• Human beings are viviparous. The
reproduction always involves sexual method.
• Sexual reproduction: It is the reproduction
takes place by formation and fusion of
• The gametes are develops in primary sex
organ testes and ovaries.
THE MALE REPRODUCTIVE SYSTEM.
• The Male
• A pair of testes.
• Accessory ducts.
• Accessory glands.
• External genitalia
• Pair of testis are present in scrotal sac outside the
abdominal cavity . Before birth testes descend to
the sac called scrotum.
• The scrotum provides low temperature about 2 to
3 0C required for spermatogenesis.
• If testes donot descend, it leads to sterility.
Because normal sperm production is inhibited by
internal body temperature.
• The failure of testes to descend down into scortal
sac is called cryptorchidism.
• Each testis has about 250 compartments called
testicular lobules.. Each lobule contains coiled
• The inner wall of seminiferous tubules lined by
male germ cells and Sertoli cells.
• Male germ cell undergoes meiosis and produce
• Sertoli cells provide nutrition to the developing
• In between the seminiferous tubule interstitial
cell or Leydig cell are present.
• Leydig cells produce male hormones called
• Accessory ducts:
• Accessory ducts includes
rete testis, vasa efferentia,
epididymis and vas
• Seminiferous tubules open
into vasa efferentia
through rete testis. The
vasa efferentia leaves the
testis and open into
• In epididymis sperms
stores and further
maturation takes place.
• The epididymis leads
to vas deferens. Vas
deferens opens into
the urethra as the
• Urethra originates
from the urinary
bladder and extends
through the penis to
its external opening
• Accessory glands:
• Accessory glands
• Paired seminal
• A prostate gland
• These glands secretes the secretion called
• It rich in fructose, calcium, and certain enzyme.
Seminal plasma with sperm forms semen.
• After puberty millions of sperms matures every
day. Each ejaculation contains 300 million
• External genitalia:
• Penis is the external genitalia.
• It is made of special tissue that helps in erection
of the penis to facilitate insemination.
• The process of formation of haploid male
gamete sperm in seminiferous tubules of
testis is called spermatogenesis.
• The inner wall of the seminiferous tubule
contains two types of cells as germ cells
(spermatogonial cells) and sertoli cells.
• germl cells divides and develops into sperms.
The sertoli cell nourishes the developing
• The spermatogenesis takes place in two stages
as spermatidogenesis and spermiogenesis
• Spermatidogenesis: It is the
process of formation of
spermatids. It involves 3 sub
• Multiplication phase: The
undergoes repeated mitotic
division and forms large
number of diploid
• Growth phase: The
spermatogonial cells grow in
size by increasing cytoplasm
and gets ready for
maturation. Now the
spermatogonial cells are
called primary spermatocytes
• Maturation phase: The diploid primary spermatocyte
undergoes first meiosis resulting in the formation of two
haploid cells called secondary spermatocyte. This later
undergoes second meiotic division to produce four
• Spermiogenesis: It is The process of formation of inactive
non-motile spermatid into active motile spermatozoa .
• The spermatid undergoes following structural changes.
1. The small vesicles of Golgi complex fuse to form a large
cup like acrosome anterior to the nucleus.
2. The two centrioles of spermatid moves towards the
nucleus and arrange beneath the nucleus as a proximal
and distal centriole.
3. The distal centriole elongates to form a tail.
4. The mitochondria forms a large mass at neck region.
5. The nucleus becomes elongated and forms a spherical
Structure of human sperm:
• Sperm is a male haploid
gamete. It measures about 60 μ
in length. It contains three
regions as head, middle piece
• Head: The head of the sperm is
arrow shaped contains a large
• anteriorly nucleus is covered by
a cap like structure called
acrosome. It is formed by Golgi
complex. It contains the lytic
enzymes to dissolve the egg
membrane during fertilization
• Neck: Below the head a
small neck is present. It
contains a proximal and
• Middle piece: The distal
centriole gives rice to
axial filament and
becomes basal bodies.
• The axial filament is
surrounded spirally by
mitochondria and forms
middle piece. The
energy for motility of
• Tail: The tail is divided
into principal piece and
• The principal piece has
axial filament surrounded
by plasma membrane.
