human reproduction.pdf

HUMAN REPRODUCTION
***
www.etoosindia.com

Reproduction in Human
(pituitary & gonadal hormonal control)
Gametogenesis
↓
Insemination
↓
Syngamy (Fertilization)-Zygote formation
↓
Development of Embryo (Blastocyst stage)
↓
Implantation (=Nidation) of embryo to uterine wall
↓
Gestation Period (280 days/40 week/9 month 7 days)
↓
Parturition (Child delivery)
↓
Lactation

Male Reproduction System
Primary Sex Organ
– Testes
* 4-5cm long
* 2-3 cm wide
* 1 pair in
Scrotum (Pouch)
* Outside
abdominal cavity
* 2-2.5ºC lower
than body temp.
* Oval shape
* Covered by
Mesorchium
* Spermatid Cord
* Gubernaculum
* Dartos & Cremaster
muscles
* T. Albuginea
* Testicular Lobules
(250 in each)
External
Genitalia
– Scrotum
– Penis
Accessory Ducts
1) Rete testis (network)
– all seminiferous
tubules opens into it
2) Vasa efferentia
– 12-15, takes sperm
out from testis (Leaves testis)
– Opens into epididymis
3) Epididymis
– highly coiled tube
– on post. surface of testis
– Ciliated epith. (Stereo-cilia)
– 3 parts (cuput/Corpus/Cauda)
– Temporary storage &
maturation of sperms
– Lead to vasa deferens
4) Vasa deferens
– extension of Cauda epididymis
5) Ejaculatory Duct
6) Urethra
Accessory
Reproductive
Glands
– Seminal vesicle
– Prostate
– Cowpers/
Bulbourethral

Testis-
 formed inside abdominal cavity and descend
into scrotum through inguinal canal , during
seventh month of pregnancy
 Left testis- lower

 Gubernaculum-fibrousband(elastic fibres)
connects lower end of testis to scrotal wall
 Inguinal canal – connects scrotum to
abdominal cavity
 Spermatic cord –passes through inguinal
canal , carry testicular vessels , lymphatics ,
nerves , vasa deferens

Maintainance of temperature in
scrotum-
 Contracts in cold weather-
1.Cremaster muscle (scrotum & inguinal canal)-
contraction(quick)→pulls scrotum towards
abdomen / wrinkles in scrotal skin →surface
area reduces → heat loss / dissipation reduces
2.Dartos muscle (scrotum) - contraction(slow) →
wrinkles in scrotal skin → surface area reduces
→ heat loss / dissipation reduces

 Intra-abdominal testis – Elephants, whale,
dolphin, oviparous mammals

 Functions:
1. Sperm formation
2. Androgen formation
a) helps in spermatogenesis
b) helps in sperm maturation in epididymis
c) male secondary sex organ development and
maturation
d) male secondary sex characters development
and maturation
e) responsible for libido (sex desire)
f) descend of testis

 L.S OfTestis – coverings of testis
1.Tunica vaginalis – double layered peritoneum , outermost
Parietal & visceral , in between space- little fluid
Covers whole testis , except posterior border , where
testicular vessels& nerves enter
2.Tunica albuginea – surround testis ,W.F.C.T , protection
Testicular septa – invagination ofT. Albuginea into testis
Testicular lobules – 200-250 in each testis , formed by septa
3.Tunica vasculosa – innermost layer , lines testicular
lobules , highly vascular

 Structural and functional unit of testis –
Seminiferous tubules – 1-3 in each lobule ,
total 500-750 in each testis
 Tubuli recti – straightened part of
seminiferous tubule
 Rete testis – by fusion of tubuli recti
 Vasa efferentia / ductuli efferentes –leaves
testis ( part of testis )

 Epididymis–
 Highly coiled , 6 meter long
 Along Posterior surface of each testis
 Vasa efferentia opens into it
 3 parts- caput(most coiled) , corpus , cauda
 Store ( upto 1 month) & functionally mature
sperms (physiological maturity)
 Outer -Circular smooth muscle
 Inner-Pseudo Stratified Ciliated Epithelium
(non-motile stereo cilia)
 Continue into Vas deferens
 Develops from Wolffian / Mesonephric Duct

 Vas deferens / vas deferentia (Plural) –
 Thin narrow tube
 origin from cauda epididymis
 ascends to abdomen (through spermatic cord),
loops over urinary bladder, forms Ampulla
(dilated part of Vasa deferens)
 receives a duct from seminal vesicle
 opens into urethra as ejaculatory duct
 Circular smooth muscle
 Pseudo stratified stereo-ciliated epithelium
 Develops from Wolffian / Mesonephric Duct

Ejaculatory duct-
 enters into urethra , after passing
through prostate gland
Urethra–20 cm long , originates from
urinary bladder & extends through
penis to its external opening called
urethral meatus

 Cryptorchidism / Undescended testis –
failure of descent of testis into scrotum ,
failure of sperm formation , sterility
 Monorchidism – single testis e.g. Ascaris
 Orchiopexy – descent of testis from abdomen
into scrotal sac by surgery
 Castration – surgical removal of testis
 Vasectomy – cutting & ligation of vasa
deferens , permanent sterilization

 Seminal vesicle gland –
 1 pair , tubular , coiled
 Develops from Wolffian / Mesonephric Duct
 Dorso-lateral surface of urinary bladder
(posterior)
 Joins vasa deferens to form ejaculatory duct

 Seminal vesicle Secretions-
 Alkaline (pH 7.2-7.8)
 Transparent , jelly like
 60-70% of semen
 Fructose (fuel for sperm nutrient, forensic test for
rape)
 Inositol
 Prostaglandins – induce contraction in female
reproductive tract
 Fibrinogen - clots semen (reduce sperm motility,
so conserves energy)
 Citrate ions

 Prostate gland -
 Single , At base of urinary bladder
 Chest nut shaped
 Duct opens into urethra
 Helps in sperm activation
 Secretion –
 Alkaline , milky , jelly like
 25-30% of semen
 Calcium and phosphate ions
 Citrate ions
 Albumin , fats
 Profibrinolysin – liquefies semen

 Cowper’s/ Bulbo-urethral gland-
 1 pair
 Pea-sized
 Lateral side of membranous urethra
 Duct opens into penile urethra
 Secretions-
 Transparent , jelly like , alkaline,
lubrication of penis and neutralize acidity
of urethra and vagina (pre-ejaculatory
fluid)

Path of Sperm through the Male Body
Rete
testis
Seminiferous
tubules
Vasa
efferentia
Epididymis
Vas
deferens
Urethra Ejaculatory
duct

ST RT
a
Seminiferus
Tubule
DE Varun Dhawan,
Trick for pathway of Sperm/semen :-
Rete Testis
EP
Ductus
Efferentia
Epididymis Vasa deferens
Somewhere Exit Comedy of
Seminal Vesicle
Purani
Ejaculatory
Duct
Prostate Cowper’s
Ur
Urethra
Papa
Penis

 Penis-
 Cylindrical , muscular , Copulatory organ
 External genitilia , in front of scrotum
 Enclosed in T. albuginea (fibrous sheath)
 Glans penis – enlarged end , covered by
foreskin
 Prepuce / foreskin – loose retractile skin fold
at glans penis

 External urethral orifice-slit at tip of glans
penis , by which urethra comes out
 Tyson / preputial glands –sebaceous gland on
prepuce ,secretes smegma
(lubricates glans penis)
 Circumcision – removal of prepuce by
surgery

1.Corpora cavernosa – 2 dorsolateral ,
longitudinal erectile tissue
2.Corpus spongiosum/urethrae– single
ventral , longitudinal , erectile tissue
 Urethra passes through Corpus
spongiosum
 Blood sinuses in erectile tissue of penis

 During intercourse / arousal → dilatation of
penile arteries due to NO Signal (act as second
messenger) → increased blood supply to penis
→ blood rushes into blood sinuses →
enlargement & hardening of penis
(Erection of penis)

