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9.3 Fertilization and Foetal Development and 9.5 Growth

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Published by Sallehattun Salleh, 2022-11-29 21:40:36

LECTURE NOTE WEEK 18

9.3 Fertilization and Foetal Development and 9.5 Growth

CHAPTER 9:

REPRODUCTION AND DEVELOPMENT


9.3 FERTILIZATION AND
FOETAL DEVELOPMENT

b) Define embryogenesis.
c) State developmental stages from zygote to the formation of morula,

blastocyst and gastrula through cleavage.
d) Define organogenesis
e) State the organ formed from each germ layers during organogenesis


FERTILIZATION

The union of a (haploid) male and (haploid) female gametes

zygote


EMBRYOGENESIS

A process by which embryo is formed and
developed.

Process by which the number of
cells in the developing embryo is
multiplied through cell division.


Developmental stages

• After fertilization the fertilized egg starts traveling down
the fallopian tube toward the uterus.

• Zygote undergoes cleavage (rapid mitotic divisions) and cell differentiation.

Fertilized
egg/zygote

FERTILIZATION


Developmental stages 2nd division of the zygote
become 4 cells.
1st division of the zygote
become 2 cells. 3rd division of
the zygote
24 hours after fertilization and become 8 cells
completed about 30 hours after with 2 tier of 4
fertilization. cells.

Completes in
about 70-72
hours after
fertilization.


Developmental stages A fertilized zygote
becomes a morula
As cleavage continues,
the zygote develops The morula
into a ball of cell passing travels to the
down the oviduct to the uterus around 3-
uterus. 4 days after
fertilization.

At about 4 days after fertilization a fluid-filled space
called the blastocoel cavity appears and the morula
becomes a blastocyst.


Zona pellucida blastocoel Zona
Inner cell mass pellucida shedding
(detaching)
MORULA
BLASTOCYST

-Solid sphere of cells. trophoblast
-Smaller cells produced by cleavage
are called blastomeres. -A fluid-filled hollow sphere
-One pole differentiates into inner
-The size of the original zygote. cell mass – from which the embryo
-Surrounded by zona pellucida. will form
-Completes at the end of the third
day -Outer cell mass = trophoblast
-An internal fluid-filled cavity =
blastocoel.


Shedding of Blastocyst • The blastocyst Trophoblast
zona pellucida attaches to the enlarges. secretes human
endometrium chorionic
• Trophoblast secretes gonadotropin
Implantation enzymes: (hCG) - sustain
corpus luteum
enable the blastocyst to to secrete
penetrate the uterine progesterone
lining by digesting and and estrogens.
liquefying (dissolve) the
endometrial cells.

Endometrium of uterus


Developmental stages
AFTER IMPLANTATION COMPLETED

Gastrula: early
embryo with 3 germ
(tissue) layers

• Ectoderm
• Mesoderm
• Endoderm

GASTRULATION

Migration/ invagination of cells: the epiblast is pushed
inward ,the blastocoel disappears and archenteron (gut)
forms.


ORGANOGENESIS

The process in which organ rudiments develop
from three germ layers after gastrulation


Organs formed from germ layers during
ORGANOGENESIS

Endoderm layer become: Mesoderm layer become: Ectoderm layer become:
1)Digestive system 1)Circulatory system 1)Hair
2)Liver 2)Lung (epithelial layers) 2)Nail
3)Pancreas 3)Skeletal system 3)Skin
4)Lung (inner layers) 4)Muscular system 4)Nervous system


Organs formed from germ layers during
ORGANOGENESIS

Ectoderm Mesoderm Endoderm

Epidermis of skin Skeletal dan Epithelial lining of
and derivatives muscular systems digestive tract and
(including sweat Circulatory ang associated organs
gland, hair follicles) lymphatic systems Epithelial lining of
Nervous and sensory Excretory and respiratory,
systems reproductive excretory and
Pituitary gland, systems (except reproductive tracts
adrenal medulla germ cells) and ducts
Jaws and teeth Dermis of skin Thymus, thyroid and
Adrenal cortex parathyroid glands


9.5 GROWTH PATTERNS IN
HUMAN AND PLANT

a) Definition of growth


GROWTH

• Growth is the irreversible permanent

increase in quantitative parameters such as
size, volume, length (or height) or surface
area, that can be measured.


Definition Growth Growth patterns

Human Growth Curve

Limited growth Unlimited growth Allometric
(annual plants) (parennial plants) growth

(human organs)

16


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