BLASTULATION Flashcards
(129 cards)
1
Q
- process in early embryonic development where the solid ball of cells, the morula,undergoes a series of rapid cell divisions (cleavage)
and rearranges itself to form a hollow cavity filled with
fluid. This fluid-filled cavity is called the blastocoel.
A
blastulation
2
Q
Blastulation marks a significant transition in what
A
embryonic development
3
Q
blastulation sets the stage for what
A
gastrulation
4
Q
what is gastrulation
A
where the germ layers (ectoderm, mesoderm, and endoderm) that will
give rise to all the tissues and organs of the developing organism are established.
5
Q
Importance of Blastulation in Embryonic Development
A
- Formation of the Balstocoel
- Cellular Differentiation and Specialization
- Preparation for Gastrulation
6
Q
The fluid-filled cavity within the blastula
A
blstocoel
7
Q
importance of blastocoel
A
- essential for creating an internal environment that allows for cell movement and signaling, which is criticaal fro gastrulation .
- aids in nutrient distribution within the early embryo.
8
Q
what is involved in gastrulation
A
segregation of cells into the:
1. inner cell mass (which will give rise to the embryo proper) and the 2. trophoblast (which will contribute to the placenta in mammals).
9
Q
foundation for the development of distinct tissues and organs later on.
A
early specialization
10
Q
sets the stage for the dramatic cell
rearrangements and migrations that occur during gastrulation.
A
The blastula’s structure, with its defined layers of cells and the
blastocoel
11
Q
overview of processes leading
up to blastulation
A
- Fertilization
- Cleavage
12
Q
This process is where a sperm cell and an egg cell merge to form a zygote.
A
fertilization
13
Q
where does fertilization occurs?
A
fallopian tube
14
Q
process of fertilization
A
- sperm binds to the egg’s outer layer (zona pellucida), releasing enzymes from the acrosome to
penetrate it. - Once a single sperm enters the egg, their membranes fuse, and the egg completes its second
meiotic division. - The genetic material from the sperm and egg then combine to form a diploid zygote, marking the
start of embryonic development.
15
Q
what happens to zygotes after fertilization
A
undergoes to a rapid series of divisions (cleavage)
16
Q
what is formed as zygote divides
A
smaller cells called blastomeres
17
Q
a solid mass of 16-32 blastomeres.
A
morula
18
Q
begin to compact closely, enhancing cell-to-cell contact, while the structure remains encased in the zona pellucida.
A
The cells
within the morula
19
Q
key process in blastulation
A
- continued cell divisions (cleavage)
- formation of the blastocoel
- cell differentiation
- implantation
20
Q
This stage does not increase the size of the embryo, butdecreases the size of the cells and increases their number.
A
cleavage
21
Q
As the embryo reaches about 32-64 cells, its fluid secretion creates blastocoel
A
trophoblast cell
22
Q
whatbhappens to morula after fluid secretion of trophoblast cell
A
morula -> hallow blastocyst
23
Q
cell differentiation of inner cell mass and trophoblast
A
- inner cell mass (embryoblast) - forms at one pole and will develop into the embryo
- trophoblast - forms the placenta and supporting tissues.
24
Q
when is blastulation completed
A
around day 5-7 and prepares the embryo for implantation and start of gastrulation
25
blastulation process: stages that occurs in uterine tube
2 cell
4 cell
8 cell
26
blastulation process: stages that occurs in uterus
morula (16 cells)
blastocyst (70-100 cells)
27
results of the early divisions of cleavage
solid ball of cells, which is called morula.
28
The cells that make up the morula has been formed by?
mitosis
29
when is the developing embryo called morula?
when there are 16-32 blastomeres
30
formed about 3 days after fertilization
spherical morula
31
when deos morula reaches the uterine cavity
by the 3rd day after fertilization, &
remains free for one or two days.
32
Fluid passes from where
uterine cavity to the Morula
33
what happens once the morula reaches about 64 cells
the inner and outer cells take on
different roles.
34
Once the morula reaches about 64 cells, what happens to inner mass cell
will later
become the embryo and its surrounding membranes.
35
Once the morula reaches about 64 cells, what happens to outer cells
outer cells, called trophoblasts, will help the embryo attach to the uterus and later form the chorion.
36
mechanism of blastula formation
trophoblast cells release fluid into the center-> creating a blastocoel ->
embryo becomes a blastula -> trophoblast cells form an outer layer-> the inner cell mass gathers on one side inside the blastula.
