(Beginning of third week to end of
(Conception to end of second week)
eighth week)
- Fertilization
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- Cleavage - Formation of placenta, umbilical- Implantation cord, and extraembryonic membranes
- Differentiation of germ layers into
> |- Formation of germ layers
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specific body organs
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Flowchart 1.1 Subdivisions of prenatal period and events occurring in these periods.(Beginning of ninth week to birth)
? Growth and specialization of
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?> GashulaWen . (21Manin)
Division oe fm\oYJdUa .
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#)
) Mitosis
?Y Meiosis ? X
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L =Neven
G s\ed.
/> Eei?o\asl' > 33\. ( ;)
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(?
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Dark type A Dark type A
G spermatogonium spermatogonium
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Light type A Dark type A ?rimary spermatogonium spermatogonium
spermatocyte
) (largest
germ cell) Type B
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} /I \ spermatogonium spermatogonium) Secondar
2 | Y
spermatocytes [
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Second meiotic
division
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s gpumalid
@ bpermatids @ @ &= r?MdB?gO?
?
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Spermlogene5|s
}
Fig. 3.4 Spermatogenesis (simplified form). Figure in the inset shows spermatocytogws/
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? keD peints -
Semmma eNiSt S
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\W<
:;\zi
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Clinical Correlation )Abnormal sperms: The abnormality of sperms is common as
compared to the oocytes. Morphologically for clinicians the
sperm consists of two parts of head and tail.
T ities are as under.
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1 hological abnormaliti(@) Head and tail of sperms may be abnormal (viz., two
h?ads, two tails) ?
%&) Sperms may be giant or dwarf X XX
c
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) Sperms may be joined
2. Immotility: For potential fertility, 50% sperms should be Jam
motile after 2 hours of ejaculation and some should be 0._?_?
motile after 24 hours.
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3. Genetic abnormalities: Sperm having abnormal chromo-_? i
somal content (rare as compared to the oocytes).
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GI
?
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Parts of sperm Structure of different parts@) Head
@ Acvoso mak
@ Zoaq paie-
3 Cth.(o-? (bl\.
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Cel membrane=l ?;19
? Nine outer dense fibers
Axial filament (cilium
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with 9+2 arrahgement)Cell membrane
et L
Fibrous sheath
oo e
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Seven outer dense fibers?_?
Axial filament
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Cell membrane
Axial filament
Fig.3.5 Human sperm. The parts of mature sperm are shown on the left side whereas the sections through the head, neck, middle
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piece, principal piece, and end piece along with their composition are shown onto the right side.?.K
o () | Speman g
| s
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)B L\
Second meiotic
division
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First polar
body
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Ovum \(mature oocyte)
Fig. 3.7 Oogenesis.
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C?
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Primordial germ cell
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Oogonium
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Primary oocyte
(44XX, 4nDN
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nter into seconmeiotic division
Mature oocyte
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(22X, nDNA)Enlarges to form
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Enter the prophase of first meioticdivisi hich is prolonged up to
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Second polar body
Flowchart 3.2 Steps of oogenesis.
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?mby a onte =) 1m\o A
?
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Risw - G-8% \alkhhWS Differences between male and female
LSS
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Two types: (a) X-bearing
sperms (22+X) and (b) (22+X)
?Y-bearing sperms (22+Y)
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wan.
O gemen
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Single layer of flattenedfollicular cells Cg 3 ZOY\ Qa ?wuj dq
kvm\ed ?Y ?
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Primary oocyte
Single layer of columnar
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Primary follicular cells (follicularfollicle cells become columnar)
Stroma
Multiple layers of follicular cells
Maturing (membrana granulosa cells)
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primaryfollicle Zona pellucida
(glycoprotein substance)
& Stromal cells
Basement membrane
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Small fluid-filled lacunae (cavities)(i.e., appearance of small lacunae
Secondary in the granulosa cells)
follicle
Ovarian surface
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Theca interna?_?
Follicular cavity S A ?
Maturing
secondary Cumulus
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follicle ? oophoricusZona
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pellucidaDiscus proligerus
Graafian follicle S
?
Fig.
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Otow
?
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Freshly ovulated
secondary oocyte
in second meiotic division
Granulosa cells Luteal cells
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Corpus luteumTheca interna
S, ? Cortex of
? s ? \? Degenerating
A o) ovary
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< corpus luteumBlood L
vessels Corpus
albicans
Fig.
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=) VvV "><\
d
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Proges. o[ @?
(G,
=
Q) Movmone cecye Yed 2
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Sperm
? Zona pellucida
it ? =
Vitelline membrane First polar body
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Secondary oocyte s g eyi000y Second meiotic division
Perivitelline space
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Centrioles of sperm moveto opposjte ppbles
First and sg
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B enetration of sperm Ethrough zona pellucida female pronuclei
2= o %
Chromosomes
Breakdown o
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membranes ofpronuclei
C Fusion of cell membranes F Replication of DNA
of oocyte and sperm 2 from 1nto 2n
?amy
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Cleavage spindleFemale
pronucleus
D Formation of zygote
(chromosomes of the zygote get
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aganged on the equatorial plane)#) ( L\Qh:}e)
?) Zvaaoh. O
@
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o e @?_W\ ? ? DC
oWdn 43 cal [A Movalls
(uhion in 029 colled Mattary)
=
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ddivideanbe 2D C
d
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@) |enRisatien
ke Gad Zong
Peldua A & RQ"?Qai?.
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(D ?> M
& -t 0|
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/FN X - MoToRpd ?s@ QO UL,
N
Saremen < |