Embryology Test 2 Flashcards
(190 cards)
1
Q
What are the four extra embryonic layers?
A
Amnion
Yolk
Chorion
Allantois
2
Q
What germ layer is the Chorion from?
A
Part of fetal maternal interface
3
Q
What germ layer is the yolk from?
A
Inner cell mass; hypoblast derivative
4
Q
Two trophoblastic derivatives of the fetal-maternal interface?
A
Placenta Chorion
5
Q
What germ layer is the amnion from?
A
Inner cell mass: epiblast derivative
6
Q
Four function of the amnion
A
- Buffer against mechanical injury
- Accommodate growth
- Allow normal movement
- Protects fetus from adhesions
7
Q
What germ layer is the allantois from?
A
Inner cell mass; interfaces with placenta via umbilical cord
8
Q
What is an excessive amount of amniotic fluid? Liquid amount? What is it associated with?
A
Hydramnios >2000 mL
Associated esophageal atresia or anencephally
9
Q
Hydratiform mole is related to what
A
Paternal imprinting
10
Q
What is the condition with too little amniotic fluid? Liquid amount? What is it associated with?
A
Oligohydramnios
Renal agenesis
11
Q
What does testing A-fetoprotein tell you? What is A-fetoprotein?
A
High concentration in amniotic fluid is a strong indicator of a neural tube defect -A protein in CNS
12
Q
Possible Yolk sac functions May concentrate (2)? Relationships (2)? Traces persist as?
A
May concentrate
- Folic acid
- Vitamin A, B12, E
Relationships
- Site of origin of primordial germ cells
- Location of blood islands
(Origin of initial blood cells)
Traces of yolk duct persists as Meckel’s diverticulum
-Outgrowth of ileum
13
Q
Blood islands?
A
Origin of initial blood cells (extra embryonic hematopolesis)
14
Q
Meckel’s diverticulum?
A
Traces of yolk duct persist as a fibrous cord or an out pouching of the small intestine
15
Q
Development of allantoic vessels and relation of allantois to the urinary bladder and median umbilical ligament?
A
1)Allantoic vessels develop into mesoderm of the allantois 2)Proximal part of allantois= urachus -Associated with the formation of the urinary bladder -Becomes median umbilical lig
16
Q
Four stages of chorionic villi development?
A
Previllous embryo Primary villous Secondary villous Tertiary villous
17
Q
What happens in secondary villous stage?
A
Mesodermal cores appear within the primary villi
18
Q
What tissue in the mature placenta interfaces directly with maternal uterine connective tissue?
A
Cytotrophoblast
19
Q
What happens in the primary villous stage?
A
Solid, cytotrophoblastic ectodermal primary villi appear
20
Q
Anchoring villi?
A
Villi that are anchored to the cytotrophoblastic shell (as opposed to floating villi)
21
Q
What happens in the tertiary stage?
A
Characterized by the appearance of blood vessels within the mesenchymal core of the secondary villi
22
Q
Chorionic plate (2)
A
- Mesoderm
Faces away from the chorionic villi and toward chorionic cavity
23
Q
What happens in the previllous embryo?
A
No villi have been formed on the trophoblast
24
Q
Cytrotrophoblastic shells
A
- Formed by expansion of the cytotrophoblastic columns over the maternal decidual cells
25
Layers of Embryo (6)
1. Chorionic cavity 2. Amnion 3. Chorionic plate 4. Syncytiotrophoblast, Intervillous space, villi 5. Outer cytotrophoblastic shell 6. Decidua capsularis
26
What maternal tissue is lost at childbirth?
Decidua capsularis
Chorion laevae
Amnion
27
Fate of decidua capsularis?
Undergoes atrophy Fuses with decidua parietalis
Decidua= shed
28
Early placenta (4)
Thick
perm low
Small surface area
Total diffusion conductance is miniscule
29
Late placenta (4)
Thin
Perm high
Large surface area
Large increase in placental diffusion
30
Bohr effect
Hemoglobin can carry more O2 at low PCO2
- Fetal blood carries more CO2
- Excess CO2 diffuses into maternal [Maternal more acidic, fetal more alkaline]
Increase capacity of fetal blood to combine with O2, decrease for maternal
Shift of oxygen hemoglobin curve to right and downward forces oxygen away from hemoglobin and into tissues
31
Double Bohr effect
Double shift in the maternal blood and in fetal blood
32
Human chorionic gonadotropin Timing? Secretion? Targets (2) ? Effects (4) ?
