Exam 2 Review Flashcards
(117 cards)
1
Q
Characterize the location of and fate of each of the three areas of mesoderm in the early embryo
(Paraxial (segmental plate) mesoderm, Intermediate Mesoderm, and Lateral Plate Mesoderm)
A
Paraxial (segmental plate) mesoderm: thick column of mesoderm closest to and parallel with the notochord
Becomes segmented into somites
Intermediate Mesoderm: Narrow column of mesoderm lateral to the paraxial mesoderm
Gives rise to the urogenital system
Lateral Plate mesoderm: Thin plate of mesoderm lateral to the intermediate mesoderm
Splits to form the lining of body cavities and mesoderm of most internal organs as well as limbs
2
Q
Where does the Mesoderm originate from? explain how it eventually gets between the ectoderm and endoderm.
A
It originates from the epiblast
It passes through the primitive streak as “bottle cells”
Then spreads laterally and flattens out
3
Q
Distinguish between somitomeres and somites.
A
Somitomeres: initial pairs of segments of mesenchyme (barely discernible as segments) that begin to develop along and on either side of the neural plate in the paraxial mesoderm
Somites: more dense blocks of mesoderm that form along the notochord
4
Q
Explain the 2 mechanisms involved in somitogenesis (include the tissues they form from)
A
- somitomeres begin to form along either side of the neural plate in the paraxial mesoderm and continue to add caudaly until the 7th pair is formed
- once there are 7 somitomeres, somites form from the caudal somitomeres from the mesoderm
(somitomeres are then added anteriorly at the same time)
5
Q
What is the relationship of ephrin B, Wnt-6, snail, and paraxis to somite formation?
A
Cells of the posterior border will express Eph B, which works with Eph A from cells at the anterior border of the somite in order to create a fissure between the 2 adjacent somites
Wnt-6 signals for the ectoderm that is dorsal to somites to create paraxis in somite
Paraxis then causes the downregulation of Snail, which leads to the “mesenchymal cell to epithelial cell conversion
6
Q
Relate Shh, noggin, Pax1 and Pax9 to the formation of the sclerotome.
A
Shh + Noggin leads to the expression of Pax1 and Pax 9.
Pax1 and Pax9 in the ventral part of the somite causes the development of the sclerotome
7
Q
List the derivatives from the final subdivisions of the somites. (sclerotomal portion and the posterior portion of each somite)
A
The sclerotomal portion of each somite breaks up into and anterior and posterior portion
The posterior portion of the somite will join the anterior portion of an adjacent somite in order to create gaps that grow out from the neural tube into the epaxial segmental musculature derived from the myotomes
8
Q
List the factors involved in the formation of the intermediate mesoderm and list the derivatives.
A
The intermediate mesoderm is formed when BMP (from the lateral ectoderm) and Activin (from the paraxial mesoderm) stimulate the expression of Pax2
Pax2 expression is what causes the formation of the intermediate mesoderm
The intermediate mesoderm will eventually form the pronephros and will later form the mesonephros
9
Q
Differentiate between the intraembryonic coelom and the extraembryonic coelom. (what do these 2 give rise to?)
A
Intraembryonic coelom gives rise to the thoracic and abdominal cavities
Extraembryonic coelom gives rise to the chorionic cavity (gestational sac)
(these 2 are connected early on in development)
10
Q
Distinguish between somatic and splanchnic mesoderm. (What do these give rise to?)
A
Somatic mesoderm forms the body cavity, pelvis, and limb bones
Splanchnic mesoderm forms soft tissues (organs)
11
Q
Distinguish between the somatopleure and the splanchnopleure.
(What do these give rise to?)
