Term
What is the role of each of the following genes in embryogenesis?
1) Sonic hedgehog gene
2) Wnt-7
3) FGF
4) Hox |
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Definition
1) Produced at base of limbs in zone of polarizing activity
- patterning along anterior-posterior
2) Produced at apical ectodermal ridge (thickened ectoderm at distal end of each developing limb)
- dorsal/ventral axis organization
3) Produced at apical ectodermal ridge
- Stimulates mitosis of underlying mesoderm for limb lengthening
4) Involved in segmental organization of embryo in craniocaudal direction (appendages in wrong locations with mutations) |
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Term
What fetal landmarks occur at each of the following time points?
1) Day 0
2) 1st week
2) 2nd week
3) 3rd week
4) 3-8 (embryonic period)
5) week 4
6) week 8 (fetal period)
7) week 10 |
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Definition
1) Fertilization by sperm forming zygote (initiating embryogenesis)
2) hCG secretion begins after implantation of blastocyst
3) Bilaminar disk (epiblast, hypoblast)
4) Trilaminar disc- Gastrulation. Primitize streak, notochord, mesoderm and its organization, and neural plate begin to form.
5) Heart begins to beat
- Upper and lower limb buds begin to form
6) Fetal movement, looks like baby
7) Genitalia have male/female characteristics |
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Term
| What are the alar and basal plates? |
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Definition
| Dorsal/Sensory (Alar) and Ventral/Motor (Basal) plates of embryo that follow the orientation of the spinal chord. |
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Term
| What is the role of the notochord in neural development? What does it ultimately become? |
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Definition
- Induces overlying ectoderm to differentiate into neuroectoderm and form the neural plate
- Neural plate gives rise to neural tube (which closes by day 21) and neural crest cells, while the notochord becomes the nucleus pulpuosus of the IV disk in adults. |
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Term
| What are the major events that take place in weeks 2, 3 and 4 of early embryonic development? |
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Definition
1) Rule of 2's
- 2 germ layers (bilaminar): epiblast (embryo) and hypoblast
- 2 cavities: amniotic cavity, yolk sac
- 2 components to placenta: cytotrophoblast, syncytiotrophoblast
2) Rule of 3's
- 3 germ layers (gastrua): ectoderm, mesoderm, endoderm
3) Rule of 4's
- 4 Heart chambers
- 4 limb buds grow |
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Term
| What structures arise from the epiblast? |
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Definition
Precursor to embryo that invaginates to form the primitive streak during the 3rd week.
Cells from the primitive streak give rise to intra-embryonic mesoderm and part of endoderm. |
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Term
What are the embryological derivatives from each of the following sub-divisions of the ectoderm?
1) Surface ectoderm
2) Neuroectoderm
3) Neural crest |
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Definition
1) Surface ectoderm
- Adenohypophysis (Rathke's pouch),
- lens
- epithelial linings of oral cavity
- sensory organs of ear
- olfactory epitheium
- Epidermiss
- Anal canal below the pectinate line (external hemorrhoids)
- Parotid, sweat and mammary glands
2) Neuroectoderm: CNS and Brain
- Brain (neurohypophysis, CNS, oligodendrocytes, astrocytes, ependymal cells and pineal gland)
- Retina
- Spinal chord
3) Neural crest: PNS and non-neural structures nearby
- PNS, DRG, CN, Celiac ganglion, melanocytes, chromaffin cells of adrenal medulla, parafollicular (C) cells of thyroid, Schwann cells, pia and arachnoid, bones of skull, odontoblasts, aorticopulmonary septum |
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Term
What is the embryonic derivative from which each of the following is derived?
1) Schwann cells
2) Ependymal cells
3) Adenohypophysis
4) Bones of skull
5) Olfactory epithelium
6) Astrocytes |
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Definition
First this is that these are all ectodermal derivatives.
Opetions are surface ectoderm, neuroectoderm (brain and CNS) and neural crest
1) PNS= Neural crest
2) CNS= Neuroectoderm
3) Surface ectoderm
4) Neural crest
5) Surface ectoderm
6) Neuroectoderm |
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Term
| What is the embryonic origin of a Craniopharyngioma? |
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Definition
Most common cause of hypopituitarism in a child (often hitting optic chiasm)
Derived from Rathke's pouch, which is embryonic precursor to Adenohypothesis and comes from Surface ectoderm.
Other structures from surface ectoderm include epithelial linings of sensory cavities (ear, olfaction, oral) |
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Term
What is the embryonic derivative from which each of the following is derived?
