 , Chapter 1: Embryology of the urogenital tract ( full text ).
  • Raimund Stein, Rolf Beetz, Joachim W. Thüroff: Pediatric urology in clinic and practice. 3rd edition, Thieme, Stuttgart / New York 2012, ISBN 978-3-13-674803-9 , p. 440 ff. → Section 37, Urogenital sinus and anomalies of the female genitalia.