CHAPTER > 03
Human
Reproduction
NEET KEY NOTES
Humans are sexually reproducing and viviparous (i.e. give The testes are situated outside the abdominal cavity within a
birth to young ones) organisms, having distinct male and pouch called scrotum. The scrotum helps in maintaining the
female sexes. low temperature of the testes (2-2.5°C lower than the normal
internal body temperature) necessary for the production
Male Reproductive System of
The male reproductive system is located in the pelvis region. sperms (spermatogenesis).
In adults, each testis is oval in shape, with a length of about
4-5 cm and width of about 2-3 cm.
It includes a pair of testes, accessory ducts, glands and the
external genitalia (penis). Each testis has about 250 compartments called
testicular
lobules and each lobule contains one to three highly
coiled
seminiferous tubules.
Ureter Seminiferous tubules are lined inside by two types of
Seminal vesicle cells, i.e. male germ cells (spermatogonia), undergo
meiotic divisions leading to sperm formation and Sertoli
Urinary bladder cells, provide nutrition to the dividing germ cells. Region
Vas deferens outside the seminiferous tubules has Leydig cells or
Prostate gland Ejaculatory duct interstitial cells, which secrete testicular hormones called
Penis Rectum androgens.
Urethra Anus The male sex accessory ducts include rete testis, vasa
Glans penis efferentia, epididymis and vas deferens. These ducts store
Foreskin Bulbourethral gland and transport the sperms from the testis to the outside
Testis
Scrotum through urethra. The urethra originates from urinary bladder
and extends through the penis to its external opening, i.e.
Diagrammatic sectional view of male pelvis showing reproductive
urethral meatus.
system
, The penis is the highly vascularised external copulatory The oviducts (Fallopian tube), uterus and vagina
organ in males. The enlarged end of penis called the glans constitute the female accessory ducts.
penis, covered by a loose fold of skin called foreskin. Each Fallopian tube is about 10-12 cm long and extends
Ureter Urinary from the periphery of each ovary to the uterus, the part
bladder closer to the ovary is the funnel-shaped infundibulum. The
Vas deferens edges of the infundibulum possess finger-like projections
Seminal
vesicle
called fimbriae, which help in collection of the ovum after
Prostate gland ovulation.Theinfundibulumleadstoawiderpartofthe
Bulbourethral oviductcalledampulla.Thelastpartoftheoviduct,
gland isthmushasanarrowlumenanditjoinstheuterus.
Uterine fundus
Epididymis
Urethra Uterine cavity
Vasa efferentia Isthmus
Rete testis
Ampulla Fallopian
Testicular Infundibulum tube
lobules Testis
Ovary
Glans penis Foreskin Endometrium Fimbriae
Myometrium Cervix
Diagrammatic view of male reproductive system (part of testis is
open to show inner details) Perimetrium Cervical canal
Vagina
The male accessory glands include paired seminal
vesicles, a prostate and paired bulbourethral glands. Diagrammatic sectional view of the female reproductive system
Secretions of these glands constitute the seminal plasma Uterus (womb) opens into vagina through a narrow
which is rich in fructose, calcium and certain enzymes. cervix. The cavity of the cervix is called cervical canal
This secretion along with the sperm forms semen. which forms the birth canal along with the vagina.
Female Reproductive System The uterus has three layers of tissue, i.e. the external
thin
It includes a pair of ovaries, pair of Fallopian tubes membranous perimetrium, middle thick layer of
(oviducts), uterus, cervix, vagina and external smooth
genitalia
and a pair of mammary glands. The female external genitalia include
Mons pubis A cushion of fatty tissue covered by skin
I
and pubic hair.
Cervix
I Labia majora Fat padded skin folds, extend from mons
Uterus Rectum pubis and surround the vaginal opening.
Urinary bladder I Labia minora A pair of inner folds of tissue under labia
Pubic symphysis Vagina majora.
Urethra
Clitoris I Hymen The membrane that partially covers the vaginal
Labium minora opening.
Anus Clitoris A tiny finger-like structure, lying at the upper
Labium majora I
Vaginal orifice junction of two labia minora above the urethral
Diagrammatic sectional view of female In females, the mammary glands are one of the secondary
pelvis showing reproductive system
sexual characteristics. These are paired structures that
contain glandular tissue and variable amount of fat.
Ovaries are the primary female sex organ that produce
ova and ovarian hormones. Glandular tissue is divided into 15-20 mammary lobes,
The ovaries are located one on each side of the lower having clusters of cells called alveoli.
abdomen. Each ovary is about 2-4 cm in length and is The mammary alveolus secretes milk and stores in its
connected to the pelvic wall and uterus by ligaments. Each lumen. These alveoli open into mammary tubules, which
ovary is covered by a thin epithelium which encloses the join to form mammary duct. The numerous mammary
ovarian stroma. The stroma is divided into two zones, i.e. ducts connect to form wider ampulla which connects to
lactiferous duct from which milk is sucked out.
a peripheral cortex and an inner medulla.