1) Teeth
2) Adrenal medulla chromaffin cells
3) Parotid, sweat and mammary glands
4) Retina
5) Aorticopulmonary septum
6) Pia |
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Definition
All are ectodermal derivatives
1) Neural crest
2) Neural crest
3) Surface ectoderm
4) Neuroectoderm
5) Neural crest
6) Neural crest |
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Term
| List the possible mesodermal defects. |
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Definition
VACTERL
1) Vertebral defects
2) Anal atresia
3) Cardiac defects
4) Tracheo-Esophageal atresia
5) Renal defects
6) Limb defects |
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Term
| What structures arise from the embryonic mesoderm? |
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Definition
**Notochord induces overlying ectoderm to form neuroectoderm (Neural plate). Its postnatal derivative is the nucleus pulposis**
- Muscle
- Bone
- Connective Tissue
- Serous lining of body cavities (peritoneum)
- Spleen
- CV structures
- Lymphatics
- Blood
- Gut tube wall, bladder wall
- Urethra
- Vagina
- Kidneys
- Adrenal cortex
- Skin dermis
- Testes
- Ovary |
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Term
Which of the following is NOT a mesodermal derivative?
1) Bone
2) Kidney
3) Spleen
4) Pancreas
5) Ovaries
6) Adrenal cortex |
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Definition
| 4- Pancreas is an endodermal derivative |
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Term
Which of the following is NOT an endodermal derivative
1) Gut tube epithelium (including anal canal above pectinate line)
2) Liver
3) Kidney
4) Pancreas
5) Lungs
6) Parathyroid |
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Definition
3- Kidney is a mesodermal derivative.
Endoderm is
- Gut tube epithelium
- Luminal epithelial derivatives (Liver, lungs, pancreas, thymus, parathyroid, thyroid follicular cell)
- Eustachian tube
- Gallbladder |
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Term
Which of the following is NOT a mesodermal defect?
1) Vertebral defect
2) Pulmonary defect
3) Renal defect
4) Tracheoesophageal fistula
5) Cardiac defect
6) Limb abnormalities. |
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Definition
2- Lungs are derived from endoderm.
VACTERL
- Vertebral
- Anal atresia
- Cardiac defecgt
- Tracheoesophageal fistula
- Renal defect
- Limb defect |
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Term
What do each of the following types of errors in organ morphogenesis refer to?
1) Malformation
2) Deformation
3) Agenesis
4) Hypoplasia
5) Aplasia |
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Definition
1) Intrinsic disruption; occurs during embryonic period (week 3-8)
2) Extrinsic disruption; occurs after embryonic period
3) Absent organ due to absent primordial tissue
4) Incomplete organ development; primordial tissue present
5) Absent organ despite primordial tissue present |
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Term
| How does Aplasia differ from Agenesis? |
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Definition
Agenesis is absent organ due to absent primordial tissue (e.g. bilateral renal agenesis of the newborn).
Aplasia is absent organ WITH primordial tissue present (Thymic aplasia) |
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Term
What effects on the fetus do each of the following teratogenic medications have?
1) Ace inhibitors
2) Alkylating agents (Cyclophosphamide)
3) Aminoglycosides
4) Carbamazepine
5) Diethylstilbestrol (DES) |
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Definition
1) Renal damage
2) Absense of digits (multiple anomalies)
3) CN VIII toxicity
4) Neural tube defects, craniofacial, fingernail hypoplasia, developmental delay and IUGR
5) Vaginal clear cell adenocarcinoma |
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Term
What effects on the fetus do each of the following teratogenic medications have?
1) Folate antagonists (MTX, 5-FU)
2) Lithium
3) Phenytoin
4) Tetracyclines
5) Thalidomide
6) Valproate
7) Warfarin |
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Definition
1) Neural tube defects
2) Ebstein's anomaly
- atrialized RV
3) Fetal hydantoin syndrome; microcephaly, dysmoprhic craniofacial features, hypoplastic nails and distal phalanges, cardiac defects, IUGR, mental retardation.
4) Discolored teeth
5) Limb defects ("Flipper" limbs)
6) Neural Tube
- Inhibition of maternal folate absorption
7) Eyes, Bones and Bleeding
- Bone deformities, fetal hemorrhage, abortion, opthalmologic abnormalities |
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Term
Which drugs cause the following effects on the fetus?
1) Atrialization of right ventricle
2) Microcephaly, hypoplastic nails, cardiac defects and mental retardation
3) Discolored teeth
4) Limb defects (flippers)
5) Bone deformities, fetal hemorrhage, abortion and/or opthalmic defects
6) CN VIII toxicity |
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Definition
More susceptible betwenn 3-8 of pregnancy
- Before week 3 (all or none)
- After 8 (growth and function affected)
1) Ebstein's anomaly: Lithium
2) Fetal hydrantoin syndrome: Phenytoin
3) Tetracyclines
4) Thalidomide
5) Warfarin
6) Aminoglycosides |
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Term
Which drugs cause each of the following effects on the fetus?
1) Neural tube defects
2) Vaginal clear cell adenocarcinoma
3) Absence of digits with multiple anomalies
4) Renal damage
5) Neural tube defects with craniofacial defects, fingernail hypoplasia, developmental delay and IUGR |
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Definition
More susceptible betwenn 3-8 of pregnancy
- Before week 3 (all or none)
- After 8 (growth and function affected)
1) Drugs that hit folate metabolism (MTX, 5-FU) or absorption (Valproic acid)
2) DES
3) Alkylating agents (Cyclophosphamide)
4) Ace inhibitors
5) Carbamazepine |
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Term
What can consumption of each of the following substances during weeks 3-8 of pregnancy do to a fetus?
