Basic Male Reproductive

Anatomy & Functions

Before moving on to the in-depth sections on the male reproductive system, it’s good to have a general overview of male hormones, male reproductive anatomy and functions.  Detailed sections on this site will dive more into the specifics about different parts of the male anatomy and how the reproductive system actually functions. So let’s start with the basics.

MALE HORMONES

The growth, development, and maintenance of male characteristics (muscle mass, body hair growth, genital growth, and sexual functions) are dictated by male sex hormones called androgens.  The most common androgen is testosterone.  A more potent androgen called DHT helps with the growth of sexual tissues and body hair and the production of sexual fluids.  The vast majority of testosterone is produced by the testicles.

shutterstock_149250950.jpg

TESTICLES & SCROTUM

The two testicles reside in a sac of skin called the scrotum.  The scrotum is loose

and hangs away from the body to help keep the testicles cooler than body

temperature.  The muscles in the scrotum relax and contract allowing the testicles to hang further away from the body when it’s warm and closer to the body when it’s cold in order to help regulate a consistent temperature for sperm production.  On the back of each testicle is a structure that feels like a soft mass – this is the

epididymis.  The epididymis is a long coiled tube that sperm pass through before

heading up the vas deferens and spermatic cord.  The vas deferens is a long tube that sperm move through after leaving the epididymis on their way to the male reproductive glands found inside the body.  The spermatic cord consists of nerves (that’s why the testicles are so sensitive), blood vessels, and the vas deferens. 

Cross Section.jpg

PENIS

The penis is the male’s main external sexual organ.  It contains three main portions – the tip, the shaft, and the root.  The bell-shaped tip of the penis is called the “glans” and is hairless and sensitive to sexual touch.  The “shaft” is the remainder of the penis that is visible as it exits the body to the base of the glans (tip).  On the upper portion of the shaft of the penis is the foreskin, a loose piece of skin that covers the glans.  Many men don’t have this piece of foreskin as it is often removed in many cultures shortly after birth in a surgery called circumcision.  Men who have been circumcised often have a band of skin on the upper shaft near the “neck” of the penis left over from the circumcision. 

The interior structures of the penis include three columns of erectile tissue that can

swell with blood to make the penis become rigid and stand upright – this is called an erection.  Two of these columns are called the corpus cavernosa and sit on either side of the back of the penis.  The third column is called the corpus spongiosum and it lies on the underside of the penis.  The urethra extends from the bladder, through the prostate, then passes through the center of the corpus spongiosum until it surfaces on the tip of the penis.  The opening of the urethra at the tip of the penis is called the urethral meatus.  The urethra is the pathway for urine, semen, and pre-ejaculate to exit the body.

 

The three columns of erectile tissue also extend inside the male body – this is called the root of the penis.  The root of the penis connects to muscles, tendons, and ligaments to help anchor the penis during an erection and to assist the penis in ejaculating semen.

Genitals.jpg

REPRODUCTIVE GLANDS

There are four main male reproductive glands – the ampulla of the vas deferens,

the prostate, the seminal vesicles, and the bulbourethral glands (Cowper’s glands).   The ampulla are the bulging ends of the vas deferens that store sperm, while the prostate and seminal vesicles make other sexual fluids that will mix with the sperm to make semen.  The bulbourethral glands produce pre-ejaculate fluid. 

Glands.jpg

SEXUAL STIMULATION & PRE-EJACULATE FLUID

Erections occur when a man is exposed to sexual stimulation.  Sexual stimulation can occur in three ways:

  • Hormonal – testosterone triggers erections to occur four to five times a night while a man is sleeping

  • Mental (also called psychogenic) – occurs when thoughts, sights, smells, or words stimulate erections and sexual excitement

  • Physical (also called reflexogenic) – occurs when nerves on the penis and scrotum are stimulated through physical touch

 

During sexual stimulation, the bulbourethral glands produce a clear, slippery liquid that is called pre-ejaculate.  It’s not uncommon in many men for a few drops of pre-ejaculate fluid to be released from the urethra prior to ejaculation.  When sexual stimulation reaches a certain threshold, ejaculation occurs.

 

EJACULATION & SEMEN

 

During ejaculation, the contents of the ampulla, prostate, and seminal vesicles empty into a space in the prostate called the ejaculatory duct, where they mix together to form semen.  Semen is a thick, white sexual fluid that contains sperm.  Ejaculation is the process by which semen is forced in rapid contractions from the reproductive glands and out of the penis.  Ejaculation occurs due to a combination of contractions from the prostate and muscle contractions in the root of the penis.  Ejaculation can occur involuntarily during sleep (wet dreams) or voluntarily through sexual stimulation.

 

Orgasm is an intense, pleasurable sensation that causes muscle contractions throughout the body, and almost always occurs at the same time semen is ejaculated. 

Images on this page from top to bottom include:

  1. CLIPAREA/Shutterstock.com

  2. Sergeant Illustration, Owned

  3. Sergeant Illustration, Owned

  4. Sergeant Illustration, Owned