Timing -Measureable 8-9 days -Max: 10-12th week -Lower levels: 16-20th week Secretion -Secreted by the syncytial trophoblast cells into maternal fluids Targets -Corpus luteum & testes Effects 1) Prevents involution of CL 2) Causes CL to increase secretion of progesterone and estrogen 3) Caues increased growth in CL 4) Exert interstitial cell-stimulating effect on testes of male fetus (results in production of testosterone until birth)
33
Estrogen Timing? Secretion? Targets? Effects (6)
Timing -Towards end of preg. secretion levels are 30x mother's normal level Secretion - secreted by syncytotrophoblast cells of placenta -placenta estrogen formed from adrogenic steroid compounds: (formed from mother and fetal adrenal glands, converted by trophoblast cells into estradiol, estrone, estriol) Target -external genitla Effects 1) uterine enlargement 2) Breast enlargement 3) Growth of breast ductal structure 4) Enlargement of maternal ext. genitalia 5) relaxation of pelvic log 6) May affect aspects of fetal development
34
Progesterone Timing? Secretion? Target? Effect (4)
Timing -early by CL -Late in placenta Secretion -Secreted in small quantities by CL (early) -Secreted in large quantities by placenta (late) Targets -Decidual cells, uterus, fallopian tubes, breasts Effects 1) Causes decimal cells to develop in the endometrium 2) Decrease contractility of pregnant uterus 3) Increase secretion of fallopian tubes and uterus 4) May work with estrogen to prepare breasts for lactation
35
Human chorinic somatomammotropin Timing? Secretion? Target? Effect (3)?
Timing -Beginning 5th week of prey Secretion -Secreted by placenta Target -Mother Effects 1) Decrease insulin sensitivity in mother 2) Decrease utilization of glucose in mother 3) General metabolic hormone
36
Oxygen pressure gradient
- Mother: ?
- Fetus: ?
Reasons why adequate oxygenation can occur with such a lower pressure gradient (3)
Mother= 50
Fetus= 30
1. Fetal hemoglobin has a higher affinity for oxygen
2. Fetal blood hemoglobin concentration is aobut 50% greater than maternal
3. Bohr effect
37
What causes limb defects, ear defects, and cardiovascular anomalies a) alcohol b) thalidomide c) retinoic acid
Thalidomide
38
Respriatory distress syndrome
What?
Incidence?
Fundamental deficiency in?
Condition related to immature lungs where lungs are under inflated, alveoli partially filled with proteinaceous fluid that forms membrane over respiratory surfaces
Incidence inversely proportional to gestational age
Funamental deficiency is in the lack of pulmonary surfactant
39
Why Hyaline membrane disease
Membrane composed of proteins and dead cell lines that covers the alveoli making gas exchange difficult or impossible
40
Rh disease consequences
Jaundice (bilirubin) Low muscle tone (hypotonia) Lethargy
41
Kernicturus
Brain damage from excess jaundice
42
What causes defects involving a variety of facial structures, outflow of heart and thymus
a) alcohol b) thalidomide c) retinoic acid
retinoic acid
43
Why no developmental insults during first 3 weeks?
Insults will either kill embryo or be compensated for by powerful regulatory properties
44
No major structural anomalies after week 8?
By this point, most organs have become well established
45
Malformation
are primary errors of morphogensis. Usually multifactoral
46
What causes growth and mental retardation, microcephaly, various malformation of face and trunk a) alcohol b) thalidomide c) retinoic acid
alcohol
47
Deformation
disturbances in otherwise morphogenetic processes. These are typically caused by abnormal biomechanics forces such as uterine constraints Clubfoot
48
Disruption
are disturbances in otherwise normal morphogenetic processes. Amniotic bands
49
Syndrome
are constellations of congenital anomalies that are thought to be pathologically related but cannot be explained on the basis of a single local initiation event -often caused by single event like infection
50
Critical period
time period during pregnancy where embryos are more susceptible to agents or factors causing abnormal development than at other times
51
Sequence
is a series (cascade) of events triggered by one initiating factor Oligohydraminos
52
Fetal alcohol syndrome characteristics
poor postnatal growth
micrcephaly
mental retardation
heart defects
long thin upper lip
epicanthic folds
palpebral fissures
53
Deficiency in folic acid in pregnagncy lead to what?