1) Alcohol
2) Cocaine
3) Smoking (nicotine, CO) |
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Definition
1) Leading cause of birth defects and mental retardation; FAS
2) Abnormal fetal evelopment and fetal addiction; placental abruption
3) Preterm labor, placental problems, IUGR, ADHD |
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Term
How might each of the following influence a growing fetus?
1) Iiodide (lack or excess)
2) Maternal diabetes
3) Vitamin A (excess)
4) X-rays |
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Definition
1) Congenital goiter or hypothyroidism (Cretinism)
2) Anus, Heart and Brain
- Caudal regression syndrome (anal atresia to sirenomelia), congenital heart defects, neural tube defects
3) Risk of spontaneous abortions and birth defects (Cleft palate and cardiac)
4) Microcephaly, mental retardation |
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Term
What is the leading cause of congenital malformations in the US?
What are some common consequences for the fetus? |
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Definition
Fetal alcohol syndrome (OH- may inhibit cell migration)
- Risk of congenital abnormalities (pre- and postnatal developmental retardtion)
- Microcepahaly, Holoprosencephaly
- Facial abnormalities
- Limb dislocation
- Heart/lung fistulas |
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Term
| What determines the degree of separation between monozygotic twins in uterine development? |
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Definition
1 fertilized egg (1 egg + 1 sperm) splits into 2 zygotes
Depends upon timing of split, which determines the number of chorions and amnions.
1) 0-4 days (between 2 cell and morula)
- Dichorionic and Diamniotic
- 25% of monozygotic twins
2) 4-8 days (between morula and blastocyst)
- Monochorionic and diamniotic
- 75% of monozygotes
3) 8-12 days (Blastocyst cleaved)
- Monochorionic and monoamniotic
4) >13 days (after embryonic disc forms)
- Conjoined |
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Term
| What is the difference between monozygotic and dizygotic twins? |
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Definition
1) Monozygotic= 1 fertilized egg (1 sperm + 1 egg) that splits
- Degree of separation in utero depends on timing of split (anywhere from day 1->13)
2) Dizygotic
- 2 eggs + 2 sperms |
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Term
The placenta is the primary site of nutrient and gas exchange between mom and fetus.
Describe the fetal and maternal components and how they interact. |
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Definition
Fetal Trophoblast tissue in branched chorionic villi invade uterine Decidua basalis and remodel vascular tissue leading to dilation of maternal spiral arteries, which release maternal blood to base villi.
1) Fetal
- Cytotrophobloast: inner layer of chorionic villi (makes cells)
- Syncytiotrophoblast: outer layer that secretes hCG to stimulate corpus luteum to produce progesterone during the 1st trimester.
2) Maternal
- Decidual basalis (Derived from endometrium)
- Maternal blood in lacunae (pits forms in invading trophoblastic tissue) |
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Term
| What is the structure/function of the umbilical cord? |
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Definition
Contains
- 2 umbilical arteries (return deoxygenated blood from fetal internal iliac arteries to placenta)
- 1 umbilical vein (carrying oxygenated blood from placenta to fetus, draining into IVC)
- Arteries and vein lay in Wharton's jelly substance, which is surrounded by amniotic epithelium on the outer surface of the chord.
- Connects fetus to placenta.
- Arteries and veins are derived from allantosis |
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Term
| What is the Urachus, how does it develop and what abnormalities are associated with it? |
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Definition
During 3rd week, yolk sac forms allantois, which runs within umbilical chord and extends into urogenital sinus, draining fetal urinary bladder.
The allantois becomes the urachus, a duct between the bladder and yolk sac
2) Failure of urachus to obliterate:
- Patent urachus- urine discharge from ubilicus
- Vesicourachal diverticulum- Outpouching of bladder |
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Term
| What is the Vitelline duct, how does it develop and what abnormalities are associated with it? |
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Definition
Connects yolk sac to midgut lumen.
- During week 7, obliteration of vitelline duct (omphalomesenteric duct) occurs
1) Vitelline fistula
- Duct does not close resulting in meconium discharge from umbilicus
2) Meckel's diverticulum
- Partial closure with patent portion attached to ileum
- Ectopic gastric mucosa- leading to melena and periumbilical pain. |
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Term
What do each of the following cardiac embyronic structures give rise to?
1) Truncus arteriosus (TA)
2) Bulbus cordis
3) Primitive ventricle
4) Primitive atria
5) Left horn of sinus venosus (SV)
6) Right horn of SV
7) Right common cardinal vein and right anterior cardinal vein |
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Definition
1) Ascending aorta and pulmonary trunk
2) Smooth parts (outflow tracts) of ventricles
3) Trabeculated L/R ventricles
4) Trabecularted L/R atrium
5) Coronary sinus
6) Smooth part of RA (forms SA node)
7) SVC |
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Term
What is the Truncus arteriosus and what does it give rise to?
What happens in each of the following?
1) Transposition of great vessels
2) Tetralogy of fallot
3) Persistent TA |
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Definition
Neural crest migration leads to truncal and bulbar ridges that spiral and fuse to form the aorticopulmonary septum (dividing line).