• The end piece lacks the
• The tail is used for
swimming movement in
the liquid media.
• Hormonal control of
• This process is initiated at puberty
due to secretion of gonadotrophin
releasing hormone (GnRH)
• GnRH secreted form hypothalamus
stimulates anterior pituitary to
secrete two gonadotrophin.
• Luteinizing hormone (LH) and
Follicle stimulating Hormone (FSH)
• LH acts on Leydig cells (Interstitial
calls) to stimulates synthesis of
• Androgen stimulates
• FSH acts on Sertoli cells and
THE FEMALE REPRODUCTIVE SYSTEM
• The female
reproduction system is
located in the pelvic
• It includes:
1. A pair of ovaries
2. A pair of oviduct.
6. External genitalia.
Female gonads: Ovaries.
• Ovaries are the primary female sex organs
that produce the female gamete (ovum). It
also produces several female steroid
• The ovaries located in the lower abdomen.
• Each ovary is about 2-4 cm in length.
These are Connected to the pelvic wall
and uterus by ligaments.
• Each ovary is covered by thin epithelium.
With in this covering small sac like
structures called ovarian follicles.
• The ovarian stroma or folicle has two
• A peripheral cortex.
• An inner medulla.
• Oviduct :
• Each fallopian tube is about 1012 cm long and extends from
the of each ovary to the uterus.
• Close to the ovary the oviduct
has a funnel shaped structure
• The infundibulum leads to a
wider part of the oviduct called
• The edges of the infundibulum
possess finger-like projections
called fimbriae, which helps in
collection of the ovum after
• The last part of the oviduct is
called isthmus which joined to
• It is a hallow pear shaped muscular
organ. Single uterus is present in
lower abdomen region is also
• Inside the uterus fertilized ovum
grows and develops in to embryo.
• The wall of the uterus has three
layers of tissues
• Perimetrium: external thin
• Myometrium: middle thick layer of
• Endometrium: inner glandular
• Endometrium undergoes cyclical
changes during menstrual cycle.
• Myometrium exhibits strong contraction during
delivery of the baby
• The uterus opens into vagina through a narrow
• The lumen of cervix is called cervical canal.
• Cervical canal along with vagina form the birth canal..
It includes following structure:
Mons Pubis: cushion of fatty tissue covered by skin.
Labia majora: fleshy folds of tissue that surrounds
the vaginal opening.
• Labia minora: are paired folds of tissue under the
• Hymen: the opening of vagina is covered partially
by a membrane called hymen.
• Clitoris: It is a tiny finger-like structure lies at the
upper junction of two labia minora above the
• The mammals has
mammary gland that
secretes milk to feed
young ones. Human
beings are mammals. The
pair of mammary glands
in females are active.
• Each mammary gland
consists of glandular
tissue and fat.
• Glandular tissue of each
breast divided into 15-20
• Mammary lobes contain
cluster of cells called alveoli.
The cells of alveoli secrete
milk, stored in the lumen of
• The alveoli open into
• The tubules of each lobe join
to form a mammary duct.
Several mammary ducts join
to form a wider mammary
• Mammary ampulla
connected to lactiferous duct
that opens at nipple. Through
this milk is sucked out by
Section of ovary.
• The ovary contains
number of ovarian
follicle with immature
• After puberty primary follicles get surrounded by
more layers of granulosa cells and a new theca to
form secondary follicles.
• The secondary follicle transformed into tertiary
follicle, characterized by a fluid filled cavity called
• As one of the oocyte matures the ovarian follicle
develops into graafine follicle.
• The wall of the graafine follicle is made up of outer
fibrous theca externa and inner vascular theca interna.
Inner to the theca interna 10-15 layers of follicle cells
forms the membrana granulosa.
• The graafine follicle encloses the cavity called antrum. The
matured haploid ovum is present inside the graafine follicle.
• The plasma membrane of the ovum is externally covered by a
thick and transparent primary membrane called zona
• On the outer side of zona pellucid, the ovum is covered by a
layer of follicle cells forming corona radiata.
• Corona radiata attaches to any one side of the membrana
• The C-shaped antrum is filled by fluid secreted by
follicle cells. It is rich with F.S.H, L.H and estrogen.
• During ovulation graafine follicle releases the ovum
and changes into corpus luteum. It secrets
progesterone hormone to maintain the pregnancy.
