Hello,

I think it's important for every man to understand his penis and how it actually works. So consider this Penis 101. You would be surprised at how many fellas that don't understand how an erection happens and how a weak erection could be a tell tale sign of other health issues. Enjoy!

This excerpt was taken from: https://www.netdoctor.co.uk

The penis and how it works

Reviewed by Dr John Dean, specialist in sexual medicine

What is an erection?

A man gets an erection when the penis enlarges and stiffens.

It is a complex process that happens as a result of changes within the muscles, nerves and blood vessels of the penis.

The regulation of blood flow into and out of the penis is what makes an erection possible.

1. Specialised tissues in the shaft of the penis trap blood. This increases the pressure within the penis and causes it to lengthen and then become firm.
2. Following orgasm or the withdrawal of sexual stimulation, the process is reversed. Blood flows out of the penis and back into your circulation so the penis becomes soft.

The anatomy of the penis

Corpora cavernosa: two cylindrical tissues run the length of either side of the penis. Like sponges, they are capable of filling with blood. When the penis is soft, the muscle fibres in the corpora are contracted.

Tunica: a tough outer sheath that surrounds the corpora and limits the amount they can expand. As the tunica becomes tight, blood flowing into the penis raises the pressure within it, making it hard.

Corpus spongeosum: a third cylinder of tissue between the two corpora. This contains the urethra, through which urine and semen pass out of the body. It thickens towards the tip of the penis to form the helmet-shaped glans, which is covered by foreskin in uncircumcised men.

How an erection happens

1. Touch, sights, sounds, erotic memories, fantasies etc, cause sexual excitement.
2. These stimuli increase signal output from a part of the brain called the para-ventricular nucleus.
3. These signals then pass through special autonomic nerves in the spinal cord, the pelvic nerves and the cavernous nerves that run along the prostate gland to reach the corpora cavernosa and the arteries that supply them with blood.
4. In response to these signals, the muscle fibres in the corpora relax, allowing blood to fill the spaces between them.
5. Muscle fibres in the arteries that supply the penis also relax, and there is an eight-fold increase in blood flow to the penis. The increased blood flow expands the corpora, then stretches the surrounding sheath (the tunica).
6. As the tunica stretches, it blocks off the veins that take blood away from the corpora cavernosa. This traps blood within the penis, the pressure becomes very high and the penis becomes erect.
7. During an erection pressure in the penis is at least twice the pressure of blood in the main circulation. This is possible because the muscles of the pelvic floor contract around the base of the corpora cavernosa.
8. At orgasm, the signalling from the brain changes dramatically. There is a sudden increase in noradrenaline production from nerves in the genitalia. This seems to both trigger orgasm and contract the muscle fibres in the corpora cavernosa and their supplying arteries.
9. The pressure within the corpora drops, which also relaxes the tunica and so allows blood to flow out of the penis.

The inability to get or sustain an erection can happen as a result of one or more of these processes breaking down. Fortunately, there are treatments available for erectile dysfunction.