 Erection of penis–facilitates/ essential
for insemination (parasympathetic ANS)
 Ejaculation – forceful release of semen
(sympathetic ANS)
 Erectile dysfunction (ED) –
 Absence of erection of penis
T/t – Sildenafil citrate (= Viagra)

 Semen = Sperm + Accessory reproductive gland fluid
 Volume – 2-3 ml /intercourse
 White, alkaline (7.2-7.4), viscous
 1 ml semen - 100 million sperms
 1 Ejaculate -200-300 million sperms
 Normal semen – 60% normal shape & size
and 40% vigorous motility

1. Aspermia – no semen production
2. Azoospermia-absence of sperms in semen
3. Oligospermia - < 20 million sperm / ml semen
4. Asthenospermia-reduced motility of sperms in
semen
5. Teratospermia – sperms with abnormal morphology

 Seminiferous tubule –
 Structural & functional unit of testis
 Covering – Tunica Propria (WFCT)
 Germinal epithelium-
a) Male germ cells – simple cuboidal
b) Sertoli cells –columnar, nourish sperms

 Leydig / Interstitial cells –interstitial space
 in between seminiferous tubules
 Endocrinal cells
 produce Androgens
 stimulated by LH/ICSH (anterior pituitary)

Primordial germ cells (PGC)-
 Form germinal epithelium
 Cuboidal , diploid , 46 chromosome
 Extra-gonadal in origin
 Origin - mesoderm of yolk sac of embryo
 Migrate into gonads at 5th week of pregnancy
 Gonads differentiate into testis/ovary after 8
weeks of pregnancy
 Formation of male gamete

 Functions of sertoli cells / sustentacular /nurse
cells
 In germinal epithelium of seminiferous tubule
1. Nourish developing sperms
2. Act as barrier to protect sperms
(Sertoli cell barrier/Blood Testis Barrier)
3. Phagocytize dead & abnormal sperms
4. Absorb parts shed by developing sperms
( cytoplasm , organelle etc)

4. Produce Aromatase enzyme - converts
testosterone into estradiol (essential for sperm
sustainance)
5. Produce three hormones (AIM) –
A)AndogenBinding Protein(ABP)
- concentrate testosterone
B) Inhibin- suppress FSH
C) Mullerian Inhibitory Hormone (MIH /
AMH)-Suppress mullerian duct to form uterus ,
FT etc. , only in embryonic life

Hormonal Control of Male Reproductive System
LH/ICSH
FSH
Hypothalamus
GnRh
Ant. Pituitary
Leydig cells
Sertoli cells
Development of sec. sex
organs & characters
Inhibin-Spermatogenesis Testosterone
Testis
If in
excess

 Disorders :
1. ADAM –Androgen Deficiency in Ageing Male
 Andropause –
 after 50 yr age-----reduced androgen secretion
 Deficiency of ABP
 Reduced Spermatogenesis
 Reduced sex desire/libido
2. BPH – Benign Prostatic Hypertrophy
 Enlarged prostate , in old age
 Compress urethra
 Increase frequency of micturition , esp. during night

3. Malignant prostatic cancer
4. Inguinal hernia – passage of dislocated
intestine into scrotum through inguinal
canal
5. Hydrocoel - collection of ‘serous fluid’
inside Tunica vaginalis

Spermatogenesis –
Sperm formation
Inside seminiferous tubules
Starts at puberty – under effect of
GnRH & FSH
3 events-
a) Spermatocytogenesis
b) Spermiogenesis
c) Spermiation

 Spermatocytogenesis : 3 stages
1. Multiplicationphase-(mitosis)-
spermatogonia (germ cells)-type A & B
produced (2n)
2. Growth phase –spermatogonia type-B
enlarge to form primary spermatocyte (2n)
3. Maturation-meiosis-spermatid(n) formed

 Followed by Spermiogenesis/
Spermateleosis –
Transformation of Spermatid into
Sperms

Spermatid – non motile , heavy , cell organelles
like mt . , GB etc present
Sperms –
weight reduced
Nucleus becomes compact
Development of locomotory structures
GB forms Acrosome
2 centrioles arranged one behind other
Mitochondria arranged spirally
Much of cytoplasm lost

 Developing sperm embeds its head into sertoli
cell to draw nourishment, after spermatogenesis
 Spermiation – detachment of sperm head from
sertoli cells , comes into luminal part / liberation
of sperms from sertoli cells into seminiferous
tubule lumen , prior to their passage to
epididymis

 1 primary spermatocyte (2n) – 2 secondary
spermatocyte
 1 secondary spermatocyte –2 spermatid(n)
 1 secondary spermatocyte(n) – 2 sperm(n)
 1 primary spermatocyte - 4 sperms
 1 primary spermatocyte– 4 spermatid(n)

Germ
Cell in Testis
Spermatogenesis :-
At Pubertry
GnRH
FSH
1st mitosis
Wall of semini ferous tubules
Type A Act as
Germ cells
Spermatogonium
Type B
2n = 46
7 mitosis &
meiosis
512 sperms
2 sec. spermatocytes
4 spermatids
4 sperms
2 spermatids
2 sperms
* 1 prim. spermatocyte
(2n = 46)
* 1 Sec. spermatocyte
74
days

Human sperm –
 Discovery –A.V. Leeuwenhoek
 Size – 55 (L) X 5 (W) micron
 Motile, flagellated except Ascaris
(roundworm)
 Plasma membrane envelops whole body of
sperm

1. Head-
 Acrosome (Cap like golgi , spermlysins like hyaluronidase
, digest egg membrane )
 Nucleus (elongated , haploid , highly condensed chromatin
– DNA + protamine basic protein , genetic/heredity)
2. Neck - 2 centrioles
 Distal – forms basal body (9+0) for axonema / flagella
 Proximal- role in first cleavage division
3. Middle piece –
 Mitochondria (power house /energy store)-25-30
 Axonema /Axial filament(9+2microtubular)
4. Tail (longest) - flagella (9+2) – 50 micron long

 Axial filament begins just behind distal centriole
, passes through middle piece & extends into tail
 Nebenkern–spirally arranged fused
mitochondria
 Manchette – thin cytoplasmic sheath in middle
piece
 Annulus / Ring centriole / zensons ring-where
middle piece joins tail , axial filament passes
through a ring-like structure, unknown function

Ante-Natal
Acrosome
Checkups Must
Trick for human sperm
Nucleus
Are
Centrioles (2)
(Neck)
Axoneme mt
Head middle piece
(Energy chamber)
in
Flagella
(Tail)
Full pregnancy

Female Reproduction System
Primary
Sex Organ
– Ovary
E
M
C
V
L
xternal
Genitalia
– ons pubis
– litoris
– estibule
– abia
Sec. Sex Organs
(=Genital duct)
– F.T.
– Uterus
– Cervix
– Vagina
– ammary
– artholin
– kene gland
Reproductive
Glands
MBS
M
B
S
E m
C V L
xercise of aths &
hemistry are ery engthy

THE FEMALE REPRODUCTIVE SYSTEM
The female reproductive system consists of a pair of ovaries
along with a pair of oviducts, uterus, cervix, vagina and the
external genitalia located in pelvic region.
These parts of the system along with a pair of the mammary
glands are integrated structurally and functionally to support
the processes of ovulation, fertilisation, pregnancy, birth and
child care.

