What is an Erection? What is Erectile Dysfunction?
Anatomy and physiology of an erection and what is erectile dysfunction?
The next few blog post series will focus on those with a penis. This is a multi part blog post. Part 1 will focus on the what is erection and how to get an erection, second part 2 will focus on what is ejaculation, and part 3 will focus on orgasm. After discussing this, we will discuss what is premature ejaculation? And then what is erectile dysfunction? And what are treatments for erectile dysfunction? Lots of interesting topics to look forward to for the next few months, so stay tuned!
Pants with banana as an erection
Pelvic Floor Anatomy of those with a penis
Erections are an interaction between blood vessels (engorgement and then compression to maintain erection), muscle contraction (muscles further increase pressure in the penis), and the nervous system (including nerves in the pelvis, nerves within the spinal cord, and the brain). Penile erection can happen with input through visual and audio stimuli which is processed from the brain through the spinal cord and to the penis and/or can happen with stimulation and touch through the genitals themselves. Pending on the mode of stimulation, determines the type of neuronal pathway involved in erection. It is a complex interplay between the nervous system, though, this is an advanced conversation for another time.
Sexual stimulation, whether by touch, smell, or through audio/visual stimulus results in a series of events triggering the events of an erection. The penis is composed of tissue at the base (closest to the body) and along the shaft of the penis that participate in erection. During arousal, the arteries dilate and expand allowing for an influx of blood flow. As blood floods the penis, it is trapped by expanding sinusoids. Sinusoids are a complex series of blood vessels in the corpora cavernosa, which is important erectile tissue in the penis. As arousal continues, specific blood vessels are compressed which prevents fluid from leaving the penis As the penis becomes erect, the penile tissue continues to stretch which further compresses the vascular supply in the penis and keeps fluid in the penis contributing to an erection.
While blood vessels are occluded, pressure rises in the penis and raises it into a fully erect position. There is a further increase in pressure from contraction of the pelvic floor muscles, specifically the ischiocavernosus and bulbocavernosus.
The angle of an erect penis is determined by the size of penis, the attachments of the roots of the penis to the ischial rami, and the attachment of the suspensory and funiform ligament to the pubic bone. Due to the anatomy of the ligaments or a longer and thus heavier penis, may affect the angle of an erect penis; thus it may be directed more to one side over the other or it may not reach 90 degrees when fully erected. This is completely normal and can be attributed to anatomical differences between people.
Erections can happen under three types of stimulation: psychogenic, reflexogenic, and nocturnal.
Psychogenic: result of audio or visual stimuli or thoughts of a fantasy
Reflexogenic (reflex) erection: produced by touching of the genitals
Nocturnal (night) erection: occurs during Rapid Eye Movement (REM) sleep which explains why erections may occur in the middle of the night or upon waking in the morning
Picture of person sleeping to emphasize REM erections.
NEXT UP: ERECTILE DYSFUNCTION
References
Dean RC, Lue TF. Physiology of penile erection and pathophysiology of erectile dysfunction. Urol Clin North Am. 2005;32(4):379-v. doi:10.1016/j.ucl.2005.08.007