NCERT Textbook: Human Reproduction | Biology Class 12 - NEET PDF Download

 Page 1


As you are aware, humans are sexually reproducing and
viviparous. The reproductive events in humans include
formation of gametes (gametogenesis), i.e., sperms in males
and ovum in females, transfer of sperms into the female
genital tract (insemination) and fusion of male and female
gametes (fertilisation) leading to formation of zygote. This
is followed by formation and development of blastocyst
and its attachment to the uterine wall (implantation),
embryonic development (gestation) and delivery of the
baby (parturition). You have learnt that these reproductive
events occur after puberty. There are remarkable
differences between the reproductive events in the male
and in the female, for example, sperm formation continues
even in old men, but formation of ovum ceases in women
around the age of fifty years. Let us examine the male and
female reproductive systems in human.
2.1 THE MALE REPRODUCTIVE SYSTEM
The male reproductive system is located in the pelvis region
(Figure 2.1a). It includes a pair of testes alongwith
accessory ducts, glands and the external genitalia.
CHAPTER 2
HUMAN REPRODUCTION
2.1 The Male Reproductive
System
2.2 The Female Reproductive
System
2.3 Gametogenesis
2.4 Menstrual Cycle
2.5 Fertilisation and
Implantation
2.6 Pregnancy and Embryonic
Development
2.7 Parturition and Lactation
2024-25
Page 2


As you are aware, humans are sexually reproducing and
viviparous. The reproductive events in humans include
formation of gametes (gametogenesis), i.e., sperms in males
and ovum in females, transfer of sperms into the female
genital tract (insemination) and fusion of male and female
gametes (fertilisation) leading to formation of zygote. This
is followed by formation and development of blastocyst
and its attachment to the uterine wall (implantation),
embryonic development (gestation) and delivery of the
baby (parturition). You have learnt that these reproductive
events occur after puberty. There are remarkable
differences between the reproductive events in the male
and in the female, for example, sperm formation continues
even in old men, but formation of ovum ceases in women
around the age of fifty years. Let us examine the male and
female reproductive systems in human.
2.1 THE MALE REPRODUCTIVE SYSTEM
The male reproductive system is located in the pelvis region
(Figure 2.1a). It includes a pair of testes alongwith
accessory ducts, glands and the external genitalia.
CHAPTER 2
HUMAN REPRODUCTION
2.1 The Male Reproductive
System
2.2 The Female Reproductive
System
2.3 Gametogenesis
2.4 Menstrual Cycle
2.5 Fertilisation and
Implantation
2.6 Pregnancy and Embryonic
Development
2.7 Parturition and Lactation
2024-25
The testes are situated outside the
abdominal cavity within a pouch
called scrotum. The scrotum helps
in maintaining the low temperature
of the testes (2–2.5
o 
C lower than
the normal internal body
temperature) necessary for
spermatogenesis. In adults, each
testis is oval in shape, with a length
of about 4 to 5 cm and a width of
about 2 to 3 cm. The testis is
covered by a dense covering. Each
testis has about 250 compartments
called testicular lobules
(Figure 2.1b).
Each lobule contains one to
three highly coiled seminiferous
tubules in which sperms are
produced. Each seminiferous tubule
is lined on its inside by two types
of cells called male germ cells
(spermatogonia) and Sertoli cells
(Figure 2.2 ). The male germ cells
undergo meiotic divisions finally
leading to sperm formation, while
Sertoli cells provide nutrition to the
germ cells. The regions outside the
seminiferous tubules called
interstitial spaces, contain small
blood vessels and interstitial cells
or Leydig cells (Figure 2.2). Leydig
cells synthesise and secrete
testicular hormones called
androgens. Other  immunologically
competent cells are also present.
The male sex accessory ducts include rete testis, vasa efferentia,
epididymis and vas deferens (Figure 2.1b). The seminiferous tubules of
the testis open into the vasa efferentia through rete testis. The vasa efferentia
leave the testis and open into epididymis located along the posterior surface
of each testis. The epididymis leads to vas deferens that ascends to the
abdomen and loops over the urinary bladder. It receives a duct from seminal
vesicle and opens into urethra as the ejaculatory duct (Figure 2.1a). These
ducts store and transport the sperms from the testis to the outside through
urethra. The urethra originates from the urinary bladder and extends
through the penis to its external opening called urethral meatus.