Ovary - primary female sex organ
 produce gamete (ovum) & steroid ovarian hormones
 located one on each side of the lower abdomen
 4 X 3 X 2 cm , almond shaped
 2 to 4 cm in length
 Connected to pelvic wall and uterus by ligaments
 Attached to uterus – ovarian ligament
 Attached to Body wall – Mesovarium
 Covered by ‘thin epithelium’ , which encloses
‘ovarian stroma’

 Germinal epithelium - outside surface of ovary,
simple cuboidal cells – PGC / Oogonia (diploid)
 Ovarian stroma- Internal fibrous CT
 Cortex – outer , ovarian follicles in various stages
 Medulla –loose CT , smooth muscle , peripheral
blood vessels, nerves
 Tunica albuginea – covers cortex , protective
WFCT

Fallopian tube/ Uterine tube/ Oviducts/
Salpinges –
 Extends from periphery of each ovary to
uterus
 Passage of eggs/ zygote from ovary to uterus
 Site for fertilization
 10-12cm long

 Four parts –
1. Infundibulum – funnel shaped, part closer to
ovary, fimbriae (finger like projections which
help in collection of ovum after ovulation),
ostium (opens into peritoneal cavity)
2. Ampulla – widest, longest
3. Isthmus – narrow lumen and it joins uterus
4. Intramural/ interstitial-joins uterus

Fertilization site –
 Ampullary - Isthmic junction
 Mesosalpinx - double fold of peritoneum
, suspends FT

 Internally 3 layers –
1. Serosa-peritoneum+ areolar CT
2. Muscular-Smooth muscle(circular & long)
3. Ciliated columnar epithelium (Kinocilia)-
 Uniform movement of egg/zygote towards uterus
 Estrogen increase cilia no.
 Peg cells : non-ciliated secretory cells , in inner
lining of FT , in between ciliated cells , secrete
‘tubular fluid’-nourishes egg/sperm/zygote

3) Uterus /Womb/ Hystera –
 Supported by ligaments attached to pelvic wall
 Shape - inverted pear
 Location-betweenbladder(anterior) & rectum(posterior)
 Size -7.5 X 5 X 2.5 cm
 Hollow , muscular , highly distensible
 Simplex type - both halves fused
 Anteflex / anteverted – bent forwards on itself

 Three parts –
1. Fundus -upper , dome shaped , above opening
of FT
2. Body – middle main part
3. Cervix-lower (opens into vagina, cervical canal
, external and internal os)
 Internal os – between cervix & uterus
 External os- between cervix & vagina
 Cervical os- most powerful sphincters of body
 Cervical canal + Vagina = Birth canal

 Wall of uterus – 3 layers
1. Perimetrium – outer ,thin membranous ,
mesothelium + areolar CT
2. Myometrium – middle ,thick , smooth ms
(circular/long/oblique) , Parturition
3. Endometrium – inner ,lines uterine cavity ,
highly vascular, glandular , columnar
epithelium + mucus membrane, undergoes
cyclical changes during menstrual cycle

 Endometrium – 2 layers
1.Stratum basalis – inner to myometrium ,
straight blood vessels , gives rise to
S.functionalis
2.Stratum functionalis –
 Inner to stratum basalis
Adjacent to uterine cavity
Tortuous blood vessels
Tubular glands (construction-estrogen , cork
screw shaped – progesterone)

Progesterone , after ovulation –
 Increase thickness of stratum functionalis
 Convert tubular glands into cork screw shaped
Cork screw tubular glands secrete uterine milk
Uterine milk-glycogen, protein rich nutritive
fluid to embryo , before implantation

If no fertilization –
 Decrease in progesterone level
 Sloughing off / breaking / shedding off
endometrium ( stratum functionalis) -
menstruation

Decidua-3 Layers
1) D. Parietalis/
D.vera
– no relation
with embryo
2) D. placentalis/
D. basalis
– Contributes in
Placenta formation
3) D. Capsularis
– Surround Embryo
from all sides till 26
wks of pregnancy
Protects Embryo from
mothers immune system
 Decidua – Endometrium in pregnancy

Cervical canal fluid– 30-50 ml / day thick / chalky
fluid
During fertile period – cervical canal fluid – thin &
stretchable (ovulation test)

 Functions of uterus –
1.Site of fetal growth during pregnancy
2.Participate in placenta formation
3.Expulsion of baby during delivery

4) Vagina-
 7.5-10 cm long fibro-muscular tube , from
cervix to outside
 NKSSE
 No glands
 Lactobacillus - natural microflora
 Acidic pH - 3.5-4.8
 Copulatory organ
 Birth canal , along with cervical canal
 Vaginal Rugae – transverse mucosal folds in
vagina

Hymen – membrane covering partially opening
of vagina
 Often torn during first coitus, also can be
broken by a sudden fall or jolt, insertion of
vaginal tampon, horse riding, cycling etc
 In some women, persist even after coitus
 Presence or absence of hymen is not a reliable
indicator of virginity or sexual experience

Vulva /External genitilia –
 Vestibule - bowl shaped cavity , 2 openings
 2 openings–
1. Vaginal (posterior)
2. Urethral (anterior)

1. Mons pubis/M. veneris – cushion of fatty tissue
over pubic bone, covered by skin and pubic hair
2. Labia majora – fleshy folds of tissue (skin, extent
down from mons pubis and surround vaginal
opening) , covers labia minora
3. Labia minora – paired folds of tissue under labia
majora , surrounds vestibule , tip – prepuce
4. Clitoris – tiny finger like, at upper junction of two
labia minora above urethral opening, Erectile tissue
for pleasure sensation

 Fourchette - folds of skin at posterior
junction of labia minora
 Perineum – area between fourchette
and anus

 Female reproductive glands –
1. Bartholin / Greater vestibular glands –
 One pair , on each side vaginal opening
 Mucoid alkaline secretion
 Lubricates & reduce acidity of vagina , before
coitus
2. Glands of Skene / Peri / Para-urethral / Lesser
vestibular glands –
 Several , around urethral opening
 Lubricates, reduce acidity of vagina and vestibule

Homologus Organs
Female Male
1. Labia Majora Scrotum
2. Labia minora Penile Urethra
3. Clitoris Penis
4. Bartholin gland Cowper’s gland
5. Glands of Skene Prostate gland

Mammary glands –
 Characteristics feature of all female mammals
 Non-functional in male mammals
 Prototherian mammals –mammary gland without nipples
 Develops at puberty
 Paired exocrine gland
 SAT- modified Sweat gland, Apocrine, Tubulo – alveolar
gland
 Over pectoralis major muscle in thoracic region

 Suspended by ‘Coopers ligament’-maintain
structural integrity of gland
Contains Glandular tissue & variable
amount of Fat (determine size of breast)
Provide nourishment to new born

 Glandular tissue of each breast –
 15-20 mammary lobes – cluster of milk secreting cells
(cuboidal – alveoli , functional unit)
 milk stored in cavities (lumen) of alveoli
 Alveoli opens into mammary tubule
 Tubules of each lobe joins to form a mammary duct
 Several mammary ducts join to form a wider
mammary ampulla / lactiferous sinus connected to
lactiferous duct, through which milk is sucked out

Note:-
 Mammary ampulla – temporary storage of
milk
 Areola–dark pigmented area around nipple ,
modified sebaceous glands – keeps nipples
moist

Passage of Milk
Many alveoli
↓
Many mammary tubules
↓
One mammary duct
Several mammary ducts joins to form
↓
Lactiferous Sinus/Mammary Ampulla
(Dilated part, just before nipple)
↓
Lactiferous Duct
Opens outside through nipple

Mother
Mammary
LacTating
Trick for milk passage :-
Tubule
Daily,
Lobe Duct
Love
Sinus
Simply
( actiferous)
L Duct
Develops with baby

 Hormonal control –
1. Thelarche – at puberty, estrogen-development
of ductal system , fibrous & fatty fissue
2. Progesterone – multiplication of milk alveoli
3. Prolactin – milk production
4. Oxytocin – milk ejection / milk- let down
hormone
5. Human placental lactogen (hPL) - production
of milk during pregnancy

BRIEF REVIEW
Development of secondary sex organ -
Male Female
Wolffian duct or
Mesonephric duct
Epididymis
Vas deferens
Seminal vesicle
Mullerian duct – Fallopian tube,
uterus and vagina
(Oviduct)

 Follicle development inside ovary (cortex of stroma)
1. Primordial follicle –smaller , dormant , primary
oocyte , surrounded by single layer of squamous
stromal cells
 Formed in fetal life, before birth
(max by 22 week gestation-7 million)
 At birth : 2 million / 20 lac /ovary
 At puberty : 2 lac / ovary