• If the ovum is unfertilized corpus luteum generates
into a mass of fibrous tissue called corpus albicans
• The process of formation of
haploid female gamete
ovum in the follicles of
ovary is called oogenesis.
• Oogenesis starts during
• Germinal epithelium of
ovary divided mitotically to
produce millions of gamete
mother cell or oogonia.
• No oogonia formed or
added after birth.
• Oogonia enters into
meiosis-I. It proceeds
Prophase-I , get
suspended and forms
• during puberty, the
primary oocyte restarts its
first meiotic division.
• Oogenesis takes place by
three stages as follows.
1. Multiplication phase:
The ovary is lined by
germinal epithelium. These
cells undergo mitotic cell
division to form large
number of diploid oogonia
and follicle cells.
2. Growth phase: One
of the diploid oogonia
increasing in cytoplasm
and accumulation of
yolk. This enlarged
oogonia is called primary
3. Maturation phase: A
oocyte undergoes I
meiotic division results
in the formation of two
unequaled sized haploid
• The large secondary
oocyte and a small sterile
polocyte (polar body).
The secondary oocyte
undergoes II meiotic
division to form a large
ootid and a small sterile
2ed polar body.
• The 1st polar body also
undergoes equal division
to produce two cells.
• Thus during oogenesis four cells are produced.
Among them one is functional ootid and three are
non-functional polar bodies. The ootid with very
little change becomes an ovum.
• Reproductive cycle of female primates is called
• The menstrual cycle begins when a female reaches the
age of puberty. The first menstruation begins at
puberty is called Menarche.
• During the menstrual cycle the uterus endometrium
prepares itself for implantation of a fertilized egg. If
fertilization does not occur the uterus lining is shed
from the body. This is known as menstruation .
• Menstrual cycle repeated at an average interval of 28
• One ovum is released in the middle usually 14th day of
each menstrual cycle.
Menstrual cycle has
The cycle can be divided
into four phases
1. Menstrual phase
2. follicular (before the
egg is released).
3. ovulatory (egg is
4. luteal (after release of
• Menstrual phase (bleeding
• It is the 1st phase of
menstrual cycle lasts for 3-5
• Breakdown of endometrial
lining and blood vessel occurs.
It leads to bleeding comes out
• It occurs only when ovum
released and fertilization does
• Lack of menstruation is the
indication of pregnancy.
• Menstrual phase
followed by follicular
• During this phase the
pituitary gland increases
the production of
• This hormone
stimulates the growth of
primary follicle to
• The levels of FSH
hormone decreases and
the graafian follicles
begin to secrete
oestrogen. Level of
• This helps regeneration
and proliferation of
• It lasts for 5-13 days.
• Ovulatory Phase
• Usually this phase occurs
at 14th day.
• This phase begins with the
luteinizing hormone surge
(LH surge). The level of
FSH increases to a lesser
• LH stimulates enzymes in
the graafin follicle to
follicle rupture and release
of egg (ovulation).
• The egg travels into the
fallopian tube, ready
for fertilisation. The
egg can survive for 12
to 24 hours after
• The ovulatory phase
usually lasts 16 to 32
hours and ends when
the egg is released.
• Luteal phase:
• This phase begins after
• Ruptured Graafian follicle
transformed into corpus
luteum. It produces large
amount of progesterone.
• LH and FSH levels fall back to
low and steady levels.
• Progesterone maintains
prepares it for
• Thickness of uterine
in many folds, due to
• If fertilization occurs
corpus luteum grows
further and pregnancy
cycle stops up.
• In the absence of
luteum degenerates into
• Decrease in progesterone
hormone leads to
• Menstrual cycle stops
around 50 years of age.
The condition is called
• During copulation (coitus or
sexual activity) semen is
released by the penis into
the vagina is called
• The motile sperm swim
rapidly, pass through cervix,
uterus and finally reach the
junction of isthmus and
ampulla (ammpullaryisthmic junction).
• The ovum released from the ovary also transported to
ampullary isthmic junction. The fertilization takes place
in that place.
• Fertilization only takes place if both sperm and ovum
reach ampullary – isthmic junction simultaneously.