A
The somatopleure is formed by a layer of ectoderm and mesoderm (the anterior walls of the embryo nearest to the gut tube)
The splanchnopleure is formed by a layer of endoderm and mesoderm (the wall of the yolk sac)
12
Q
Describe the formation of the lateral plate mesoderm and then the 2 structures it splits into
A
Somites form the lateral plate mesoderm but it then splits into the visceral and parietal mesoderm
13
Q
Distinguish between the cardiac crescent and the secondary heart field in terms of their structure
A
The cardiac crescent is thicker and lies to the exterior (big spoon) of the secondary heart field (little spoon)
Both create a U shape
14
Q
Describe the early formation of the heart (from the top down)
A
Outflow tracts
Right ventricle
Left ventricle
Atria
The the middle portion folds over itself (like a garden hose kink), alines the ventricles properly and flops underneath the atria
The outflow tract stays up top and is the vessels at the top of the heart
15
Q
List the genes important in early heart formation (3 of them)
A
(Nkx2-5, MEF2, GATA4).
16
Q
Describe the derivative of the cardiogenic mesodermal cells.
A
The cardiogenic mesoderm contains a cell populations which develop to become the endocardium, or the inner lining of the heart (a second population which forms the myocardium and gives rise to the heart muscles)
17
Q
The following are all functions of what?
Buffer against mechanical injury
Accommodates growth
Allows normal movements
Protects the fetus from adhesions
A
The amnion
18
Q
Explain Hydraminios and Oligohydramnios
A
Hydramnios: Related to esophageal atresia and anencephaly
Oligohydramnios: related to renal agenesis
19
Q
Describe the development of the allantoic vessels and the relation of the allantois to the urinary bladder and the median umbilical ligament.
A
The Allantoic (umbilical) vessels develop in the mesoderm of the allantois
The proximal part of the allantois = urachus.
This is associated with the formation of the urinary bladder and becomes the median umbilical ligament
20
Q
Of the following, Sort them into being Extraembryonic or Fetal-Maternal interface tissues. (one of these is Both
Yolk Sac Chorion Allantois Placenta Amnion
A
Extraembryonic Tissues: Amnion Yolk Sac Chorion Allantois
Fetal-Maternal Interface Tissues:
Placenta
Chorion
21
Q
Inner cell mass cells become ______ tissues, while Trophoblast derivatives become part of the _________.
A
Extraembryonic
Fetal-Maternal Interface
22
Q
What tissue/structure in the mature placenta directly interfaces with the maternal uterine connective tissue?
A
The chorion
23
Q
List and describe the layers from the amnion outward to the outer layer of the endometrium (5 layers)
A
Amnion
Chorionic cavity
Chorionic plate
Villi and intervillous spaces between them
Decidua capsularis
24
Q
What is the fate of the decidua capsularis?
A
The decidua capsularis eventually degenerates because of reduced blood supply
(the decidua capsularis is the endometrial lining during pregnancy)
25
In the maternal-fetal blood flow pattern, indicate where the exchange of materials occurs.
Within the placenta
26
Describe fetal alcohol syndrome in relation to placental transfer.
Growth and Mental retardation
Microcephaly
various malformations of the face and trunk
(the placenta is highly permeable to etoh)
27
Describe hydatidiform mole and relate it to the structure of the placenta. What is the genetic basis for the hydatidiform mole?
Hydatidiform Mole: condition in which many of the chorionic villi are characterized by nodular swellings (looks like grapes) and do not show vascularization.
The mother's pronucleus does not participate in the embryo formation so the chromosomes are paternally derived 46, XX
(2 sperm contribute or 1 sperm's genes are duplicated)
28
Describe placenta previa and relate to the structure of the placenta.
Placenta Previa: when part of the placenta covers the uterine outlet.
This abnormal placenta placement causes a mechanical obstacle in the birth canal and commonly leads to hemorrhage (fetus dies)
29
The following are all functions of what?
Diffusion of oxygen and CO2: PCO2 of fetal blood = 2-3 times greater than maternal blood
Diffusion of foodstuffs:
Excretion of waste products: urea, uric acid, and creatinine diffuse from the fetus to maternal blood
The placenta
30
Compare the early placenta with the late placenta. (in terms of thickness, pemeability, SA size, amount of diffusion)
```
Early placenta:
Thick
Low permeability
Small SA
Total diffusion conductance is miniscule
```
```
Late placenta:
Thin
High permeability
Large SA
Large increase in placental diffusion
```
31
Describe the oxygen pressure gradient (near end of pregnancy) (give PO2 of fetus and mother)
PO2 of the mother = 50 mm Hg
PO2 of the fetus = 20 mm Hg
32
Explain why adequate oxygenation can occur with such a low pressure gradient . (3 reasons)
Fetal hemoglobin has a higher affinity for O2
Fetal blood hemoglobin concentration is about 50% greater than maternal
Bohr effect (hemoglobin carries more O2 at lower PCO2 values)
33
Describe the Bohr effect and explain what is meant by the double Bohr effect.
