What is an Erection?
An erection is where the penis fills will blood to become erect, enlarged and firm. It is caused by a complex set of processes. In order to understand these processes, it's first important to understand the anatomy of the penis.
There are three main sections or parts of the penis:
- The Root: This refers to where the penis attaches to the pelvic wall and the abdomen.
- The Shaft (or Body): This is the longest part of the penis and is the visible part that extends from the root to the head of the penis.
- The Glans (or Head): This is the cone shaped head at the top of the penis. The ridge that separates the shaft from the glans is called the corona. A loose fold of skin called the prepuce, or foreskin covers the Glans of the penis in uncircumcised men.
A look inside the body of the penis
The shaft of the penis is made up of three columns of erectile tissue, which can be seen in the diagram below.
- Corpora Cavernosum: These are the two columns of erectile tissue that run along the sides of the penis and fill up with blood during an erection. They are made up of supporting fibres called Trabeculae and Cavemosal spaces. They are partially separated by the Septum, a fibrous partition.
- Corpus Spongiosum: This is the third column of erectile tissue that runs along the front of the penis. The Urethra runs through the Corpus spongiosum, carrying urine out of the body.
- Tunica Albuginea: This is the membrane that surrounds the corpora providing a tough outer sheath.
- Deep Dorsal Vein: This vein runs the length of the penis shaft. It drains the deoxygenated blood from the glans.
- Cavemosal Artery: These are deep-paired arteries than run near the centre of each of the corpus cavernosum. They allow blood to flow to and fill the corpora.
How does an erection work?
In simple terms, an erection is the process by where blood fills the corpora cavernosum with blood causing the penis to become enlarged, elongated and firm.
For this to occur, there is a series of complex processes that need to happen, beginning in the brain. The erection process starts with mental or sensory stimulation that causes arousal.
When this happens, impulses are sent from the brain to local nerves to instruct the muscles around the corpora cavernosum to relax and allow blood flow in through the penile artery so that the penis expands. The blood flow to the penis at this point can be eight times that of normal blood flow.
At the same time, the tunica albuginea membrane around the corpora cavernosum stretches and blocks off the veins that drain the blood. The blood is now trapped in the penis, and the pressure increases allowing the penis to become, and remain, erect. At this point the blood pressure in the penis can be as much as twice that of the pressure in the rest of the bodies circulation system.
An erection is stopped when the muscles in the penis contract. The tunica contracts and opens up the channels for draining blood. The deoxygenated blood is then carried away via the deep dorsal veins and the penis becomes flaccid.
The need for an erection
An erection is required for penetrative sexual intercourse. An erection also allows for sperm during ejaculation to be deposited within a woman's vagina allowing for fertilisation of an egg. It is possible for a male to experience an orgasm or ejaculation without an erection, but it will not be possible to have full sexual intercourse without one.
The most common problem with erections is having difficulty in forming one – a condition known as Impotence or Erectile Dysfunction (ED). This condition affects several million men in the UK so it's not exactly uncommon.
Most men will experience problems with an erection from time to time, but if you are experiencing issues with getting or maintaining an erection over a number of weeks, you should consult a medical professional.
Traditionally, the causes for Erectile Dysfunction (ED) were thought to be psychological in nature. And while anxiety, stress and other psychological factors can be the cause, Erectile Dysfunction can also be a symptom of bigger physiological issues. Common physical causes include hormone imbalances and vascular conditions that can limit the blood flow to the penis – conditions such as atherosclerosis, a narrowing and hardening of the arteries.
The complications for an individual suffering from Erectile Dysfunction can be very significant and negatively impact on their life and relationships. These include:
- Anxiety and depression
- Embarrassment and low self esteem
- Relationship problems
- Dissatisfaction with sex life
There are, however, a wide range of options and treatments for people who are experiencing difficulties with erections. These include lifestyle changes, addressing underlying health and physiological factors, and oral medications such as Viagra (sildenafil), Levitra (vardenafil) and Cialis (tadalafil).