Neural tube defects
54
Fetal Hydrops
what?
common cause
causes x2
Refers to accumulation of edema fluid in teh fetus during intrauterine growth
Hemolytic anemia, incompatibliiyt between mother and fetus
Immune and nonimmune
55
Immune Hydrop
antigen?
Fetus is?
Blood group incompatibility
D antigen of Rh group
Rh+ fetus
56
Nonimmune Hydrops
cardiovacular defects such as congenital cardiac defects
anomalies turners, trisomies 21 and 18
Kernictureus
57
Melanoblasts From? Function (3)
From neural crest Migrate to dermis and then into epidermis Stain with HMB-45 Produce pigment by mid preg
58
Preeclampsia --\> Eclampsia
Definition
Preclampsia (5)
Eclampsia (3)
Pregnancy induced hypertension
Preclampsia
1. more serious condition
2. blood pressure is higher
3. proteinuria
4. weight gain
5. edema
Edema
1. extremely serious
2. extreme high blood pressure
3. grand mal seizures or coma
59
Langerhans' cells From? Function?
Derived from bone marrow Antigen presenting cells
60
Merkel cells From? Function?
Neural crest Slow adapting mechano-receptors
61
Induction of ectodermal placode (thickening)
Induction from?
A and B from what causes ectoderm to express C?
D from what causes ectoderm to express E
E and C in ectoderm block F
In interfollicular zones
What blocks wnt
What inhibits follicle development?
Dermal induction
Wnt-11 and FGF from mesoderm cause ectoderm to express NOggin
Eda from mesoderm causes ectoderm to express Edar
Edar adn NOggin in ectoderm block BMP
Dickkopf block Wnt
BMP inhibits follicle development
62
Wnt-1
Induced Wnt 11
63
Wnt 11
With FGF cause ectoderm to express Noggin
64
BMP
inhibits folicle development
65
Eda/Edar
Eda causes ectoderm to express Edar Edar with Noggin block BMP Edar stimulates expression of Shh
66
Noggin
With Edar block BMP
67
Dickkopf
Blocks Wnt
68
Shh
Formation of dermal papilla below epidermal placode -With Cyclin D1 stimulate further down growth of proliferation of epidermal placodes
69
Induction dermal papilla
Induction?
Expression of A via the signaling pathway involves B recpetor stimualtes formation of waht below what
1. Epidermal induction
2. Expression of Shh by Edar stimulates formation of dermal papilla below epidermal placode
70
Induction of hair germ (3)
Induction?
Various inducers from dermal papilla along with A and B in epidermal placode stimlate further downgrowth of proliferation of epidermal placode
Final differentiaton of hair primordial involves what?
1. Dermal induction
2. Various inducers from dermal papilla along w/ Shh and Cyclin D1 in epidermal placode stimulate further down growth of proliferation of epidermal placodes
3. Final differentiation of hair primordial involves Hox genes
71
Estrogen
Stimulate growth of duct system
72
Progesterone
Stimulates formation of secretory alveoli
73
Prolactin
Stimulates synthesis of milk protein and fat
74
Oxytocin
Cuases milk letdown
75
Common pathway
what is induced to enter pathway?
Produces what, which promote?
A stimualtes synthesis of B and C
What is stabilized
1. Mesenchyme is induced to enter common pathway 2. Production of N-cadherins which promotes mesenchymal condensation 3. TGF-beta stimulates synthesis of fibronectin and N-CAM 4. Aggregated state of mesenchymal cells is stabilized
76
Membranous bone pathway
Requires what?
What happens?
1. Required transcription factors Runx-2 and Osm 2. Mesenchymal cells differentiate into osteoblasts
77
Permanent cartilage pathway
What happens?
A causes what to do waht?
A is contiually expressed
1. Mesenchymal condensation forms chondroblasts 2. Sox-9 causes chondroblasts to secrete collagen II and cartilage matrix 3. Sox-9 is continually expressed in permanent cartilage
78
Endocondral bone pathway
A, B, C induces this cartilage to under go what?
