There are 5 stages of an erection –
- Latency phase: penis shaft starts to elongate because of constant penile intra-pressure.
- Tumescence phase: there is an increase of girth and rigidity because of the increasing inflow of arterial blood.
- Erection phase: the penis is completely elongated with the shaft pulsating, stabilization of intra-penile blood pressure and constant volume due to reduced inflow of arterial blood.
- Rigidity Phase: full girth and rigidity with penile blood pressure that can easily exceed the rest of the body’s systolic blood pressure. There is only minimal inflow of blood but no outflow.
- Detumescence phase: there is a loss of rigidity, also penis volume and blood pressure is reduced as blood outflows back to the abdomen. The penis will gradually return to its flaccid state.
Types of Erections
There are three different types of erection –
- Reflexogenic erections will occur when the genital area is stimulated through direct contact.
- Psychogenic erections happen when neurotransmitters are released into the brain following erotic stimulation, e.g. viewing pornography. These transmitters include nitric oxide and dopamine.
- Nocturnal erections as the name suggests, occur at night when asleep, and are usually the result of erotic stimuli, e.g. an erotic dream, and as in psychogenic erections, happen after the release of neurotransmitters into the brain.
Angle of Erection
The erect penis rests at an angle that is determined by the size of the penis and its attachment to the surface of the pubic bone by suspending ligaments. In those males with a long and heavy penis, or those men with a loose suspending ligament, the angle will usually not be greater than ninety degrees, even when the penis is fully rigid.
Depending on the nature and intensity of genital stimulation, several spinal reflexes can be produced. The most common of these is the bulbocavernosus reflex. Although this muscle impairment may not affect penile erection, the relevance of obtaining this reflex in erectile dysfunction assessment is still quite controversial.