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52 Cards in this Set

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Where is Sonic Hedgehog Gene produced and what is its function?
SHH:
- produced @ BASE of limbs
(in the ZPA)
- Involves A-P Axis patterning
(anterior-posterior)
- Mediated ECTOdermal fx
A mutation of what gene leads to holoprosencephaly?
Defect in sonic hedgehog (SHH).

Holoprosenchephaly = Failure to develop 2 hemispheres in brain
What is the function of WNT-7 gene?
- Produced at the DISTAL end of developing limbs
(Apical Ectodermal Ridge)
- Necessary for D-V Axis organization
(dorsal-ventral)
What is the FGF Gene and what is its function?
FGF = Fibroblast Growth Factor
- produced at Apical Ectodermal Ridge
- Stimulates mitosis of MESODERM
- Results in lengthening of limbs
What embryological gene is associated with Achondroplasia?
Mutation in the FGF Gene
(fibroblast growth factor)
What is the Hox gene & what is its function? What teratogen can interfere with it?
Hox = Homeobox Gene
- involved in SEGMENTAL organization
(cranio-caudal direction)
- is the blueprint for skeletal morphology
(mutations = appendages in wrong location)

Teratogen = Retinoic acid (Vit A)
What gene mutation results in Synpolydactyly?
Mutation of HOX-D13

Synpolydactyly = extra fused digit b/w the 3rd and 4th digits
Stages and timing from fertilization --> implantation of a pregnancy?
Day 2 = Zygote (in tube)
Day 3 = Morula
Day 5 = Blastocyst
Day 6 = Implantation

Implantation --> release of ßhCG
What is the primitive streak?
First asymmetry in embryogenesis:
- Formed in the 3rd week
- Epiblast invaginates to form.
- Creates antero-posterior axis

This marks beginning of gastrulation.

Cells of primitive streak give rise to:
- Mesoderm
- Endoderm
What embryological developments have taken place by week 2?
Rule of 2's:

- 2 Germ cell layers
1) epiblast
2) hypoblast
- 2 Cavities:
1) amniotic cavity
2) yolk sac
- 2 Placental components
1) cytotrophoblast
2) syncytiotrophoblast
What embryological developments have taken place by week 3?
Rule of 3's:
- 3 Germ layers:
1) ectoderm
2) mesoderm
3) endoderm
(these are the Tri-Laminar Disc)
This is now the Gastrula.

Also:
- primitive streak has formed
- notochord & neural plate
What is the bilaminar disc?
This is the 2 germ layers that are present by week 2 of embryogenesis.

Includes:
- Epiblast
- Hypoblast
What is the trilaminar disc?
This is the 3 germ layers that make up the Gastrula in week 3 of development:
- Ectoderm
- Mesoderm
- Endoderm
What are the early stages of neural development?
1) Notochord induces ectoderm --> neuroectoderm --> neural plate

2) Neural plate --> invaginates forming Neural crest

3) Neural Crest --> Neural tube & Neural crest cells
What happens to the notochord?
After stimulating ecotderm --> neuroectoderm, it becomes the nucleus pulposus of the intervertebral disk in adults
What are the landmarks of week 4 of embryological development?
Rule of 4:
- 4 heart chambers (begins to beat)
- 4 limb buds formed

Also, the neural tube has closed by week 4 (problems e.g. spina bifida has occured by this point)
Why is folic acid important to pregnant women immediately when they conceive?
Folic acid is necessary for neural tube development, most of which is completed by week 4 of development.
What is the embryonic period?
Weeks 3-8 of development
- Organogenesis takes place.
- Extemely susceptible to teratogens
When does the fetal period begin?
Week 8 of development.

There is fetal movement and fetus looks like a baby
By what time does the fetus have male/female genital characteristics?
Week 10 of development
(12 Weeks since LMP)
What are the embryologic derivatives of the Surface ectoderm?
1) Adenohypophysis (anterior pituitary)
2) Lens (anterior of eye)
3) Epithelia:
- oral cavity
- olfactory
- anal canal (below pectinate)
- epidermis
4) Sensory organs of ear
5) Glands:
- sweat
- salivary
- mammary
What is a craniopharyngioma and from what does it develop?
A benign tumor from Rathke's pouch (surface ectoderm).

Seen with:
- cholesterol crystals
- calcifications
What are the embryological derivatives of Neuroectoderm?
Think CNS and Brain:
1) Brain
- CNS neurons
- neurohypophysis (posterior pituitary)
- pineal gland
- ependymal cells (line ventricles)
- glia (astrocytes, oligodendrocytes)
2) Retina (posterior eye)
3) Spinal Cord
What are the embyrological derivatives of the Neural Crest?
CACA MOTEL PASS:

C = Cranial Nerves
A = ANS - chain ganglia
C = Craniofacial structures (skull)
A = Arachnoid, pia

M = Melanocytes
O = Odontoblasts
T = Tracheal cartilage
E = Enterochromaffin cells - Adrenal medulla
L = Laryngeal cartilage

P - Parafollicular cells (C cells) - of thyroid
A = All ganglia - Dorsal root, Celiac, CN, ANS Chain
S = Schwann cells
S = Spiral septum - Aorticopulmonary septum

