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==Introduction==

==Introduction==

The penis is the male copulatory organ. It is formed from three parts; two Corpora cavernosa, comprising of cavernous tissue and a connective tissue sheath the tunica albuginea, and the single Corpus Spongiosum which contains the urethra encased in a vascular tissue sleeve. There are two types of penis: the musculovascular and fibroelastic penis.

The penis is the male copulatory organ. It is formed from three parts; two Corpora cavernosa, comprising of cavernous tissue and a connective tissue sheath the tunica albuginea, and the single Corpus Spongiosum which contains the urethra encased in a vascular tissue sleeve. There are two types of penis: the musculovascular and fibroelastic penis.

The corpus cavernosum is made up from the paired columns of cavernous tissue surrounded by connective tissue known as the crura of the penis or corpora cavernosa.  

The corpus cavernosum is made up from the paired columns of cavernous tissue surrounded by connective tissue known as the crura of the penis or corpora cavernosa.  

*In the dog the distal corpus cavernosum is transformed into bone to form the [[Reproductive_Behaviour_-_Copulatory_Behaviour_Dog_-_Anatomy_%26_Physiology|Os penis]] which plays an important part in the dog achieving intromission with the bitch during copulation.

*In the dog the distal corpus cavernosum is transformed into bone to form the [[Dog Copulatory_Behaviour - Anatomy & Physiology|Os penis]] which plays an important part in the dog achieving intromission with the bitch during copulation.

'''Corpus spongiosum'''

'''Corpus spongiosum'''

The corpus spongiosum is a vascular tissue sleeve surrounding the urethra. It commences at the bulb of the penis as an enlargement of the spongy tissue of the pelvic urethra. At the end of the penis the copus spongiosum expands over the distal end of the corpus cavernosum to form the '''Glans penis''', bringing the urethra to the extremity of the penis. There is a great variation in the morphology of the glans penis between species which often correspond to the female tract morphology. For example the boars “corkscrew” glans penis corresponds to the many interdigitating prominences of the sow’s cervix. The glans penis is highly populated with sensory nerves.

The corpus spongiosum is a vascular tissue sleeve surrounding the urethra. It commences at the bulb of the penis as an enlargement of the spongy tissue of the pelvic urethra. At the end of the penis the corpus spongiosum expands over the distal end of the corpus cavernosum to form the '''Glans penis''', bringing the urethra to the extremity of the penis. There is a great variation in the morphology of the glans penis between species which often correspond to the female tract morphology. For example the boars “corkscrew” glans penis corresponds to the many interdigitating prominences of the sow’s cervix. The glans penis is highly populated with sensory nerves.

'''Prepuce'''

'''Prepuce'''

*Ram – large extension of the urethral process

*Ram – large extension of the urethral process

*Stallion – Mushroom shaped with slight protrusion of the urethral process

*Stallion – Mushroom shaped with slight protrusion of the urethral process

*Dog – substantial glans penis which is devided into the '''bulbus glandis''' found proximally and the '''pars longa glandis''' found distally

*Dog – substantial glans penis which is divided into the '''bulbus glandis''' found proximally and the '''pars longa glandis''' found distally

*Tom cat – cone shaped with Keratinised Papillae, directed caudally

*Tom cat – cone shaped with Keratinised Papillae, directed caudally

 

==Types of Penis==

==Types of Penis==

'''Fibroelastic'''

'''Fibroelastic'''

==Muscles associated with the penis==

==Muscles associated with the penis==

'''Bulbospongiosus'''

'''Bulbospongiosus'''

*A single muscle that covers the root and ventral surface of the penis as well as the Bulbourethral glands (link to glands page)

*A single muscle that covers the root and ventral surface of the penis as well as the bulbourethral glands (link to glands page)

*The function of this muscle is to empty the extrapelvic urethra of sperm in a similar way to the Urethralis muscle emptying the pelvic urethra.

*The function of this muscle is to empty the extrapelvic urethra of sperm in a similar way to the urethralis muscle emptying the pelvic urethra.

'''Ischiocavernosus Muscles'''

'''Ischiocavernosus Muscles'''

'''Retractor penis Muscles'''

'''Retractor penis Muscles'''

*Paired muscles oringinating on the caudal vertebrae and inserting on the ventrolateral surfaces of the penis.

*Paired muscles originating on the caudal vertebrae and inserting on the ventrolateral surfaces of the penis.

*Maintains the sigmoid flexure of the fibroelastic penis when the muscles are contracted.

*Maintains the sigmoid flexure of the fibroelastic penis when the muscles are contracted.

*When the muscles are relaxed the penis protrudes through the prepuce as the sigmoid flexure unbends.

*When the muscles are relaxed the penis protrudes through the prepuce as the sigmoid flexure unbends.

==Lymphatics==

==Lymphatics==

Lymph from the penis and prepuce drains into the superficial inguinal lymph nodes.

Lymph from the penis and prepuce drains into the superficial inguinal lymph nodes.