Organogenesis Flashcards
(126 cards)
1
Q
The process by which the ectoderm, mesoderm and endoderm are converted into the internal organs of the body.
A
Organogenesis
2
Q
Organogenesis takes place between about _____ to the end of ______.
A
week 3 , week 8
3
Q
At the end of organogenesis the embryo is referred to as a ______.
A
fetus
4
Q
Stages of Pre-organogenesis
A
Zygote —>Cleavage —> Eight-cell stage —> Blastula —> Gastrulation
5
Q
Endoderm will form
A
-Lung cells (alveolar cell)
- Thyroid cells
- Digestive cells (pancreatic cell)
6
Q
Mesoderm wll form:
A
- Cardiac muscle cells
- Skeletal muscle cells
- Tubule cells of the kidney
- Red blood cells
- Smooth muscle cells (in gut)
7
Q
Ectoderm will form:
A
- Skin cells of epidermis
- Neuron of brain
- Pigment cells
8
Q
Establishes the basic framework of organs.
A
Primary organogenesis
9
Q
involves the refinement and functional maturation of these structures.
A
Secondary organogenesis
10
Q
Key Events and Organ Systems in primary organogenesis
A
- Neurulation
- Cardiovascular system development
- Somitgenesis
- Early development of Other systems
11
Q
Formation of the neual tube from the etoderm (which gives rise to the central nervous system)
A
Neurulation
12
Q
What does neurulation involves?
A
Neural pplate formation, folding, fusion
13
Q
Factors in neurulation
A
Signaling molecules (e.g., sonic hedgehog gene expression)
14
Q
The heart and major blood vessels begin to form
A
Cardiovascular System development
15
Q
Involve in cardiovascular system development
A
Heart tube formation, folding, septation
16
Q
Factors in cardiovascular system development
A
Cardiogenic mesoderm, growth factors
17
Q
Formation of somites from the mesoderm in primary organogenesis
A
Somitogenesis
18
Q
Involve in Somitogenesis
A
Segmentation of mesoderm, differentiation into sclerotome, myotome, and dermatome
19
Q
Initil development of the digestive system (endoderm). Early kidney development (mesoderm). Limb bud formation (mesoderm and ectoderm).
A
Early development of other systems in primary organogenesis
20
Q
The mesoderm that lies on either side of thevetebrate neural tube forms a set of temporary structures called _______.
A
Somites
21
Q
Later i development, the cells within the somites will migrate to different parts of the body to develop into ______, ________, and _________ of the skin.
A
bone, skeletal muscle, and connective tissue
22
Q
The specific pattern of induction from nearby tissues, including the ______, ________, _______ and surrounding _______, wll determine what type of tissue a particular region of a somite will become.
A
ectoderm, the neural tube, the notochord and surrounding mesoderm
23
Q
The refinement and maturation of organ structures. This stage involves further differentiation, growth, and functional specialization
A
Secondary Organogenesis
24
Q
Key events and Organ systems in secondary organogenesis
A
- Refinement of the Nervous system
- Maturation of the Cardiovascular System
- development of the Specialized Tissues
- Organ-specific Maturation
25
Events in the refinement of Nervous system
Synaptogenesis, myelination, regional specialization of the brain
26
Factorsin the refinement of the Nervous System
Neutrophic Factors, neural activity
27
Events in the maturation of the cardiovascular system
Further heart remodeling, formation of valves, development of the circulatory system
28
Factors in the maturation of the cardiovascular system
Hemodynamics, growth factors
29
Differentiation of muscle tissue, formation of bone and cartilage, developmnt of skin and it appendages
development of Specialized Tissues
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- Lung branching and alveoli formation
- Kidney nephron development
- development of the endocrine glands
Organ-specific maturation
31
Mechanisms driving Orgnogenesis
- Induction and cell competence
- Morphogen Gradients and Pattern formation
- Apoptosis in organ shaping
32
refers to the change in fate of a group of cells in response to ignals from other cells.
Induction
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The signal-receiving cells, must be capable of responding, a property termed _________.
competence
34
ensure that tissues form in the right place and time
combination of indution and competence
35
These gradients provide positional information to cells, enabling them to differentitate into specific cell types and organize ito tissues and organs.
Morphogen Gradients
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Secreted from specific sources within deveoping tissues, create a concentration gradient, instructing cells to adopt different fates, and are examples of growth factors like Decapentaplegic and Wingless in Drosophila
Morphogens
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Morphogens diffuse frely, but their transport is influences by interactions with other molecules and actie transport mechanisms, while their oncentration is maintained by cell degradation or uptake.
Gradient formation
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Cells respond to morphogen gradients by varying concntration thresholds, triggering the expression of specific genes, whic in turn drives cell differentiation and tissue patterning
Pattern formation
39
Like cellular contractions and tissue tension, can influence morphogen gradients and pattern formation, correcting noisy gradients and ensuring robust tissue patterns.
Mechanical Forces
40
involve interactions between substances, can generate spatial patterns of morphogen concentration in developing tssues, in addition to morphogen gradients.