2. Primary follicle –
 Larger , mitotic follicles
 Primary oocyte surrounded by single layer of
cuboidal stromal / granulosa cells
 Formed from primordial after onset of puberty.
 At puberty : 60000 - 80000 / ovary
(follicular atresia)

3. Secondary follicle –
 Primaryoocyte surrounded by multiple
layers of granulosa / follicular cells
 A new theca layer (fibrous)
 After puberty (1-2/month)

4. Tertiary follicle –
 Fluid filled cavity /Antrum , theca interna and externa(outer
fibrous) organized
 Primary oocyte grows in size & completes its first meiotic
division (unequal – haploid large secondary oocyte and
tiny first polar body formed)
 Secondary oocyte secretes zona pellucida (glycoprotein,
non- cellular membrane surrounding secondary oocyte ,
species specific glycoproteins)
 Theca interna – glandular/secretary –LH Receptors ,
androgen formation by granulosa cells (aromatization of
androgen into estrogen)

5. Graafian follicle – most ripened, mature follicle
 Antrum surrounding oocyte divides granulosa cells into
cumulus oophorus (cluster of cells around sec.oocyte) and
membrana granulosa
 Discus proligerus / germ hill –granulosa cells which
connects sec.oocyte with wall of follicle
 Zona pellucida , T.externa and interna , liquor folliculi
present
 Corona radiata – innermost cells of cumulus oophorus ,
lying in vicinity of oocyte & zona pellucida

The process of formation of a mature female gamete is called
oogenesis which is markedly different from spermatogenesis.
Oogenesis is initiated during the embryonic development
stage when a couple of million gamete mother cells (oogonia)
are formed within each fetal ovary; no more oogonia
are formed and added after birth. These cells start division
and enter into prophase-I of the meiotic division and get
temporarily arrested at that stage, called primary oocytes.

Each primary oocyte then gets surrounded by a layer of
granulosa cells and is called the primary follicle (Figure 3.7).
A large number of these follicles degenerate during the phase
from birth to puberty. Therefore, at puberty only 60,000-
80,000 primary follicles are left in each ovary.
The primary follicles get surrounded by more layers of
granulosa cells and a new theca and are called secondary
follicles.
The secondary follicle soon transforms into a tertiary follicle
which is characterised by a fluid filled cavity called antrum.
The theca layer is organised into an inner theca interna and
an outer theca externa.

 Ovulation – rupture of graafian follicle to release
secondary oocyte from ovary (along with zona pellucida
and corona radiata) , under LH hormone
 Corpus haemorrhagicum – bleeding CL , convert into-
 Corpus luteum – yellow (Lutein pigment) /
transformed graafian follicle (granulosa & theca cells)
after ovulation, glandular (under LH effect)
 Secretes progesterone (essential for maintenance of
endometrium) , little estrogen, relaxin , inhibin
 Corpus albicans – white , non-glandular, after 10 days ,
CL degenerates if no fertilization

 Oogenesis – formation of mature female gamete/
ovum/ ootid
 Germ cells – extragonadal (extra-embryonic
mesoderm, yolk sac)
 Starts before birth (in-utero) from second month of
pregnancy
 Completes only after fertilization
 Reproductive life of female – limited

 Three phase –
1. Multiplication –
 germ cells – mitosis – produce daughter oogonia
(2n)
 Starts by 8 week gestation & completed before birth
 Maximum oogonia formed by 22 week gestation
 No multiplication after birth
 No new oogonia formed or added after birth

2. Growth phase -
 Occurs in utero / Fetal life
 Oogonia grow in size & transform into primary
oocyte (later get arrested in diplotene of
prophase – I of meiosis – I)
 Longest phase in oviparous animals due to
vitellogenesis (yolk synthesis)

 Follicular atresia – degeneration of ovarian
follicles occurs
 At 22 weeks gestation – 7 million primordial
follicles in ovary
 At birth – 4 million / 40 lac primordial follicles
in ovary
 At puberty – 1,20,000 to 1,60,000 primary
follicles in ovary

3. Maturation phase – due to rise in GnRH and FSH
 Longest , includes both meiosis
 Starts in fetal life , arrested in diplotene of prophase – I
of meiosis – I
 Every month – one primary oocyte completes meiosis-I
(unequal cytokinesis) to produce one secondary
oocyte (n) (arrested at metaphase-II of meiosis-II) & 1
polar body
 Secondary follicle – 1-2/month/ovary
 Tertiary & Graafian follicle – 1 / month /ovary

 Ovulation occurs by alternate ovary every month
 12 secondary oocyte produced every year till
menopause
 Maximum 500 in complete reproductive life)
 From birth till puberty – primary oocyte

Ovulation :
 Secondary oocyte enters into FT from ovary,
completes meiosis-II only if fertilization
occurs (MPF off & APC turned on)

 1 primary oocyte - one secondary oocyte and 1 polar body
 one secondary oocyte – one ovum + one polar body
 1 oogonia – one ovum & 2-3 polar body
 One primary oocyte – one ovum + 2 - 3 polar body
 1st polar body – degenerates in human & most vertebrates

Priyanka
Primary
oocyte
Admires
Trick for Arrest in Oogenesis
Diplotene
Padmavat-I
Arrested Prophase-I
(Meiosis-I)
Shahid
Arrested
Admired
Secondary
oocyte
Metaphase-II
(Meiosis-II)
Maharaja-II
as
Dipika as
is

Fraternal / unidentical twins –
2 follicles mature simultaneously
(2 ovum fertilized by 2 separate sperms)
 25 ovum produced by 25 oogonia /
primary/ secondary oocyte

Spermatogenesis Oogenesis
Occurs inside testis ,
starts at puberty
Occurs inside
ovary,starts before
birth
All stages completed
in testis
Later stages occur in
fallopian tube
Continuous process Discontinuous process

Spermatogonia
develop from germinal
epithelium , Lining
seminiferous tubules
Oogonia develop from
germinal epithelium ,
overlying ovary
Primary spermatocyte-2
sec spermatocyte
Primary oocyte-1 sec
oocyte+1 polar body
Sec spermatocyte – 2
spermatids
Sec oocyte – 1 ovum+1
polar body

1 spermatocyte –
4 sperms
1 oocyte – 1
ovum/egg
nuclear condensation
in sperm
Nucleus remain
uncondensed
Little reserve food in
sperm
Lot of reserve food
Sperms are motile
gametes
Ovum non-motile
gametes

Low concentration of estrogen →ve feedback
→ LH Reduces
High concentration of estrogen → +ve
feedback → LH Increase

 Menstrual cycle : Mensum=month / moon
 Reproductive cycle in female primates (monkeys, apes,
human beings)
 Periodic / cyclical shedding off endometrium (stratum
functionalis) , f/b its proliferation , to prepare itself for
implantation
 Menarche – first menstruation, at puberty
 Duration – 28 days (21-35 days) i.e from Day 1 of m.c to
day 1 of next m.c

 Menstrual blood (liquid) doesn’t clot due to
plasmin protein (fibrinolysin)
 One ovum is released (ovulation) during
middle of each menstrual cycle
 Menstruation only occurs if released ovum is
not fertilized

 Regulation by-
1.pituitary hormones (FSH and LH)
-ovarian cycle
2.ovarian hormones (estrogen and
progesterone)-uterine cycle

 Four phases –
1. Menstrual phase (day 1-5)-
 cycle starts , lasts for 3-5 days
 CL of previous m.c regress completely(day 1)
 low level of estrogen and progesterone-bleeding occur
 menstrual flow due to break down of endometrial lining
uterus and its blood vessels (forms liquid – comes out
through vagina)
 FSH & LH free of inhibition
 Stimulation of follicle development in ovary

