Penis

PENIS

  • It consists of a body and glands. Body consists of
    • The erectile corpus cavernosum penis, whose two crura are attached to the ischial arch.
    • Corpus cavermosum urethrae or corpus spongiosum penis surrounding urethra muscles.
  • Glans penis forms the tip of penis.

Body of penis

  • Consists of the corpora cavernosa, which have a capsule, a system of trabeculae and the true erectile tissue.
  • The fibrous capsule the tunica albuginea is a thick membrane of dense collagenous tissue with elastic fibres.
  • It gives off similarly constructed trabeculae which are inter-connected to form a coarse frame work.
  • The trabeculae forms a median septum between two corpora, between the trabeculae is the erectile tissue proper, which is a vast-sponge like system of irregular vascular spaces intercalated between afferent arteries and efferent veins.
  • It consists of a fine framework of lamellae and cords, continuous with the trabeculae and albuginea and encloses communicating spaces called cavernous spaces. The spaces are longitudinal and are best developed in the crura. The spaces are lined by endothelium, which is continued into that of arteries and veins. 
  • They are bounded by the intercavernous lamellae and trabeculae, which carry vessels and nerves. The spaces are largest in the central zone of corpus cavernosum penis.
  • Erection of the body of penis is brought about by filling in of the cavernous spaces with arterial blood and prevention of regress of blood through veins. Constriction of arteries and slow emptying of cavernous spaces by contraction of smooth muscle and elastic fibres terminate erection.
  • The corpus spongiousum or corpus cavernosum urethrae have a similar structure but the albuginea is thin and contains more elastic fibres. The trabeculae are thin lacunae are more or less of uniform size. The urethra (penile part) passes through the corpus spongiosum. The mucous membrane is thrown into folds and is lined by transitional epithelium.

Species differences

  • In man, three distinct bodies form penis and a median septum clearly demarcates the two corpora cavernosa. The median septum is present only near the root of the penis in ruminants and boar but is continuous throughout the body in dog. In stallion and cat, the septum is not continuous.
  • The intercavernous framework is composed of fibroelastic tissue in ruminants and boar and smooth muscle is also present in the horse and dog.
  • Scattered adipose tissue occurs in the penis of domestic animals. In the bull, the corpus cavernosum largely consists of fibrous tissue but the erectile tissue is also present to a limited extent, which serves to stiffen the penis rather to enlarge it.
Last modified: Saturday, 21 August 2010, 9:43 AM