37
what is implantation
:It is the process by which the
Blastocyst penetrates the superficial (Compact)
layer of the endometrium of the uterus.
38
site for the implantation
posterior wall of the body of the uterus near the fundus.
39
time for implantation
- It begins about the 6th day after fertilization.
- It is completed by the 11th or 12th day.
40
mechanism of implantation
1. Zona pellucida degenerates & disappears by the 5th day -> allows
the blastocyst to increase in size and penetrates the endometrium.
2. The embryoblast projects into the blastocystic cavity, while the
trophoblast forms the wall of the blastocyst.
3. By 6th day the blastocyst adheres to the endometrium (beginning of
implantation).
4. By 7th day, Trophoblast differentiated into 2 layers:
* Syncytiotrophoblast and
* Cytotrophoblast
5. By 8th day the blastocyst is superficially embedded in the compact layer of the endometrium
41
invades the endometrium; (It is
outer multinucleated cytoplasmic mass, with indistinct cell
boundary.
Syncytiotrophoblast
42
inner layer, mitotically active.
Cytotrophoblast
43
appear in the Syncytiotrophoblast which communicate forming
a lacunar network by the 10th or 11th day.
blood-filled lacunae
44
where does Blood-filled Lacunae appear
Syncytiotrophoblast
45
erodes the endothelial lining
of the maternal capillaries which known as sinusoids.
Syncytiotrophoblast
46
established when blood of maternal capillaries reaches the
lacunae
uteroplacental circulation - estblaished by 11th or 12th day
47
undergo a process called
apoptosis (programmed cell death) to facilitates
invasion of endometrium by the
Syncytiotrophoblast.
endometrial cells
48
engulf these degenerated cells
for nutrition of the embryo.
Syncytiotrophoblast
49
Implantation can be detected by:
1- Ultrasonography.
2-hCG (human chorionic gonadotrophin which is
secreted by the Syncytiotrophoblast) about the
end of 2nd week (Home Pregnancy Test):
50
- Is an immunosuppressant protein.
- Secreted by trophoblast cells.
- Appears in maternal serum within 24--48 hrs., after implantation.
- It is the basis for EPT (Early pregnancy test) in the first 10 days of development.
Early Pregnancy Factor(EPF)
51
when does the cells within
the blastocyst start to organize into
layers.
During the second week of
development, with the embryo
implanted in the uterus,
52
extra-embryonic membranes
needed to support and protect the
growing embryo:
the amnion, the yolk sac, the allantois, and the chorion.
53
- Originates from epiblast cells.
- Encases the amniotic cavity, fills with amniotic fluid.
Amnion
54
Functions of amnion
* Protects embryo from trauma and temperature changes.
* Allows movement, practice of swallowing and breathing.
* Fluid initially maternal plasma; later includes fetal urine (~week 8).
55
- Formed by hypoblast cells on the ventral side.
- Early nutrient supplier and circulatory support (weeks 2-3).
- Becomes source of blood cells and germ cells after placenta takes over (~week 4).
yolk sac
56
- Outpouching from the yolk sac in week 3.
- Contributes to the development of the urinary bladder.
- With yolk sac stalk, helps form the umbilical cord.
Allantois
57
- Outermost membrane, enclosing all others.
- Plays a key role in placenta formation.
Chorion
58
Gastrulation begins with the formation of what
primitive streak, a crucial structure
that marks the start of cell migration and germ layer formation.
59
- A dynamic process that involves migration of epiblast cells towards the midline of the embryonic disc
- Undergo an epithelial-to-mesenchymal transition (EMT)
- They then ingress (move inward) to form the underlying layers of the
embryo.
Gastrulation
60
how the primitive streak forms
- Location: Appears along the midline of the epiblast (the upper layer of the bilaminar disc).
- Development: Starts as a thickening of epiblast cells at the caudal (posterior) end and elongates towards the cranial (anterior) end.
- Primitive Node and Pit: At the anterior end of the primitive streak, a swelling called the primitive node forms, with a depression called the
primitive pit.
61
outermost layer
ectoderm
62
key derivatives of ectoderm
1. epidermis
2. nervous system
3. sensory organs
4. neural crest
63
The outer layer of the skin, including
hair and nails.
epidermis
64
brain, spinal cord, and peripheral nerves
nervous system
65
eyes, lens, cornea, inner ear
sensory organs
66
A transient population of cells that
gives rise to a diverse array of structures.
including pigment cells, parts of the peripheral
nervous system, and facial cartilage.
neural crest
67
Middle Germ Layer
Mesoderm
68
key derivatives of mesoderm
- Musculoskeletal System: Muscles, bones, cartilage.