Bohr Effect: Hemoglobin can carry more O2 at a low PCO2
Fetal blood coming into the placenta carries more CO2, which makes it alkaline
This means that the O2 is more likely to combine with the alkaline, low PCO2 fetal hemoglobin, compared to the more acidic, higher PCO2 maternal hemoglobin
Double Bohr Effect: refers to the oxygenation graph shift in the fetus to the left and to the right in the mother
34
Describe the timing, method of secretion, targets, and effects of Human Chorionic Gonadotropin
Timing: measurable secretion 8-9 days after ovulation
Maximal secretion occurs during the 10th-12th week of pregnancy
Lowest levels of secretion occurs during the 16th-20th weeks
Method of secretion: secreted by the syncytial trophoblast cells into maternal fluids
Targets: CL and testes of the male fetus
Effects:
Prevents the involution of the corpus luteum
Causes CL to increase secretion of progesterone and estrogens
Causes increased growth in CL
Exerts interstitial cell-stimulating effect on the testes of male fetus (this results in testosterone production until birth)
35
Describe the timing, method of secretion, targets, and effects of Progesterone
Timing: secreted early in pregnancy (there is a large spike of progesterone 24 hrs prior to ovulation as well)
Method of secretion:
Secreted in small quantities by the corpus luteum (CL)
Secreted in large quantities by the placenta
Targets: endometrium, uterus, breasts
Effects: Causes decidual cells to develop in the endometrium
Decreases contractility of the pregnant uterus
Increases secretions of fallopian tubes and uterus
May work with estrogen to prepare breasts for lactation
36
Describe the timing, method of secretion, and effects of Human chorionic Somatomammotropin
Timing: begins in the 5th week of pregnancy
Method of secretion: secreted by the placenta
Effects: Causes decreased insulin sensitivity and decreased utilization of glucose by the mother
General metabolic hormone
37
The following describe the effects of what Teratogen?
Limb defects
Ear defects
Cardiovascular abnormalities
thalidomide
38
The following describe the effects of what Teratogen?
affects cranial Hox genes
This causes abnormalities of the face, outflow tract of the heart, and thymus
Retinoic acid (Vitamin A)
39
The following describe the effects of what Teratogen?
```
anencephaly
growth retardation
cleft lip/palate
hydrocephalus
hypoplastic mandible
low set ears
```
(was used to cause abortion but a 4th of babies survive with deformities)
Folic Acid Antagonists
40
Compare Turner Syndrome and Poly-X Syndrome in terms of Genotype, and rarity.
Turner Syndrome: X0 (total of 45 chromosomes and 1 X chromosome)
1 in 3000
Poly-X Syndrome: XXX
1 in 1000
41
The following characteristics are consistent with which syndrome?
```
Female with underdeveloped sex characteristics
Low hairline
Broad chest
Folds on neck
Usually Sterile
Usually of normal intelligence
```
Turner Syndrome
42
The following characteristics are consistent with which syndrome?
Usually Tall and Thin
Often fertile
Usually of normal intelligence
Poly-X syndrome
43
Describe Immune Hydrops
The D antigen of the Rh group may be different between the mother and the fetus
After the 1st pregnancy allows the mother's immune system to gain Abs for it, the mother's Abs attack the blood of the fetus, causing hydrops in the last trimester
44
Define kernicterus and state some of it's consequences
When bilirubin levels are so high that it displaces the blood in the brain, turns the brain yellow, and causes brain damage
45
Describe the formation of a multiple layered epidermis (basal (germinative) layer, Intermediate layer, Superficial Peridermal layer) including the derivatives from the intermediate layer.
Begins as periderm (single layer) and becomes 3 layers when p63 is activated.
