Human Reproduction
Introduction-
- Humans are sexually reproducing and viviparous
- Sequence of reproductive events → gametogenesis (sperm and ovum) →
transfer of the gametes into the female genital tract (insemination) →
fertilisation, leading to the formation of the single-celled zygote →
development of the zygote leading to the formation of the blastocyst →
implantation of the blastocyst in the uterine wall → further development of
the blastocyst (gestation) → parturition → lactation
+ Sperm formation continues even in old men, but the formation of ova
ceases in women at around 50 years of age.
Primary Sex Organs-
● These are the ones which are directly concerned with the formation of
gametes and the secretion of sex hormones.
Secondary / Accessory Sex Organs-
● These organs neither produce gametes nor secrete hormones, but are
concerned with the transfer and meeting of gametes
Male Reproductive System-
● The male reproductive system is located in the pelvic region
Scrotum-
- The testes are situated outside the abdominal cavity within a pouch called
the scrotum. This pouch is suspended from the groin.
- The scrotum has two compartments formed due to a scrotal septum, which
is visible externally as the ‘raphe’
- Each compartment contains one testis.
- The testes are located in the scrotum as the temperature there is 2-2.5℃
lower than the normal body temperature, which is necessary for
spermatogenesis.
- The scrotum remains connected with the abdominal cavity by the inguinal
canals.
- The testes are suspended from the body wall by a spermatic cord through
the inguinal canal.
- Each spermatic cord contains the vas deferens, testicular artery, testicular
veins, and testicular nerve.
- Scrotal skin → dartos muscle → cremaster muscle, which is more abundant in
the spermatic cord.
, - The testes are then attached to these layers with the help of ‘gubernaculum’,
which is made up of a fibrous tissue + fat.
- These muscular layers help in the regulation of temperature inside the
scrotum.
Testes-
● In adults, each testis is oval in
shape
● 4-5 cm in length, 2-3 cm in
width
● The testis is covered by a
dense covering made up of 3
layers → tunica vaginalis,
tunica albuginea, and tunica
vasculosa.
● Each testis has around 250
testicular lobules.
● Each lobule contains 1-3
seminiferous tubules in
which sperms are produced.
● Seminiferous tubules → tubuli
recti → rete testis → vasa efferentia → epididymis.
Epididymis-
+ The epididymis is a large coiled tube consisting of a head (caput), body
(corpora), and tail (caudal)
+ The epididymis is the site of sperm maturation.
+ It is also the place where sperms become motile and acquire the capacity to
fertilise an ovum
It also serves to store sperm temporarily.
Vas Deferens-
- The epididymis leads to the vas deferens which ascends to the abdomen and
loops around the ureter, over the urinary bladder.
- From here, near the bladder, the vas deferens dilates to form an ‘ampulla’
which receives the duct of the seminal vesicles, together forming the
ejaculatory duct.
- The ejaculatory duct opens into the prostatic urethra.
- The main function of the vas deferens is to convey sperm during sexual
arousal from the epididymis towards the urethra by the peristaltic
contractions of its muscular wall
, - The ampulla of the vas deferens also acts as a reservoir of sperms. (NOT OF
SEMEN)
Male Accessory Glands-
Seminal Vesicles-
+ Seminal vesicles are paired glands which lie at the dorsolateral sides of the
base of the urinary bladder.
+ These glands secrete an alkaline viscous fluid, called the seminal fluid
rich in fructose, fibrinogen, prostaglandins, etc.
+ About ⅔ volume of the seminal plasma is secreted by the seminal vesicles.
Prostate Gland-
+ The prostate gland lies below the urinary bladder
+ The alkaline, milky secretion of this gland makes up around ⅓ of the total
volume of the seminal plasma.
+ The secretion of the prostate gland enters the prostatic urethra through
several tiny ducts.
+ The prostatic fluid contains calcium (milky), clotting enzymes, and
profibrinolysin.
Bulbo-urethral Glands-
+ The paired bulbo-urethral glands are located on either side of the
membranous urethra, but their ducts open into the penile urethra.
+ During arousal, these glands secrete an alkaline fluid into the urethra which
protects the passing sperm by neutralising the acidity of the urethra from
urine and also serves to lubricate the penis.
During a single ejaculation:
→ 200-300 million sperm are released.
→ for normal fertility, 60% must have normal size and shape
→ at least 40% of them must show vigorous motility.
Azospermia → absence or near absence of sperms in semen
Asthenospermia → reduced motility of sperms in semen
Penis-
● The enlarged end of the penis is called the ‘glans penis’ which is covered by a
loose fold of skin called the ‘foreskin’ or ‘prepuce’.
● The opening of the urethra to the outside through the penis is called the
urethral meatus.
