The screen shows a side view of a naked male body from the abdomen to just below the knees.
Sperm are produced and released by the male reproductive organs.
A box around the pelvis expands to show a cross section of the male sexual organs.
The testes are where sperm are produced.
The testes are linked to the rest of the male reproductive organs by the vas deferens,
which extends over the base of the pelvic bone or ilium,
and wraps around to the ampulla, seminal vesicle, and prostate.
The urethra then runs from the bladder through the penis.
Sperm production in the testes takes place in coiled structures called seminiferous tubules.
A close up shows six chambers with coiled seminiferous tubules
attached to the back wall of the testis.
Outside the wall is a layer of fleshy tissue.
Along the top of each testicle is the epididymis.
This is a cordlike structure where the sperm mature and are stored.
The image reverts to the original cross section.
As the sperm's movement is described, the parts mentioned are highlighted.
The release process starts when the penis fills with blood and becomes erect.
Continuing to stimulate the penis will cause an ejaculation.
Mature sperm begin their journey by travelling from the epididymis to the vas deferens,
which propels sperm forward with smooth muscle contractions.
The sperm arrive first at the ampulla just above the prostate gland.
Here, secretions from the seminal vesicle located next to the ampulla are added.
The ampulla is the enlarged end of the vas deferens.
The seminal vesicle is a small pouch feeding into it.
A small tube, or duct, connects the vas deferens to the urethra.
Next, the seminal fluid is propelled forward
through the ejaculatory ducts toward the urethra.
As it passes the prostate gland, a milky fluid is added to make semen.
Finally, the semen is ejaculated from the penis through the urethra.