The derivatives of the Intermediate layer separate when p63 is inhibited by miR-203
Intermediate Layer: The stratum spinosum and Stratum granulosum form from the intermediate layer of the epidermis
46
List major groups of immigrant cells, tell where they are derived from, and list basic functions.
(3 of them)
Melanoblasts: produce pigment by mid-pregnancy
Migrate from the neural crest into the dermis initially, and then finally into the epidermis as well
Langerhan's cells: antigen presenting cells
Derived from bone marrow
Merkle cells: slow-adapting mechano-receptors
From the neural crest
47
Describe the source of dermal cells in the following areas.
Dorsal surface of the body:
Ventral and lateral surfaces of the body:
Cranial and anterior neck:
Dermal cells of the dorsal surface of the body: come from mesenchyme from the dermatome
Dermal cells of the Ventral and lateral surfaces of the body: come from mesenchyme from the lateral plate mesoderm
Dermal cells of the cranial and anterior neck: come from the mesenchyme mostly from the cranial neural crest
48
Describe the results of the following recombination experiments that are meant to demonstrate instructive induction signaling that occurs between the mesoderm and the ectoderm.
Ectoderm and mesoderm are separated:
Abdominal Ectoderm is combined with sole mesoderm:
Sole ectoderm is combined with scalp mesoderm:
Ectoderm and mesoderm are separated: neither differentiates any futher
Abdominal Ectoderm is combined with sole mesoderm: Abdominal ectoderm differentiates as thickened skin (typical of the sole)
Sole ectoderm is combined with scalp mesoderm: Ectoderm differentiates as scalp epidermis with hair
49
Describe the developmental pathway for hair development. (4 stages)
Hair primordium
Early hair peg
Bulbous hair follicle
Adult hair (then the adult hair cycle begins to occur)
50
Explain the effects of prolactin and oxytocin in the development of mammary glands.
Prolactin: mile and protein fat synthesis
Oxytocin: Milk letdown
(P for produce ; O for "ooze" milk)
51
The stratum spinosum and stratum granulosum are both mitotic derivatives of what layer? which has keratohyalin granules and which as fillagrin?
the intermediate layer of the 3 layered epidermis (basal layer, intermediate layer, and the superficial peridermal layer)
Stratum spinosum has keratohyalin granules
Stratum granulosum is interconnected by fillagrin
(these 2 layers appear after miR-203 inactivates p63)
52
Be able to diagram the major steps in the differentiation of bone and cartilage, including the roles of morphogenetic factors such as BMP-6, CAMs, ihh, Runx-2, Osx, Sox9 and TGF-β and others. (4 pathways)
Common pathway:
Membranous pathway:
Permanent cartilage pathway:
Endochondral bone pathway:
Common pathway: TGF-beta stimulates mesenchyme to produce N-cadherins, aggregate and become bone
Membranous pathway: Runx-2 and Osx cause mesenchymal cells to become osteoblasts
Permanent cartilage pathway: Sox-9 causes chondroblasts to secrete collagen II and cartilage matrix
Endochondral bone pathway: Runx-2, ihh, and BMP-6 cause cartilage to undergo hypertrophy. Blood vessels then invade and bring in osteoclasts to make bone
53
Describe the origin of following parts of the vertebra, including costal processes and ribs.
Centrum:
Neural Arches:
Costal processes/ribs: (proximal and distal developments)
Centrum: derived form the ventral and medial parts of paired sclerotomes
Neural arches: arise from dorsal regions of sclerotomes
The costal processes/ribs:
The proximal development of these depends on the expression of myotomic myogenic factors, Myf-5 and Myf-6
The distal development of these depends on BMP signals from the somatopleural mesoderm
54
Differentiate the Hox gene boundaries for the different regions of the vertebral column. (3 regions)
Occipital-cervical boundary:
Cervical-thoracic boundary:
Attached-floating ribs boundary:
Occipital-cervical boundary: Hox3
Cervical-thoracic boundary: Hox6
Attached-floating ribs boundary: Hox9
55
What is the relationship of Hox gene expression and the development of the vertebral column
All 11 Hox genes contribute a portion of the gene expression needed to properly develop the vertebral column
if 1 hox gene is defective, only slight issues will occur. However, the greater the number of defective hox genes, the greater the misplacement of the ribs
(if 10 or 11 of them are defective, the ribs will form on the lumbar/sacrum)
56
How does retinoic acid affect the expression of hox genes and the development of the vertebral column?
retinoic acid activates Hox genes
57
What are homeotic transformations?
when a normal body part is replaced by another normal body part that is supposed to be in another location
58
Describe the effects of the following Hox gene knockout experiments.