2. Follicular /proliferative phase (day 6-13)-
 Gonadotropins (LH and FSH) increase gradually –
stimulates follicular development in ovary and
secretion of estrogen by growing follicles
 By day 7 – one dominant follicle selected
 Rise in estrogen – rebuilding of endometrium
 High level estrogen +ve feedback on LH
 Sudden increase in LH
 Both LH and FSH attain peak in middle of cycle (day
14)

3. Ovulation/ ovulatory phase - day14
LH surge (rapid secretion to its max.
level) – rupture of graafian follicle –
release of secondary oocyte/ ovum

4. Luteal / secretory phase – day 15 -28
 Fixed duration (day of ovulation = duration of m.c-14)
 Formation of CL (under LH) from remaining parts of graafian
follicle
 CL secretes progesterone, E2, relaxin , inhibin
 CL is formed & maintained by LH
 Progesterone –makes endometrium glandular/ secretary
(necessary for implantation of fertilized ovum)
 progesterone & estrogen levels inhibits FSH & LH
 By day 25 , Absence of fertilization – CL begins to regress ,
progesterone & estrogen levels fall
 Day 28- CL degenerates , , progesterone & estrogen levels fall
, disintegration of endometrium – menstruation (new cycle
begins)

 Menstrual phase – due to decreased progesterone
and estrogen
 Proliferative phase– increased estrogen
 Secretory phase - increased progesterone
 Follicular phase – increased FSH
 Luteal phase – increased LH
 Ovulation – increased LH

 FSH and LH peak (single)– day 12-14
 Progesterone begins to form from day 15 and peak
(single) at day 21
 Estrogen (2 peaks) - Follicular day 12-14 and luteal
phase
 Secretary phase corresponds to luteal phase
 Proliferative phase corresponds to later follicular
phase

Father
Follicular
Lucy
Trick for Menstrual Cycle
Menstrual phase
Paid
Luteal
Proliferative
Mensy
Of
Ovulation
& School fee
Secretory
FSH LH
LH
decreased
E /Progesterone
2
Estrogen
Progesteron
Secretory Endom.
Follicle
develop
Form &
maint. of CL
Ovarian Cycle Uterine Cycle
Menstrual Cycle

 Normal duration – 28 days
 Normal blood flow: 40 – 80 ml (upto 100 ml)
 Menarche –
 onset of menstrual cycle
 Indicates onset of puberty
 1st menses
 Precocious puberty – menarche before 8 years of age
 Menopause - ceasation of M.C & ovulation , around 50
years of age
 Amenorrhoea-
 temporary stoppage of menses
 Lack of menstruation may be indicative of pregnancy, stress,
poor health etc.

 Oligomenorrhoea – decreased frequency of m.c
(> 35 days duration)
 Polymennorrhoea-increased frequency of m.c
(< 21 days duration)
 Menorrhagia-excessive blood loss during m.c
(> 100 ml)
 Dysmenorrhoea–painful menstruation
( due to prostaglandins)

Cyclic menstruation is an indicator of
normal reproductive phase and extents
between menarche and menopause

 Estrous cycle (non- primate mammals)
 No bleeding / menstruation (proliferated endometrium
gets reabsorbed by uterine wall
 4 phases-
1. Pro-estrous-follicular development
2. Estrous / heat period –
 ovulation
 female becomes receptive , attracts male
 Copulation occurs only during estrous phase/ heat
period due to increased estrogen
3. Meta-estrous – CL forms
4. Diestrous – CL secrete progesterone

Mono-estrous animals –
 1 estrous cycle / year
eg. Dogs , fox , wolf , bear bats etc
Poly-estrous animals-
 >1 estrous cycle / year
eg- cattles , cat , rat,horse , pigs
Anestrum – quiescent stage between 2 estrous cycles

 Rut cycle –
Seasonal testicular activity in males of some
species.
Cause sexual excitement & increased
aggressive behaviour in males
Eg- male elephant , Stag

 Egg= Oocyte + Egg membranes
Egg membranes – 3 types
1. Primary –around PM
 secreted by oocyte itself Eg- zona pellucida (mammals)
2. Secondary –
around primary membrane
secreted by ovary / ovarian follicles ( granulosa / follicular
cells) Eg – corona radiata (mammals)
3. Tertiary –
Around secondary membrane
Secreted by oviducts / uterus
Eg- jelly coat (frog) , Shell membrane ( reptiles , birds)

 Functions of Egg membranes –
1.Provide protection
2.Check polyspermy

On basis of amount of yolk - Vitellogenesis , GB
1. Alecithal -
yolk absent / negligible , eg-human
2. Microlecithal / oligolecithal -
yolk small amount , Eg-marsupials , amphioxus , sea urchin
3. Mesolecithal –
Yolk amount moderate , Eg- frog , toads( amphibia)
4. Megalecithal / macrolecithal / polylecithal –
Yolk amount large , Eg- reptiles , birds , insects , oviparous
mammals

On basis of distribution of yolk-
1. Homolecithal / Isolecithal eggs –
 Uniform distribution
 Alecithal & microlecithal eggs
 Eg- viviparous mammals , marsupials , amphioxus , sea urchin
2. Heterolecithal –
 Yolk not evenly distributed
 Meso & megalecithal eggs
 3 types-
a) Telolecithal- amphibian (yolk at vegetal pole)
b)Discoidal – reptiles , birds , oviparous mammals
c) Centrolecithal - insects

On basis of presence of shell - prevent dessication ,
land adaptation
1.Cleidoic – shell present , Eg-
reptiles (leathery coat)
birds ( calcareous)
insects (chitinous)
oviparous mammals (calcareous)
2.Non – Cleidoic – shell absent
 Eg- fishes , amphibia , viviparous mammals

Structure of human egg –
Unfertilized female gamete (secondary oocyte)
Largest cell of human body – diameter 100 micron/ 0.1 mm)
Alecithal – yolk absent
Cytoplasm – ooplasm , PM- oolema
Large nucleus- germinal vesicle
Prominent nucleolus

Numerous mt- energy for cleevage in zygote
Cortical granules – beneath oolema , hydrolytic
enzymes & mucopolysaccharide
No centriole / centrosome(degenerate at time of
2nd maturation division)
Animal pole - Part of egg from where polar body
extrudes out
Peri-vitelline space – between zona pellucida &
oolema

Surrounded by 2 egg membranes
1. Zona pellucida –
Primary egg membrane
Secreted by both oocyte & granulosa cells
Non cellular , glycoprotein layer
Species specific receptors for sperms
2. Corona radiata-
Secondary egg membrane
Secreted by granulosa cells
( 2-3 layers of elongated granulosa cells)

Largest egg – Ostrich
Smallest egg - Polychaeta

 Insemination –
 Release of semen by penis into vagina of
female , during copulation (coitus)

 Fertilization – fusion of sperm with an ovum
 Motile sperms swim rapidly , pass through cervix ,
enter into uterus & finally reach site of fertilization
 Site - ampullary region of FT
(ampullary - isthmic junction)
 Fusion of male and female gamete (sperm with an
ovum)
 Plasmogamy , karyogamy , amphimixis

 Can occur only if sperm and ovum are
transported he simultaneously to ampullary
region
 So , Not all copulation lead to fertilization and
pregnancy

Sperm viability : 24 - 48 hours (many weeks in
male genital tract)
Egg viability : 48 -72 hours
Oscar Hertwig first observed fertilization in sea –
urchin

1.Capacitation –
 physiological maturation of sperms inside female
reproductive tract (becomes hyperactive) , takes 6-7 hours
 Destabilization of PM of sperms ( rearrangement of
glycoproteins & cholesterol dissolution)
 Influx of calcium ions into sperms , becomes hyper motile
(1-2 to 4-5 mm / min , undulating→ whiplash movement
of tail)
 Prostaglandins of semen and vagina helps to propel sperms
forwards towards uterine cavity and FT

2. Antifertilizin – Fertilizin reaction
 Acidic protein on sperm surface and
glycoprotein/ ZP3 on egg surface
 Chemo attraction – binding of sperms to egg
surface
 Leads to agglutination
 Binding of sperm to egg surface
 Species-specific
 Method of reproductive isolation