What secretes what and what
Invading what erode the somehting and bring in D to replace cartilage with bone
1. Runx-2, ihh, and BMP-6 induce this cartilage to undergo hypertrophy 2. Hypertrophy cartilage secrete boen proteins and vascular endothelial growth factor 3. Invading blood vessels erode the hypertrophic cartilage and bring osteoblasts in to replace cartilage with bone
79
Mesodermal sclerotomes (3)
Vertebral column
Ribs
sternum
80
Vertebral column
Hox10 knock cuases what
proatalas anlage contributes to what
ribs formon lumbar adn sacral vertebrae
The proatlas anlage contributes to the formation of the occipital bone and the dens of atlas
81
Lateral plate mesoderm
Limb bones
GIrdles
82
Head mesoderm
Calvaria adn base of skull
83
Neural crest
Facial bones
84
Median Hinge point (3)
- Induced by
- Involved in
- Requires
Induced by notochord
Involved in changes in shape of columnar cells to pyramidal shaped cells via apical constriction
Requires synthesis of actin filaments at apical ends of cells
85
Lateral Hinge point
Also involved in apical constriction by actin filament
86
Elevation of neural folds is due to?
Due to pushing inward by expanding non-neural epithelium
87
Head organizing region
- Consists of
- Results from express of _____ where?
Consists of anterior visceral ectoderm adn prechordal plate
Results in expression of Otx-2 in forebrain/midbrain region
88
Anterior notochord
Expression of and where?
Expression of Gbx-2 in hindbrain region
89
Anterior posterior gradient
Established by?
Wnt-8
90
Isthmic organizer
Is what?
Established by what?
Organizes what?
Releases what?
Makes what?
Signaling center established by boundary between osx-2 and gbx-2
Important in organizing midbrain and cerebellum
Releases Wnt-1 anterior and FGF-8 Posteriorly
Induces gradients of En-1 (anterior) and En-2 (posterior)
91
Anterior neural ridge signaling center
Important in?
Secretes?
Important in organizing telencephalon, parts of diencephalon, olfactory and pituitary gland
Secretes Shh and FGF-8
92
Zona limitans signaling center
Organizes?
Secretes?
Organizes border between dorsal and ventral thalamus
Secretes Shh
93
Krox 20 patterning in hindbrain --\>
r3 and r5
94
Kreisler and Hoxa-1 in hindbrain
r5
95
Retinoic acid gradient in hindbrain
r4-r7
96
Gbx-2 in hindbrain
r1-r3
97
Pattern of Hox genes expression in hindbrain segmentation does what?
Stimulated by what?
Initiates expression of what?
Determines cranial nerve and pharyngeal arch derivatives
Stimulated by retinoic acid gradient
which initiates expression of Hoxa-1 and Hoxb-1
98
Spinal cord Segmentation
What area serves as stem cell zone?
Cells in this area do what?
Presomitic mesoderm flanking posterior region secretes what?
Which does what?
Which direction does the neural tube advance?
Once fall out, what happens and is under influence of what?
Retinoic acid blocks what?
Caudal part of neural plate
Cells produced in this region as a result of mitotic activity continue to proliferate but do not differentiate as long as they are in this zone
Presomitic mesoderm flanking posterior regions of neural tube secrete FGF-8 which maintains these cells in a proliferative state
Advances posteriorly
Differentiate as they fall out, under influence of retionic acid
Which blocks FGF-8 and Wnt-3a
99
Paraxial (segemental plate) mesoderm
What is it and where is it located?
Segmented into?
Subdivided into?
Thick column of mesoderm closest to and parallel with the notochord
Becomes segmented into somites
Becomes subdivided into dermatomes, myotomes, and sclerotomes
100
Intermediate mesoderm
What and where?
Gives rise to?
Narrow column of mesoderm lateral to paraxial mesoderm
Gives rise to urogenital system
101
Lateral plate mesoderm
What and where?
Splits to what?
Thin plate of mesoderm lateral to intermediate mesoderm
Splits to form lining of body cavities and mesoderm of most internal organs as well as limbs
102
Somitomeres vs Somites
Somitomeres develop where in what?
Added to what end?
After 20 pairs, somites if first formed where?
At expense of what?
How do somites differ from somitomeres?
In what direction do somites replace somitomeres?
How many pairs constant at caudal end?
Somitomeres initial pair develop along neural plate in paraxial mesoderm
Added caudally
First somites addes behind 7th pair
Lose 8th pair
Somites are more dense blocks
In caudal direction somites replace somitomeres and somitomeres are replaces at caudal end
11 pairs constant
103
Wave Front mechanism
Gradient of what two things?
Aka?
Results in?
What is expressed because of the specific balance?
FGF-8 and Retinoic acid
Determination Front
Results in cellular determination toward somitogenesis
Mesp-2
104
Segmentation Clock
What molecules?