(think the PNS and non-neural surrounding structures)
What are the embryological derivatives of Endoderm?
1) Gut tube epithelium (above pectinate line)
2) Derivatives (2L, 2P, 2T):
- Lung
- Liver
- Pancreas
- Para-Thyroid
- Thymus
- Thyroid (follicular cells)
What are the embryological derivatives of Mesoderm?
1) Muscle, bone, CT
2) Linings (e.g. peritoneum)
3) Spleen
4) Circulation (CV, Blood, Lymphatics)
5) Uro-Genital & Gonads
6) Dermis (skin)
7) Notochord --> nucleus pulposus of intervertebral disk
Birth defects related to Mesoderm?
VACTERL Defects:

V = Vertebral defects
A = Anal atresia
C = Cardiac defects
T-E = Tracheo-Esophageal Fistula
R = Renal defects
L = Limb defects (muscle/bone)
Classic characteristics of Fetal Alcohol Syndrome?
1) Facial Abnormalities:
- nose = flat
- philtrum = smooth
- ears = low set ("railroad track")
- eyes = epicanthal folds
2) Retardation
3) Limb dislocation
4) Fistulas (heart and lung)
5) Cranial development (microcephaly, holoprosencephaly)
When is developing baby most susceptible to teratogens?
Embryonic period (3-8 weeks)

Time of organogenesis.
- before week 3 = all or nothing
- after week 8 = growth & fx
What is the teratogenic effect of ACE Inhibitors?
Renal damage
What is the teratogenic effect of alkylating agents?
Absent digits.
Multiple anomalies.

Are used in chemo to stop cell growth.
What is the teratogenic effect of Aminoglycosides?
CN VIII toxicity (hearing defects)
What is the teratogenic effect of Carbamezepine?
Neural tube defects (inhibit maternal folate absorption ~ like valproate)
Also:
- Craniofacial defects
- Fingernail hypoplasia
- Developmental delay
- IUGR
What is the teratogenic effect of Diethylstilbestrol (DES)?
Mullerian abnormalities (fallopian tubes, uterus, cervix, vagina)

Also increased vaginal clear cell adenocarcinoma risk.

Affects the "DES Daughters"
What is the teratogenic effect of Tetracyclines?
Discolored teeth
What is the teratogenic effect of Thalidomide?
Phocomelia = Limb defects
("flipper" limbs)
What is the teratogenic effect of Warfarin?
Bone deformities
Fetal hemorrhage
Ophthalmic abnormalities
Abortion

(use Heparin instead b/c it doesn't cross placenta)
What is the teratogenic effect of DM?
Caudal regression syndrome
Heart defects (transposition of great vessels)
Neural tube defects
Macrosomia
What is the teratogenic effect of Retinoic Acid?
Spontaneous abortions
Many birth defects d/t interference w/ HOX Gene
What are the fetal components of the placenta and what do they do?
1) Cytotrophoblast = INNER layer of chorionic villi that makes cells

2) Syncytiotrophoblast = OUTER layer of chorionic villi that makes hCG
(stimulates corpus luteum to continue to secrete PROG)
What is the maternal component of the placenta and where does it develop from?
The Decidua basalis.

It is derived from endometrium.
What are the vessels in the umbilical cord?
- 2 x Umbilical arteries = return DE-OXYGENATED blood from the fetal internal iliacs

- 1 x Umbilical Vein = brings OXYGENATED blood to fetus, draining into the fetal IVC

NOTE: umbilical vessels are derived from the allantois
What is the most common congenital abnormality?
Single umbilical artery.

Usually inconsequential, however commonly associated w/ renal problems; also associated w/ other congenital and chromosomal abnormalities.
What problems occur if the urachal duct fails to close?
Should obliterate in 3rd week.

1) Patent urachus = urine discharged from umbilicus

2) Vesicourachal diverticulum = outpouched bladder
What problems occur if vitelline duct fails to close?
Should obliterate in 7th week.

1) Vitelline fistula = meconium discharged from umbilicus

2) Meckel's diverticulum = partial closure
What is Meckel's diverticulum, what is its cause, and what are some symptoms?
Incomplete closure of vitelline duct leads to diverticulum @ the ileum.

Syx = periumbilical pain and melena
(can be d/t ectopic gastric mucosa)
What are congenital anomalies associated with the Truncus arteriosus?
Gives rise to ascending aorta & pulmonary trunk; neural crest cells --> aorticopulmonary septum

1) Transpotition of great vessels (failure to spiral)
2) Tetralogy of Fallot (skewed AP septum)
3) Persistant truncus arteriosus (partial AP septum)
Where does fetal erythropoeisis occur?
"Young Liver Synthesizes Blood"

Y = Yolk Sac (up to 8 weeks)
L = Liver (8-28 weeks)
S = Spleen (8-28 weeks)
B = Bone Marrow (28 weeks +)
Difference b/w fetal and adult hemoglobin?
Fetal has 2 gamma chains
Adult has 2 beta chains

Gamma has higher O2 affinity / lower 2,3-DPG affinity

Results in O2 shunt from mom --> infant
Why does the foramen ovale close?
Infant's first breaths cause:
1) decrease pulmonary pressure
2) increase (relative) LA pressure (vs RA pressure)

Foramen ovale --> Fossa ovalis
What causes closure of the ductus arteriosus?
Increase in O2 --> decrease in PG's

Rx = Indomethacin (helps close PDA)

PG's will keep PDA open
What drug can help close a PDA?
Indomethacin.

PG's will keep a PDA open.