2. Gametogenesis
Spermatogenesis Oogenesis
Occurs in seminiferous tubules of testes Occurs mostly in ovary
Begins at puberty Begins at foetal developmental stage
Continuous process and is completed
without any interruptions
Discontinuous process, get arrested at
various stages of development
Duration of one spermatogenesis cycle is
nearly 64 days
Duration may not be predictable. It may
took years to complete or sometimes
remain incomplete
Entire process of spermatogenesis begins
and completed within the testes
Oogenesis begins in ovary but get
completed in oviduct (female
reproductive tract) when sperm penetrates
egg membranes
Spermiogenesis (differentiation) present No differentiation process
3. Spermatogenesis Oogenesis
Spermatogonial cells continuously being
produced in the testes from puberty to old
age
No more oogonia are added after birth
During phase of growth, all the
spermatogonial cells change to primary
spermatocytes
During phase of growth, those oogonial
cells which destined to become an ova,
only change to primary oocytes
Growth phase is of shorter duration Growth phase is of longer duration and
takes years to complete
Maturation divisions (meiosis) are equal
in nature
Maturation divisions (meiosis) are
unequal in nature
Each primary spermatocyte divides
equally to form 2 secondary
spermatocytes
A primary oocyte divides unequally to
form one large secondary oocyte and one
small first polar body
4. Spermatogenesis Oogenesis
Each secondary spermatocytes divides to
form 2 equal sized spermatids
A secondary oocyte divides unequally to
form one large ootid (ova) and one small
second polar body
No polar body formed Polar bodies formed and later get
degenerated
Each spermatocytes ultimately produces 4
functional sperms
Each oocyte produces one functional
ovum and 3 polar bodies
Meiosis I is completed normally without
any interruption
During meiosis I, except one, all other
primary oocytes get arrested at Prophase I
stage
Meiosis II is not at all interrupted During meiosis II, the secondary oocyte
get arrested at metaphase II stage
Mature sperms are released from testes A secondary oocytes with I polar body
arrested at metaphase II stage is released
from ovary during ovulation.
5. Spermatogenesis Oogenesis
After maturation divisions, immature,
round non-motile spermatids are produced
After maturation divisions, mature
functional ovum/ootid is produced
Sperms are motile, stream lined
microgametes
Ovum is non-motile, round macrogamete
Millions of sperms are produced after one
spermatogenesis cycle
Only one functional ovum is produced
after the completion of one oogenesis
cycle
Spermatogenesis cycle can be continued
even in old age
Entire process of oogenesis get terminated
at menopause
Entire phase of spermatogenesis can be
repeated several times during the life time
In oogenesis, phase of multiplication is
completed during foetal life, phase of
growth during childhood and phase of
maturation is performed after puberty
6. Gametes
Spermatozoa Ova
Produced in the seminiferous tubules of
testes
Produced in ovary
Four sperms are formed from each
spermatocytes
Only one functional ovum is formed from
one oocyte
It is externally divided into a head, neck,
middle piece and tail
It is not externally differentiated into
regions
It is stream lined, motile, flagellated
microgamete
It is oval shaped non-motile macrogamete
It has a thin layer of cytoplasm It has large amount of cytoplasm called
ooplasm
Externally covered by plasma membrane
only
Outside plasma membrane (oolemma),
ovum is covered by egg membranes like
zona pellucida and corona radiata
7. Gametes
Spermatozoa Ova
Mitochondria form a spiral in the middle
piece region
Mitochondria are scattered in the ooplasm
3 centrioles present Centrioles absent
Sperm penetrates the ovum at the time of
fertilization by releasing lytic enzymes
Ovum engulfs the sperm by forming a
reception cone at the time of fertilization
8. Menstrual Cycle
Follicular Phase Luteal Phase
It extends for about 9-10 days usually from
day 5th to 13 in a 28 day cycle
It is always 14 days duration usually
extending from day 15 – 28 in a 28 day
cycle
It is pre-ovulatory and post-menstrual in
nature
It is post-ovulatory and pre-menstrual in
nature
Primary follicle changes into a mature
Graafian follicle in the ovary, hence the
name
Empty ruptured Graafian follicle changes
into a corpus luteum, hence the name
Oestrogen are secreted Progesterone is secreted
Endometrium is about 2-3 mm thick. The
uterine secretions do not secrete any watery
secretions
Endometrium is about 5-6 mm thick. The
uterine glands secrete watery secretions
Also known as proliferative phase Also known as secretory phase
9. Embryogenesis
Cleavage Typical Mitosis
It occurs in zygote or parthenogenetic egg It occurs in most of the somatic cells
Short interphase Interphase is of long duration
Growth does not occur Growth occurs during interphase
Oxygen consumption is high as it is a rapid
process
Oxygen consumption is less as it is a slow
process
Size of blastomeres decreases after each
division
Size of daughter cells remains same after
growth
DNA synthesis is faster DNA synthesis is slower
Nuclear-cytoplasmic ratio increases Nuclear-cytoplasmic ratio remains same
10. Fate of germ Layers
Skin Epidermis, hair, arrector pili muscle of hair follicle, nail, sweat glands,
sebaceous glands, melanocytes (except Dermis)
Mouth Enamel of teeth, lips, cheeks, gums, nasal cavity, salivary glands
Nervous System Neurons, glial cells and meninges (except dura matter and microglia)
Eye Conjunctiva, cornea, lens, iris muscles, vitreous humour, retina, lachrymal
glands
Ear External ear, tympanum, membranous labyrinth
Endocrine glands Pituitary gland, pineal gland, adrenal medulla
Reproductive
system
Mammary glands
Ectoderm Derivatives
11. Fate of germ Layers
Muscular System All muscles (except iris muscles of eye and arrector pili of hair
follicle)
Connective tissue Tendons, ligaments, bone, cartilage, blood, adipose tissue and areolar
tissue
Circulatory System Complete
Excretory System All parts (except urinary bladder)
Endocrine glands Adrenal cortex
Reproductive system All parts (except prostate gland, Cowper’s glands & mammary glands)
Eye Sclera, choroid, iris, ciliary body
Other parts Coelom, notochord, dura matter and microglia of brain
Mesoderm Derivatives
12. Fate of germ Layers
Digestive System Oesophagus – rectum, all digestive glands (except salivary glands),
liver, pancreas
Respiratory System From Larynx to Lungs
Excretory System Urinary bladder
Reproductive System Prostate gland, Cowper’s gland
Endocrine system Thyroid gland, parathyroid gland, thymus gland
Endoderm Derivatives