When single Hox genes are KNOCKED OUT:
When all 10 Hox paralogues are knocked out:
When all 11 Hox paralogues are knocked out:
When there is a MUTATION of a single Hox gene:
When single Hox genes are KNOCKED OUT: only minor morphological effects are noted
When all 10 Hox paralogues are knocked out: ribs form on the lumbar and sacral vertebrae
When all 11 Hox paralogues are knocked out: Hox11 suppresses the influence of Hox10 so ribs form on the lumbar and sacral vertebrae as well
When there is a MUTATION of a single Hox gene: produces only minor anatomical defects
59
State the primordia for the atlas and axis vertebrae
(The axis/atlas complex forms from 3 primordia: The occipital, the Proatlas anlage, C1, and C2 primordia
Occipital primordia becomes the MAJORITY of the basioccipital bone)
The Proatlas anlage splits into 2 ; one of them adding to and forming the inferior portion of the basioccipital bone and the other adds to and forms the top of the Dens (raised part of the axis)
C1 forms the atlas
C2 forms the majority of the axis (besides the Dens, which comes from the proatlas anlage)
60
Describe the origin of the sternum and clavicle
Sternum: Derived from the lateral plate mesoderm and arises as a pair of cartilaginous bands.
These fused cartilaginous bands then secondarily subdivide into craniocaudal elements
Clavicle: They arise from the neural crest by way of the intramembranous pathway
(Clavicles are also the first bone to become ossified in a fetus)
61
Describe the generalized neurocranium/chondrocranium.
Neurocranium: the part of the skull that surrounds the brain
Chondrocranium: the cartilaginous base of the neurocranium (prior to endochondral pathway formation of the neurocranium)
62
Describe the generalized viscerocranium and the bones that develop from the viscerocranium. Where did these cells come from?
The Viscerocranium is mostly comprised of branchial (pharyngeal) arches and there are actually 6 pairs of pharyngeal arches (really only recognize 4 pairs in humans however)
The mesenchyme that forms the viscerocranium is mostly from the neural crest
63
Describe the 4 components of a pharyngeal arch
A skeletal element
Muscles
A branch of a specific cranial nerve
An Artery
64
Define fontanelle and describe the pathway leading to the closure of fontanelles.
Fontanelle: a space between the bones of the skull in an infant or fetus, where ossification is not complete and the sutures not fully formed.
Noggin is expressed in all of the sutures of the skull and inhibits the premature closure of the sutures by inhibiting the action of BMP (BMP's action causes the closure of the sutures)
When the time is right, FGF-2 will inhibit noggin which in turn allows BMP to trigger the closure of the sutures
65
Where is the basioccipital portion of the chondrocranium derived from? What causes the elongation of the ossification centers that form in the cartilage to eventually produce the bones of the skull?
The Basioccipital portion of the chondrocranium is derived from: parachordal cartilages and occipital sclerotomes
Elongation of the these primary ossification centers is due to Shh
66
Describe skeletal muscle development from the mononuclear myoblast stage to the multinucleated myotubes
Myoblasts: Derived from myogenic cells
Postmitotic
Myotubes: Formed when myoblasts line up and adhere to one another and are characterized by the presence of actin, myosin, troponin, and tropomyosin
67
Explain the role of satellite cells.
Satellite cells are mitotic and myogenic in nature and function as stem cells that are used to fuse with muscle fibers in order to provide growth
They become mitotic in times of stress when Hepatic growth factor (HGF) binds to the C-met receptor on the satellite cell
Satellite cells DO NOT form new muscle fibers (they just help build up what is already there)
68
Differentiate between primary and secondary myotubes.