Leads to establishment of what?
Why is it called segmentation clock?
What is concentrated at anterior border of somite
What is concentrated at posterior border of anterior somite?
Cells at anterior border express?
Cells at posterior border express?
What does it result in?
Notch, Wnt, FGF
Leads to establishment of the pattern of somite formation
Expressed along a timeline
Lunatic fringe at anterior border
c-hairy at posterior border
Eph A (receptor) by anterior cells
Eph B (ligand) by posterior border cells
Results in a fissure between adjacent somites
105
Somite Differentiation
Ectoderm dorsal to somites --\> A? --\> B?
B? + Decrease in C? --\> mesenchymal cell to epithelial cell conversion
Formation of what?
Notochord --\> D? + E? --\> F? + G? in what part of somite= sclerotome
H? in what --\> transformation of what half of somite into dermomyotome
Dermomyotome --\> expresses I?, J?, k? --\> separation of dermomyotome into ____ dermotome and ___ myotome
Wnt 6 --\> Paraxis in somite
Paraxis + decrease in snail
Somitocoel
Shh + noggin --\> Pax1 + Pax9 in ventral part of somite
Wnt genes in dorsal neural tube --\> transformation of dorsal half of somite into dermomyotome
Expression of Pax3, Pax7, Paraxis--\> separation into dorsal dermotome and ventral myotome
106
Dermomyotome
What part of somite?
Signaling from what from where (x2) create a balance that causes the myotome portion to commit to the myogenic lineage
What inhibits BMP-4
What does BMP-4 do?
What produces BMP-4?
What does it cause to happen?
What from where signals the sclerotome to produce scleraxis, which causes what
Which is the precursor for what?
Dorso-lateral part of somite
Shh signaling from notochord
Wnt signaling from dorsal neural tube
Noggin inhibits BMP-4
BMP-4 inhibits myogenesis in ventrolateral dermomyotome and stimulates cells from this area to migrate from the somite into the limb bud
From Lateral plate
FGF from myotome signals sclerotome to produce scleraxis
Which cuases teh anterior and posterior borders of each somite to form the syndetome which is the precursor for tendons
107
Intermediate Mesoderm
Responds to what from where? x2 to become intermediate mesoderm and epress what?
Associated with formation of what two things?
Cranial and caudal extent of IM is dependent on expression of ?
Respoonds to BMP (lateral ectoderm) and Activin (paraxial mesoderm)
Express Pax-2
FOrmation of pronephrox and mesonephros
Dependent of expression of Hox4-Hox11
108
Early heart forming cells
Arise where?
Migrate through what?
Anterior visceral ectoderm is induced by what to form what?
Express what 3 factors
Epiblast
Primitive streak
BMPs and FGFs to form cardiac crescent
Nkx2-5, MEF2, GATA4
109
Cells migrating through anterior primitive streak form?
Outflow tract
110
Cells migrating through middle of primitve streak?
Form ventricles
111
Cells entering streak most posteriorly
Form atria
112
Cardiogenic plate
Arises from?
It will do what?
Arise from splanchnic mesoderm rostal to the oropharynx membrane
It will thicken to become the myocardial primordium and will form cardiac crescent
113
Bilaterally paired tubes taht form cardiogenic mesoderm fuse where?
Outer layer=
Inner layer=
Fuse beneath foregut
Outer= myocardium
Inner= Endocardium
114
Source of pericardium and myocardial fibroblast
Proepicardial primordium
115
Neurocranium
Part of skull that?
Base if formed from what?
Origin of what?
Membranous part?
Part of skull that surrounds the brain
Base if formed from chondrocranium (cartilaginous)
-Origin of part of occipital, sphenoid, ethmoid, part of temporal
Membranous: part occcipital, part temporal, parietal, frontals
116
Viscerocranium
Surronds what?
Cartilagionous portion:
A ( parts?)
B (parts?)
Membrnous portion
Surrounds oral cavity and pharynx
Cartilaginous portion forms
Pharyngeal arch I (mechel cartialge malleus, incus)
Pharyngeal arch II (reichert cartilge, stapes styloid)
Membranous: part temporal, zygomatic, maxillary, nasal, lacrimal, alatine, vomar, pterygoind paltes, mandible, typanic ring
117
The mesenchyme that forms teh viscerocranium is mostly from what?