- Circulatory System: Heart, blood vessels, blood cells.
- Excretory System: Kidneys.
Reproductive System: Gonads (testes and ovaries).
* Connective Tissues: Dermis of the skin, tendons, ligaments
* Lining of Body Cavities: Peritoneum, pleura, pericardium.
69
what does meoderm provides
structural framework, the transportsystems, and the internal support of the body.
70
inner most germ layer
endoderm
71
key derivatives of endoderm
* Lining of the Digestive Tract: Stomach, intestines, liver, pancreas.* Lining of the Respiratory System: Lungs, trachea, bronchi.
* Thyroid and Parathyroid Glands.
* Thymus.
* Lining of the Urinary Bladder and Urethra.
72
what does endoderm froms
the linings of the internal tubes and associated organs responsible for digestion, respiration, and hormone production
73
establishment of germ layers and body plan
foudation for ectoderm, mesoderm, and endoderm
74
types of symmetry
1. Radial symmetry
2. Bilateral symmetry
3. No symmetry
75
- Characterized by body parts arranged around a central axis
(e.g., jellyfish).
- Often seen in organisms that are sessile or drift passively.
radial symmetry
76
Characterized by a distinct left and right side, a dorsal (back)and ventral (belly) surface, and an anterior (head) and posterior (tail) end (e.g.. humans, insects).
- Associated with directional movement.
bilateral symmetry
77
Lacks symmetry and has irregular shapes that may vary between
individuals.
no symmetry
78
intrinsically linked to the orientation of the body plan
establishment of the primary germ layers
79
key axes established
- anterior-posterior (cranial -caudal) axis
- dorsal-ventral axis
- left-right axis
80
- head to tail
- defined early during gastrulation, often by the orientation of
the primitive streak (in amniotes) or similar organizing
centers.
anterior-posterior (cranial-caudal) axis
81
- Back to belly.
- Determined by signaling gradients and cell interactions during gastrulation.
dorsal-ventral axis
82
- While initially symmetrical, this axis is later established through specific signaling pathways,
leading to asymmetries in organ placement (e.g., heart
location).
left-right axis
83
critical signaling center, often referred to as the organizer.
primitive node
84
what does primitive node secretes
various signaling molecules that induce the formation of the neural
tube, somites, and other key embryonic structures.
85
Cells passing through the node contribute to the formation of what?
notochord, a rodlike structure that provides structural support to the developing embryo and plays
a crucial role in neural tube induction.
86
- Specialized regions within the early embryo
- play a crucial role
in establishing the body plan and inducing the formation of the germ layers and the
neural tube.
organizers
87
- is a powerful organizer
that secretes signaling molecules to pattern the developing embryo along the anteriorposterior and dorsal-ventral axes.
Hensen's Node
88
Through the primitive streak, epiblast cells migrate inward (a process called
invagination) to form what
* Endoderm (inner layer)
- Mesoderm (middle layer)
* Remaining epiblast becomes the ectoderm (outer layer)
89
dictates the interactions between cells and tissues that are essential for correct organ
development.
The precise spatial arrangement of these germ layers, established during gastrulation,
90
are crucial for the
formation of limbs
interactions between the mesoderm and ectoderm
91
are vital
for the development of the digestive system.
interactions between the endoderm and mesoderm
92
- Cells rolling over an overhang of the posterior of the blastula.
- Meroblastic cleavage
- segregation into epithelial layer and mesenchymal cells
Chondrichthyans (Cartilaginous Fish)
93
- It is the whole of the blastula, comprising the multi-layered dome
of the animal hemisphere and the mass of cells in the vegetal
hemisphere.
* cortical rotation; holoblastic cleavage
- blastocoel starts from first cell division; cells segregate into bilayered dome and presumptive
endoderm
amphibians
94
- It is the upper surface of the blastula, comprising a single-cel
thick epithelial layer, overlying the hypoblast
- meroblastic cleavage
Reptiles & Birds
95
segregation into epiblast and hypoblast
with blastocoel in-between, and marginal
cells
reptiles
96
partial segregation into two cell layers and marginal cells; hypoblast
grows from posterior margin
birds
97
- It is part of the inner cell mass, within the outer trophoblast.
