Penis
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Bull
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The penis is the male copulatory organ and is composed of white fibrous tissue and a little erectile tissue
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It extends from the ischial arch forward between the thighs to the umbilical region of the abdominal wall
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It is supported by the fascia penis and its prescrotal part is situated in a cutaneous pouch -the prepuce
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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
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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
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The urethra passes over the arch between the crura, curves forward to become incorporated in the substance of the penis
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The body begins at junction of the crura and forms the bulk of the organ
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It is flattened from above downward and it presents four surfaces -dorsal, ventral and two lateral surfaces
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At its origin it is attached to the symphysis ischii by two strong bands -the suspensory ligaments of the penis
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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
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The glans penis is the free end of the organ and is 8 cm long. Its extremity is pointed and twisted
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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
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The penis is principally made up of white fibrous tissue
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It is remarkably dense and firm even in the non-erect condition
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The organ undergoes very little enlargement during erection but it becomes more rigid
Species difference
Ram and Buck
Stallion
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It is shorter but has a larger diameter, the length being about 50cm in the quiescent state
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It undergoes 50% increase during erection
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The erectile tissue is very rich in elastic and muscular tissues and hence very soft
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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
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The urethra protrudes into the fossa glandis as the free urethral process
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Dorsal to the urethral process, the fossa forms a diverticulum, the urethral sinus, which is the site of accumulation for smegma
Boar
Dog
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In the cranial part there is a bone-os penis, which is grooved ventrally for the lodgment of the urethra
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The glans is very long and is extended over the entire length of the os penis
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The cranial part of the glans penis is cylindrical with pointed free end
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In the caudal part, there is a rounded enlargement, the bulbous glandis
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Both are composed of erectile tissue
Rabbit
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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
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Its free extremity is known as pars libera
Cock
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Absent
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The copulatory apparatus is placed at the ventral aspects of the caudal end of cloaca
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It comprises of two papillae of vas deferens, two vascular bodies, a phallus and two lymphatic folds
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Last modified: Friday, 20 April 2012, 10:48 AM