The penis is the male sex organ, reaching its full size
during puberty. In addition to its sexual function, the penis acts as a conduit
for urine to leave the body.
The internal structure of the penis consists of two
cylinder-shaped vascular tissue bodies (corpora cavernosa) that run throughout
the penis; the urethra (tube for expelling urine and ejaculate); erectile
tissue surrounding the urethra; two main arteries; and several veins and
nerves. The longest part of the penis is the shaft, at the end of which is the
head, or glans penis.
When a man becomes sexually excited, the nerves surrounding
his penis become active, causing the muscles around the arteries to relax and
more blood to flow into the penis. The sponge like material then absorbs the
additional blood, making the penis stiff and hard, or erect. This erection tightens
the veins so the blood can’t leave the penis, enabling the penis to remain
erect. After a man ejaculates or if his arousal fades, detumescence
occurs, in which the brain sends a signal to allow the blood to leave the erect
penis, and it returns to its flaccid state.
Penis anatomy is
remarkably complex. Following is the definitions for the most important parts.
1. The Corpora Cavernosa. The corpora cavernosa are two chambers that fill most of the penis. The chambers are filled with a spongy tissue that includes muscles, open spaces, veins and arteries. An erection occurs when the corpora cavernosa become engorged with blood and expand.
2. The Tunica Albuginea. A membrane called the tunica
albuginea surrounds the corpora cavenosa. This membrane helps keep blood in
the penis during an erection.
3. Urethra. The urethra is the tube through
which urine travels. Ejaculate also travels through the urethra. It runs down
the underside of the penis, beneath the corpora cavernosa and widens at its
opening, called the meatus. The meatus is located at the glans (the head
of the penis).
4. Corpus Spongiosum. The corpus spongiosum is
a chamber that surrounds the urethra. It becomes engorged with blood during an
erection.
5. The Prostate. The prostate is a small gland
located in the pelvis. It surrounds the urethra and plays an important role in
ejaculation. Sperm, which is produced in the testicles and stored in the
seminal vesicles, is mixed with prostatic fluid and secretions from the
bulbourethral gland to form semen. During ejaculation, semen is expelled
through the urethra from the ejaculatory ducts.
6. Glans (head) of
the penis. In uncircumcised men, the glans is covered with pink, moist
tissue called mucosa. Covering the glans is the foreskin (prepuce). In
circumcised men, the foreskin is surgically removed and the mucosa on the glans
transforms into dry skin. The glans serves several purposes: increasing the
chances for fertilization of an egg, creating extra friction during sex, and
acting as a shock absorber within the vagina during intercourse.
7. Corona. The 'crown,' a ridge of flesh demarcating
where the head of the penis and the shaft join.
8. Frenulum, Frenum. A thin
strip of flesh on the underside of the penis that connects the shaft to the
head.
9.
Smegma. A substance with the texture of cheese secreted by glands on each
side of the frenulum in uncircumsized men.
10. Scrotum. The scrotum is a sac
that hangs behind and below the penis, and contains the testes (testicles), the
male sexual glands. The scrotum's primary function is to maintain the testes at
approximately 34 C, the temperature at which the testes most effectively
produce sperm.
11. Testes, Testicles. The
male sexual glands, the two testes within the scrotum produce sperm and
testosterone. Within each testis is a kilometer of ducts called the seminiferous
tubules, the organs which generate sperm. Each testicle produces nearly 150
million sperm every 24 hours.
12. Epididymis. The epididymis
is a 'holding pen' where sperm produced by the seminiferous tubules mature. The
sperm wait here until ejaculation or nocturnal emission.
13. Vas Deferens. The ducts
leading from the epididymis to the seminal vesicles. These are the ducts that
are cut during the procedure known as vasectomy.
14. Seminal Vesicles. The
seminal vesicles produce semen, a fluid that activates and protects the
sperm after it has left the penis during ejaculation
15. Prostate Gland. Also
produces a fluid that makes up the semen. The prostate gland also
squeezes shut the urethral duct to the bladder, thus preventing urine from
mixing with the semen and disturbing the pH balance required by sperm.
17. Cowper's Glands. The
Cowper's glands secrete a small amount of pre-ejaculate fluid prior to orgasm.
This fluid neutralizes the acidity within the urethra itself.
What's the average size of the penis?
In European medical literature, the average penis length is
between 7.5 cm and 10.2 cm, with a diameter of 3.2 cm. Erect, a penis will
usually be between 12 cm and 17 cm long and nearly 4 cm thick. Length when
erect is not proportionate to length when flaccid. According to Mandens
Krop, the average is 15 cm and 90% are between 13 cm and 18 cm. However, there
are medical records for fully functional penises from 1.5 cm to 30 cm in length.
In American medical literature, the average penis length is
between 5.1 and 5.7 inches (based on the data provided by Alfred C. Kinsley
Institute).
If you still think, after all these years and sexual experience,
that the penis size is too important, think about the fact that the normal vagina
is only eight to thirteen centimeters long, and even a small penis can touch
every square centimeter within the vagina.
What’s about erection
angle?
The direction the erect penis points depends on anatomy and
is not related to penile rigidity or firmness. The majority point upwards
or straight out, but a sizeable minority just point downwards. There is no
medical information that women prefer one over the other. The variation in the angle depends on the size and tension
of the ligaments holding the base of the penis. If they are tight, the
penis will point up, if not then it points down. When it loosens, the support
drops and the erection angle becomes less which typically
happens with age.
Sources and Additional
Information:
