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Definitions Flashcards

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1
Q

acrosome
egg (ovum) vs. oocyte
zona pellucida
vitelline membrane
cumulus
cortical granules
polyspermy
ampulla
capacitation

A

just all of them lol needed this here so i didnt have to go back and forth between the powerpoint

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2
Q

acrosome

A

-In front of the nucleus of a sperm (cap of nucleus)
-derived from the golgi (modified secretory elements) : basicially during spermatogenesis golgi secretes enzymes that end up coming together to form the golgi and once this occurs, the golgi isnt there no more
-so the acromosome contsins enzymes and complex sugars

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3
Q

Egg (ovum) vs Oocyte

A

Egg: female gamete that is able to bind sperm and be fertilized

OOcyte: A developing egg that is not able to bind sperm yet or be fertilized (essentially the precursor to egg)

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4
Q

What are the five stages of meiosis

A

1)leptotene –condensed chromatin becomes apparent
2)zygotene – homologous chromosomes pair up and a structure called the synaptonemal complex forms between the homologous chromosomes
3)pachytene – “thickening” of chromosomes and genetic recombination (aka crossing over) – paired chromosome structure is called a “tetrad”
4)diplotene – sister chromatids of homologous chromosomes separate from each other as the synaptonemal complex breaks down – crossover sometimes visible as chiasmata
5) diakinesis - a further condensation of the chromosomes and, simultaneously, a further separation of the chromatids takes place that, however, still hang together at the chiasmata.

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5
Q

zona pellucida

A

-extracellular envelope/ matrix that is THICK
-ONLY FOR MAMMALS

What is an extracellular matrix/envelope?
-fibrous layer around the egg: often associated with sperm recognition

Look at slide 37

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6
Q

vitelline membrane

A

-extracellular matrix of invertebrates
-thin tough layer
-many have a glycoprotein meshwork (egg jelly) surrounding the vitelline envelope (attracts or activates sperm)
(jelly coat)

What is an extracellular matrix/envelope?
-fibrous layer around the egg: often associated with sperm recognition

Look at slide 37

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7
Q

cumulus

A

-outside of MAMMALIAN CELLS cause it is found on the outside of zona pellucida
-a layer of ovarian follicle cells that were nurturing the egg at the time of release from the ovary
-innermost cumulus cells are called corona radiata

Look at slide 37

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8
Q

cortical granules

A

-membrane bound (golgi derived) containing enzymes, mucopolysaccharides, adhesive glycoproteins, hyaline glycoproteins,
-homologous to acromosome of sperm (however 1 acromosome per sperm vs 15,000 ortical granules per egg)
found underneath the cell membrane along with actin which polymerizes into actin microfilaments at fertilization

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9
Q

can fusion occur anywhere on sea urchin

A

YEP but for other people it is isite specific

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10
Q

polyspermy

A

multiple sperm entering an egg
-results in too many sets of chromosomes
-ie triploidy means 3 sets, and this leads to genetic imbalance which could lead to developmental failures (not always, things like blueberries are triploid)

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11
Q

Ampulla

A

site where fertilization occurs
oviduct, distal to uterus and near ovary where fertilization takes place

provides great environment for fertilization and helps transport gametes

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12
Q

Capacitation

A

-set of changes that allow sperm to become able to fertilize egg (become primed to undergo acrosomal rxn and primed to fuse to cell membrane)

when sperm become mature during voyage ti oviduct, if not wont be able to fertilize egg
-sperm released during ejaculation ar able to move but they vannot yet fertilize egg, need to be matured in reproductive tract
-this is because sperm is quiescent transcriptionally and translationally (means dormant) sothey rely on post translational modifications such as phosphorylation of proteins to control maturation process
-this occurs as sperm comes in contatt with natural conception lubrication
-this needed to be understood to have successful ivf treatments and stuff

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13
Q

animal hemisphere
vegetal hemisphere
cortical rotation
marginal zone
vegetal rotation
radial intercalation
convergent extension
blastopore
Nieuwkoop centre
organizer

A

things for xenopus

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14
Q

animal hemisphere

A

-darkly pigmented
-non-yolk area
-upper half
-During embryogenesis: cells divide rapidly

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15
Q

vegetal hemisphere

A

-pale region
-yolk heavy
-serves as food for developing embryo
-slow division, less movement

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16
Q

cortical rotation

A

cortex: outer layer of egg, containing membrane, cytoskeletal components, rough er

when sperm enters: cortex loosens from the inner yolky core. Develops shear zone (yolk free area between cortex and core)

During first cell division: cortex rotates 30 degrees , so vegetal cortex is displaced from sperm entry towards FUTURE dorsal area
-happens at the same time as translocation of maternal dorsal activity also from vegetal pole to future dorsal area

How does it turn:
Microtubule arrays appear mid 1st cycle, cortical and dorsalizing activity relies on this
-plus end away from sperm site of entry
-allows these to move towards dorsal anterior end
w/o microtubules, no dorsal anterior structures

RESULTS: gray crescent (inner gray cytoplasm where gastrulation starts)

without cortical rotation:dorsalizing activity remains in vegetal region where it is not active, dorsalizing activity needs to be relocated to be active

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17
Q

marginal zone

A

In amphibians: Where gastrulation begins, the region surrounding the equator of the blastula, where the animal and vegetal hemispheres meet.

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18
Q

vegetal rotation

A

During frog gastrulation, internal cell rearrangements place the prospective pharyngeal endoderm cells adjacent to the blastocoel and immediately above the involuting mesoderm.

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19
Q

radial intercalation

A

Radial intercalation refers to the movement of cells from deeper layers of a tissue (radial layers) into more superficial layers, resulting in the thinning and expansion of the tissue.
-essentially the integration of several cell layers into one

ex: the involuting marginal zone (IMZ) and the noninvoluting marginal zone (NIMZ) are initially several cell layers deep and become one thin broad layer

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20
Q

convergent extension

A

-medial lateral intercalation of cells
-extends the post involution marginal zone
-polarized cell intercalation drives it (protrusion of cells to eachother, cadherin adhesion, actin myosin contractility)

-the medial lateral intercalation of cells in one axis and the elongation of cells in another axis

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21
Q

blastopore

A

-invagination of cells (slit-like blastopore)
-fo9und in dorsal region
-opening of the archaentron

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22
Q

Nieuwkoop centre

A

-dorsal most vegetal cells of the blastula
-induce formation of organizer
-signalling center opposite of site of sperm entry in xenopus

during cortical rotation: he vegetal cortex opposite the sperm entry point moves towards the animal pole.
This leads to the formation of a ‘signaling centre’ opposite the site of sperm entry known as the Nieuwkoop Centre.
This process leads to bilateral symmetry with the Nieuwkoop Centre at the midline separating right and left sides of the embryo.

Importance: set up the DV polarity in the blastula and ESSENTIAL for developemnt, 1st cleavage cuts through this

Signals from this center are needed to develop dorsal structures

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23
Q

organizer

A

-the dorsal lip of the blastopore
-derived from grey crescent

Function: instruct the formation of the embyronic body axis
-also protect ectoderm from bmp signalling, allowing it to differentiate into the neural tissue (BMP changes ectoderm into epiderm, so organizer protects it from it, making it be neural tissue which is the default)

examples: noggin and chordin

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24
Q

gamete
genome
cleavage division
blastomere
zygote
morula
gastrulation
gastrula
enhancer
induction
competence
morphogen
commitment
specification
a) autonomous specification
b) conditional specification
c) syncytial specification
determination
holoblastic cleavage
meroblastic cleavage
invagination
involution
ingression
delamination
epiboly
archenteron
convergent extension
deuterostome
protostome

A

General development biology

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25
Q

gamate

A

a specialized reproductive cell through which sexually reproducing parents pass chromosomes to their offspring (a sperm or an egg

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26
Q

genome

A

the complete DNA sequence of an individual organism

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27
Q

cleavage division

A

a series of rapid biotic cell divisions following fertilization in many early embryos
- it divides the embryo without increasing its mass

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28
Q

blastomere

A

a cleavage-stage cell resulting from mitosis

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29
Q

zygote

A

a fertilized egg with a diploid chromosomal complement in its zygote nucleus generated by fusion of the haploid male and female pronuclei

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30
Q

morula

A

vertebrate embryo of 16-64 cells
- proceeds the blastula/ blastocyst stage

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31
Q

gastrulation

A

a process involving movement of the blastomer of the embryo relative to one another resulting in the formation of three germ layers of the embryo

hey buddy

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32
Q

gastrula

A

a stage of the embryo following gastrulation that contains the three germs layers that will interact to GENERATE THE ORGANS OF THE BODY

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33
Q

enhancer

A

DNA sequence that controls the efficiency and rate of transcription from a specific promoter

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34
Q

induction

A

the process by which one cell population influences the development of neighbouring cells via interactions at close range

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35
Q

competence

A

the ability of cells or tissue to respond to a specific inductive signal

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36
Q

morphogens

A

substances that, by their differing concentrations differently specify cell fates

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37
Q

commitment

A

a state in which a cells developmental fate has become restricted even though it is not yet displaying overt changes in cellular biochem and function, it is more limited to what it will become but won’t necessarily look different
- two stages of commitment:
1. specification
2. determination

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38
Q

specification

A

first stage of commitment of cell or tissue fate during which the cell or tissue is capable of differentiating autonomously (by itself) when placed in a neutral environment with respect to the developmental pathway
- at this stage cell commitment can still be reversed

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39
Q

autonomous specification (mosaic dev.)

A
  • ## predominates in most invertebrates
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40
Q

conditional specification

A
  • predominates in vertebrates
  • is the process by which cells achieve their respective fates through interactions with other cells
  • cleavage divisions are variable and fate assignment is flexible
  • massive cell rearrangements and migrations precede or
    accompany specification
  • known as regulative development: if a blastomere is lost the embryo can compensate
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41
Q

syncytial specification

A
  • mostly in insects
  • the interaction of nuclei and transcription factors which eventually result in cell specification, take place in a common cytoplasm
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42
Q

determination

A

the second and IRREVERSIBLE stage of cell or tissue commitment in which it is capable of differentiating autonomously even when placed into a non-neutral (such as when transplanted into another region of the embryo)

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43
Q

holoblastic cleavage

A
  • greek holos = complete
  • a cell division (cleavage) pattern in the embryo in which the entire egg is divided into smaller cells
  • frogs and mammals
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44
Q

mesoblastic cleavage

A
  • greek meros = part
  • the cell division (cleavage) pattern in zygotes containing large amounts of yolk where only a portion of the cytoplasm is cleaved.
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45
Q

invagination

A

folding of a sheet (epithelium) of cells (like the indention of a soft rubber ball when it’s poked)
- type of cell movement during gastrulation (step 1)

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46
Q

involution

A

inward movement of an expanding outer layer so that it spreads over the internal surface of the remaining external cells
- type of cell movement during gastrulation (step 2)

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47
Q

ingression

A

migration of individual cells from the surface to the embryos interior.
- individual cells become mesenchymal (separate from one another) and migrate independently
- epithelial to mesenchyme transitions (EMT)
- type of cell movement during gastrulation (step 3)

48
Q

delamitation

A

splitting one cellular sheet into two more or less parallel sheets.
- results in the formation of a new (additional) epithelial sheet of cells
- type of cell movement during gastrulation (step 4)

49
Q

epiboly

A

movement of epithelial sheets (usually ectodermal cells) spreading as a unit (rather than individually) to enclose deeper layers of the embryo.
- can occur by cells dividing, changing shape or by several layers of cells intercalating into fewer layers (all three mechanisms usually used at same time)

50
Q

archenteron

A

the primitive gut of sea urchin blastula
- formed by invagination of the vegetal plate into the blasteocel

51
Q

convergent extension

A

a phenomena wherein cells intercalate to narrow the tissue and at the same time move it forward (think of traffic on a highway where several lanes merge into one)
- basically the archenteron becomes a long thin tube
- this involves cell shape change and cell migration
- cells become thinner and intercalated

52
Q

deuterostome

A

animals which the blastopore will become the anus
- “mouth second”

53
Q

protostome

A

animal which the blastopore will become the mouth
- “mouth 1st”

54
Q

blastodisc
telolecithal
yolk syncytial layer
enveloping layer
deep cells
epiblast
hypoblast
embryonic shield
Balbiani body

A

fish

55
Q

blastodisc

A

-yolk free cytoplasm found at the animal pole
(clear island of no yolk)
-aka cytoplasmic cap
-where meroblastic divisions occur, leading blastodisc to turn into blastoderm
-after fertilization, wave of ca cause contraction of actin cytoskeleton which moves the region to animal

Summary: Small region at the animal pole of the telolecithal eggs of fish and chicks, containing the yolk-free cytoplasm where cleavage can occur and that gives rise to the embryo.

-after cortical granule reaction, the chorion (vitelline envelope) lifts from the surface of the egg (makes fertilization envelope)
-cytoplasmic streaming due to actin myosin contractions (fromwave of ca) causes NON YOLKY CYTOPLASM at animal hemisphere

56
Q

telolecithal

A

an egg in which the yolk is unevenly distributed, with most of the yolk concentrated at one pole of the egg,(vegetal pole), while the other pole, the animal pole, contains less yolk and more cytoplasm.

57
Q

yolk syncytial layer

A

-a distinct cell layer of early blastoderm
layer between the blastodisc (non yolk part that divides mesoblastic divisions, specificlly the deeo cells) and the yolky layer
-occur during mid blastula transition. (cleavage 10)
-nuclei of yolksynticial layer comes from the margin cells of blastoderm

-induce mesoderm

58
Q

enveloping layer

A

-found in early blastoderm stage
-outermost cell layer of blastoderm
-during epiboly, these cells spread over the yolk
-deep cells intercalate with these superficial cells to form this during gastrulation

-eventually joins to yolk synticial layer

59
Q

deep cells

A

-cells located between the enveloping layer (EVL) and the yolk synticial layer
-cell layer in early blastoderm

60
Q

epiblast

A

happens halfway in epiboly
thickening thorughout the margin part of Epibolizing blastoderm is called the germ ring
germ ring has two layers
1) epiblast
2) Hypoblast

Epiblast is the syperficial layer, upper layers of cells

61
Q

hypoblast

A

inner layer of the germ ring
-internalizing vells at blastoderm margin also forms this

62
Q

embryonic shield

A

-intercalation of the epiblast and the hypoblast on the dorsal side (forms this shield)
-thickening on the dorsal side (accumulation of cells on one part of germ ring)
-homologous to drosal lip of amphibians
-epiboly pauses while this shield forms

-once blastoderm margin covers entire egg, the shield converges anteriorly forming precursor to notochord and precordal plate (like blastopore lip in xeno)

Important for: dorsal ventral axis
-can convert lateral and ventral mesoderm (blood and connective tissue) into dorsal mesoderm (notochord and somites)
-can cause ectoderm to become neural rather than epiderm

63
Q

Balbiani body

A

-mitochondrial cloud
-associated with maternal mrna locatlization

-visible in early stages of growth

64
Q

Lampbrush chromosomes

A

-special type of chromosome found in growing oocytes
-transform into lampbruhs form during diplotene stage of meiosis
-come about since zebrafish are highly transcriptionally active during growth phase

65
Q

micropyle

A

-hole in vitelline envelope that sperm gies through during fertilization
-comes about since one follicle cell v(what secretes the envelope) is in contact with the envelope

66
Q

compaction
inner cell mass
trophoblasts
trophectoderm
cavitation
blastocyst
epiblast
hypoblast
bilaminar germ disc
embryonic epiblast
amniotic cavity
cytotrophoblast
syncytiotrophoblast
trophoblastic lacunae

A

amniotes/mammals

67
Q

compaction

A

-unique for mammalian cleavage
-mediated by e cadherin
-occur at 8 cell stage
-blastomeres become tightly oacked because they changed adhesive properties (more e cadherin make them bind more)

-cell cell junctions are formed
inner cells have gap junctions which allow small molecules to move between them
outter cells have tight juctions, which prevent inner cells with exchanging things with outside environment

68
Q

inner cell mass

A

occurs in 16 cell morula (goes from 8 cell to 16)
-small group of internal cells that will produce the embryo

69
Q

trophoblasts

A

in the 16 cell morula
-the large group of external cells (external to the inner cell mass)
-these cells will become the trophectoderm
-these cells do not contribute to formation of actual embryo but form the CHORION (outer layerthat surrounds embryo, which ensd up forming placenta)

they are the external cells that also bind the embryo to the uterus (task to make these is important for mammal development so that it can stick to the uterine wall (not elsewhere)

once at uterine wall, these have L-selectin on surface of cells to bind to endometrium sulfated polysaccharides of the uterine

70
Q

trophectoderm

A

-this differentiation is the first differentiation event of mammalian embryogenesis

71
Q

cavitation

A

Cavitation: A process whereby the trophoblast cells secrete fluid into the morula to create a blastocoel. The membranes of trophoblast cells pump Na+ ions into the central cavity, which draws in water osmotically, thus creating and enlarging the blastocoel.

As the blastocoel forms through cavitation, the ICM becomes positioned on one side of the trophoblast cells – this type of blastula is known as a blastocyst.

72
Q

blastocyst

A

Cavitation forms the enlarging of the blastocoel… as it forms, the inner cell mass gets positioned on one side of the trypoblast cells,

Cthis type of blastula is known as blastocyst

zona pellucida preents the blastocyst from sticking to tube wall (not uterine), eventually the blastocyst releases proteases to digest this and hatches from the zona pellucida, allowing it to bind to the uterine wall

73
Q

epiblast (mammals0

A

cells of inner mass form two layers, another name for this inner cell mass is bilaminar germ disc

this is one,

seperates into two parts:
1) Embryonic epiblast: forms embryo proper
2)cells that line amniotic cavity: aminotic fluid fills here

74
Q

hypoblast

A

Second part of inner mass cell (bilaminar germ disc)

delaminate to form a layer facing the blastocoel

75
Q

bilaminar germ disc

A

inner mass cells derives 2 layers… epiblast and hypoblast

these two together are the bilaminar germ disc (once the inner mass cells form into these two, both of them together is no longer called hte inner mass cell but called this)

76
Q

embryonic epiblast

A

a part of the epiblast (whic is a part of the bilaminar germ disc)… this is the part that turns in to the embryo (embryo proper) theother part of the epiblast turns into amniptic cavity

77
Q

amniotic cavity

A

other part of the bilaminar germ disc, this is the part that fills with amniotic fluid that is a shock absorber and prevents dehydration

78
Q

cytotrophoblast

A

-original tryphoblasts form a layer called this
-originally adheres to endrometrium layer

79
Q

syncytiotrophoblast

A

-cells that are able to grow by nuclear division without cytokinesis form this
-furthers progression of embryo into uterine wall by digesting uterine tissue

-original tryphoblast cells turn into this thing

80
Q

trophoblastic lacunae

A

Cytrotrophoblasts secrete paracrine factors that attract maternal blood vessels, and maternal vasucular tissue is DISPLACED by trophoblasts…
forming this

81
Q

amniotes
amnion
chorion
allantois
discoidal meroblastic cleavage
area pellucida
epiblast
subgerminal cavity
area opaca
marginal zone
hypoblast islands
secondary hypoblast (endoblast)
posterior marginal zone
primitive streak
primitive groove
Hensen’s node

A

Ammonites/chicks

82
Q

amniotes

A

vertebrates who’s embryos form an amnion

83
Q

amnion

A

“water sac”
- a membrane enclosing and protecting the embryo and its surroundings amnionic fluid
- water sac provides protection from desiccation and mechanical shock

84
Q

chorion

A

essential for gas exchange

85
Q

allantois

A

stores waste and helps mediates exchange

86
Q

discoidal meroblastic cleavage

A
  • occurs in bird eggs
  • cleavage only occurs in the blastodisc and doesn’t extend into the yolk
  • blastodisc: a small amount of cytoplasm sitting atop a large yolk
87
Q

area pellucida

A

a 1-cell thick transparent layer of deep cells from the centre of the blastoderm which shedded and died

88
Q

epiblast

A

upper layer of area pellucida (forms part of the area pellucida)

89
Q

subgerminal cavity

A

a space that sits between the blastoderm and the yolk

90
Q

area opaca

A

surrounds the area pellucida and is the peripheral ring that does not shed deep cells
- its opaque

91
Q

marginal zone

A

in-between thin layer of cells

92
Q

hypoblast islands

A

delaminate (divided) area pellucida cells which are primary hypoblasts/polyinvagination islands
- forms hypoblast
- found beneath epiblast

93
Q

secondary hypoblast (endoblast)

A

the pushing of the hypoblast islands anterior due to deep yolky cells of posterior margin migrates anterior beneath the epiblast

94
Q

Koller’s sickle

A

a crescent shaped cluster of cells beneath the epiblast at the posterior margin

95
Q

posterior marginal zone

A

signalling center that plays key role in the formation of primative streak and hypoblast

96
Q

primitive streak

A

the first morphological sign of gastrulation in amniotes that first arises from a local thickening of the epiblast at Koller’s sickle
- defines AP axis of avian embryo
- goes from posterior to anterior
-

97
Q

primitive groove

A

the depression formed within the primitive streak where migrating cells pass into the deep layers of the embryo

98
Q

Hensen’s node

A

a funnel shaped depression anterior end of the primitive streak
- the frog organizer and the fish shield

99
Q

neural plate
neural tube
neurulation (primary & secondary)
neural crest
cerebellum
spina bifida
neural crest early vs. late migration
melanocytes

A

ectoderm : neuraltion and neural tube

neuralation: formation of the cns and the formation of neural tube from the neural plate

100
Q

neural plate

A

region of dorsal ectoderm so specified to become neural ectoderm

Low levels of BMP caues it to be this
High levels of BMP cause it to be epidermins
Intermediate levels: cause ectoderm to be neural crest cells

101
Q

neural tube

A

neural plates folds into a tube in a process called neuralation
-precursor of the CNS

102
Q

neurulation (primary & secondary)

A

Primary: FORMS FROM EPITHELIUM
-invagination and rolling up of a sheet of cells that seperate as a tube from the overlying epithelium
Steps:
1) FOlding of neural plate
2) elevation of plate
3)Convergence of folds: making the neural groove
4)Closure of neural groove to make the neural tube
Three products of primary neuralation:
1) Epidermis
2) neural tube
3) neural crest cells
Presence of N cadherin instead of E cadherin drive cell adhesion needed for neural tube closure and seperation of neural cells from epidermis

Secondary: FORMS FROM MESENCHYME
building a new neural epithelium from mesenchymal cell condensation and subsequent cavitation. (note: mesenchyme to epithelial transition)
-more common in tail

Both can occur in the same animal, complete neural tube forms when both are combined
look at pic o slide6