The TA gives rise to the ascending aorta and the pulmonary trunk, while the Bulbus cordis gives rise to the smooth outflow tracts.
1) Failure of ridges to spiral and fuse (RV gives rise to aorta and LV gives rise to pulmonary trunk)
2) Skewed AP septum development (Pulmonic stenosis, RVH, overiding aorta, VSD)
3) Partial AP setpum development (PA arise from aorta) |
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Term
Describe the 3 major steps of IV septum development of cardiac tissue?
What defects occur from abnormal development of the IV septum? |
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Definition
To begin with, there is a single ventricular cavity that ends in a Truncus arteriosis
1) Muscular ventricular septum forms
- Opening is called IV foramen
2) Aorticopulmonary septum (Formed from truncal and bulbar ridges) meets and fuses with the muscular ventricular septum to form membranous IV septum, closing the IV foramen.
3) Growth of endocardial cushions separate atria from ventricles and contributes to both atrial separation and membranous portion of IV septum
Abnormal neural crest migration into TA can cause transposition of great arteries or persistent TA. Membranous septal defects cause left-to-right shunting, which may reverse in adulthood. |
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Term
| Describe the basic process of interatrial septum development. |
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Definition
Patent foramen ovale occurs when there is excessive resorption of septum primum and/or secundum
1) Foramen primum (RA to LA) narrows as septum primum grows toward endocardial cushions
2) Perforations in septum primum form Foramen secundum (primum dissapears)
3) Foramen secundum maintains right-to-left shunt as septum secundum begins to grow
4) Septum secundum contains a permanent opening (foramen ovale)
5) Foramen secundum enlarges and upper part of septum primum degenerates
6) Remaining portion of septum primum forms valve of foramen ovale
7) Septum secundum and septum primum fuse to form atrial septum
8) Foramen ovale usually closes after birth due to increased LA pressure. |
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Term
| How is fetal erythropoeisis handled from week 3 to adulthood? |
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Definition
HbF= a2y2
Hb adult= a2b2
Young Liver Synthesizes Blood
1) Yolk sac (3-10 weeks)
2) Liver (6 weeks to birth)
3) Spleen (15-30 weeks)
4) Bone marrow (22 weeks onward to adulthood) |
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Term
| Describe the flow of blood entering a developing fetus (what are the critical shunts?). |
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Definition
Blood in umbilical vein is 80% saturated, but very low in arteries.
1) Blood entering fetus through umbilical vein is conducted via ductus venosus into IVC to bypass the hepatic circulation
2) Most oxygenated blood reaching IVC is diverted through foramen ovale and pumped out aorta to head and body
3) Deoxygenated blood from SVC is expelled into pulmonary artery and ductus arteriosus to lower body of the fetus. |
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Term
| What changes to pulmonary physiology occur when the baby takes its first breath? |
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Definition
1) Decreased resistance in pulmonary vasculature causes increase in LA pressure vs. RA pressure
2) Foramen ovale closes (Fossa ovalis)
3) Increase in O2 leads to decrease in PGE, causing closure of ductus arteriosus (no longer needs to send SVC blood that enters RV to aorta)
**Use indomethacin to help close PDA or PGE to keep it open if needed** |
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Term
What do each of the following fetal structures become post-natally?
1) Umbilical vein
2) Umbilical artery
3) Ductus arteriosis
4) Ductus venosis
5) Foramen ovale
6) Allantois
7) Notochord |
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Definition
1) Ligamentum teres hepaticus
2) MediaL umbilical ligaments
3) Ligamentum arteriosum
4) Ligamentum venosum
5) Fossa ovalis
6) Urachus-mediaN umbilical ligament
7) Nucleus pulposis of IV disc |
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Term
There is elegant regional specification to the developing brain.
Describe how the 3 primary vesicles become the 5 primary vesicles.
What derivatives arise from each? |
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Definition
Primary
- Prosencephalon
- Mesencephalon
- Rhombencephalon
Secondary
- Telencephalon (prosencephalon)
- Diencephalon (prosencephalon)
- Mesencephalon
- Metencephalon (Rhombencephalon)
- Myelencephalon (Rhombencephalon)
Derivatives
1) Telencephalon
- Cerebral hemispheres/Lateral ventricles
2) Diencephalon
- Thalamus/3rd ventricle
3) Mesencephalon
- Midbrain/Aqueduct
4) Metencephalon
- Pons and Cerrebellum/ Upper part of 4th ventricle
5) Myelencephalon
- Medulla and lower 4th ventricle |
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Term
From which primary and secondary vesicle is each of the following neural structures derived?
1) Cerebellum
2) Aqueduct
3) Thalamus
4) Lateral ventricles
5) Pons
6) Medulla |
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Definition
1) Metencephalon derived from Rhombencephalon
2) Mesencephalon derived from Mesencephalon
3) Diencephalon from Prosencephalon
4) Telencephalon from Prosencephalon
5) Metencephalon derived from Rhombencephalon
6) Myelencephalon from Rhombencephalon |
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Term
What happens if the neuropores fail to fuse in the 4th week of development?