3. Acrosome reaction –
 When sperm binds to ZP3 receptor on zona
pellucida of ovum
 Exocytosis of sperm lysins of acrosome
(due to calcium ions)
a) Hyaluronidase (dissolves hyaluronic acid)
b) Corona penetrating enzyme (digest corona)
c) Acrosin/ Zona lysin (digest zona pellucida)

Secretions of acrosome help sperm
enter into cytoplasm of ovum
through zona pellucida & PM
A
Acrosomal
Enzymes
Huge
Trick for Acrosomal Enzymes
CPE
Apple
Hyaluronidase Acrosin
Californian

 At end – oolema protrudes out to form
fertilization cone/ cone of reception
 As sperm head comes in contact with fertilization
cone → Fast block to Polyspermy :
 Depolarization of oolema due to opening of Na+
channels

4.Cortical reaction –
 Sperm touches oolema
↓
 calcium ions influx into ooplasm
↓
 fusion of cortical granules with oolema
↓
 exocytosis of cortical granule substance into
peri-vitelline space

5. Zona reaction –
 Hardening and thickening of ZP

Note :
 Cortical and Zona reaction leads to
formation of fertilization membrane → slow
block to polyspermy (due to calcium ions)
 Sperm comes in contact with zona pellucida
layer of ovum & induces changes in
membrane that block entry of additional
sperms

6. Entry of sperms into ooplasm –
 Whole sperm enters but later middle piece and tail
degenerates
 Entry of sperm into ovum induces completion of
meiosis – II of secondary oocyte
 Sperm turn off MPF and turn on APC
 All structures of sperm dissolve in egg ooplasm
except sperm nucleus & proximal centriole

 Second polar body thrown out into peri-vitelline
space → degenerates
 Ovum (haploid, n= 23) becomes active
 Mitochondrial inheritance is maternal
 Centriole of zygote is paternal

7. Syngamy-
 Plasmogamy
 karyogamy (nuclear membrane of both nuclei
dissolve)
 Amphimixis (chromosomal membrane dissolve)
 Zygote / synkaryon
 Zygote is the first cell of new individual

Significance of fertilization –
1. To block polyspermy
2. To restore diploidy
3. Determination of sex -
decided at time of fertilization
male (father) decide the sex
All female gametes – X-chromosome
50% male gametes - X-chromosome
50% male gametes – Y-chromosome

Movement of sperms towards the secondary oocyte.
↓
AF-F Reaction
↓
Adherence of sperm to the ZP3 receptors on zona pellucida, the glycoprotein layer
surrounding the oocyte
↓
Sperm bind to a sperm receptor on the zona & leads to initiation of acrosomal
reaction . Eg. Hyaluronidase, Acrosin (Zona lysin) are released
↓
Acrosin facilitate the penetration of sperm through zona pellucida.
↓
Structural changes in ZP through cortical reaction & discharge of cortical
granules in perivitelline space form fertilization membrane.
↓
In the event of fertilization , complete sperm enters inside the ovum
↓
Completion of meiosis-II of secondary oocyte during phagocytosis to form ovum
and simultaneously it releases 2nd polar body.
↓
Followed by plasmogamy, karyogamy and amphimixis i.e. completion of
fertilization.

Trick for Steps in Fertilization
Celina  Capacitation of sperms (Ca2+)
And  AF-F reaction &
Acrosome reaction (Ca2+)
* Fast block to polyspermy (Na+)
Company went to  Cortical reaction (Ca2+)
*Slow block to polyspermy (Ca+)
Zyed  Zona reaction
Mallika’s  Meiosis-II Completion
Shaadi  Syngamy

Embryogenesis / Embryology /
Developmental biology –
 Study of first 8 weeks of pregnancy
after fertilization (= embryo)
Father of animal embryology –
Karl Von Baer ( term cleevage)

Zygote – cleavage – morula – blastula /
blastocyst – gastrula – neurula –
organogenesis

Cleavage :
 Rapid mitotic division, starts as the zygote
moves through the isthmus of oviduct towards
uterus
 Interphase is only S- phase (G1/G2 absent /
negligible)
 ZP intact throughout cleevage

 Size of daughter cells (= blastomeres) gradually
decreases (Nucleo- Cytoplasmic index
increase)
 Size & volume of embryo remains constant
 Rate of cleevage inversely proportional to
yolk amount
 Changes unicellular zygote into multicellular
structure

 First cleavage-
 30 hours after fertilization
(on day 2)
 Second cleavage with transient 3 cell stage-
 40 hours (on day 2)
 Third cleavage
 72 hours (on day 3)

 First cleavage – meridional
 Second cleavage – meridional , at right angle to
first cleavage
 Third cleavage – equatorial

 TYPES OF CLEEVAGE –
A)Basis – plane of division
1.Meridional – longitudinal axis through centre
2.Vertical - longitudinal , but not through centre
3.Equatorial – horizontal axis through centre
4.Latitudinal - horizontal axis , not through centre

Monozygotic twins –
 If after first cleavage, 2 cells are
incidentally separated

Determinate / mosaic cleevage
– protostomes , twins not possible
Indeterminate / regulative cleevage –
deuterostomes , twins possible

Complete or
holoblastic
– When cleavage furrow
passes through the egg
completely
– Whole egg divides
Meroblastic
– Cleavage does not occur
in the part of egg.
where Yolk in present
– Cleavage occurs only in
cytoplasmic part
– Found in Megalecithal eggs.
Discoidal
meroblastic
cleavage
eg. Birds, Reptile,
Protoherian mammals
Superficial
Meroblastic
Cleavage
eg. Centrolecithal
egg of insects
Equal holoblastic
– Blastomere are of same size
eg. Homolecithal/isolecithal
egg. Mammals
(eutherian, metatherian)
Unequal holoblastic
– Blastomere unequal size
eg. Mesolecithal, Human

Patterns of cleevage –
1. Radial - deuterostomes ( echinoderm ,
hemichordates , amphioxus)
2. Bilateral – cephalopods , tunicates
3. Spiral – protostomes ( aschelminthes , annelids ,
arthropod , mollusc except cephalopods)
4. Rotational – mammals(human ) , transient 3-cell
stage

Cleavage in human –
 Holoblastic
 Unequal
 Rotational
 Indeterminate

Morula (=mulberry) –
 Solid ball of 8-16 celled stage, surrounded by ZP
 After third cleavage on third day
 Embryo is solid, mulberry ball like (compaction)
 Present in fallopian tube

Morula continues to divide & transform into
blastocyst as it moves further into uterus

Blastocyst– characterized by cavitation
inside embryo ( Blastocoel)
 Blastocyst In marsupials and eutherian
mammals , blastula in other animals
A) Cavitation-
 after 32-cell stage , seepage of uterine
milk , Starts from day 4

B) Hatching of blastocyst -
 By day 5-When enters into uterine cavity, ZP
degenerates and embryo hatches out (64-128 cell
stage) due to trophoblastic enzymes
 Phagocytosis of endometrium by phagocytic cells of
trophoblast
 ZP prevents premature implantation of embryo
 Ectopic pregnancy-if ZP rupture pre-mature ,
implantation at site other than normal uterine site (most
common - tubal ectopic)

C) Implantation / Nidation of blastocyst
into endometrium (=decidua)-Day 6 / 7

Blastomeres arranged into 2 layers –
1. Outer trophoblast / trophoectoderm – produce
chorion fetal membrane that contributes in
formation of placenta, protective
2. Inner layer ICM / inner cell mass or
embryonal disc proper – forms amnion,
allantois and yolk sac fetal membrane and
complete embryo

 Trophoblast layer gets attached to endometrium
 After attachment, uterine cells divide rapidly and
covers blastocyst
 Thus it becomes embedded in endometrium, called
implantation, leading to pregnancy