103
Q

neural crest

A

Neural crest cells: become many cell types including the PNS and melanocytes

intermediate levels of BMP cause ectoderm to be this

-form where the neural tube and epidermis meet in primary neuralation
-sometimes called fourth germ layer

Cranial neural crest cells: bone plus neurons, glial etc
Trunk neural crest cells: no bones but has rest

104
Q

cerebellum

A

Function: MOTOR COORDINATION

105
Q

spina bifida

A

Failure to close the posterior neural tube results in this

Failure to close the neural tube is a problem…

open ends of the neural tube are reffered to as anterior and posterior neuropores…

What helps prevent:
Follate vitamins (B9: folic acid)
Not understood well but there is a folate binding protein expressed on dorsalmost area of neural tube at time of fusion

Found this out cause follate receptors in mouse cause more likely neural tube failure to close posterior end in mouse

Foods can also cause disruption to the follate receptors ie fungal contaminants ( act. as a teratogen) the mycotoxin is called fumonisin

106
Q

neural crest early vs. late migration

A

early:Snail2 transcription factor down-regulates cadherin-6B, a cadherin enriched in premigratory neural crest cells.

Early cells follow a ventral pathway through the anterior part of each sclerotome (chunks of mesoderm that will eventually form vertebral cartilage); they will become sensory and sympathetic neurons, adrenomedullary cells and Schwann cells.

Late:Late cells follow a dorsolateral pathway to become melanocytes

107
Q

melanocytes

A

pigment cells

108
Q

notochord
paraxial mesoderm
somites
dermomyotome
sclerotome
limb buds
progress zone
Apical ectodermal ridge
zone of polarizing activity

A

Mesoderm

109
Q

notochord

A
  • develops from the dorsal most region of mesoderm
  • chordamesoderm forms it
110
Q

paraxial mesoderm

A
  • forms the somites which will form the axial skeleton (vertebrae, ribs), all skeletal muscle and the dorsal dermis, tendons, joints and dorsal aortic cells
  • somatic mesoderm
111
Q

somites

A

segmental block or ball of mesoderm formed for paraxial mesoderm adjacent to notochord
- forms most but not all the axial skeleton (vertebrae, ribs), all skeletal muscle, and the dorsal dermis, tendons, joints, and dorsal aortic cells
- gives rise dermomyotome and sclerotome

112
Q

dermomyotome

A
  • derived from somite forming the late somites dermatome which forms the dermis and myotome which forms the skeletal muscle
113
Q

sclerotome

A
  • the second the derivative from from somite forming the late somites syndetome which makes the tendons and sclerotome which forms the vertebral body (bones and cartilage, ribs, dorsal aorta cells
114
Q

limb buds

A

a circular bulge that will form a further limb
- formed by the proliferation of mesenchyme cells from the somatic layer of the limb field lateral plate mesoderm (the limb skeleton precursor cells) and form the somites (the limb muscle precursor cells)

115
Q

progress zone

A

underlying mesoderm
- Wnt/Fgf10 found here

116
Q

Apical ectodermal ridge

A
  • found along the distal margin of the wing bud (the boundary between dorsal and ventral)
  • critical signalling centre for limb development
  • induced by mesoderm cells secreting Fgf10
  • maintained through positive feedback loops after established where Wnt/Fgf8 is signalling in the ectoderm and Wnt/Fgf10 is signalling in the underlying mesoderm
  • maintains the underlying mesoderm in a plastic
    proliferative state – enabling elongation of the
    limb in proximal/distal axis
  • maintains expression of molecules responsible
    for the anterior-posterior limb axis (thumb to
    pinkie
  • interacts with proteins that specify
    anterior/posterior as well as dorsal ventra
117
Q

zone of polarizing activity

A
  • signals from the limb bulb that signal development of the limb along the anterior-posterior axis
  • Sonic Hedgehog (Shh)

bio 303 (18 decks)

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