Figure 2.1(a) Diagrammatic sectional view of male pelvis
showing reproductive system
Figure 2.1(b) Diagrammatic view of male reproductive system
(part of testis is open to show inner details)
27
HUMAN REPRODUCTION
2024-25
Page 3


As you are aware, humans are sexually reproducing and
viviparous. The reproductive events in humans include
formation of gametes (gametogenesis), i.e., sperms in males
and ovum in females, transfer of sperms into the female
genital tract (insemination) and fusion of male and female
gametes (fertilisation) leading to formation of zygote. This
is followed by formation and development of blastocyst
and its attachment to the uterine wall (implantation),
embryonic development (gestation) and delivery of the
baby (parturition). You have learnt that these reproductive
events occur after puberty. There are remarkable
differences between the reproductive events in the male
and in the female, for example, sperm formation continues
even in old men, but formation of ovum ceases in women
around the age of fifty years. Let us examine the male and
female reproductive systems in human.
2.1 THE MALE REPRODUCTIVE SYSTEM
The male reproductive system is located in the pelvis region
(Figure 2.1a). It includes a pair of testes alongwith
accessory ducts, glands and the external genitalia.
CHAPTER 2
HUMAN REPRODUCTION
2.1 The Male Reproductive
System
2.2 The Female Reproductive
System
2.3 Gametogenesis
2.4 Menstrual Cycle
2.5 Fertilisation and
Implantation
2.6 Pregnancy and Embryonic
Development
2.7 Parturition and Lactation
2024-25
The testes are situated outside the
abdominal cavity within a pouch
called scrotum. The scrotum helps
in maintaining the low temperature
of the testes (2–2.5
o 
C lower than
the normal internal body
temperature) necessary for
spermatogenesis. In adults, each
testis is oval in shape, with a length
of about 4 to 5 cm and a width of
about 2 to 3 cm. The testis is
covered by a dense covering. Each
testis has about 250 compartments
called testicular lobules
(Figure 2.1b).
Each lobule contains one to
three highly coiled seminiferous
tubules in which sperms are
produced. Each seminiferous tubule
is lined on its inside by two types
of cells called male germ cells
(spermatogonia) and Sertoli cells
(Figure 2.2 ). The male germ cells
undergo meiotic divisions finally
leading to sperm formation, while
Sertoli cells provide nutrition to the
germ cells. The regions outside the
seminiferous tubules called
interstitial spaces, contain small
blood vessels and interstitial cells
or Leydig cells (Figure 2.2). Leydig
cells synthesise and secrete
testicular hormones called
androgens. Other  immunologically
competent cells are also present.
The male sex accessory ducts include rete testis, vasa efferentia,
epididymis and vas deferens (Figure 2.1b). The seminiferous tubules of
the testis open into the vasa efferentia through rete testis. The vasa efferentia
leave the testis and open into epididymis located along the posterior surface
of each testis. The epididymis leads to vas deferens that ascends to the
abdomen and loops over the urinary bladder. It receives a duct from seminal
vesicle and opens into urethra as the ejaculatory duct (Figure 2.1a). These
ducts store and transport the sperms from the testis to the outside through
urethra. The urethra originates from the urinary bladder and extends
through the penis to its external opening called urethral meatus.
Figure 2.1(a) Diagrammatic sectional view of male pelvis
showing reproductive system
Figure 2.1(b) Diagrammatic view of male reproductive system
(part of testis is open to show inner details)
27
HUMAN REPRODUCTION
2024-25
28
BIOLOGY
The penis is the male external genitalia (Figure 2.1a, b). It is made up
of special tissue that helps in erection of the penis to facilitate insemination.
The enlarged end of penis called the glans penis is covered by a loose fold
of skin called foreskin.
The male accessory glands (Figure 2.1a, b) include paired seminal
vesicles, a prostate and paired bulbourethral glands. Secretions of these
glands constitute the seminal plasma which is rich in fructose, calcium
and certain enzymes. The secretions of bulbourethral glands also helps
in the lubrication of the penis.
2.2 THE FEMALE REPRODUCTIVE SYSTEM
The female reproductive system consists of a pair of ovaries alongwith a pair
of oviducts, uterus, cervix, vagina and the external genitalia located in
pelvic region (Figure 2.3a). These parts of the system alongwith a pair of the
mammary glands are integrated structurally and functionally to support
the processes of ovulation, fertilisation, pregnancy, birth and child care.