What are the major neural tube defects? |
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Definition
Associated with low Folic acid (intake or MTX/Valproic acid)
1) Persistent connection between amniotic cavity and spinal canal
2) Defects
- Spina Bifida (tuft of hair): failure of bony spinal canal to close, but no structural herniation (intact Dura)
- Meningocele: Meninges herniates through spinal canal defect
- Meningoomyelocele: Meninges and spinal cord herniate through spinal canal defect |
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Term
| What are the laboratory signs associated with a neural tube defect? |
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Definition
Elevated AFP and Acetylcholinesterase in amniotic fluid (CSF leaks into fluid) and AFP in maternal serum
Spina bifida, Meningocele and Meningomyelocele |
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Term
| What is the difference between Anencephaly and Holoprosencephaly? |
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Definition
1) Anencephaly
- malformation of anterior end of neural tube; no brain/calvarium,
- elevated AFP, polyhydramnios (no swallowing center)
2) Holoprosencepaphy
- Loss of separation of hemispheres across midline; results in cyclopia
- Associated with Patau's syndrome ( trisomy 13), severe fetal alcohol syndrome and cleft lip/palate |
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Term
| What are the posterior fossa malformations and how do they present clinically? |
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Definition
1) Chiari II
- Significant tonsillar and vermion herniation through foramen magnum with aqueductal stenosis and hydrocephaly
- Presents with thoraco-lumbar myelomeningocele and Paralysis below defect.
2) Dandy-Walker
- Large posterior fossa; absent cerebellar vermis with cystic enlargement of 4th ventricle
- Can cause hydrocephalus and spina bifida |
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Term
| What is the difference between Chiari I and II and what conditions are associated with each? |
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Definition
Both are posterior fossa malformations with cerebellar herniation through foramen magnum that are associated with non-communicating hydrocephalus.
1) Chiari I (headache/neck pain)
- Syringomyelia of cervicothoracic spinal cord (C8-T1)
- "Bilateral loss of pain and temperature sensation in upper extremities with preservation of touch"
2) Chiari II (paralysis)
- Thoracolumbar myelomeningocele
- "Bilateral paralysis below lesion" |
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Term
Patient with Marfan's syndrome presents with bilateral loss of pain and temperature sensation in her upper extremeties. She still feels light touch and vibration.
What is going on and what is this condition is this associated with? |
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Definition
1) Syringomyelia
- "Capelike" damage to crossing fibers of spinothalamic tract due to enlargement of central canal of spinal chord.
2) Chiari 1 Malformation (Tonsillar herniation and non-communicating hydrocephalus).
Connective tissue disorders like Marfan's and Ehrlo Danlos predispose to Chiari malformations |
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Term
| What are the 6 aortic arch derivatives and what do they become? |
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Definition
Develop into the arterial system
1st) Part of Maxillary artery (branch of external carotid)
2nd) Stapedial artery and hyoid artery
3rd) Common carotid artery and proximal part of internal carotid
4th) On left, aortic arch; on right, proximal part of right subclavian
6th) Proximal pulmonary arteries and (on left only) ductus arteriosus |
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Term
| Where are the right and left recurrent laryngeal nerves found in relation to the aortic arch derivatives? |
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Definition
1) LRLN runs under the arch and gets caught by the 6th derivative, which gives rise to the pulomonary arteries and ductus arteriosus on the left
2) RRLN loops around the proximal portion of the subclavian artery, which arises from the 4th aortic arch derivative (gives rise to aortic arch on left and proximal subclavian artery on right) |
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Term
| What is the "Branchial apparatus"? |
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Definition
Also called "pharyngeal apparatus," it is composed of branchial clefts, arches and pouches.
"CAP covers outside form inside"
1) Branchial clefts- ectoderm (also called grooves)
2) Branchial arches- mesoderm (muscle, arteries) and neural crests (bones, cartilage)
3) Branchial Pouches- endoderm |
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Term
List the major branchial cleft derivatives.
What is a "persistent cervical sinus"? |
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Definition
Cleft= Ectoderm
1st) External auditory meatus
2nd-4th) Temporary cervical sinuses, which are obliterated by formation of 2nd arch mesenchyme
**A persistent cervical sinus is a branchial cleft cyst within the lateral neck. |
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Term
There are many branchial arch derivatives which arise from mesodermal and neural crest precursors.
What cartilage, muscle and nerves arise from Branchial arch 1? |
|
Definition
All the M's
1) Meckel's Cartilage
- Mandible
- Malleus
- incus
- spheno-Mandibular ligament
2) Muscles
- Mastication (Medial pterygoid, Masseter, teMporalis, lateral pterygoid)
- Mylohyoid
- Anterior belly of digastric
- Tensor tympani and tensor veli palatini
3) Nerves
- V2 and V3 chew |
|
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Term
| What is the pathophysiology underlying a patient who presents with mandibular hypoplasia and facial abnormalities? |
|
Definition
Treacher Collin's
1st Branchial arch neural crest fails to migrate, so you cannot make mandibular cartilage, ligament or muscles of mastication.
