Erection - Anatomy & Physiology
Revision as of 10:16, 10 July 2008 by Lwilkie (talk | contribs) (→Vascular and Biochemical Control of Erection)
Introduction
- When sexual receptivity of the female is established and sufficient arousal is accomplished in the male, erection and protrusion of the penis ensue.
- Successful penile erection requires a complex series of neural and vasomotor reactions.
- Erection of the penis is necessary for copulation and deposition of semen in the female reproductive tract.
- Erection is characterized by a marked increase in rigidity of the penis.
- Increased rigidity is the result of increase in arterial inflow of blood compared to venous outflow.
- Erection requires that blood be trapped within the cavernous sinus of the penis.
- Increased blood flow to the penis is brought about by vasodilation of the arterioles supplying it.
Erection of the Fibroelastic Penis
- Bull,Ram and Boar
- Involves increased blood flow with subsequent increase in pressure and simultaneous relaxation of the retractor penis muscles.
- Erection and protrusion involve straightening of the penis to eliminate the sigmoid flexure.
- Does not increase significantly in diameter during erection.
Erection of the Musculovascular Penis
- Stallion
- Increases in diameter during erection.
- Retractor penis muscle still relaxes during erection, but no sigmoid flexure.
- Engorgement with blood plays a significant role in the highly vascular penis.
Mechanism
Erection of the penis requires:
- Elevated arterial inflow
- Dilation of corporal sinusoids
- Restricted venous outflow
- Elevated intrapenile pressure
- Relaxation of retractor penis muscles
- Engorgement of cavernous sinuses causes a blockage of venous circulation from the penis.
- Contractions of ischiocavernous muscles cause compression of the penile veins.
- Intermittent contractions of the muscles around the two crura create a pump-like action at the base of the penis.
- Result in the build up of blood within the corpus cavernosum.
- Very high pressure results.
Vascular and Biochemical Control of Erection
Anatomy
- Shaft of the Penis consists of two dorso-lateral corpora cavernosa and the corpus spongiosum.
- Arterial blood is supplied by the internal pudendal artery that supplies dorsal and deep cavernosal arteries.
- Corporal sinusoids are supplied by helicine arteries.
- Deep dorsal vein and superficial dorsal vein drain the erectile tissues.
- For more information on anatomy of the penis follow this link.
Flaccid Penis
- Sinusoids are flattened because adrenergic nerves secrete noradrenaline (norepinephrine).
Erect Penis