Ovaries are the primary female sex organs that produce the female
gamete (ovum) and several steroid hormones (ovarian hormones).
The ovaries are located one on each side of the lower abdomen
(Figure 2.3b). Each ovary is about 2 to 4 cm in length and is connected to
the pelvic wall and uterus by ligaments. Each ovary is covered by a thin
epithelium which encloses the ovarian stroma. The stroma is divided into
two zones – a peripheral cortex and an inner medulla.
Figure 2.2 Diagrammatic sectional view of seminiferous tubule
2024-25
Page 4


As you are aware, humans are sexually reproducing and
viviparous. The reproductive events in humans include
formation of gametes (gametogenesis), i.e., sperms in males
and ovum in females, transfer of sperms into the female
genital tract (insemination) and fusion of male and female
gametes (fertilisation) leading to formation of zygote. This
is followed by formation and development of blastocyst
and its attachment to the uterine wall (implantation),
embryonic development (gestation) and delivery of the
baby (parturition). You have learnt that these reproductive
events occur after puberty. There are remarkable
differences between the reproductive events in the male
and in the female, for example, sperm formation continues
even in old men, but formation of ovum ceases in women
around the age of fifty years. Let us examine the male and
female reproductive systems in human.
2.1 THE MALE REPRODUCTIVE SYSTEM
The male reproductive system is located in the pelvis region
(Figure 2.1a). It includes a pair of testes alongwith
accessory ducts, glands and the external genitalia.
CHAPTER 2
HUMAN REPRODUCTION
2.1 The Male Reproductive
System
2.2 The Female Reproductive
System
2.3 Gametogenesis
2.4 Menstrual Cycle
2.5 Fertilisation and
Implantation
2.6 Pregnancy and Embryonic
Development
2.7 Parturition and Lactation
2024-25
The testes are situated outside the
abdominal cavity within a pouch
called scrotum. The scrotum helps
in maintaining the low temperature
of the testes (2–2.5
o 
C lower than
the normal internal body
temperature) necessary for
spermatogenesis. In adults, each
testis is oval in shape, with a length
of about 4 to 5 cm and a width of
about 2 to 3 cm. The testis is
covered by a dense covering. Each
testis has about 250 compartments
called testicular lobules
(Figure 2.1b).
Each lobule contains one to
three highly coiled seminiferous
tubules in which sperms are
produced. Each seminiferous tubule
is lined on its inside by two types
of cells called male germ cells
(spermatogonia) and Sertoli cells
(Figure 2.2 ). The male germ cells
undergo meiotic divisions finally
leading to sperm formation, while
Sertoli cells provide nutrition to the
germ cells. The regions outside the
seminiferous tubules called
interstitial spaces, contain small
blood vessels and interstitial cells
or Leydig cells (Figure 2.2). Leydig
cells synthesise and secrete
testicular hormones called
androgens. Other  immunologically
competent cells are also present.
The male sex accessory ducts include rete testis, vasa efferentia,
epididymis and vas deferens (Figure 2.1b). The seminiferous tubules of
the testis open into the vasa efferentia through rete testis. The vasa efferentia
leave the testis and open into epididymis located along the posterior surface
of each testis. The epididymis leads to vas deferens that ascends to the
abdomen and loops over the urinary bladder. It receives a duct from seminal
vesicle and opens into urethra as the ejaculatory duct (Figure 2.1a). These
ducts store and transport the sperms from the testis to the outside through
urethra. The urethra originates from the urinary bladder and extends
through the penis to its external opening called urethral meatus.
Figure 2.1(a) Diagrammatic sectional view of male pelvis
showing reproductive system
Figure 2.1(b) Diagrammatic view of male reproductive system
(part of testis is open to show inner details)
27
HUMAN REPRODUCTION
2024-25
28
BIOLOGY
The penis is the male external genitalia (Figure 2.1a, b). It is made up
of special tissue that helps in erection of the penis to facilitate insemination.
The enlarged end of penis called the glans penis is covered by a loose fold
of skin called foreskin.
The male accessory glands (Figure 2.1a, b) include paired seminal
vesicles, a prostate and paired bulbourethral glands. Secretions of these
glands constitute the seminal plasma which is rich in fructose, calcium
and certain enzymes. The secretions of bulbourethral glands also helps
in the lubrication of the penis.
