Explanation of the different parts of the penis
The penis is the external male sexual and urination organ. It is
made up of three columns of erectile tissue and it relies solely
on engorgement with blood to reach its erect state during sex.
The erectile tissues are called "corpus spongiosum" and "corpus
cavernosum". The "corpus spongiosum" lies on the underside of
the penis, while the two "corpora cavernosa" columns lie next to
each other on the upper side. The end of the corpus spongiosum
is enlarged and cone-shaped and forms the glans penis. The glans
supports the foreskin (or prepuce), which is a loose fold of
skin that in adults can retract to expose the glans. The area on
the underside of the penis, where the foreskin is attached, is
called the frenum.
The urethra, which is the last part of the urinary tract,
traverses the "corpus spongiosum" and its opening, known as the
"meatus", lies on the tip of the glans penis. It is both a
passage for urine and for the ejaculation of semen. Sperm is
produced in the testes and stored in the attached epididymis.
During ejaculation, sperm is propelled up the vas deferens, two
ducts that pass over and behind the bladder. Fluids are added by
the seminal vesicles and the vas deferens turns into the
ejaculatory ducts, which join the urethra inside the prostate
gland. The prostate and the bulbourethral glands add further
secretions, and the resulting semen is expelled through the
penis.
The final feature of the penis is the raphe, which is the
visible ridge between the lateral halves of the penis, found on
the underside of the penis, running from the meatus (opening of
the urethra) across the scrotum to the perineum (area between
scrotum and anus).