External Male Reproductive Anatomy

Male Reproductive Anatomy

This is a posterior view of male anatomyThe study of the structure of the human body.. Let’s begin by thinking about the purpose of the male reproductive organs—which is to make and deliver sperm. Sperm is produced in the testis from cell divisions of the stem cell. Once made, sperm is stored in the epididymis. This structure looks like a bubbly formation. It is sort of like half a wig sitting atop the testis.  Sperm is then transported via the ductus or vas deferens to the urethraThe tube that carries urine from the bladder to the outside of the body. and out through the external urethral orifice.  Along the way, accessory organs contribute fluids and solutes to the interstitial fluids to create semen. 

The Scrotum

The scrotum is essentially a fleshy pouch that contains the testes. It is divided into right and left chambers by a septum, called the raphe.  The left testis usually hangs lower than the right, but I sincerely forget why right now.  Sorry.

From superficialNear the surface of the body. to deepAway from the surface of the body., the layers of the scrotum include:

Scrotal skinThe body’s largest organ, providing protection and regulation. is the outermost covering.  This skin has more sebaceous glandsOil-producing glands in the skin that secrete sebum., dark pigmentation and has vellus or fine hair on it.  The dartos muscle is just deep to the scrotal skin and contracts to wrinkle the skin and reduce heat exchange.  The scrotal fascia, a connective tissue layer, separates the dartos muscle from the cremaster muscle.  The cremaster muscle pulls the testes and spermatic cord closer to the body when it’s cold. 

Spermatic Cord

The spermatic cord is a significant anatomical structure that people often don’t learn about until a class like this. It’s a bundle that includes nerves, arteriesBlood vessels that carry oxygenated blood away from the heart (except pulmonary arteries, which carr, veinsBlood vessels that return deoxygenated blood to the heart (except pulmonary veins, which carry oxyge, and the ductus deferens. The spermatic cord punches through the abdominal wall and suspends the testis outside of the body, into the scrotum.

Inside the spermatic cord is the genitofemoral nerve, which includes both sympathetic and parasympathetic fibers. The sympathetic fibers that cause ejaculation come from the T10 T11 level of the spinal cordThe central nervous system structure that relays signals between the brain and body..  They direct vasomotion to regulate blood flow to the testes. 

Vascularizing the testes, the veins and arteries within the cord form something called the pampiniform plexus. This plexus regulates the temperature of the testis, which needs to be lower than body temperature for correct sperm developmentThe process of growth and differentiation.. If the testes are held too close to the body, sperm may not develop properly. The little tails (flagellaLong, whip-like structures used by some cells (e.g., sperm) for movement.) may be impaired.

The pampiniform plexus helps maintain testicular temperature through a heat exchange process. Hot arterial blood traveling toward the testis transfers heat to the cooler venous blood traveling back to the body. This process keeps the testis cooler overall.

All the Urethras

I need you to create a mid-sagittal view with me.  Here, are the testes.  This is the pubic symphysisCartilaginous joint connecting the two pubic bones at the midline. and here is the bladderA muscular organ that stores urine before excretion..  The vas deferens extends from the testes. It goes up through the spermatic cord and moves anteriorThe front of the body or toward the front when standing in the anatomical position. to the pubic symphysis. Then, it travels across the superiorAbove or toward the upper part of the body. wall of the bladder and across the posterior wall of the bladder. Finally, it goes below the pubic symphysis to join with the urethra.  That is a long route.  The urethra is divided into different sections. First, there’s the ejaculatory duct, which is where the ductus deferens joins with structures near the urinary bladder. The sperm passes through the membranous urethra. It continues through the spongy urethra. Finally, it exits through the external opening of the urethra.

Testes Descent

A structure called the gubernaculum is a connective tissue anchor that secures the testes to the abdominal-pelvic cavity floor.  The gubernaculum passes between the internal and external obliqueFlexor Runs vertically along belly; flexes spine, the ‘six-pack’ muscle. muscles. It enters the inguinal canal, which is anterior to the pubic symphysis.

At 6 weeks, the testes start descending.  At month 7, they will pass through the inguinal canal. The spermatic cord will develop from tissue of the internal obliqueFlexor / Rotator Under external oblique; helps twist and compress abdomen..  Undescended testes is called cryptorchidism.