- rotational cleavage; compaction
- segregation into ICM comprising epiblast and
hypoblast, and trophoblast
Mammals
98
environmental factors influencing blastulation
1. culture conditions
2. Maternal Health and Lifestyle Choices
99
In assisted reproductive technologies, the quality of the culture
medium, temperature, pH, and oxygen levels can significantly
affect blastocyst formation
Culture conditions
100
- Factors like maternal age, hormonal balance, and overall health can influence the environment in which blastulation occurs
- Smoking, alcohol consumption, and stress can negatively impact
embryo development
Maternal Health and Lifestyle Choices
101
Genetci Factors affecting blastulation
1. embryonic genome actibvation
2. epigenetic modifications
3. chromosomal abnormalities
102
Proper activation of the embryonic genome is crucial for
successful blastulation
embryonic genome activation
103
Changes in gene expression without altering the DNA sequence
can affect blastocyst quality
epigenetic modifications
104
Genetic defects or aneuploidy can hinder blastocyst development
chromosomal abnormalities
105
role of blastulation in reproductive technology
embryo development
embryo transfer
Preimplantation Genetic Testing (PGT)
Cryopreservation (Embryo Freezing)
106
Blastulation is the stage where a fertilized egg develops into a
blastocyst, a hollow structure with an inner cell mass. This stage
is critical for selecting viable embryos for implantation.
embryo development
107
In IVF, embryos are often cultured until the blastocyst stage
before being transferred to the uterus. Blastocysts have a higher
chance of successful implantation compared to earlier-stage
embryos.
Embryo transfer
108
Blastulation allows for safe biopsy of a few trophectoderm cells
for genetic testing (e.g., PGT-A for aneuploidy or PGT-M for
monogenic diseases) without significantly harming the embryo.
This helps screen for chromosomal abnormalities and genetic
mutations before implantation
Preimplantation Genetic Testing (PGT)
109
Blastocysts can be effectively cryopreserved through vitrification
(rapid freezing) due to their cellular differentiation and blastocoel
cavity, allowing high survival rates and storage of extra highquality embryos.
Cryopreservation (Embryo Freezing)
110
Advances in understandinf development biology and regenerative medicine
1. Stem cell research and therapy
2. Gene Editing Technologies
3. Tissue Engineering and Biomaterials
4. Organoids and Disease Modeling
5. Epigenetics and Deevelopment plasticity
111
Adult cells
reprogrammed to become pluripotent, capable of
differentiating into various cell types
Induced Pluripotent Stem Cells (iPSCs):
112
Induced Pluripotent Stem Cells (iPSCs) applications
a. Disease modeling (e.g., Parkinson's disease)
b. Drug screening
c. Regenerative therapies
113
Use of single-cell RNA sequencing and
live imaging to explore stem cell heterogeneity and lineage
trajectories.
Single-Cell Analysis:
114
Single-Cell Analysis example
Tracking dynamic changes during blastocyst
formation.
115
Uses guide RNA and Cas9 nuclease to introduce sitespecific DNA breaks for gene editing.
.CRISPR-Cas9 Technolog:
116
.CRISPR-Cas9 Technolog application
Correcting genetic mutations causing diseases
like Duchenne Muscular Dystrophy (DMD)
117
Delivery of CRISPR systems via viral vectors (e.g., AAV)
directly into the body.
In Vivo Gene Editing:
118
In Vivo Gene Editing example
In vivo editing to treat hereditary blindness (LCA10) in
clinical trials.
119
Layer-by-layer printing of bioinks (cells
biomaterials) to build tissue constructs.
3D Bioprinting
120
Responsive to environmental stimuli
(e.g., pH, enzymes) to release drugs or guide cell behavior.
Smart Biomaterails
121
Tissues
stripped of cells, preserving ECM architecture for reseeding
with new cells.
Decellularized Extracellular Matrices (dECMs)
122
- 3D structures derived from stem cells mimicking
human organs to study human development and diseases.
* Highly similar to the source tissues in terms of tissue
structure, cell type, and function.
otganoids
123
Growing 3D mini-organs from stem cells
that mimic in vivo organ development.
Organoid Culture:
124
Microengineered devices that
simulate organ functions with living cells and microfluidics.
Organ-on-a-Chip Technology:
125
involves heritable changes in gene expression
without altering DNA sequence
epigenetics
126
are regulated by epigenetic
changes (e.g., activation of pluripotency genes like Oct4).
Stem cell fate and plasticity
127
rely on resetting
epigenetic marks (e.g., in iPSC creation and limb
regeneration)
Reprogramming and regeneration
128
allows cells to adapt or switch
fates under stress (e.g., B-cells transforming to a-cells)
Developmental plasticity
129