 Implantation / nidation of blastocyst (embryo) occurs
on day 6th or 7th post- fertilization
 On day 8th,trophoblast –
1. outer syncytiotrophoblast (many free nuclei) –
cell boundary lost
2. inner cytotrophoblast – inner cellular layer
 Syncytiotrophoblast forms finger like projections-
chorionic villi (to form placenta)

Trophoblast secrete hCG hormone(acts like
LH) - day 8 onwards till 12 weeks (1st
trimester) of pregnancy
 Maintains CL for first 3 months
 Rescues dying CL
 Urine pregnancy test/ Gravidex test
 Behavioural & physiological changes in pregnancy
 Increased progesterone leads to Amennorhoea
( Pregnancy hormone)

 Types of blastula –
1.Coeloblastula – hollow eg- frog
2.Stereoblastula – solid eg- nereis , coelenterates
3.Peri-blastula / superficial – eg-insects
4.Disco-blastula – eg-reptiles , birds , prototherian
mammals

 ICM has stem cells which have potency to give
rise to all tissues & organs
 On day 8th, ICM-
1. upper epiblast
2. lower hypoblast (primitive endoderm)
 Cavitation –
1. Formation of amniotic cavity starts
( from epiblast)
2. Formation of primary yolk sac
( from hypoblast)

 Formation of extra-embryonic mesoderm –
 Proliferation of hypoblast / trophoblast / lateral extension
of embryonic mesoderm (epiblast)
 Amniotic cavity & secondary yolk sac
 Formation of extra embryonic coelom /chorionic cavity
 Formation of extra-embryonic membranes – chorion ,
amnion , allantois , yolk sac
 Completion of formation of amniotic cavity
 Formation of connecting stalk (future umbilical cord –
extra embryonic mesoderm)

Extra- embryonic membranes-
1. Chorion-
 Cytotrophoblast (outside) + extra –
embryonic mesoderm(inside)
 protection to embryo
 placenta formation (chorionic villi)-Chorionic
frundosum

2. Amnion –
 extra- embryonic mesoderm (outside) + ectoderm
(inside / epiblast)
 Forms amniotic cavity filled with amniotic fluid
 acts as shock absorber, prevents embryo from
dessication (land adaptation) , temperature
flctuations
 Amniocentesis –stem cells in amniotic fluid

Extra-embryonic coelom- space between
amnion & chorion

3.Yolk sac –
 extra- embryonic mesoderm(outside)+ endoderm
(inside / hypoblast)
 In Birds and reptiles, filled with yolk (nutritive
for embryo)
 In human, regress after 8 weeks – Haemopoietic
and formation of male and female germ cells

4. Allantois –
 Extra-embryonic mesoderm(outside) +
endoderm (inside / Hypoblast)
 In Birds and reptiles – called urinary bladder of
embryo , stores uric acid (nitrogenous waste)
 In human – formation of umbilical blood vessels
and Wharton’s jelly(umbilical cord)

Gastrulation-
 Formation of 3 primary germ layers from bilaminar
disc
 Endoderm , mesoderm , ectoderm
 On day 8th , ICM-upper epiblast & lower
hypoblast (primitive endoderm)
 Day 15,primitive streak appearance on dorsal surface
of epiblast & this marks beginning of gastrulation

 Primitive streak-
 runs from tail to head part
 decides embryonal axis & bilateral symmetry
 Dynamic process – Emboly (delamination) -
morphogenetic movement of sheets of cells
 Epiblast has prospective endodermal & mesodermal
cells (source of all three germ layer)
 Hypoblast contributes in formation of endoderm

 First germ layer formed –
 Endoderm
 Formed by delamination of prospective
endodermal cells from epiblast , between
hypoblast layer)

 Primitive groove –
 formed by migratory force of cell movement
 Has ‘Henson’s node’ at anterior end – prospective
mesodermal cells that will form Notochord later in
embryo (chorda-mesodermal cells)
 Formation of Mesoderm (between endoderm &
ectoderm)
 By delamination of Epiblast
 Formation of Ectoderm – remaining epiblast

 Organogenesis-
 Chorda-mesodermal cells-
 acts as ‘Primary organizers / Inducers’
 Secrete chemicals that decide for organ
formation
 First organ formed –
 Heart (21 days after fertilization / after one
month of pregnancy)

 ICM contains stem cells which has potency
to give rise to all tissues and organs

 Neurulation –
 Marks beginning of CNS Formation
 Conversion of neural plate into neural tube
 First organ system formed – Nervous system
 Nervous system develops from ectoderm , lie over ‘ notochord
region’
 Neural plate – neural fold & neural groove
 Neural groove – after separation from neural plate k/a Neural tube
( form CNS)
 Neural crest – form PNS

 First sign of growing fetus is noticed by listening
heart sound through stethoscope
 By end of second month – limbs and digits
developed
 By end of 12 weeks / first trimester – most of the
major organ system formed (limbs and external
genital organs well developed)
 4th month – Maximum growth rate ( 61/2 – 7 inch)

 During 5th month – first movement of fetus and
appearance of hair on head
 By end of 24 weeks / end of second trimester- body
covered with fine hair, eyelids separate, eye lashes
formed
 7th month – surfactant secretion in lung alveoli ,
Descent of Testis
 By end of nine months – fetus fully formed, ready
for delivery

Ectoderm
Epidermis
Cutaneous glands
Nervous system (except
microglia)
Pituitary & Pineal
Eye (Retina, lens and
cornea)
Nasal epithelium
Stomodaeum
Proctodaeum
Enamel
Internal ear and external ear
Adrenal medulla
Lateral line sense organ
Mesoderm
Dermis
Muscular tissue
Connective tissue
Endoskeleton(Bone ,
cartilage)
Vascular system-heart ,
blood , blood vessels) , Spleen
Lymphatic system
Teeth except enamel (
dentine)
Kidney & urinary duct
(ureter)
Gonads & genital ducts
Adrenal cortex
Choroid and sclera
Notochord
Coelomic epithelium
(peritoneum)
Endoderm
Gut -Tongue , Palate ,
pharynx , tonsils ,
esophagus , stomach ,SI , LI
,upper anal canal
GIT Glands-stomach ,
intestine , liver , pancreas ,
GB
Trachea , bronchi , lungs
Thyroid gland
Parathyroid
Thymus
Urinary bladder ,urethra
Middle ear
 Eustachian tube
Gills

Placenta:
 Structural(physical)& functional(physiological)
unit between developing embryo (fetus) and
maternal body
 Temporary organ

A ) Basis= no. of placental barriers
1. Epithelio – chorial placenta-all 6 barriers
Eg- horse , pig
2. Syndesmo-chorial placenta – 5 barriers (maternal epithelium lost)
Eg- cattles (cow , buffalo,goat,sheep,camel)
3. Endothelio-chorial placenta- 4 barriers (maternal epithelium & CT Lost)
Eg- Carnivores (tiger , lion , dog , cat)
4. Haemo – chorial placenta – 3 barriers (fetal) , all maternal barriers lost
 Maternal blood bathes fetal chorion
 Eg- Primates (Human , apes , lemur , monkey)
5. Haemo – endothelial placenta – 1 barrier (fetal endothelium)
Eg – rat , rabbit

B ) Basis= Extra embryonic membrane
contribution
1.Yolk – sac placenta – sarks (most primitive )
2.Chorio – vitelline placenta – chorion + yolk sac
eg – marsupials
3.Chorio – allantoic placenta – chorion+ allantois ,
eg- mammals
Note Human – chorionic placenta

C ) Basis= fate of uterine wall after parturition
1.Non – deciduate – only fetal part of placenta delivered
eg – horse , pig , cattle , camel , giraffe
2. Deciduate / true placenta – both fetal & maternal
parts delivered
eg – mammals ( Human)
3. Contra – deciduate – both fetal & maternal parts not
delivered ( reabsorbed)
eg – Perameles ( Bandicoot) , Talpa ( Mole)

