The Basics of the Origin of Life - Male
Male Sperm Production
are the essential sex organs (gonads) in the male that serve
to produce the male gametes (sperms) and the male sex
hormone testosterone. The accessory male reproductive glands
aid in the maturation, nourishment and transport of the
sperms through the male reproductive system and into the
female's body for fertilization. Unlike the female
reproductive structures that are located within the pelvic
cavity, the male reproductive organs lie outside the
abdomen. The male reproductive structures and their
locations are shown in the figure.
The testes and scrotum
The testicles lie outside of the abdomen, suspended
in a fleshy sack called the scrotum. Testes are made
from the same embryonic material that becomes the
ovaries in the female. The testes develop within the
abdomen, but about two months before birth they
descend through the abdominal wall into the scrotum.
The testes are connected to the body through scrotal
tissue and two spermatic cords that are composed of
nerves, blood vessels and the vas deferens, or sperm
The functions of the testes are to produce sperm and
the male sex hormone testosterone. In order to
produce and nurture sperm, the temperature within
the testes must remain approximately 1-2�C cooler
than normal body temperature. Part of the function
of the scrotum is to maintain this optimal
temperature by holding the testes further from the
body during warm weather or contracting and bringing
them closer to the body during cold weather.
The testes are composed of narrow, tightly coiled
structures called seminiferous tubules. The testes
also contain interstitial Leydig's cells and
Sertoli's cells. The Leydig cells produce
| The Sertoli cells nurture the immature sperm by mechanically supporting and protecting them until they can reach maturity and are released into the tubules. Sertoli cells also play an active role in releasing the mature sperm into the tubules.
The various structures within the testes are shown in the following cross-sectional diagram.
epididymis is a tightly coiled tube located on the
top of the testes. Stretched out, it would measure
metres in length. The sperm are stored in the
up to 2 weeks where they mature, develop motility
capable of fertilisation.
|The vas deferens is a long curving tube that begins at the tail end of the epididymis and rises out of the scrotum into the abdominal region. It then passes over the urinary bladder and connects to the seminal vesicle in the pelvic region to form the ejaculatory duct. Besides functioning as part of the sperm transport system, it also acts as a storage site for most of the sperm produced until ejaculation. The entire process of sperm maturation,
from their primitive beginnings in the seminiferous tubules to their fully mature form in the vas deferens, takes about 74 days.
vesicles are two pouches located in the pelvic region behind
the urinary bladder. Their primary purpose is to supply a
viscous, alkaline secretion that forms a part of the seminal
fluid. Seminal fluid is often referred to as semen and
includes secretions from the seminal vesicles, prostate and
bulbourethral glands, as well as sperm cells. The seminal
vesicles supply about 30% of the seminal fluid volume. The
fluid from the seminal vesicles is rich in nutrients,
including citric and amino acids and fructose to provide an
energy source for sperm metabolism and to enhance sperm
gland, the largest of all the male reproductive glands, is
chestnut-sized and located just below the bladder, near the
exit of the urethra. The prostate contributes about 60% of
the seminal fluid, secreting a thin, milky-white alkaline
fluid similar to that of the seminal vesicles. The fluid is
discharged into the urethra during ejaculation to help
neutralise the acidic fluids in the male urethra and the
female vagina. This function is important because acids can
have an adverse effect on sperm and, at higher
concentrations, can kill them.
ejaculatory ducts are two short tubes that descend through
the prostate gland and into the urethra. They are formed by
the union of the vas deferens and the ducts of the seminal
vesicles. The following figure shows the formation of the
is a tube running from the bladder through the prostate
gland to the end of the penis, forming the final section of
the seminal fluid passageway. The urethra functions as the
exit point for both semen and urine. The closing of muscular
sphincters automatically blocks the flow of one process when
the other is occurring.
bulbourethral glands (sometimes called Cowper's glands) are
two pea-sized glands located just below the prostate. They
also secrete an alkaline fluid, although it amounts to less
than 5% of the seminal fluid volume.
|The penis is
the male organ through which both sperm and urine pass from
the body. It is covered by a loose layer of skin and is
composed of sponge-like erectile tissue containing large
sinuses interspersed with veins and arteries. During sexual
stimulation, the arteries dilate and the penis becomes erect
as the spongy tissues fill with blood. The tissue at the end
of the penis forms the glans penis. In an uncircumcised
male, a fold of loose skin called the foreskin covers the
glans penis. In the process of ejaculation, the penis
delivers sperm contained in seminal fluid into the female's
body for fertilization of the ovum.
Summary of Male Reproductive System
that follows summarizes the organs of the male reproductive
|Organs of the male reproductive system
||Two oval-shaped glands located outside of the abdomen Considered essential male sex organs.
||Produce sperm cells and testosterone.
||Loose sack of skin containing the testes.
||Holds testes Maintains proper temperature in the testes.
||Two cords attached to the testes.
||Help attach testes to scrotum Function as sperm ducts.
||Tightly coiled tube on top of testes.
||Sperm stored here to mature.
||Long curved tube running off the epididymis into abdominal region.
||Sperm storage and transport.
||Two pouches located in pelvic region behind bladder.
||Produce elements of seminal fluid, which transports and nourishes sperm.
||Chestnut-sized gland located below the urethra.
||Produces elements of seminal fluid, which transports and nourishes sperm.
||Two short tubes descending through the prostate gland into the urethra.
||Form merger point between the vas deferens and the seminal vesicle.
||Tube running from the bladder through the prostate to the end of the penis.
||Final portion of sperm transport system. Also carries urine from body.
||Also called Cowper's glands Two pea-sized glands located below the prostate gland.
||Secrete small amounts of seminal fluid.
||Male sex organ extending out from the abdomen and comprised of erectile tissue, blood vessels and sinus cavities
||Delivers sperm into the female's body. Eliminates urine from the body.