- You also may lose CN V2/V3 |
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Term
There are many branchial arch derivatives which arise from mesodermal and neural crest precursors.
What cartilage, muscle and nerves arise from Branchial arch 2? |
|
Definition
All the S's
1) Reichert's cartilage
- Stapes
- Styloid process
- Lesser horn of hyoid
- Stylohyoid ligament
2) Muscles
- Facial expression
- Stapedius
- Stylohyoid
- Posterior belly of digastric
3) Nerves
- CN VII (facial expression) |
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Term
There are many branchial arch derivatives which arise from mesodermal and neural crest precursors.
What cartilage, muscle and nerves arise from Branchial arch 3? |
|
Definition
1) Cartilage
- Greater horn of hyoid (lesser horn is arch 2)
2) Muscles
- Stylopharyngeus
3) Nerve
- CN IX (swallow stylishly) |
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Term
| What is the pathophysiological basis of congenital pharyngocutaneous fistula? |
|
Definition
| Persistence of 3rd branchial cleft and pouch leading to fistula between tonsillar area and cleft in lateral neck. |
|
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Term
There are many branchial arch derivatives which arise from mesodermal and neural crest precursors.
What cartilage, muscle and nerves arise from Branchial arches 4-6? |
|
Definition
1) Cartilages
- Thyroid
- Cricoid
- Arytenoid
- Corniculate
- Cuneiform
2) Muscles
- 4th: pharyngeal constrictors; cricothyroid, levator veli palatini
- 6th: Intrinsic laryngeal muscles EXCEPT cricothyroid (4th)
3) Nerves
- 4th: CN X (superior laryngeal branch) simply swallow
- 6th: CN X (recurrent laryngeal) Speak |
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Term
Which branchial arches form the tounge?
How does this relate to the nervous system innervation for motor, sensation and taste? |
|
Definition
Motor: CN XII
Taste: CN XII, IX, X (solitary nucleus)
Sensation: CN V3, IX, X
1) Arch 1 forms anterior 2/3
- sensation via CN V3
- taste via CN VII
2) Arch 3-4 make posterior 1/3
- Sensation and taste via CN IX and X (extreme posterior) |
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Term
| What are the broad functions of branchial arches 1-6? |
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Definition
Derived from neural crest and mesoderm
"When at the restaurant of the golden arches, children tend to first chew (1), then smile (2), then swallow stylishly (3) or simply swallow (4), before they speak (6)" |
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Term
Which branchial pouch derivative develops into each of the following?
1) Middle ear cavity, eustachian tube and mastoid air cells
2) Inferior parathyroids
3) Thymus
4) Superior parathyroids
5) Epithelial lining of palatine tonsil |
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Definition
Pouches are Endoderm
"Ears, tonsils, bottom-to-top"
1) 1st pouch (endoderm-lined structures of middle ear)
2) Dorsal wings of 3rd pouch
3) Ventral wings of 3rd pouch
4) 4th pouch
5) 2nd pouch
"3rd pouch structures end up below 4th pouch structures- inferior below superior parathyroids" |
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Term
| Why might patients with DiGeorge syndrome present with both thymic aplasia and hypocalcemia? |
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Definition
Abberant development of 3rd and 4th pouches.
Both the Thymus (ventral wings) and Inferior parathyroid glands (dorsal wings) arise from the 3rd Branchial pouch.
Superior parathyroids comes from 4th pouch |
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Term
| How does the MEN2A syndrome relate to branchial pouches? |
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Definition
Mutation in germline RET tyrosine kinase (neural crest cells)
1) Adrenal medulla (pheochromocytoma)
2) Parathyroid (tumor): 3rd/4th branchial pouch
3) Parafollicular cells (medullary thyroid cancer) from neural crest cells associated with 4th and 5th pharyngeal pouches. |
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Term
Name that branchial arch.
1) Stapedius muscle
2) Stylopharyngeus muscle
3) Greater horn of hyoid cartilage
4) Lesser horn of hyoid cartilage
5) CN IX
6) Spheno-mandibular ligament
7) Posterior belly of digastric
8) Anterior belly of digastric |
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Definition
1) Arch 2
2) Arch 3
3) Arch 3
4) Arch 2
5) Arch 3
6) Arch 1
7) Arch 2
8) Arch 1 |
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Term
Name that branchial arch.
1) Cricothyroid muscle
2) Posterior belly of digastric
3) Stylohyoid muscle
4) Stapedius muscle
5) Tensor tympani
6) Levator vili palatini
7) Tensor veli palatini
8) Arytenoid cartilage
9) Intrinsic muscles of larynx |
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Definition
1) Arch 4
2) Arch 2
3) Arch 2
4) Arch 2
5) Arch 1
6) Arch 4
7) Arch 1
8) Arch 4-6
9) Arch 6 |
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Term
| What is the function and innervation of the Tensor veli palatini muscle? |
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Definition
Tenses the soft palate
Innervated by medial pterygoid branch of V3 and is the only pallatal muscle NOT innervated by CN X (it is derived from branchial arch 1 vs. 4-6) |
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Term
Describe the embryonic development of the the thyroid.