NEET KEY NOTES
, The increased level of GnRH acts at the anterior
Gametogenesis pituitary and stimulates Luteinizing Hormone (LH)
It is the process by which the primary sex organs, the and
testis Follicle Stimulating Hormone (FSH).
in the males and the ovaries in the females produce LH acts on the Leydig cells and stimulates synthesis
gametes, and
i.e. sperms and ovum. secretion of androgens, which in turn stimulate the
process of spermatogenesis.
Spermatogenesis
FSH acts on the Sertoli cells and stimulates secretion of
It is a process of formation of sperm through meiotic division
some factors which help in the process
and later some structural modifications from germ cells
of
present in testes in males.
spermiogenesis.
The germ cells called spermatogonia are present on the
A normal human sperm structure is composed of
I
inside wall of the seminiferous tubules.
a
I These cells are diploid and increase in number through head, neck, a middle piece and a tail.
mitosis.
Head contains anterior small acrosome, which is filled
I Some of the spermatogonia, primary with enzymes and help in the fertilisation of the ovum.
spermatocytes,
Middle piece possesses numerous mitochondria,
undergo meiosis, forming two equal cells called
which
secondary spermatocytes. They are haploid
produce energy for the movement of tail that
(with 23
facilitates
chromosomes but are still duplicate).
sperm motility essential for fertilisation.
I Each of the two secondary spermatocytes
undergoes Oogenesis
second cell division (to separate the duplicate
chromosomes) producing four haploid
spermatids.
Each has only one set of 23 (unpaired,
unduplicated)
chromosomes.
I Spermatids transform into spermatozoa (sperm cells)
by
developing a head, neck, middle piece and a tail. This
process is called spermiogenesis.
Spermatogonia At puberty Chromosomes
Mitosis and number per cell
differentiation (46)
Primary spermatocytes
1st meiotic
division
Secondary spermatocytes (23)
2nd meiotic
division
(23)
Spermatids
Differentiation
Spermatozoa
Diagrammatic view of phases in spermatogenesis
It starts at the age of puberty due to significant increase in
the secretion of Gonadotropin Releasing Hormone
(GnRH).
Human
Reproduction
NEET KEY NOTES
Humans are sexually reproducing and viviparous (i.e. give The testes are situated outside the abdominal cavity within a
birth to young ones) organisms, having distinct male and pouch called scrotum. The scrotum helps in maintaining the
female sexes. low temperature of the testes (2-2.5°C lower than the normal
internal body temperature) necessary for the production
Male Reproductive System of
The male reproductive system is located in the pelvis region. sperms (spermatogenesis).
In adults, each testis is oval in shape, with a length of about
4-5 cm and width of about 2-3 cm.
It includes a pair of testes, accessory ducts, glands and the
external genitalia (penis). Each testis has about 250 compartments called
testicular
lobules and each lobule contains one to three highly
coiled
seminiferous tubules.
Ureter Seminiferous tubules are lined inside by two types of
Seminal vesicle cells, i.e. male germ cells (spermatogonia), undergo
meiotic divisions leading to sperm formation and Sertoli
Urinary bladder cells, provide nutrition to the dividing germ cells. Region
Vas deferens outside the seminiferous tubules has Leydig cells or
Prostate gland Ejaculatory duct interstitial cells, which secrete testicular hormones called
Penis Rectum androgens.
Urethra Anus The male sex accessory ducts include rete testis, vasa
Glans penis efferentia, epididymis and vas deferens. These ducts store
Foreskin Bulbourethral gland and transport the sperms from the testis to the outside
Testis
Scrotum through urethra. The urethra originates from urinary bladder
and extends through the penis to its external opening, i.e.
Diagrammatic sectional view of male pelvis showing reproductive
urethral meatus.
system
, The penis is the highly vascularised external copulatory The oviducts (Fallopian tube), uterus and vagina
organ in males. The enlarged end of penis called the glans constitute the female accessory ducts.
penis, covered by a loose fold of skin called foreskin. Each Fallopian tube is about 10-12 cm long and extends
Ureter Urinary from the periphery of each ovary to the uterus, the part
bladder closer to the ovary is the funnel-shaped infundibulum. The
Vas deferens edges of the infundibulum possess finger-like projections
Seminal
vesicle
called fimbriae, which help in collection of the ovum after
Prostate gland ovulation.Theinfundibulumleadstoawiderpartofthe
Bulbourethral oviductcalledampulla.Thelastpartoftheoviduct,
gland isthmushasanarrowlumenanditjoinstheuterus.