D ) Basis= Chorionic Villi distribution
1. Diffuse type – villi uniformly distributed all over surface
eg – horse , pigs
2. Coteledonary – clusters / tufts of chorionic villi
eg – cattles (cow buffalo ,sheep)
3. Intermediate type –single + tufts of villi , eg- giraffe , camels
4. Zonary type – girdle shaped placenta – carnivores , elephants
5. Discoidal – villi arranged in disc , eg- rabbit , rat , bat
6. Meta – discoidal –villi initially diffuse , later form cluster / disc in decidua
basalis region
eg - primates (human)
Note – 1 , 2 , 3 – non-deciduate type & 4 , 5 , 6 – deciduate type

 Human placenta –
 Haemo – chorial (3 foetal barriers present, all 3
maternal barriers lost i.e. maternal blood bathes fetal
chorion)
 Chorionic
 Deciduate(both fetal and maternal parts delivered)
 Meta-discoidal(chorionic villi were diffuse initially
but later forms cluster / disc)

Maternal contribution – Decidua basalis
( endometrium , uterine tissue)
Fetal contribution – Chorion ( chorionic villi)
Chorionic villi & uterine tissue (endometrium) become
interdigitated with each other
Fully developed by 10-12 weeks of pregnancy
Acts as barrier between maternal and fetal blood
(their blood does not get mixed)

Functions of Placenta :
1. Provide nutrients to fetus
2. Gaseous exchange(O2- CO2) –called Fetal lung
3. Waste elimination from fetus into maternal blood
4. Provides immunity to fetus
(via IgG antibodies from mother)
5. Temporary endocrine gland

Hormones produced by placenta –
1. Progestogens- maintains pregnancy and increase number of
milk alveoli in mammary gland
2. Estrogens – proliferates endometrium and breast
development during pregnancy
3. Human Chorionic Gonadotropin (hCG)- max at 12
weeks, maintains CL in first trimester
4. Human Chorionic Thyrotropin (hCT)- stimulates
maternal thyroid gland – physical and mental development
of fetus

5. Human chorionic somatomammotropin (hCS) / Human
Placental Lactogen (hPL) – helps in milk secretion , fetal
growth ( diabetogenic effect in mother)
6. Human Chorionic Corticotropin (hCACTH)- placental
steroidogenesis - increase estrogen at delivery, determine time of
child birth
7. Relaxin – peaks at 14 weeks and at delivery(later phase of
pregnancy)
 At delivery – produced by ovary (CL) and placenta, relaxes
pubic symphysis and pelvic ligaments for easy child birth
 Increase Maternal CO , Renal blood flow , arterial complaince

 Note :- hCG, hPL, hCACTH, hCT, relaxin are
produced in women only during pregnancy
 During pregnancy levels of estrogens, progestogens
, cortisol , prolactin, thyroxin etc are increased
several folds in maternal blood , essential for
supporting fetal growth, metabolic changes in
mother and maintenance of pregnancy

Substances which cross placenta –
Glucose
O2-CO2
IgG Antibody
Thyroxine
Insulin
Caffeine
Nicotine
Coccaine
Alcohol

 Pathogens which cross placenta –
 Toxoplasma
 Rubella virus
 CMV
 HSV
 Varicella virus (chickenpox)
 Treponema pallidum (syphilis)
 HBV
 HIV

 UMBILICAL CORD –
 Placenta is connected to fetus through umbilical
cord which helps in transport of substances to and
from embryo
 2 umbilical artery – deoxygenated blood
 1 umbilical vein – oxygenated blood
 Umbilical vessels have 100 % fetal blood
 Placenta & umbilical cord – stem cells preservation
after delivery

 Gestation period:
 Time between conception to birth
 266 days / 38 week (from fertilization)
 280 days / 40 weeks (from LMP day 1)
 Cow – 9 months
 Rabbit - 28 – 32 days
 Dogs – 60-65 days
 Cat – 52-65 days
 Elephants-22 months (607 – 641 days , longest gestation)

Teratogens/ monster forming agents
 Substances which produce malformed fetus
 Most sensitive during first 12 weeks of pregnancy
 Thalidomide drug (given for morning sickness,
cause Phocomelia/Amelia – malformed limbs,
like seal)

 Gynaecomastia – Development of breast in
male.
 Hystereotomy – Surgical removal of uterus.
 Oopherectomy – Removal of ovaries
 Tubectomy - Tubal ligation for permanent
steriliztion

Parturition –
 Process of delivery of fetus/ child birth /
expulsion of baby out of uterus through birth
canal
 Caused by vigrous contraction of uterus
(myometrium) at end of pregnancy
 At delivery → placental progesterone fall →
fetus separated from uterine walls

 Induced by complex neuroendocrine
mechanism
 First stimulus originate from fully developed
fetus (PG-F) and placenta (hCACTH) , which
induces mild uterine contraction called
Foetal Ejection Reflex (FER)

 Mild uterine contractions → stimulate
maternal posterior pituitary → release
Oxytocin → Oxytocin acts on uterine muscles
and cause stronger uterine contraction, which
inturn stimulates further oxytocin secretion,
resulting in stronger and stronger contraction
 Oxytocin – main parturition hormone / child
birth / delivery hormone

 also hCACTH → increase estrogen at delivery
a)Increase oxytocin receptors → frequency &
intensity of uterine contractions increases →
cervical dilatation
b)Cervical dilatation
 At delivery - Relaxin increase ( placenta & ovary)
a)Softens pubic symphysis
b)Loosen pelvic ligaments

Soon after infant is delivered, the placenta is
expelled out of uterus (stage of after birth)

 3 stages of parturition –
1. Dilation stage - from onset of labour pain(uterine
contraction) to cervical dilation
Cervical dilation
Amnion rupture & release of amniotic fluid out
through vagina

2. Expulsion stage – from full cervical dilation to
expulsion of fetus
Expulsion of fetus through birth canal
Head comes out first
Cutting of umbilical cord
Infants lungs expands & it begins breathing
( switchover from placental to pulmonary circulation due
to NO-Vasodilator)
Blood flow , ductus arteriosus ,foramen ovale closes
Blood flow begins through eart , aorta & pulmonary
arteries begins

3 . Stage of After Birth / Placental stage-
15 to 20 min
From child delivery to delivery of ‘after births’
( remaining umbilical cord , placenta , decidua basalis)

Lactation-
 Secretion & release of milk from mammary
gland
 Helps mother in feeding the new born
 Milk secretion/ production – Prolactin, hPL
 Milk ejection- Oxytocin

 Note –
 Female mammary glands undergo differentiation
during pregnancy & starts producing milk towards
end of pregnancy
 Prolactin from maternal anterior pituitary
increases from 5th week of pregnancy until birth of
fetus (10-20 times the normal non-pregnant levels)

Milk ejection reflex –
When baby suckles mothers nipple → sensory
impulses from nipples to mothers spinal cord →
then to mothers hypothalamus → mothers
posterior pituitary → oxytocin release →
oxytocin carried through blood to breast → cause
contraction of myoepithelial cells → expel milk

When baby is not suckling milk-
Milk has ‘ Inhibitory Peptide’ → inhibits milk
production
Lactation also influenced by mothers psyche

 Colostrum –viscous , yellow colored
 Milk produced during initial few days of lactation
 Contains IgA antibodies (provides passive
immunity to new born, essential to develop
resistance for new born)
 Same proteins & lactose as milk
 Almost no fat

Breast feeding during initial period of
infant growth is recommended by
doctors for bringing up a healthy baby

Human reproduction
Page 51
Menstrual hygiene :

 Maintainance of hygiene and sanitation during
menstruation is very important
 Take bath & clean yourself regularly
 Use sanitary napkins or clean home made pads .
 Change sanitary napkins or home made pads after
every 4-5 hours as per requirement
 Dispose off the used sanitary napkins properly
wrapping it with a used paper
 Do not throw the used napkins in the drainpipes of
toilets or in an open area
 After handling napkin , wash hands with soap

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