What is the normal remnant of the thyroglossal duct?
What is the difference between a thyroglossal cyst and a branchial arch cyst? |
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Definition
1) Thyroid diverticulum arises from floor of primitive pharynx and then descends into the neck.
Follicular cells derive from endoderm and Parafollicular (C) cells derive from neural crest.
2) It is connected to the tongue by the thyroglossal duct, which normally disappears, but may persist as the pyramidal lobe (normal remnant is foramen cecum)
3) Thyroglossal duct cyst is midline and will move with swallowing (vs. persistent cervical sinus leading to branchial cleft cyst in the lateral neck). |
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Term
| What is the most common location of ectopic thyroid tissue? |
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Definition
| Tongue (connected in development via thyroglossal duct) |
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Term
What is the difference between a Cleft palate and a Cleft lip?
How do they develop? |
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Definition
Distinct etiologies, but occur together.
1) Cleft lip: failure of fusion of maxillary and medial nasal processes (formation of primary palate)
2) Cleft palate: Failure of fusion of lateral palatine processes, the nasal septum and/or the medial palatine process (formation of secondary palate) |
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Term
| What are the derivatives of the embryonic foregut, midgut and hindgut? |
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Definition
1) Foregut (Celiac trunk)
- Pharynx to duodenum
2) Midgut (SMA)
- Duodenum to transverse colon
- at 6 weeks, herniates through umbilical ring (persistent in Omphalocele)
- At 10 weeks, returns to abdominal cavity + rotates around SMA
3) Hindgut (IMA)
- Transverse colon to rectum |
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Term
| What is the difference between Gastroschisis and Omphalocele? |
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Definition
Defects of anterior abdominal wall closure (lateral folds)
Omphalocele has peritoneum covering by Gastroschisis does not
1) Gastroschisis: Extrusion of abdominal contents through abdominal folds; not covered by peritoneum
2) Omphalocele: Herniation of abdominal contents into umbilical cord (perists past 10 weeks, when it should have gone back and wrapped around SMA), covered by peritoneum |
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Term
Developmental defects of anterior abdominal wall closure can present with congenital defects.
Which of the following results from the following?
1) Failed rostral fold closure
2) Failed lateral fold closure
3) Failed caudal fold closure |
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Definition
1) Sternal defects
2) Omphalocele, Gastroschisis
3) Bladder exstrophy |
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Term
Duodenal atresia is caused by a different defect then Jejunal, Illeal and colonic atresia.
What are these different causes? |
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Definition
1) Duodenal: Failure to recanalize (trisomy 21)
2) Jejunal, ileal, colonic: Vascular accident (apple peel atresia) |
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Term
Which of the following is associated with Down's syndrome?
1) Duodenal atresia
2) Jejunal atresia
3) Ileal atresia
4) Colonic atresia |
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Definition
| 1- Failure to recanalize in trisomy 21 |
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Term
Between 6 weeks and 10 weeks of development, the midgut protrudes into the umbilical chord and then returns to the abdomen to wrap around the SMA.
What can happen if this fails? |
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Definition
1) Omphalocele
2) Malrotation of gut
3) Intestinal atresia or stenosis
4) Volvulus |
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Term
One mesodermal defect is TE fistula.
How does this present clinically and what are the common sub-types of this defect? |
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Definition
1) Presentation
- Cyanosis
- Choking and vomiting with feeding
- Air bubble in stomach on CXR
- Polyhydramnios and failure to pass NG tube.
2) Types
- Type C most common: Blind upper esophagus with lower esophagus connected to trachea
Type A- stenosis between upper and lower esophagus without tracheal attachment
Type B- Upper esophagus attaches to trachea and lower is blind. |
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Term
An 2 week old infant present with a palpable "olive" mass in the epigastric region and non-bilious projectile vomiting.
What is going on and how do you treat? |
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Definition
Congenital pyloric stenosis (1:600 live births, often in 1st born)
- Treat with surgery |
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Term
Describe the embryological development of the pancreas.
What is an annular pancreas and Pancreas divisum? |
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Definition
Foregut derivative from Endoderm.
1) Development
- Ventral buds (head, main duct, and uncinate process)
- Dorsal bud: everything else (Body, tail, isthmus and accessory duct)
2) Annular pancreas: Ventral bud abnormally encircles 2nd part of duodenum, forming a ring of tissue that may cause duodenal narrowing/stenosis
3) Pancreas divisum: ventral and dorsal parts fail to fuse at 8 weeks. |
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Term
| Where does the spleen arise from? |
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Definition
| Dorsal mesentery (mesoderm), but is still supplied by artery of foregut (celiac) |
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Term
| Describe the embryological development of the kidney. What are the 3 successive precursor forms? |
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Definition
1) Pronephros arises by week 4, then degenerates
2) Mesonephros functions as interim kidney for 1st trimester and later contributes to male genital system.
- Ureteric bud is derived from caudal end of mesonephros, giving rise to ureter, pelvises, calyces and collecting ducts (fully canalized by 10 weeks)
3) Metanephros
- Begins to appear during 5th week and continues to develop through 32-36 weeks.
