The document summarizes the processes of gametogenesis, which includes spermatogenesis and oogenesis. Spermatogenesis occurs in the testes and produces millions of sperm continuously from puberty to old age. Oogenesis occurs in the ovaries and is discontinuous, producing a single ovum after a long growth phase. The document also compares the structures and development of sperm and ova, the phases of the menstrual cycle, early human embryogenesis, and the fate of the three germ layers.

1. Human Reproduction

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

13. Thank You