Primary Myotubes: formed by the fusion of the earliest (embryonic) myoblasts
May already be distinguished as fast or slow muscle fibers by this point
Differentiation occurs before innervation
Secondary Myotubes: Smaller than they primary myotubes that they are formed alongside
Derived from late (fetal) myoblasts
The presence of motor axons may be necessary to form secondary myotubes
Contained within the same basal lamina and are electrically coupled at this point
69
Explain the role of the following transcription factor:
Myf-5
Myf-5: can activate MyoD to cause myogenic cells to become myoblasts
70
Explain the role of the following transcription factor:
Myf-6
Myf-6: leads to the expression of myofiber genes
71
Explain the role of the following transcription factor:
Pax-3
Pax-3: can activate MyoD to cause myogenic cells to become myoblasts (Pax-7 also does this)
72
Explain the role of the following transcription factor:
Pax-7
Pax-7: can activate MyoD to cause myogenic cells to become myoblasts (not as well as Pax-3)
73
Explain the role of the following transcription factor:
FGF
FGF: works alongside TGF-beta to maintain myogenic cells in a labile state (able to conduct mitotic activities)
74
Explain the role of the following transcription factor:
TGF-beta:
TGF-beta: works alongside FGF to maintain myogenic cells in a labile state (able to conduct mitotic activities)
75
Explain the role of the following transcription factor:
MyoD:
MyoD: a family of Helix-loop-helix transcription factors that are able to convert non-muscle cells to cells that are capable of expressing muscle proteins
76
Explain the role of the following transcription factor:
Myogenin:
Myogenin: results in the expression of myotube genes and Myf-6
77
State the origin of the following:
Epaxial Muscles and Tendons
Epaxial muscles arise from the dorsal lip of the myotome
Epaxial tendons arise from syndetome layer within somites
78
State the origin of the following:
Hypaxial muscles and tendons
Hypaxial muscles arise from the ventral buds of the lateral plate mesoderm
Hypaxial tendons arise from the lateral plate mesoderm
79
State the origin of the following:
Limb muscles and tendons
Limb Muscles: arise from ventrolateral dermomyotome
Tendons of limb muscles arise from lateral plate mesoderm.
80
State the origin of the following:
Muscles of the head and neck (extraocular, upper cranial musculature, and cranial musculature of the jaw)
Muscles of the head and neck: are mostly derived from paraxial somitomeres
Extraocular muscles arise from the prechordal plate
The upper part of the cranial musculature is derived from the unsegmented paraxial mesoderm
The lower jaw musculature, however, is derived from the splanchnic mesoderm
81
State the origin of Cardiac muscle (include how they are attached to one another)
Cardiac Muscle: are derived from splanchnic mesoderm and remain as mononucleated cells that are attached to one another via intercalated discs
Early cardiac muscles do not express MyoD
(Both cardiac and skeletal muscles express MADS)
(Early cardiac muscles maintain their ability to divide (this is tough to do bc cardiac muscles begin to contract VERY early in development) by partially disassembling their contractile apparatus just before each round of cell division that occurs)
82
State which portion of the pentapartite brain forms the following adult structures.
Paleocortex, Corpus Striatum, and Neocortex
Telencephalon: Paleocortex, Corpus Striatum, and Neocortex
83
State which portion of the pentapartite brain forms the following adult structures.
Tectum, Tegmentum, and Cerebral Peduncles
Mesencephalon: Tectum, Tegmentum, and Cerebral Peduncles
84
State which portion of the pentapartite brain forms the following adult structures.
Epithalamus, Thalamus, Hypothalamus, and the Infundibulum
Diencephalon: Epithalamus, Thalamus, Hypothalamus, and the Infundibulum
85
State which portion of the pentapartite brain forms the following adult structures.
Medulla
Myelencephalon: medulla
86
State which portion of the pentapartite brain forms the following adult structures.
