Penis Anatomy

Anatomy 101: A Guide to Your Junk

Written by: Joshua Gonzalez

Penile Anatomy

Meat and potatoes, twig and berries, turkey neck and dumplings, dangly bits… That’s right folks, today we’re giving an anatomy lesson on the dick and balls. I’m always surprised by how little people know about their junk. Blame it on the Puritans if you like, but Americans in general seem very hesitant to look at their genitals, touch their genitals or talk about their genitals. If we’re lucky, we get a brief and awkward sex ed lesson in school, but most information we have comes from hearsay or the internet, which can be dubious information at best. 

Having a good understanding of the inner workings of your genitalia is a necessary part of good sexual health and good health in general. And for our conversation today, we’re going to be talking to all people with a rod and giggleberries – not just men. It’s important to note that a person’s genitals don’t necessarily translate to that person’s gender identity and vice versa. If you have a penis and scrotum, but you don’t identify as a male, this article is for you, too. We want everyone to have working knowledge of the equipment they’re carrying. 

At the risk of triggering unpleasant middle-school-science-class-like flashbacks, we’re including a couple of labeled diagrams to aid in the discussion. 

Penis Anatomy

Parts of the Penis

We don’t expect you to be a fully licensed healthcare practitioner after this penile anatomy 101 article, so we’ll try to keep our penile anatomy lesson short, sweet and easy to understand. However, the parts of the penis and balls that you know and love, are just a fraction of the amazing anatomy that makes up these sexual organs. The penis is like an iceberg in that way. We only see the tip. (Insert just-the-tip joke here). 

Most people are familiar with the parts of the penis that we see – the shaft and glans (a.k.a. the head) – but the penis actually reaches way down into the ischiopubic rami which is part of your pelvis. It’s composed of three chambers, which include one corpus spongiosum chamber, the spongy tissue that surrounds the urethra, and two corpora cavernosa chambers, the erectile tissue that fills with blood during and erection. These two chambers of corpora cavernosa are what extend down deep into the pelvis. 

In addition, the penis is home to several important neurovascular structures, including the dorsal artery and nerve, the superficial and deep dorsal veins, and the cavernosal arteries. The cavernosal arteries carry blood into the penis to fill the corpus cavernosa, which causes the penis to become erect and collapse the surrounding veins. After ejaculation, the veins carry blood from the penis back to the body, causing the penis to become soft or flaccid once more.

The urethra is a tube that runs down the underside of the penis. This is the passageway that allows urine to flow from the bladder and out of the body. The urethra also carries semen out of the body during an ejaculation. Proper hygiene is important to keep this plumbing healthy. Washing your genitals with soap and water is all it takes to keep that area so fresh and so clean. Scented powders and sprays can cause irritation, so make sure to stay away from those. If you have your foreskin intact, you’ll want to pull it back gently and wash the skin underneath so that smegma doesn’t build up and begin to irritate the area.

Anatomy of a Scrotum

Along with the penis, the scrotum makes up the remainder of the external sex anatomy. The scrotum, also called the balls or the ball sack, is what holds the testicles in place and keeps them at the right temperature. Temperature affects sperm production, so if the temperature is cold, the scrotum will pull your testicles up into your body. If the temperature is hot, the scrotum will let your testicles cool off by hanging away from your body. 

Testicles are generally the same size, but they can be slightly asymmetrical or hang at different heights, which is totally normal. However, if you see that one or both of your testicles have drastically changed size, shape or location, it’s best to get that checked out by your doctor, stat. Also, a fact that you undoubtedly know already is that the scrotum and testicles are ridiculously sensitive, so it’s important to protect your family jewels at all costs.

Another important landmark is the epididymis, a small structure located behind the testicles that transports sperm from the testicles into the vas deferens. The vas deferens is another tube that sperm into the seminal fluid.