Introduction-
- Humans are sexually reproducing and viviparous
- Sequence of reproductive events → gametogenesis (sperm and ovum) →
transfer of the gametes into the female genital tract (insemination) →
fertilisation, leading to the formation of the single-celled zygote →
development of the zygote leading to the formation of the blastocyst →
implantation of the blastocyst in the uterine wall → further development of
the blastocyst (gestation) → parturition → lactation
+ Sperm formation continues even in old men, but the formation of ova
ceases in women at around 50 years of age.
Primary Sex Organs-
● These are the ones which are directly concerned with the formation of
gametes and the secretion of sex hormones.
Secondary / Accessory Sex Organs-
● These organs neither produce gametes nor secrete hormones, but are
concerned with the transfer and meeting of gametes
Male Reproductive System-
● The male reproductive system is located in the pelvic region
Scrotum-
- The testes are situated outside the abdominal cavity within a pouch called
the scrotum. This pouch is suspended from the groin.
- The scrotum has two compartments formed due to a scrotal septum, which
is visible externally as the ‘raphe’
- Each compartment contains one testis.
- The testes are located in the scrotum as the temperature there is 2-2.5℃
lower than the normal body temperature, which is necessary for
spermatogenesis.
- The scrotum remains connected with the abdominal cavity by the inguinal
canals.
- The testes are suspended from the body wall by a spermatic cord through
the inguinal canal.
- Each spermatic cord contains the vas deferens, testicular artery, testicular
veins, and testicular nerve.
- Scrotal skin → dartos muscle → cremaster muscle, which is more abundant in
the spermatic cord.
, - The testes are then attached to these layers with the help of ‘gubernaculum’,
which is made up of a fibrous tissue + fat.
- These muscular layers help in the regulation of temperature inside the
scrotum.
Testes-
● In adults, each testis is oval in
shape
● 4-5 cm in length, 2-3 cm in
width
● The testis is covered by a
dense covering made up of 3
layers → tunica vaginalis,
tunica albuginea, and tunica
vasculosa.
● Each testis has around 250
testicular lobules.
● Each lobule contains 1-3
seminiferous tubules in
which sperms are produced.
● Seminiferous tubules → tubuli
recti → rete testis → vasa efferentia → epididymis.
Epididymis-
+ The epididymis is a large coiled tube consisting of a head (caput), body
(corpora), and tail (caudal)
+ The epididymis is the site of sperm maturation.
+ It is also the place where sperms become motile and acquire the capacity to
fertilise an ovum
It also serves to store sperm temporarily.
Vas Deferens-
- The epididymis leads to the vas deferens which ascends to the abdomen and
loops around the ureter, over the urinary bladder.
- From here, near the bladder, the vas deferens dilates to form an ‘ampulla’
which receives the duct of the seminal vesicles, together forming the
ejaculatory duct.
- The ejaculatory duct opens into the prostatic urethra.
- The main function of the vas deferens is to convey sperm during sexual
arousal from the epididymis towards the urethra by the peristaltic
contractions of its muscular wall
, - The ampulla of the vas deferens also acts as a reservoir of sperms. (NOT OF
SEMEN)
Male Accessory Glands-
Seminal Vesicles-
+ Seminal vesicles are paired glands which lie at the dorsolateral sides of the
base of the urinary bladder.
+ These glands secrete an alkaline viscous fluid, called the seminal fluid
rich in fructose, fibrinogen, prostaglandins, etc.
+ About ⅔ volume of the seminal plasma is secreted by the seminal vesicles.
Prostate Gland-
+ The prostate gland lies below the urinary bladder
+ The alkaline, milky secretion of this gland makes up around ⅓ of the total
volume of the seminal plasma.
+ The secretion of the prostate gland enters the prostatic urethra through
several tiny ducts.
+ The prostatic fluid contains calcium (milky), clotting enzymes, and
profibrinolysin.
Bulbo-urethral Glands-
+ The paired bulbo-urethral glands are located on either side of the
membranous urethra, but their ducts open into the penile urethra.
+ During arousal, these glands secrete an alkaline fluid into the urethra which
protects the passing sperm by neutralising the acidity of the urethra from
urine and also serves to lubricate the penis.
During a single ejaculation:
→ 200-300 million sperm are released.
→ for normal fertility, 60% must have normal size and shape
→ at least 40% of them must show vigorous motility.
Azospermia → absence or near absence of sperms in semen
Asthenospermia → reduced motility of sperms in semen
Penis-
● The enlarged end of the penis is called the ‘glans penis’ which is covered by a
loose fold of skin called the ‘foreskin’ or ‘prepuce’.
● The opening of the urethra to the outside through the penis is called the
urethral meatus.