NEural crest
118
How many pairs of pharyngeal arches?
Each pharyngeal arch consists of four components:
6
Skeletal element
Muscles
A branch of specific CN
Artery
119
Pharyngeal arch I associate with
CN V
120
PHaryngeal arch II assocaited with?
CN VII
121
Fontanelles and Sutures
What allows continual growth?
Separated by what?
Elongation due to A?
Intersection of more than 2 bones is?
What is expressed in all sutures?
What does it suppress, and prevent?
Ossification centers
Separated by synchondroses
Elongation of primary center by Shh
Intersection of more than 2 bones= fontanella
Noggin in all sutures
Suppress BMP which otherwise leads to closure of sutures
122
Myogenic cells
Originate?
Restricted?
Type of cells?
Originate in somites
REstricte to muscle forming line
Mitotic cells
123
Myoblasts
derived from?
type of cell?
myogenic cells
postmitotic
124
Myotubes
form when?
characterized by presence of what?
FOrmation of what?
What move where
Formed when myoblasts line up and adhere
Characteric by actin, myosin, troponin, tropomyosin
Formation myofibrils with sacromeric arrangment
Nuclei move to periphery
125
Primary myotubes
formed by?
differentiation occurs?
Formed by fusion of earliest myoblast
Differentiation occurs before innervation
126
Secondary myoblasts
Compared to primary?
FOrmed where?
Presence of waht is necessary to form what?
Contained within?
Are what?
Smaller than primary
Formed along side primary from late myoblasts
Presence of motor axons may be necessary to form secondary myotues
Contained within same basal lamina
Are electronically coupled
127
Satellite cells role (4)
Located
Type
Function
Note
Located between sacrolemma and basal lamina of myofiber
Mitotic and myogenic
Able to fuse with muscle fibers and provide for grwoth
NOte taht satellite cells do not form new msucle fibers
128
Molecular regulation of muscle development
Maintain myogenic cells in labile state
FGF adn TGF beta
129
Molecular regulation of muscle development
Does loss of mitotic capability
p21
130
Molecular regulation of muscle development
What convert non-muscle cells to cells capable to expressing muscle proteins
MyoD family
131
Molecular regulation of muscle development
Separately can actiavte MyoD and cause mygoenic cellst o become myoblasts
Pax3 and Myf5
132
Molecular regulation of muscle development
Increasing levels of what resutls in expression of myoblast genes by myoblast
Which express what?
MyoD and Myf5
Myogenin
133
Results in expression of myotube gnes and myf-6
Myogenin
134
Leads to expression of myofiber genes
Myf-6
135
Actual morphogeneis of muscles is dependent on what?
Associated connective tissue framework
136
Epaxial muscles arise from
Dorsal lip of myotome
137
Expaxial tendons arise from
syndetome layer of somites
138
Hypaxial muscles from
Ventral buds of myotome
139
Hypaxial tendoms from
Lateral plate mesoderm
140
Limb muscles arise from
Ventrolateral dermomyotome
141
Muscles of head and neck from
Derived from paraxial somitomeres
142
Extraocular muscles arise from
Prechordal plate
143
Cranial musculature from
unsegmented paraxial mesoderm
144
Some cranial musculature (lowe jaw) is from
Splanchnic mesoderm
145
Cardaic muscle is derived from
Early cardiac muscualture does not express?
Splanchinc mesoderm
MyoD
146
Remove half of limb disc
Remaining half will form complete limb
147
Vertically dividing the limb disc into two halves adn physically separate teh two halves
Each half will form a complete limb
148
Fuse two limb discs together
A single normal limb will form
149
Initiation of Limb Development
Initated by
Caues to express
Each does what?
Which leads to expression of?
This causes expression of what
Initiated by paraxial mesoderm using retinoic acid based on HOx code
Causes limb mesoderm to epress Tbx5 or Tbx4
- Tbx5= forelimb
- Tbx4= hindlimb
Tbx5 0r 4 caues mesoderm to express FGF10
FGF10 causes expression FGF8
FGF8 maintains expression FGF10
150
Transplant a limb disc to opposite side
The AP axis is reversed but not the DV axis
A normal limb will form but its AP axis is reversed
151
Rotate a limb disc 180 degrees
Both the AP axis and the DV axis will be reversed
A normal limb will form but only its AP axis is reversed
152
Transplant a strip of flank tissue from just posterior to the limb disc to an ectopic site just anterior to the limb disc
The resulting limb consists of two posterior halves arranged in a mirror-image fashion
Conclusion: the strip of flank tissue just posterior to the limb disc organizes the posterior edge of the disc
153
Formation of Anterior-Posterior Axis
A induces expression of B
B determines position of what via highest conc
Posterior organizting region express C?