2.2 THE FEMALE REPRODUCTIVE SYSTEM
The female reproductive system consists of a pair of ovaries alongwith a pair
of oviducts, uterus, cervix, vagina and the external genitalia located in
pelvic region (Figure 2.3a). These parts of the system alongwith a pair of the
mammary glands are integrated structurally and functionally to support
the processes of ovulation, fertilisation, pregnancy, birth and child care.
Ovaries are the primary female sex organs that produce the female
gamete (ovum) and several steroid hormones (ovarian hormones).
The ovaries are located one on each side of the lower abdomen
(Figure 2.3b). Each ovary is about 2 to 4 cm in length and is connected to
the pelvic wall and uterus by ligaments. Each ovary is covered by a thin
epithelium which encloses the ovarian stroma. The stroma is divided into
two zones – a peripheral cortex and an inner medulla.
Figure 2.2 Diagrammatic sectional view of seminiferous tubule
2024-25
29
HUMAN REPRODUCTION
The oviducts (fallopian tubes), uterus and vagina constitute the female
accessory ducts. Each fallopian tube is about 10-12 cm long and extends
from the periphery of each ovary to the uterus (Figure 2.3b), the part closer
to the ovary is the funnel-shaped infundibulum. The edges of the
infundibulum possess finger-like projections called fimbriae, which help in
collection of the ovum after ovulation. The infundibulum leads to a wider
Figure 2.3 (b) Diagrammatic sectional view of the female reproductive system
Figure 2.3 (a) Diagrammatic sectional view of female pelvis showing
reproductive system
2024-25
Page 5


As you are aware, humans are sexually reproducing and
viviparous. The reproductive events in humans include
formation of gametes (gametogenesis), i.e., sperms in males
and ovum in females, transfer of sperms into the female
genital tract (insemination) and fusion of male and female
gametes (fertilisation) leading to formation of zygote. This
is followed by formation and development of blastocyst
and its attachment to the uterine wall (implantation),
embryonic development (gestation) and delivery of the
baby (parturition). You have learnt that these reproductive
events occur after puberty. There are remarkable
differences between the reproductive events in the male
and in the female, for example, sperm formation continues
even in old men, but formation of ovum ceases in women
around the age of fifty years. Let us examine the male and
female reproductive systems in human.
2.1 THE MALE REPRODUCTIVE SYSTEM
The male reproductive system is located in the pelvis region
(Figure 2.1a). It includes a pair of testes alongwith
accessory ducts, glands and the external genitalia.
CHAPTER 2
HUMAN REPRODUCTION
2.1 The Male Reproductive
System
2.2 The Female Reproductive
System
2.3 Gametogenesis
2.4 Menstrual Cycle
2.5 Fertilisation and
Implantation
2.6 Pregnancy and Embryonic
Development
2.7 Parturition and Lactation
2024-25
The testes are situated outside the
abdominal cavity within a pouch
called scrotum. The scrotum helps
in maintaining the low temperature
of the testes (2–2.5
o 
C lower than
the normal internal body
temperature) necessary for
spermatogenesis. In adults, each
testis is oval in shape, with a length
of about 4 to 5 cm and a width of
about 2 to 3 cm. The testis is
covered by a dense covering. Each
testis has about 250 compartments
called testicular lobules
(Figure 2.1b).
Each lobule contains one to
three highly coiled seminiferous
tubules in which sperms are
produced. Each seminiferous tubule
is lined on its inside by two types
of cells called male germ cells
(spermatogonia) and Sertoli cells
(Figure 2.2 ). The male germ cells
undergo meiotic divisions finally
leading to sperm formation, while
Sertoli cells provide nutrition to the
germ cells. The regions outside the
seminiferous tubules called
interstitial spaces, contain small
blood vessels and interstitial cells
or Leydig cells (Figure 2.2). Leydig
cells synthesise and secrete
testicular hormones called
androgens. Other  immunologically
competent cells are also present.