Turing’s reaction-diffusion models
41
- a normal, programmed process where ceclls self-destruct or die
- key role: shapes organs and srutures during development
- essential for achieving complex body forms
Apoptosis
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Steps and mechanisms of Apoptosis in Organ shaping
a. Initiation and signaling
b. Activation of the Apoptosic Machinery (Caspase Cascade)
c. Execution Phase and Cellular changes
d. Clearance of Dying cells
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Triggered by genetic and biochemical signals in specific times and locations
Ex. Thyroid Hormones (TH) in amphibians triggers apoptosis
Initiation and signalling
44
cysteine proteases
Caspases
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Exist as inactive precursor
procaspases
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Activation pathway of the apoptotic machinery
- Initiator caspases (caspase-8, -9) acivated by death signals
- Initiator caspases activate effector caspases (caspase-3, -6, -7)
47
- Caspases-cysteine proteases
- Exist as inactive precursors (procaspases)
- Activation pathway:
1. initiator caspases (caspase-8, -9) activated by death signals
2. Initiator caspases activate effector caspases (caspase-3, -6, -7)
Activation of the Apoptotic Machinery (Caspase cascade)
48
Effector caspases cleave critical proteins → cell dismantling
Morphological changes:
- Cell shrinkage, chromatin condensation, nuclear
fragmentation
- Membrane blebbing due to actomyosin contraction (ROCK I
cleavage)
Apoptotic bodies:
- Cell fragments enclosed in membrane
Execution phase and Cellular changes
49
Effetor caspases cleave critical proteins
cell dismantling
50
Morphological changes in execution phase and cellular changes
- cell shrinkage, chromatin condensation, nuclear fragmentation
- Membrane blebbing due to actomyosin contraction (ROCK I cleavage)
51
Cell frgaments enclosed in membrane
Apoptotic bodies
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-Apoptotic cells expose “eat-me”
signals (e.g., phosphatidylserine)
-Attracted phagocytes (e.g.,
macrophages) engulf apoptotic
bodies
-Prevents inflammation, recycles
materials
Example: Amphibian intestine show
phagocytosis in action
Clearance of Dying cells
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Apoptotic cells expose ________ _____ (e.g., phosphatidylserine)
“eat-me” signals
54
“eat me” signals
Phosphatidylserine
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Attracted ______ (e.g., macrophages) engulf apoptotic bodies
phagocytes
56
Targeted cell removal sculpts tissue
Example: Digit Formation
- During the development of limbs,
the initial structure often has webbing
- Massive apoptosis of the
interdigital mesoderm between
developing digits removes the webbing
Sculpting by Elimination
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Attracted ______ (e.g., macrophages) engulf apoptotic bodies
phagocytes
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Example of sculpting by elimination
Digit Formation
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Apoptosis contributes to tissue movement and reorganization
Tissue remodeling and Mechanical Functions
60
Apoptotic cells generate pulling forces
Force Generation
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Localized apoptosis severs tissue constraints
Brake-Release Mechanism
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First functional organ to develop
human heart
63
Begins as early as day 18 post-fertilization
Heart development
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Development of the heart includes,
formation, folding and partitioning
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Development of mesodermal tissue
around days 18-19
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Where is the mesdermal tissue formed?
In the cardiogenic area, located near the head region of the embryo
67
Signals from theunderlying endoderm stimulae mesodermal cells to form two ________ _____.
cardiogenic cords
68
A lumen froms within each cardiogenic cord, trandforming them into endocardial tubes.
Formation of endocardial tubes
69
These tubes are the precursors to the future heart’s inner lining.
Endocardial tubes
70
Around day 21-22, the two endocardial tubes fuse at the midline, forming a single primitive heart tube
Fusion into the Primitive Heart Tube
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his tube already exhiits peristaltic contractions that push blood from the sinus venosus to the truncus arteriosus
Primitive heart tube
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The heart tube is composed of five distinct regions, what are those?
Truncus arteriosus
Bulbus cordis
Primitive ventricle
Primitive atrium
Sinus venosus
73
As the primitive heart tube lengthens, it begiins to loop and fold within the pericardial cavity.
Cardiac looping
74
CArdiac looping creates a characeristic __ _____, with rightward (dextral) bending.
S-shape
75
- This folding properly aligns the future chambers and major outflow tracts.
- It lays the groundwork for spatial separation and correct left-right patterning of the heart.
Functional Orientation
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- The heart begins beating and pumping blood as early as day 21-22
- Early blood flow s crucial for nutrient and oxygen transport to support embryonic development
Functional Onset
77
Beginning around day 28, the heart begins forming internal septa to divide it into four chambers.
Chamber septation
78
Chamber septation includes the development of what?
Interatrial septum
Interventricular septum
Atrioventricular septum
79
Separates the right and left atria
Interatrial septum
80
Divides the two ventricles
Interventricular septum
81
Forms between atria and ventricles
Atrioventricular septum
82
Atrioventricular valves (tricuspid and
mitral) begin forming between weeks 5
and 8.
Semilunar valves (aortic and pulmonary)
form between weeks 5 and 9.