Cerebellum and Pons
Metencephalon: Cerebellum and Pons
87
Describe the stages of the neural tube wall from that of a simple cuboidal epithelium to a stratified epithelium. (Early neural epithelium, Neural plate, Early neural tube wall, and Late neural tube wall)
Simple cuboidal = Early neural epithelium
Simple columnar epithelium = Neural plate
Pseudostratified epithelium with the basal lamina as a limiting membrane = Early neural tube wall
Stratified epithelium = Late neural tube wall
88
Describe and explain the importance of the orientation of the metaphase plate during proliferation of cells within the neural tube. (state what happens when it is perpendicular to the margin of the neural tube and when it is parallel to the inner margin )
If the metaphase plate is perpendicular to the margin of the neural tube (next to the lumen): the 2 resulting daughter cells will remain proliferative
If the metaphase plate is parallel to the inner margin:
The daughter cell closest to the lumen will remain proliferative
The daughter cell further from the lumen will express Notch receptor, become post mitotic, move to the external limiting membrane, and become a neuroblast (pre-neuron)
89
Describe the developmental pathways of the following types of cells and include whether or not they are still mitotically active.
Bipotential progenitor cells:
Glial lineage progenitor cells:
Radial progenitor cells:
Neuronal lineage progenitor cells:
Bipotential progenitor cells: can become either Neuronal lineage, glial lineage or radial progenitor cells (mitotic)
Glial lineage progenitor cells: Can become a variety of glial cell types (mitotic)(oligodendrocyte, type-2 astrocyte, type-1 astrocyte)
Radial progenitor cells: become radial glial cells that are mitotically active until they are no longer mitotic and become ependymal cells
Neuronal lineage progenitor cells: can become mature neurons (NOT mitotically active)
90
For the following experiment, describe the effects that are to be expected.
Graft secondary notochord near neural tube:
Graft secondary notochord near neural tube: Induces a secondary floor plate
91
For the following experiment, describe the effects that are to be expected.
Remove notochord (notochord is absent):
Remove notochord (notochord is absent): A very incomplete floor plate forms and nerve fibers exit from multiple sites around the spinal cord
92
For the following experiment, describe the effects that are to be expected.
Slit neural plate on one side of the floor plate:
Slit neural plate on one side of the floor plate: Removes the wall of the neural tube from the influence of the notochord, allowing the disorganized exit of nerve fibers from that part of the spinal cord
93
Describe the signaling pathways and factors that establish the dorsal-ventral axis of the developing neural tube. Include what roles the notochord and non-nervous ectoderm play
Ventral Signaling:
The notochord induces formation of the floor plate of the neural tube via sonic hedgehog
Sonic hedgehog induces the formation of the motor neurons
Dorsal Signaling:
The ectoderm that is flanking the neural plate uses BMPs to induce Snail-2 in the future neural crest and later to maintain Pax-3 and Pax-7 to create a dorsalizing effect
The expression of Pax-3 and Pax-7 is suppressed by Shh from the floor plate to suppress the dorsalizing effect in the basal plate
94
For cranial nerves 5, 7, and 9, describe which pharyngeal arch strucutures they innervate and the rhombomeres they are associated with
Cranial Nerve 5 innervates structures from the 1st pharyngeal arch
Rhombomeres 2 and 3 are associated with the 1st pharyngeal arch
The AXONS of rhombomeres 3 extend to join rhombomere 2 (their cell bodies stay in the same place)
Cranial Nerve 7 innervates structures from the 2nd pharyngeal arch
Rhombomeres 4 and 5 are associated with the 2nd pharyngeal arch
The AXONS of rhombomeres 5 extend to join rhombomere 24 (their cell bodies stay in the same place)
Cranial Nerve 9 innervates structures derived from the 3rd pharyngeal arch
Rhombomeres 6 and 7 are associated with the 3rd pharyngeal arch
The AXONS of rhombomeres 7 extend to join rhombomere 6 (their cell bodies stay in the same place)
95
How is the segmented nature of spinal nerves related to the somatic mesoderm pattern?
The segmented nature of the spinal nerves is due to the pattern of somatic mesoderm along the neural tube
(Motor neurons can penetrate the anterior mesoderm of somites, but CANNOT penetrate the posterior mesoderm of somites)
96
What is the role of the isthmic organizer, and what signaling/transcription factors are involved?
The isthmic organizer is a signaling center that is located between the mesencephalon and the metencephalon and serves to organize/polarize the dorsal midbrain and cerebellum
It's principle signaling molecule is FGF-8
97
How does shh determine the midbrain dorsoventral axis?