The male sex accessory ducts include rete testis, vasa efferentia,
epididymis and vas deferens (Figure 2.1b). The seminiferous tubules of
the testis open into the vasa efferentia through rete testis. The vasa efferentia
leave the testis and open into epididymis located along the posterior surface
of each testis. The epididymis leads to vas deferens that ascends to the
abdomen and loops over the urinary bladder. It receives a duct from seminal
vesicle and opens into urethra as the ejaculatory duct (Figure 2.1a). These
ducts store and transport the sperms from the testis to the outside through
urethra. The urethra originates from the urinary bladder and extends
through the penis to its external opening called urethral meatus.
Figure 2.1(a) Diagrammatic sectional view of male pelvis
showing reproductive system
Figure 2.1(b) Diagrammatic view of male reproductive system
(part of testis is open to show inner details)
27
HUMAN REPRODUCTION
2024-25
28
BIOLOGY
The penis is the male external genitalia (Figure 2.1a, b). It is made up
of special tissue that helps in erection of the penis to facilitate insemination.
The enlarged end of penis called the glans penis is covered by a loose fold
of skin called foreskin.
The male accessory glands (Figure 2.1a, b) include paired seminal
vesicles, a prostate and paired bulbourethral glands. Secretions of these
glands constitute the seminal plasma which is rich in fructose, calcium
and certain enzymes. The secretions of bulbourethral glands also helps
in the lubrication of the penis.
2.2 THE FEMALE REPRODUCTIVE SYSTEM
The female reproductive system consists of a pair of ovaries alongwith a pair
of oviducts, uterus, cervix, vagina and the external genitalia located in
pelvic region (Figure 2.3a). These parts of the system alongwith a pair of the
mammary glands are integrated structurally and functionally to support
the processes of ovulation, fertilisation, pregnancy, birth and child care.
Ovaries are the primary female sex organs that produce the female
gamete (ovum) and several steroid hormones (ovarian hormones).
The ovaries are located one on each side of the lower abdomen
(Figure 2.3b). Each ovary is about 2 to 4 cm in length and is connected to
the pelvic wall and uterus by ligaments. Each ovary is covered by a thin
epithelium which encloses the ovarian stroma. The stroma is divided into
two zones – a peripheral cortex and an inner medulla.
Figure 2.2 Diagrammatic sectional view of seminiferous tubule
2024-25
29
HUMAN REPRODUCTION
The oviducts (fallopian tubes), uterus and vagina constitute the female
accessory ducts. Each fallopian tube is about 10-12 cm long and extends
from the periphery of each ovary to the uterus (Figure 2.3b), the part closer
to the ovary is the funnel-shaped infundibulum. The edges of the
infundibulum possess finger-like projections called fimbriae, which help in
collection of the ovum after ovulation. The infundibulum leads to a wider
Figure 2.3 (b) Diagrammatic sectional view of the female reproductive system
Figure 2.3 (a) Diagrammatic sectional view of female pelvis showing
reproductive system
2024-25
30
BIOLOGY
part of the oviduct called ampulla. The last part of the oviduct, isthmus has
a narrow lumen and it joins the uterus.
The uterus is single and it is also called womb. The shape of the uterus
is like an inverted pear. It is supported by ligaments attached to the pelvic
wall. The uterus opens into vagina through a narrow cervix. The cavity of
the cervix is called cervical canal (Figure 2.3b) which alongwith vagina
forms the birth canal. The wall of the uterus has three layers of tissue. The
external thin membranous perimetrium, middle thick layer of smooth
muscle, myometrium and inner glandular layer called endometrium that
lines the uterine cavity. The endometrium undergoes cyclical changes during
menstrual cycle while the myometrium exhibits strong contraction during
delivery of the baby.
The female external genitalia include mons pubis, labia majora, labia
minora, hymen and clitoris (Figure 2.3a). Mons pubis is a cushion of fatty
tissue covered by skin and pubic hair. The labia majora are fleshy folds of
tissue, which extend down from the mons pubis and surround the vaginal
opening. The labia minora are paired folds of tissue under the labia majora.
The opening of the vagina is often covered partially by a membrane called
hymen. The clitoris is a tiny finger-like structure which lies at the upper
junction of the two labia minora above the urethral opening.  The hymen is
often torn during the first coitus (intercourse). However , it can also be broken
by a sudden fall or jolt, insertion of a vaginal tampon, active participation
in some sports like horseback riding, cycling, etc. In some women the hymen
persists even after coitus. In fact, the presence or absence of hymen is not
a reliable indicator of virginity or sexual experience.
Figure 2.4 A diagrammatic sectional view of Mammary gland
2024-25