Getting to grips with the male reproductive system

The male reproductive system is a group of organs and glands that make sperm and move it out of the body during sex. It includes the penis, scrotum, testicles, epididymis, vas deferens, seminal vesicles, prostate, Cowper's glands and urethra, and each part has its own job in erections and ejaculation.

What is the male reproductive system?

The male reproductive system is the group of organs and glands that produce sperm and make sex and ejaculation possible (Sam & LaGrange, 2023). Here's what each part does, at a glance.

Source: (Sam & LaGrange, 2023)

The penis

The penis has two jobs: passing urine out of the body, and enabling sex through erection and ejaculation (Sam & LaGrange, 2023). It has three main parts: the root, the shaft (also called the body), and the glans, or head (Sam & LaGrange, 2023). The root is the part you can't see. It sits inside the body, between the legs, and anchors the penis in place. The urethra is a tube that runs through the inside of the penis (Sam & LaGrange, 2023).

Blood flow drives the mechanics of an erection itself. If you want the full picture of how an erection actually happens, that's covered in our guide to erectile dysfunction.

The glans and the crown (corona)

The glans is the tip of the penis, sometimes called the head (Sam & LaGrange, 2023). The corona, or crown, is the rounded ridge where the glans meets the shaft (Sam & LaGrange, 2023). This area is packed with nerve endings, which is why it's so sensitive during sex. Some men find that always using a very tight grip during masturbation gets them used to one kind of touch, so other touch can feel less intense for a while. There's little evidence that this causes lasting nerve damage or permanent loss of feeling. We cover this pattern in our guide to desensitization from grip pressure.

The foreskin and frenulum

The foreskin covers the glans in men who aren't circumcised (Sam & LaGrange, 2023). Some men have it removed in infancy or later, for medical, cultural, or religious reasons. The frenulum sits on the underside of the penis and connects the foreskin to the glans (Sam & LaGrange, 2023).

The urethra and urinary meatus

The urethra runs through the inside of the penis and carries urine out of the body (Sam & LaGrange, 2023). During ejaculation, it carries semen out too. It ends at the urinary meatus, the small opening at the tip of the penis (Sam & LaGrange, 2023).

The scrotum and testicles

The scrotum is a sac of skin that holds the testicles and helps keep them at the right temperature for making sperm (Garcia & Sajjad, 2023; Ivell, 2007). Sitting pressure on this area, like the kind caused by long cycling sessions, can affect that temperature balance and blood flow. We cover how prolonged pressure on the perineum affects erections in more detail in our cycling guide.

Why do testicles need to stay cool?

Sperm production works best when the testicles sit a few degrees below core body temperature (Ivell, 2007). The cremaster muscle handles the adjustment. It contracts to pull the testicles closer to the body in the cold, and relaxes to let them hang further away in the warmth (Tiwana & Leslie, 2023; Garcia & Sajjad, 2023). The dartos muscle, a thin layer of muscle just under the skin of the scrotum, helps too (Garcia & Sajjad, 2023). It tightens the scrotal skin when it's cold and loosens it when it's warm (Encyclopaedia Britannica, 2026).

The epididymis

The epididymis sits behind each testicle and is where sperm matures (Tiwana & Leslie, 2023). It's also a common site for small lumps and cysts, and these are very common and usually harmless, affecting roughly 1 in 3 adult men (Tiwana & Leslie, 2023; Cleveland Clinic, 2023). Once a doctor has confirmed a lump is an epididymal cyst, you can relax: these cysts are harmless and don't turn into testicular cancer (Cleveland Clinic, 2023).

But you can't tell what a lump is from where it sits or how it feels. Testicular cancer often shows up as a lump in the testicle itself (American Cancer Society, n.d.). So any new or unexplained lump in the scrotum needs a doctor to check it, usually with a physical exam and sometimes an ultrasound scan (Cleveland Clinic, 2023).

The prostate and reproductive glands

Several glands add fluid to semen and support both ejaculation and pleasure.

What does the prostate do?

The prostate is roughly the size of a walnut and produces fluid that helps sperm survive (National Institute of Diabetes and Digestive and Kidney Diseases, 2016; Singh & Bolla, 2023). Some men find pressure on the prostate pleasurable, and for them, stimulating it can help trigger orgasm. Experiences vary, and most of the evidence so far comes from personal reports and case studies rather than controlled research (Levin, 2018).

If you notice changes in this area alongside other common erectile dysfunction symptoms, mention them to a doctor.

Seminal vesicles and the vas deferens

The seminal vesicles sit behind the bladder, above the prostate, and produce fluid that becomes part of semen (Singh & Bolla, 2023). The vas deferens is the tube that carries sperm from the epididymis toward the seminal vesicles and ejaculatory ducts during ejaculation (Sam & LaGrange, 2023).

Cowper's glands and pre-ejaculate

Cowper's glands, also called the bulbourethral glands, sit near the base of the penis (Akita et al., 2021). During arousal, they release pre-ejaculate, often called precum, which helps clear and lubricate the urethra before ejaculation.

When to get something checked

Many lumps in the scrotum turn out to be harmless. Some can be caused by an infection, like epididymitis (MedlinePlus, 2024), or by testicular cancer or another condition that needs treatment. See a doctor if you notice a new lump, swelling, or a change in the size or shape of a testicle (American Cancer Society, n.d.).

Sudden, severe pain in a testicle needs emergency medical care, especially if it comes with swelling, nausea, or vomiting (MedlinePlus, 2025). This can be a sign of testicular torsion, where a testicle twists and cuts off its own blood supply (Garcia & Sajjad, 2023).

If you're due a check-up, our guide to what a doctor checks during an ED diagnosis explains what to expect.

Understanding your body, understanding your erections

Knowing how your body works is a good starting point for understanding your erections. The Erection Reset, built with Dr. Shannon Chavez, a clinical psychologist and sex therapist, helps you learn how sexual function works. It also helps you explore the psychological factors, like stress and performance anxiety, that can affect erections.