Penile and Testicular FUNction

The penis and testicles are necessary for sexual, reproductive and urinary function – some of the most fantastic and fun functions of the human body. The penis is the primary organ for sexual intercourse. When the penis is in its aroused and erect state, it’s able to penetrate a vagina or an anus, although penetrative sex is by no means the end-all and be-all of sexual activity. The penis can take a great deal of pounding pressure, but it can be injured during sex. A penile fracture happens most often when your thrusting misses its intended target during penetrative sex. This can lead to pain, bruising, swelling, long-term deformities and erectile dysfunction, so please, be adventurous but be careful!

As if sexual intercourse and sexual pleasure weren’t enough, the penis also facilitates urination and ejaculation. Urination is simply the removal of filtered liquid waste from the kidneys and out the tip of the penis through the urethra. The urethra runs like a river through the prostate gland, and because the prostate grows as people get older, its increasing size can sometimes restrict the flow of urine. Urinary tract infections and scarring can also cause difficulties with urination, so if you have any pain, burning or changes in your ability to urinate, make sure you check in with your doctor to see what’s going on. 

Ejaculation is when semen is ejected out of the body through the penis, and it’s by far our favorite topic of conversation over here at the Popstar team. Semen contains sperm, but it’s also made up of water, plasma, mucus, calcium, lactic acid, glucose, fructose, magnesium, protein, zinc and potassium. Ejaculation is a team effort between the penis, testicles, epididymis, prostate and vas deferens. For more information on ejaculation, make sure you read the other articles in our  Sex Stuff blog and check out our Popstar supplement, which enhances ejaculatory function. 

Sperm are made in the testicles. In humans, sperm is necessary to fertilize an egg in order to make a baby. Thanks to modern medicine, the uniting of a sperm and an egg can be done in many, many different ways, so penetrative sexual intercourse is no longer necessary to conceive. In addition to housing the testes, the scrotum can also be responsible for sexual pleasure. Its sensitivity makes it one of the body’s many erogenous zones, and it can be gently aroused during sexual activity.

Protecting the Family Jewels

Your genitals are amazing in a million different ways, but occasionally things can go wrong. It’s important to be intimately familiar with your penis and scrotum so that you know how they normally look and feel. I recommend doing a self-examination about once a month to see if there are any changes. Warning signs to be on the lookout for are changes in size, swelling, pain, lumps, bumps, dark spots, lesions, cysts and redness. However, this is not an exhaustive list, so make sure to pay attention to any deviations from the norm. 

While issues that we see in my medical practice are usually benign, cancer and other serious conditions do occur. Testicular cancer is often painless, so if something seems off, but it doesn’t hurt, don’t assume that it’s nothing. Cancer often presents as a hard lump, while pain, inflammation, and/or swelling often signal an infection. Luckily your body does have natural protections like pubic hair. Although pubic hairstyles come and go, remember that this patch of fur is an important part of genitalia that actually helps to prevent against bacterial infections and irritation caused by sex. That means you might want to think twice before opting for that full Brazilian waxed look.

Other threats to your genitals come in the form of sexually transmitted infections or STIs. Common STIs include gonorrhea, herpes, human immunodeficiency virus (HIV), human papillomavirus (HPV), chlamydia, molluscum, syphilis, hepatitis and trichomoniasis. These STIs can present with symptoms of burning, discharge, lesions and pain. However, some STIs show no symptoms at all. Your best defense against STIs and penile health complications that come with them is to practice safe sex and get tested regularly. STI testing can be done at your doctor’s office or at low-cost and free health clinics nationwide. There are even at-home STI testing kits!

A Final Word

No matter what pet names you choose to use for your genitals, make sure you become acquainted with them on an intimate level. There is nothing shameful or gross about touching, feeling, looking at or examining your private parts. It’s not only important to know your bits and pieces, but it is also necessary for your overall health and wellbeing. I promise, your John Thomas and his yam bag will thank you.

Dr. Joshua Gonzalez

Dr. Joshua Gonzalez

Dr. Joshua Gonzalez is a board-certified urologist who is fellowship-trained in Sexual Medicine and specializes in the management of male and female sexual dysfunctions. He completed his medical education at Columbia University and his urological residency at the Mount Sinai Medical Center. Throughout his career, Dr. Gonzalez has focused on advocating for sexual health and providing improved healthcare to the LGBTQ+ community.