Shh restricts the expression of Pax-7 and similar molecules which leads to the dorsoventral pattering of the midbrain
98
What role do prosomeres P1-P3 play in forebrain patterning?
P1-P3 define the diencephalon
P2-P3 define the dorsal and ventral thalamus
99
What is the relationship between shh and holoprosencephaly?
many mutations in the shh gene lead to the midline facial deformities of holoprosencephaly
100
Describe steps in the outgrowth of a motor neuron and compare with a sensory neuron; what are growth cones?
Motor axons grow out from the motor neuroblasts located in the basal plate of the spinal cord (sensory ones grow towards the spinal cord and to the periphery)
Boundary gaps created by the neural crest cells maintain separation between the CNS components and the PNS components (in motor and sensory neurons)
Growth Cone: an expanded region of cytoplasm with filopodia on an neuron that advance via extension/resorption cycles (of actin and microfilaments) in order to grow axons
101
How do environmental factors affect growth? What role do netrins and semaphorins play?
environmental factors can act in either chemoattraction/repulsion or contact attraction/repulsion
Netrins form attractant concentration gradients
Semaphorins form repulsive concentration gradients
102
Describe the steps in the formation of a synaptic junction
Once the motor neuron reaches the muscle, it stops growing and prepares it's ACh synaptic vesicles
The muscle concentrates it's ACh receptors in the postsynaptic folds and eliminates all other receptors.
(ACh-esterase also accumulates in the basal lamina of the muscle)
103
compare the origin of the sympathetic preganglionic neurons with the origin of the parasympathetic preganglionic neurons.
Sympathetic preganglionic neurons originate from the intermediate (lateral) horns of gray matter from T1 through L2
Parasympathetic preganglionic neurons originate from the midbrain, hindbrain, S2-S4, and some CNs
104
What factors determine whether migrating neural crest cells differentiate into autonomic neurons or other neural crest derivatives?
BMPs
105
The topographical arrangement of the myelencephalon is almost identical to the spinal cord. What is the major topographical change?
Pronounced expansion of the roof plate to form the thin roof over the 4th ventricle
106
Expression of which set of genes seems to be responsible for the differentiation of specific nuclei in the myelencephalon?
Hox Genes
107
What are the major derivatives of the metencephalon? (2 of them)
Pons (basal plate)
Cerebellum (Alar plate)
108
The cerebellum forms in the region of the rhombic lips (rhombomeres 1-8). The rhombic lips are the product of what inductive interaction?
The inductive action that occurs between the roof plate and the neural tube via BMP signaling
109
Explain the migration of the following
Granule cells migrating anteriorly:
Granule cells migrating Interiorly:
Purkinje cells migrating:
Granule cells migrate anteriorly along the dorsal region of the rhombomere 1
Granule cells migrate interiorly through the Purkinje layers
Purkinje cells migrate radially through granule cells
110
What are the superior cerebellar peduncles and what 2 structures are they found between?
Massive fiber bundles between the cerebellum and the mesencephalon
111
What are the major derivative(s) of the alar plates of the mesencephalon?
Tectum (corpora quadrigemina)
| Subdivisions of the tectum include the Superior colliculi and the Inferior colliculi
112
Where is Otx-2 located and how is it related to shh?
It confines Shh to the basal part of the midbrain
113
Where do the cerebral peduncles form and what is their function?
The cerebral peduncles form in the ventrolateral region of the mesencephalon
Their function is to carry fibers between the cerebral hemispheres and the spinal cord
114
What are the major derivatives of the diencephalon?
| 3 things
Epithalamus
Thalamus
Hypothalamus
115
What are the three patterning centers in the forebrain? include their signal molecules.
Rostral Patterning center (FGF-8)
Dorsal Patterning center (BMPs and Wnts)
Ventral Patterning center (Shh)
116
Describe the formation of the corpus striatum and corpus callosum.
The corpus striatum forms beneath the lateral ventricle
The corpus callosum forms next to the hippocampal commissure
117
Define rachischisis.
Embryologic failure of fusion of the vertebral arches and neural tube, resulting in the exposure of neural tissue at the surface