• The process of fusion of a
sperm and ovum is called
• Acrosome of sperm secretes
lytic enzymes helps in
penetration into the ovum.
• Once a sperm comes contact
with the zona pellucida of
ovum, it induces the changes
in the membrane that blocks
the entry of other sperms.
• Only one sperm fertilize with
• Haploid nucleus of sperm
fused with the haploid nucleus
of ovum to form a diploid
• Sex of a baby is determined during fertilization and
in the zygote.
• Sex is determined by the sex-chromosomes present
• Human female contain XX chromosomes and male
contain XY chromosomes.
• All the female gametes produced has 22 autosome
and only ‘X’ chromosome. Hence are homogametic.
• Sperms produced by male, 50% has 22 autosome
with ‘X’ and 50 % has 22 autosome with ‘Y’
chromosome. Hence heterogametic.
• The fusion of androsperm (22+Y) with ovum
results in male baby.
• The fusion of gynosperm (22+X) with ovum
results in female baby.
• Zygote with XX chromosomes develop into
female and with XY chromosome develops
• Early embryonic development.
• The development of zygote in to full embryo is
called early embryonic development.
• It occurs by cleavage, blastulation, gastrulation and
• Repeated mitotic division of the zygote without
growth resulting a multicellular ball is called
• Cleavage starts soon after fertilization. The cells
formed by cleavage are called blastomere. It results
in formation of ball of cells called murula.
• The morula continues to divide and transformed
into blastocyst (blastula).
• The blastomeres in
blastocyst arranged into two
layers. An outer layer called
trophoblast and an inner
cells called inner cell mass.
• Trophoblast cells attaches to
the endometrium. It helps in
development of placenta.
• Inner cell mass gets
differentiated into the
• The complete attachment
Blastocyst to the uterine
endometrium is called
• Implantation requires 3 to 5days. It completes in
9 to 10th day after fertilization.
• After implantation trophoblast
develops finger like
projections called chorionic
• It surrounded by uterine
tissue and maternal blood.
• The placenta is a connecting
vascularised organ develops
between embryo and mothe
• The chorionic villi and
maternal tissue together
• Function of placenta:
• The embryo connected to the placenta by umbilical
• It facilitate transport of oxygen and nutrient from
mother to embryo.
• Removes CO2 and waste material from the embryo.
• It is barrier for number of pathogens.
• It acts as endocrine gland and produces several
hormones. Among them Imp are
a. Human chorionic gonadotrophins (hCG)
b. Human placental lactogen (hPL)
• Human chorionic gonadotrophins (hCG):
Along with progesterone, HCG is also
important to maintain pregnancy.
• The urine test is done to identify the presence
of HCG. in urine confirms the pregnancy.
• Embryonic development:
• The inner cell mass of blastula are called stem cells.
They had the potency to produce all types of cell,
tissues and organs by differentiation.
• After implantation the stem cells of blastocyst
differentiated into an outer layer ectoderm, inner layer
endoderm and middle mesoderm.
• Formation of different organs in the embryo is called
• After one month of pregnancy heart is formed in the
• By the end of 2nd month the foetus develops limbs and
• By the end of 12 weeks (first trimester) most
of organ system is formed (limbs and external
genitalia are well developed).
• In the 5th month first movement of foetus and
appearance of hairs observed.
• By the end of 24th week (6th month or 2nd
trimesters) the body is covered with fine hairs,
eye-lids separate, and eyelashes are formed.
• By the end of 9 months the foetus is fully
developed and is ready for delivery.
• PARTURATION :
• The period of pregnancy is called gestation period. It
is 9 months in human.
• The delivery of foetus is called parturition. It occurs by
the contraction of uterine Myometrium.
• The signal of parturition is originated from the fully
developed foetus and the placenta. It induces mild
contraction of uterus called fetal ejection reflex.
• Fetal ejection reflex triggers the release of Oxytocin
• Oxytocin induces stronger contraction of uterine
• After delivery the placenta is also expelled out of the
• Process of milk production in mammary gland is
• The mammary gland starts producing milk
towards the end of the pregnancy.
• Milk produced during initial days of lactation is
called colostrum.It contains several antibodies
which provide immunity to the new born baby.
• The milk production is controlled by Lacto trophic
or prolactin hormone secreted by pituitary.