C activates D
Anterior posterior axis is fixed by expression what in where?
Retinoic acid induces expression Hoxb8
Hoxb8 determiens postion ZPA
Post. organize region express Retionic acid
Retinoic acid activates Shh
Anterior posterior axis is fixed by expression of Gli-3 in anterior limb and Hand-2 in posterior limb bud
154
Shh?
Function
Induce
INhibits
Maintains structure and function AER
Induce expression gremlin
INhibits GLi-33 in poster limb bud
155
Gli-3
Active wehre?
Inhibits what?
Active in ant. part of limb bud
Inhibits Shh in anterior limb bud
156
Formation of Dorsal Ventral Axis
Dorsal limb ectoderm --\> A
A does what
Ventral limb bud ectoderm --\> B
B does what?
Dorsal limb bud ectoderm signals Wnt-7a
Wnt7a induces dorsal limb mesoderm to express Lmx-1b
Ventral limb bud ectoderm signals En1
En-1 inhibits Wnt-71
157
Formation of Proximal distal axis
Apcial ectodermal ridge uses A and B to keep cells in teh underlying lim bud in proliferative state
Cells that get left behind?
Morphology of limb due to ?
FGFs and Wnts
Become postmitotic and differrentiate
Morphology due to Hox
158
AER/ LImb mesoderm interactions
Structure of developing imb is determiend by?
Effect of limb mesoderm on overylying ectoderm?
Mesoderm produce what to maintain AER
AER maintains
What carves shape of limb/ separation digits
nature of mesodermal componets
instructive induction, mutant AER will not form AER
apical ectodermal maintance factor AEMF
Necrotic zones
159
LImb bud mesenchyme cells from
Gives rise to?
What cuses cartialge to be restrained to central core
Lateral plate mesoderm
appendicualr skeletal elements
CT
BV
Wnt-7a
160
Hypertrophic cells express?
Indian hedhog (ihh)
161
Limb muscle devleopment
Migrate pre-muscles express
Before migrationg pre muscle cells in somite express which is the receptor for?
Differentiation into muscle depends on ?
What is expressed by CT and is assocated with what?
Pax3 adn N-cadherin
Express c-met, receptor for scatter factor
Wnt-6
Tcf-4, associated with muscle masses
162
Axons originate from more medial lcoates in teh spinal cord grow into teh
Ventral muscle mass
163
Axons originating from teh more lateral locations in spinal cord grow into
dorsal muscle mass
164
If the forelimb rudiment of a salamander embryo is removed so that the limb fails to develop:
The nerve of the brachial plexus ramin smaller (thinner) than they would have been if the limb were still there
Spinal ganglia three, four, and five (associated with the brachial plexus in the salamder) are also smaller. The number of cells in each ganglion may be reduced by as much as 50%
165
If an additional limb rudiment is transplanted to the flank of a salamander embryo
The local spinal nerves supply the innervation to the transplanted limb and these local nerves increase in thickness
Ganglia associated with the nerves increase in size; the increase in number of cells may be as much as 40%
166
If the forelimb rudiment of an amphibian embryo, prior to the outgrowth of nerves, is cut out and transplanted to a position very near the original one:
The brachial nerves will deviate from their normal paths and will be deflected in the direction of the transplanted limb. If the distance of the transplanted limb from the original position is not too great, the brachial nerves will penetrate into the limb and ramify. The limb becomes fully functional
167
If an additional limb is transplanted into the immediate vicinity of the host limb:
The brachial nerves will develop branches running out to the additional limb and will supply it
168
If the normal path of the nerves is blocked by some obstacle:
The outgrowing nerves may avoid the obstacle, go around it, and still reach their normal destination
Hamburger inserted a piece of mica into a frog embryo between the spinal cord and the region where the hindlimb rudiments were to develop. The nerves formed loops around the mica plate and still reached the hindlimb rudiments
169
The A and B centers are interchangeable.
You can?
Limbs transplanted to the head may be supplied by?
Can be seen to?
