Download MBBS (Bachelor of Medicine, Bachelor of Surgery) Important Topics Embryo for MBBS 1st Year Important Topics, MBBS 2nd Year Important Topics, MBBS 3rd Year Important Topics & MBBS Final Year Important Topics.
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Q- Rivth
(Beginning of third week to end of
(Conception to end of second week)
eighth week)
- Fertilization
- Cleavage - Formation of placenta, umbilical
- Implantation cord, and extraembryonic membranes
- Differentiation of germ layers into
> |- Formation of germ layers
specific body organs
Flowchart 1.1 Subdivisions of prenatal period and events occurring in these periods.
(Beginning of ninth week to birth)
? Growth and specialization of
the body structures
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Division oe fm\oYJdUa .
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) Mitosis
?Y Meiosis ? X
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Dark type A Dark type A
G spermatogonium spermatogonium
Light type A Dark type A ?
rimary spermatogonium spermatogonium
spermatocyte
) (largest
germ cell) Type B
} /I \ spermatogonium spermatogonium
) Secondar
2 | Y
spermatocytes [
Second meiotic
division
s gpumalid
@ bpermatids @ @ &= r?MdB?gO?
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Spermlogene5|s
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Fig. 3.4 Spermatogenesis (simplified form). Figure in the inset shows spermatocytogws/
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Semmma eNiSt S
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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.
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
) 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.
3. Genetic abnormalities: Sperm having abnormal chromo-
_? i
somal content (rare as compared to the oocytes).
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Parts of sperm Structure of different parts
@) Head
@ Acvoso mak
@ Zoaq paie-
3 Cth.(o-? (bl\.
Cel membrane
=l ?;19
? Nine outer dense fibers
Axial filament (cilium
with 9+2 arrahgement)
Cell membrane
et L
Fibrous sheath
oo e
Seven outer dense fibers
?_?
Axial filament
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
piece, principal piece, and end piece along with their composition are shown onto the right side.
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B L\
Second meiotic
division
First polar
body
Ovum \
(mature oocyte)
Fig. 3.7 Oogenesis.
C?
Primordial germ cell
Oogonium
Primary oocyte
(44XX, 4nDN
nter into secon
meiotic division
Mature oocyte
(22X, nDNA)
Enlarges to form
Enter the prophase of first meiotic
divisi hich is prolonged up to
Second polar body
Flowchart 3.2 Steps of oogenesis.
?mby a onte =) 1m\o A
?
Risw - G-8% \alkhh
WS Differences between male and female
LSS
Two types: (a) X-bearing
sperms (22+X) and (b) (22+X)
?Y-bearing sperms (22+Y)
wan.
O gemen
Single layer of flattened
follicular cells Cg 3 ZOY\ Qa ?wuj dq
kvm\ed ?Y ?
Primary oocyte
Single layer of columnar
Primary follicular cells (follicular
follicle cells become columnar)
Stroma
Multiple layers of follicular cells
Maturing (membrana granulosa cells)
primary
follicle Zona pellucida
(glycoprotein substance)
& Stromal cells
Basement membrane
Small fluid-filled lacunae (cavities)
(i.e., appearance of small lacunae
Secondary in the granulosa cells)
follicle
Ovarian surface
Theca interna
?_?
Follicular cavity S A ??
Maturing
secondary Cumulus
follicle ? oophoricus
Zona
pellucida
Discus proligerus
Graafian follicle S
?
Fig.
Otow
?
Freshly ovulated
secondary oocyte
in second meiotic division
Granulosa cells Luteal cells
Corpus luteum
Theca interna
S, ? Cortex of
? s ? \? Degenerating
A o) ovary
< corpus luteum
Blood L
vessels Corpus
albicans
Fig.
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d
Proges. o[ @
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(G,
=
Q) Movmone cecye Yed 2
Sperm
? Zona pellucida
it ? =
Vitelline membrane First polar body
Secondary oocyte s g e
yi000y Second meiotic division
Perivitelline space
Centrioles of sperm move
to opposjte ppbles
First and sg
B enetration of sperm E
through zona pellucida female pronuclei
2= o %
Chromosomes
Breakdown o
membranes of
pronuclei
C Fusion of cell membranes F Replication of DNA
of oocyte and sperm 2 from 1nto 2n
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Cleavage spindle
Female
pronucleus
D Formation of zygote
(chromosomes of the zygote get
aganged on the equatorial plane)
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This post was last modified on 24 July 2021