Penis

PENIS
( Bull, Ram, Buck, Stallion, Boar, Dog, Rabbit, Cock )

Bull

  • The penis is the male copulatory organ and is composed of white fibrous tissue and a little erectile tissue
  • It extends from the ischial arch forward between the thighs to the umbilical region of the abdominal wall
  • It is supported by the fascia penis and its prescrotal part is situated in a cutaneous pouch -the prepuce
  • It is cylindrical in form and measures in an adult bull about 90 cm It may be divided into 3 parts -the root, body and glans
  • The root is attached to the lateral parts of the ischial arch by two crura, which converge and unite below the arch to form the root of the penis
  • The urethra passes over the arch between the crura, curves forward to become incorporated in the substance of the penis
  • The body begins at junction of the crura and forms the bulk of the organ
  • It is flattened from above downward and it presents four surfaces -dorsal, ventral and two lateral surfaces
  • At its origin it is attached to the symphysis ischii by two strong bands -the suspensory ligaments of the penis
  • Just behind the scrotum it forms a S -shaped curve-the sigmoid flexure in which 30 cm of the penis is folded which is released during erection
  • The glans penis is the free end of the organ and is 8 cm long. Its extremity is pointed and twisted
  • The twisted end shows ventro-laterally a groove and the urethral process projects as a ridge in the groove. At the end of the process is the external urethral orifice
  • The penis is principally made up of white fibrous tissue
  • It is remarkably dense and firm even in the non-erect condition
  • The organ undergoes very little enlargement during erection but it becomes more rigid

Species difference

Ram and Buck

  • The free extremity is very distinctive with well-developed urethral process continued beyond the glans penis

Stallion

  • It is shorter but has a larger diameter, the length being about 50cm in the quiescent state
  • It undergoes 50% increase during erection
  • The erectile tissue is very rich in elastic and muscular tissues and hence very soft
  • The glans is enlarged and its base forms a prominent margin -the corona glandis. There is a depression in the glans known as fossa glandis
  • The urethra protrudes into the fossa glandis as the free urethral process
  • Dorsal to the urethral process, the fossa forms a diverticulum, the urethral sinus, which is the site of accumulation for smegma

Boar

  • Resemble in general to that of the ox
  • The sigmoid flexure however is prescrotal
  • The cranial part is spirally twisted especially in erection

Dog

  • In the cranial part there is a bone-os penis, which is grooved ventrally for the lodgment of the urethra
  • The glans is very long and is extended over the entire length of the os penis
  • The cranial part of the glans penis is cylindrical with pointed free end
  • In the caudal part, there is a rounded enlargement, the bulbous glandis
  • Both are composed of erectile tissue

Rabbit

  • From the root, the body of the penis first proceeds forward and just before reaching testicles, it almost makes a U turn backward. Therefore the glans penis is directed backward
  • Its free extremity is known as pars libera

Cock

  • Absent
  • The copulatory apparatus is placed at the ventral aspects of the caudal end of cloaca
  • It comprises of two papillae of vas deferens, two vascular bodies, a phallus and two lymphatic folds
Last modified: Friday, 20 April 2012, 10:48 AM