Fore and hind limb
You can transplant forelimb buds in place of hindlimb bud
fibers of the cranial nerves, and then they can be seen to move synchronously with the respiratory movements of the jaws and gills
170
If the limb rudiment transplant is placed further away from the normal limb site, or if the obstacle between the spinal cord and limb rudiment is too great:
The nerve fibers fail to be attracted to the limb
If the limb rudiment is placed on the flank of the embryo, it will attract the local spinal nerves. These nerves will grow into the limb, but they cannot provide for the normal limb function
It appears that only the areas of the spinal cord from which the nerves of the brachial and lumbar plexuses originate possess the properties necessary for controlling the functioning of the limbs
171
An eye was transplanted into the side of an embryo after the forelimb rudiemnt was removed
The brachial nerves were deflected form their normal path and grew out toward the transplanted eye
Having approached the eye, however, the brachial nerves fial to penetrate into the eye and establish an actual connection with it
It would seem then that the attraction of the outgrowing nerves to peripheral organs seems to be unspecific to a very high degree; possibly any growing mass of tissue will attract a nerve that is sufficiently near to it Connections between a nerve and the end organ can be made only if the two correspond to each other
172
If metaphase plate is perpendicualr to inner margin of neural tube (next to lumen)?
Two daughter cells will remain proliferative
173
If metaphase palte is parallel to inner margin
Daughter cells closest to lumen will remain proliferative
Daughter cell further from lumen will:
express notch receptor
become post mitotic
MOve to external limiting membrane
become neuroblast (pre-neuron)
174
Ventral signaling
Induces formation floor plate via A
A produced by floor plae induces formation of what
Notochord induces formation floor palte of neural tube
Via sonic hedgehog
Shh produces formation of motor neurons
175
Dorsal SIgnaling
What uses A to induce B in teh future neural crest and later to maintain C and D to create what effect?
Expression of C and D is suppressd by E from floor plate to suppress dorsaling effect in teh basal plate
Ectoderm flanking neural plate uses BMPs to induce
Snail2 in future neural crest
Later maintain Pax 3 and Pax7 to create a dorsalizign effect
Expression of Pax3 and Pax7 is suppressed by Shh from floor plate to suppress dorsalizing effect in basal plate
176
Regional Differentation of Neural Tube
What is located between midbrain and hindbrain
Does what?
Acts by production of A (anteriorly) and B (posteriorly)
It is a what?
Principle signaling molecule is C?
D/E induce expression of:
Isthmic organizer
signaling center
Organizes and polarizes dorsal midbrain and cerebellum
Acts by production of Wnt-1 adn FGF-8
Principle signaling moleucles is FGF-8
FGF-8/Wnt-1 induces expression of:
En1, En2, Pax2 adn Pax5
177
Dorsoventral patterning of midbrain
Primarily due to A located where?
A restricts expression of B
B is realted to formation of what
C is expressed of what of what
C function
Primarily due to Shh located ventrally
Shh restricts expression of Pax7
Pax7 is related to formation of alar plate
Pax6 is expressed in alar palte of diencephalon and is "master gene" of eye formation
178
Cranial Nerve V (arch I)
what rhombomere?
axons of what join what?
Rhombomere 2
Axons of rhombomere 3 join rhombmere 2
179
Cranial N VII
rhombomere?
what arch?
what rhomomere joins?
Rhomomere 4
Arch II
Rhombomere 5 joins
180
Cranial nerve IX
Rhomomere?
arch?
what rhomomere joins?
Rhomomere 6
Arch 3
Rhombomere 7 joins
181
Influence of local environment (4)
Chemoattraction
Contract attraction
Chemorepulsion
Contact repulsion
182
Microenvironment cues: (4)
Cuadal half of somite
Fibronectin and laminin
Integrins
Cadherins
183
What is teh master gene of eye formation
Pax6
184
Sympathetic preganglionic motor neurons?
Arise from intermediate (lateral) horns of gray matter
Neural tube
185
Parasympathetic preganglionic motor neurons?
Arise from intermediate (lateral) horns of gray matter or from nuclei of hind brain
Neural tube
186
Preganglionic axons synapse with?
cell bodies of postsynaptic sympthateic motor enurons wiithin ganglin
neural tube
187
All autonomic ganglia are derived from
neural crest cells
188
All postgagnlionic autonomic neurons are derived from
neural crest cells
189
What is responsibel for the conversion of postganglionic sympathetic neurons from the typical form to the used inthe innervation of sweat glands
Cholinergic differential factor
190
