Anatomy of a Healthy Erection – How It Works

Article by Alice Brown

Achieving and maintaining a healthy, firm erection throughout sexual activity is among the most wonderful experiences a man can have in his life. It reaffirms his identity, virility, ability to pleasure his partner and himself, but most importantly, his ability to naturally father a child.

So how does it all work? What magic causes the penis to stiffen, sensitivity to heighten, and climax in ejaculation and exquisite sexual pleasure? First, some penis anatomy is in order…

Penis Structure

The penis is composed of three primary components that account for much of its shape and size: a pair of parallel spongy columns called the corpus cavernosum; and the lower-central corpus spongiosum, which contains the urethra, the tube that carries urine from the body, and transports semen during ejaculation.

All three regions are made up of erectile tissue, comprised of many tiny blood vessels called cavernous sinuses. The sinuses are surrounded by smooth muscles and supported by elastic fibrous tissue.

As with all vital body organs, a system of arteries delivers blood to the penis from the heart, and a similar system of veins return blood from the penis back to the heart.

At its very essence, an erection is a hydraulic event. Blood is pumped into the penis, causing it to swell and become firm and erect. As one might expect however, this action requires an amazing orchestration of body mechanisms to achieve. During the flaccid (non-erect) state, the cavernous arteries leading to the cavernous sinuses contract, reducing the inflow of blood. The smooth muscles regulating the many tiny blood vessels within the penis also contract.

The initial trigger of an erection starts in the man’s brain and involves the nervous and vascular systems. Sensory input-sight, smell, touch, or even a memory-transmits electrical signals of sexual excitement. When a man becomes aroused, his central nervous system stimulates the release of a number of chemicals (neurotransmitters, e.g., epinephrine, acetylcholine, nitric oxide) that relax the smooth muscles in the penis, allowing blood to flow into the tiny sinuses, or caverns, and flood the penis.

These signals travel from the brain to the lower part of the spinal cord, sending signals to the corpus cavernosa nerves (also known as cavernous nerves), which direct the cavernous arteries to let blood into the penis causing an erection.

The amount of blood in the penis increases six-fold during an erection. The spongy chambers nearly double in diameter due to the increase in blood flow, increasing penile girth, width, and hardness. As the veins surrounding the corpa cavernosum and corpus spongiosum are closed by the pressure of the erectile tissue, they are unable to drain blood out of the penis, causing it to remain rigid.

As men are well aware, direct genital stimulation can also produce an erection, but involve different nerve pathways. In this case, the sensory input is carried by the pudendal nerve, which runs from the penis to nerves in the lower spine. These nerves send messages that cause the arteries in the penis to admit blood.

Obviously, an erection is temporary in duration. Additional sensory input -usually an orgasm, but possibly a distraction, interruption, disinterest, or even cold temperature – brings an erection to an end. This occurs when the chemical messengers that started and maintained the erection stop being produced and other chemicals destroy the remaining messengers. Blood seeps out of the caverns of the corpora cavernosa, allowing the veins in the penis to reopen and drain blood from the penis.

The Prostate

The main function of the prostate is to produce a special milky fluid that is combined with the sperm during ejaculation. The sperm is made in the testicles and is delivered to the urethra during orgasm. Prostatic fluid contains a number of substances, including minerals, proteins, enzymes and a substance called prostatic specific antigen (PSA). These substances help the movement of the sperm through the urethra and the unfriendly environment of the vagina. They also nourish the sperm and keep it liquid by preventing it from becoming too sticky. PSA is especially useful in this regard. The prostate is made up of about 30% muscular tissue; the rest is glandular tissue. The term PSA may be familiar to some as PSA screening is relied upon as an indicator of possible prostate cancer.