Human Reproduction
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Primary sex organ :
Essential organs which form the gametes. In males, the gamete forming organs are the testes. In females,
the corresponding organs are ovaries.
The male gamete is spermatozoon. The female gamete is ovum.
Secondary sex organ :
These organs form the passage for the gametes to help the union of male & female gametes.
In male these include epididymis, vas deferens, seminal vesicles, prostate, bulbourethral glands & penis etc.
In female these organs are fallopian tube, uterus and vagina, bartholin gland etc.
Development of Sex organ :
During intra uterine life (IUL) testis & ovary develop from mesoderm. They develop in abdominal cavity. At the
time of birth, testes descend down into scrotal sac but ovaries remain in abdominal cavity.
MALE REPRODUCTIVE SYSTEM
* In man, one pair testes are the main or primary reproductive organ. Size 4-5 cm × 2-3 cm
* Both testes are located in a small bag like structure situated below & out side the abdominal cavity called as scrotum
or scrotal sac. The temperature of scrotum is 2 – 2.5°C lesser than body temperature.
* Internally scrotum is lined by dartos muscle and spermatic fascia.
Dartos muscle helps in regulation of the temperature with in the scrotum during cold season,
It becomes contracted in cold & during warm season, it becomes relaxed.
Cremaster muscles line inside the wall of scrotal & inguinal canal region and help in elevation of testes.
* Each testis is attached to the walls of the scrotal-sac through flexible, elastic fibres. This group of fibres is called
Gubernaculum or Mesorchium.
* Each testis is attached to the dorsal body wall of the abdominal-cavity through a cord termed as the Spermatic-
cord. This cord is made up of elastin fibres & spermatic fascia. The contents of cord are vas deferens, gonadal
veins, gonadal arteries, nerves and lymphatics.
During embryonic stage, testes develop in abdominal cavity & they descend to reach the scrotum at the time
of birth. When the testes does not descend to reach the scrotum but remain in abdominal cavity at the time of
birth this conditions is called undescended testes or cryptorchidism. Such testis can not develop and
function properly and may develop malignancy.
* Scrotum is connected to the abdominal cavity through a passage termed as inguinal-canal. Through this canal
the testis descend down into the scrotal-sacs at the time of birth.
Spermatic cord in males passes through the inguinal canal.
Internal Structure of Testis :
Testis is covered by three coats.
Outer most is tunica vaginalis.
Middle coat is tunica albuginea
& inner most is tunica
vasculosa.
Tunica vaginalis has a
parietal & visceral layer. It
covers the whole testis except
it's posterior border from
where the testicular vessels &
nerves enter the testis.
The Tunica albuginea is a
dense, white fibrous coat
covering the testis all around.
The posterior border tunica
albuginea is thickened to form
vertical septum called the
Mediastinum testis
Tunica vasculosa is the inner most vascular coat of the testis lining testicular lobules.
Each lobules has 1 to 3 seminiferous tubules, which join together at the apices of the lobules to form straight
tubules or tubuli recti which enter the mediastinum.
Here they form a network of tubules called as rete testis. Rete testis fuse to form 10 to 20 efferent ductule
called as vasa efferentia or ductuli efferentes. These ductules come out from upper dorsal (posterior)
surface of testis & open into common tubules, which get highly coiled to form epididymis or ductus epididymis.
This epididymis is responsible for functional maturation of sperm.
* Total number of seminiferous tubules in each testis is about 750 to 1000
Epididymis has 3 parts :
In man it is 6m in length.
(i) Upper, highly coiled part - Caput epididymis or Globus-major
(ii) Middle part - Corpus epididymis
(iii) Basal, least coiled part - Cauda epididymis or Globus minor
Cauda-epididymis enters inside the abdominal-cavity from the scrotal-sac in the form of vas deferens or
ductus deferens. Terminal dilated part of vas deferens are called ampulla. Vas deferens and epididymis both
develop from the wolffian-duct of mesonephros. Epididymis can temporarily stores the sperms for
as long as one month and here the functional maturation of sperms takes place.
The wall of epididymis is made up of 2 layers-outer circular muscle layer and inner epithelium. Wall of vas-
deferens is also made up of 2 layers-outer circular muscle layer and epithelium. The sperms reach the abdominal
cavity due to the pulsation of the vas-deferens.
Vas deferens runs upward and enter into abdominal cavity. Both vas deferens coil around the ureter of their
respective sides and then dilate to form ampulla. Ampulla of Vas deferens of each side receives the seminal
vesicle of that side. The vas deferens now forms ejaculatory duct and opens into prostatic urethra.
1 pair of seminal vesicles are situated on dorso lateral side of urinary bladder which open seperately before
the terminal ends of vas deferens. So terminal ends of vas deferens meet to form a single ejaculatory duct in
each side
Accessory Reproductive Glands
The substances secreted by the accessory reproductive glands do not form gametes but help in reproduction, these are -
Seminal vesicle
It is formed from the Wolffian duct of the embryo. Internally, it is lined by glandular epithelium which secretes
seminal fluid. This is lubricating, transparent and jelly like substance, which makes 60–70% part of semen.
It is slightly alkaline (pH 7.3). Fructose is found in seminal fluid, it act as fuel to sperm. Fibrinogen, prostaglandin,
citrate, inositol and several proteins are also present in semen
Prostate gland
This gland is located below the urinary bladder. It is unpaired and made up of 5 lobes in man. Each lobe opens into
prostatic urethra through many fine apertures. It secretes slightly alkaline prostatic fluid which is milky, thick,
sticky or jelly like. It makes about 30% part of semen and helps in sperm activation.
The secretion of prostate gland has citric acid, calcium and phosphate, clotting enzyme and profibrinolysin are
present. The secretion of the prostate gland combines with the secretion of seminal vesicle and so the semen
gets coagulated. In the coagulated semen, the mobility of sperms is reduced and so their energy is conserved.
After some time due to fibrinolysins, semen again liquefies and in this semen now the sperms can move.. Cowper's glands
It is a pair of glands found on lateral side of urethra. It is also called as bulbourethral gland. It is situated in
membranous part of urethra & opens into penile urethra. It secretes transparent, slimy, jelly like fluid. It is
slightly alkaline (pH is 7.2). This destroys the acidity of the urethra and cleans it for the movement of sperms.
It also helps in the lubrication of the penis.
Semen – Semen = Sperm + Accessory reproductive gland fluid
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