Uterine fundus
Epididymis
Urethra Uterine cavity
Vasa efferentia Isthmus
Rete testis
Ampulla Fallopian
Testicular Infundibulum tube
lobules Testis
Ovary
Glans penis Foreskin Endometrium Fimbriae
Myometrium Cervix
Diagrammatic view of male reproductive system (part of testis is
open to show inner details) Perimetrium Cervical canal
Vagina
The male accessory glands include paired seminal
vesicles, a prostate and paired bulbourethral glands. Diagrammatic sectional view of the female reproductive system
Secretions of these glands constitute the seminal plasma Uterus (womb) opens into vagina through a narrow
which is rich in fructose, calcium and certain enzymes. cervix. The cavity of the cervix is called cervical canal
This secretion along with the sperm forms semen. which forms the birth canal along with the vagina.
Female Reproductive System The uterus has three layers of tissue, i.e. the external
thin
It includes a pair of ovaries, pair of Fallopian tubes membranous perimetrium, middle thick layer of
(oviducts), uterus, cervix, vagina and external smooth
genitalia
and a pair of mammary glands. The female external genitalia include
Mons pubis A cushion of fatty tissue covered by skin
I
and pubic hair.
Cervix
I Labia majora Fat padded skin folds, extend from mons
Uterus Rectum pubis and surround the vaginal opening.
Urinary bladder I Labia minora A pair of inner folds of tissue under labia
Pubic symphysis Vagina majora.
Urethra
Clitoris I Hymen The membrane that partially covers the vaginal
Labium minora opening.
Anus Clitoris A tiny finger-like structure, lying at the upper
Labium majora I
Vaginal orifice junction of two labia minora above the urethral
Diagrammatic sectional view of female In females, the mammary glands are one of the secondary
pelvis showing reproductive system
sexual characteristics. These are paired structures that
contain glandular tissue and variable amount of fat.
Ovaries are the primary female sex organ that produce
ova and ovarian hormones. Glandular tissue is divided into 15-20 mammary lobes,
The ovaries are located one on each side of the lower having clusters of cells called alveoli.
abdomen. Each ovary is about 2-4 cm in length and is The mammary alveolus secretes milk and stores in its
connected to the pelvic wall and uterus by ligaments. Each lumen. These alveoli open into mammary tubules, which
ovary is covered by a thin epithelium which encloses the join to form mammary duct. The numerous mammary
ovarian stroma. The stroma is divided into two zones, i.e. ducts connect to form wider ampulla which connects to
lactiferous duct from which milk is sucked out.
a peripheral cortex and an inner medulla.
NEET KEY NOTES
, The increased level of GnRH acts at the anterior
Gametogenesis pituitary and stimulates Luteinizing Hormone (LH)
It is the process by which the primary sex organs, the and
testis Follicle Stimulating Hormone (FSH).
in the males and the ovaries in the females produce LH acts on the Leydig cells and stimulates synthesis
gametes, and
i.e. sperms and ovum. secretion of androgens, which in turn stimulate the
process of spermatogenesis.
Spermatogenesis
FSH acts on the Sertoli cells and stimulates secretion of
It is a process of formation of sperm through meiotic division
some factors which help in the process
and later some structural modifications from germ cells
of
present in testes in males.
spermiogenesis.
The germ cells called spermatogonia are present on the
A normal human sperm structure is composed of
I
inside wall of the seminiferous tubules.
a
I These cells are diploid and increase in number through head, neck, a middle piece and a tail.
mitosis.
Head contains anterior small acrosome, which is filled
I Some of the spermatogonia, primary with enzymes and help in the fertilisation of the ovum.
spermatocytes,
Middle piece possesses numerous mitochondria,
undergo meiosis, forming two equal cells called
which
secondary spermatocytes. They are haploid
produce energy for the movement of tail that
(with 23
facilitates
chromosomes but are still duplicate).
sperm motility essential for fertilisation.
I Each of the two secondary spermatocytes
undergoes Oogenesis
second cell division (to separate the duplicate
chromosomes) producing four haploid
spermatids.
Each has only one set of 23 (unpaired,
unduplicated)
chromosomes.
I Spermatids transform into spermatozoa (sperm cells)
by
developing a head, neck, middle piece and a tail. This
process is called spermiogenesis.
Spermatogonia At puberty Chromosomes
Mitosis and number per cell
differentiation (46)
Primary spermatocytes
1st meiotic
division
Secondary spermatocytes (23)
2nd meiotic
division
(23)
Spermatids
Differentiation
Spermatozoa
Diagrammatic view of phases in spermatogenesis
It starts at the age of puberty due to significant increase in
the secretion of Gonadotropin Releasing Hormone
(GnRH).