These valves arise from endocardial
cushion tissue, which undergoes
extensive remodeling
Valve Development
83
Formation of Atrioventricular valves (tricuspid and mitral)
between weeks 5 and 8
84
Formation of Semilunar valves (aortic and pulmonary)
between weeks 5 and 9
85
These valves (atrioventricular and semilunar valves) arise from endocardial cushion tissue, which undergoes _____ _______.
extensive remodeling
86
The bulbus cordis becomes the right
ventricle.
The primitive ventricle forms the left
ventricle.
The primitive atrium develops into both
auricles.
The sinus venosus contributes to the
posterior right atrium, the sinoatrial (SA)
node, and coronary sinus
Final Differentiation
87
Becomes the right ventricle
Bulbus cordis
88
forms the left ventricle
primitive ventricle
89
develops into both auricles
primitive atrium
90
contributes to the posterior right atrium, the sinoatrial (SA) node, and coronoary sinus
Sinus venosus
91
By week 8, the heart’s structure
closely resembles the adult heart.
However, fetal circulatory shunts like
the foramen ovale and ductus
arteriosus remain until after birth
Completion of Cardiac Structure
92
Abnormalites in Organogenesis
Genetic causes of malformations
93
Refer to developmental abnormalities in the formation of
organs due to inherited or spontaneous changes in the
DNA.
These malformations can result from mutations, chromosomal
abnormalities, or gene-environment interactions affecting the
expression of genes critical during embryonic development.
Organogenesis relies on tightly regulated gene expression
networks (e.g., HOX genes for limb and spine patterning).
Disruption can cause structural abnormalities or the absence
of entire organs.
Genetic causes of Malformations
94
Genetic causes of malformations examples
PAX6 mutation
TBX5 mutation
95
PAX6 mutation
aniridia (absence of the iris)
96
can disrupt organogenesis, particularly affecting eye development due to PAX6’s role as a master regulator of eye formation
PAX6 gene mutation
97
Mutations in the ____ ____, which is cruccial for forelimb and heart development, lead to different patterns depending on the type of mutation
TBX5 gene
98
(those that eliminate TBX5 function) cause severe abnormalities in both heart and limbs
Null mutations
99
(alter specific amino acids) results in organ-specific effects
Missence mutations
100
TBX5 is active in the heart (ht) and optic cup (op). This means the gene is starting to play a role early in heart development.
Stage 14
101
Heart (ht) and wing bud (wb) show strong TBX5 activity.
stage 20
102
Expression is seen around the trachea (tr) and notochord (no).
Stage 26
103
TBX5 is strongly expressed in different heart chambers:
la=left atrium
lv=left ventricle
rv=reight ventricle
cc=conus cordis (outflow tract)
tr=trachea
ra=right atrium
Stage 25 and 27
104
When BX5 is mutated, as in ______ ____, it can cause heart defects and limb abnormalities, depending n how the gene’s function is disrupted
Holt-Oram syndrome
105
Environmental Influences on Organogenesis
Teratogens
106
- A variety of environmental factors can disrupt this process, leading to congenital anomalies.
- are substances or conditions that can cause birth defects.
Teratogens
107
The effects of teratogens depend on several factors, including:
The stage of development
The dose of the teratogen
The duration of exposure
Genetic susceptibility
108
The embryo is most vulnerable during the first trimester, when major organs are forming.
The stage of development
109
Higher doses generally increase the risk and severity of birth defects
The dose of the teratogen
110
Longer exposure to a teratogen can have more significant effects.
The duration of exposure
111
Individual genetic differences can influence how a fetus responds to teratogen exposure
Genetic susceptiblity
112
can cause range of physical, intellectual, and behavioral problems, including facial abnormalities, growth diffeciencies, and cognitive impairment
Fetal alcohol spectrum disorders (FASD)
113
Historically, this drug caused severe limb malformations
Thalidomide
114
This anticonvulsant is associated with neural tube defects, such as spina bifida
Valproic acid
115
can lead to hearing loss, cataracts, and heart defects in the developing fetus
maternal Rubella infection
116
This virus can cause microcephaly and other brain abnormalities
Zika virus
117
Environmental pollutants
Lead
Mercury
radiation
118
Exposure to this can result in cognitive impairments
Lead
119
Exposure can cause neurological disorders
Mercury
120
Can cause microcephaly and other developmental problems
Ionizing radiation, uch as X-rays
121
Mechanisms of Teratogenesis
Interfering with cell signaling pathways
Causing cell death
Alterng gene expression
Disrupting placental function
122
Teratogens can disrupt the communication between cells that is essential fo proper organ formation
Iterfering with cell signaling pathways
123
Some teratogens can induce apotosis (programmed cell death) or necrosis (cell death due to injury), leading to structural abnormalities.
Causing cell death
124
Teratogens can affect the way genes are turned on and off, which can disrupt the complex processes of development
Altering gene expression
125
Interference with the placenta can affect nutrent and oxygen supply to the developing fetus.
Disrupting placental function
126
Thetiming of exposure to a teratogen is crucial. Different organs and systems have specific “critical periods” during which they are most vulnerable to disruption
Critical periods of development