- Metanephric mesenchyme interacts with ureteric bud to induce differentiation and formation of glomerulus and renal tubules to DCT |
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Term
| What structures are derived from the Ureteric bud and the Metanephric mesenchyme, respectively? |
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Definition
2 structures interact, and failure to do so will cause congenital malformations of kidney.
1) Ureteric Bud (mesonephros)
- Ureters, Pevlises, Calcyes and collecting ducts
- Fully canalized by week 10
2) Metanephric mesenchyme
- Glomeruli, renal tubules to DCT |
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Term
| What is the most common site of hydronephrosis? |
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Definition
Renal damage due to obstruction at Ureto-pelvic junction, which is the last to canalize in development
**Ureters and pelvises are from ureteric bud** |
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Term
| What is Potter's sequence and how does it develop? |
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Definition
Limb deformities, Facial deformities and Pulmonary hypoplasia
- Bilateral renal agenesis from Ureteric bud malformation leads to oligohydramnios, which produces to deformities. |
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Term
Why do Horshoe kidneys remain low in the abdomen rather than ascending?
Is kidney function impaired, and if so, by how much? |
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Definition
Fusion of inferior poles, especially in Turner's syndrome (XO in females with streak gonad and dysgerminoma risk)
1) Blocked by IMA
2) Renal function is intact |
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Term
| What does it mean that female genital development is the "default state"? |
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Definition
| Without SRY gene on Y chromosome, the Mesonephric (Wolffian) duct degenerates and the paramesopnephric (Mullerian) duct will develop |
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Term
| What is the role of the SRY gene in genital embryology? |
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Definition
SRY gene on Y chromosome
1) Produces testis-determining factor (TDF), which acts on testes, where it stimulates Leydig cells and Sertoli cells.
2) Leydig cells produce testosterone, which stimulates development of wolffian duct
3) Sertoli cells produce MIF to suppress paramesonephric (Mullerian) duct development |
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Term
| What structures arise from the Mesonephric and Paramesonephric ducts, respectively? |
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Definition
1) Mesonephric (Wolffian)
- Seminal vesicles, Epididymis, Ejaculatory duct and Ductus deferens (SEED)
2) Paramesonephric (Mullerian)
- Uterus, fallopian tubes and upper vagina |
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Term
| How would Mullerian duct abnormalities present clinically? |
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Definition
| Primary amenorrhea in females (uterus, fallopian tubes and vagina issues) with fully developed secondary sexual characteristics (functional ovaries) |
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Term
| What is a "Bicornuate uterus" and why is it of clinical concern? |
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Definition
Incomplete fusion of paramesonephric ducts.
Associated with UT abnormalities and infertility. |
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Term
What would each of the following produce clinically?
1) Sertoli cell dysfunction (XY)
2) 5-alpha-reductase deficiency (XY) |
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Definition
1) No MIF, so paramesonephric duct forms in addition to mesonephric, and you end up with both internal structures in the male, with normal external genitalia
2) Male internal genitalia (MIF is produced by sertoli cells), but ambiguous external genitalia until puberty (no DHT) |
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Term
| What is the role of DHT is sexual development? |
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Definition
External genitalia. Stimulates the following transitions
1) Genital tubercle becomes glans of penis and corpus cavernosum and spongiosum
2) Urogenital sinus becomes accessory glands (Bulbourethral and Prostate)
3) Uogenital folds become ventral shaft of penis (penile urethra)
4) Labioscrotal swelling becomes scrotum |
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Term
What would each of the following become with high DHT and high Estrogen, respectively?
1) Genital tubercle
2) Urogenital sinus
3) Urogenital folds
4) Labioscrotal swelling |
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Definition
1) Genital tubercle
- Glans penis and corpus cavernosum/spongiosum (DHT)
- Clitoris and Vestibular bulbs (Estrogen)
2) Urogenital sinus
- Accessory glands (DHT)
- Greater vestibular glands of Bartholin and Urethral and paraurethral glands of Skene (Estrogen)
3) Folds
- Ventral penis shaft (DHT)
- Labia minora (Estrogen)
4) Swelling
- Scrotum (DHT)
- Labia majora (Estrogen) |
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Term
| What is the difference between Hypospadias and Epispadias? |
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Definition
1) Hypospadias (more common)
- Failed closure of urogenital folds to form ventral penile shaft, causing an abnormal opening of penile urethra on inferior side of penis
**Fix to prevent UTI**
2) Epispadius (rare)
- Faulty positioning of genital tubercle leads to abnormal opening of penile urethra on superior (dorsal) side
- Exstrophy of bladder may be associated. |
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Term
The Gubernaculum and Processus vaginalis contribute to descent of gonads.
How does their role and fate differ in males and females? |
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Definition
Processus Vaginalis is evagination of peritoneum
Gubernaculum is band of fibrous tissue
1) Male
- Gubernaculum anchors tests within scrotum
- Processus vaginalis forms tunica vaginalis outside seminiferous tubules.
2) Female
- Gubernaculum becomes ovarian ligament and round ligament of uterus
- Processus vaginalis is obliterated |
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