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159 Cards in this Set

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Describe the importance of the sonic hedgehog gene in embryogenesis.
-produced at base of limbs in zone of polarizing activity
- involved in patterning along anterior-posterior axis
Describe the importance of the Wnt-7 gene in embryogenesis.
- produced at apical ectodermal ridge (thickened ectoderm at distal end of each developing limb)
- necessary for proper organization along dorsal-ventral axis
Describe the importance of the FGF gene for embryogenesis
- produced at apical ectodermal ridge
- stimulates mitosis of underlying mesoderm, providing for lengthening of limbs
Describe the importance of the Homeobox gene in embryogenesis
- involved in segmental organization of embryo in craniocaudal direction
What occurs at day 0 of embryogenesis?
- fertilization by sperm forming zygote, initiating embryogenesis
Describe what occurs within week 1 of embryogenesis.
hCG secretion begins after implantation of blastocyst
Describe what occurs within week 2 of embryogenesis.
bilaminar disk (epiblast, hypoblast)
Describe what occurs within week 3 of embryogenesis
- gastrulation
- primitive streak, notochord, and neural plate begin to form
What occurs within weeks 3-8 (embryonic period) of embryogenesis?
- neural tube formed by neuroectoderm and closes by week 4
- organogenesis
- extremely susceptible to teratogens
What occurs during week 4 of embryogenesis?
- heart begins to beat
- upper and lower limb buds begin to form
What occurs during week 8 (fetal period) of embryogenesis?
fetal movement, fetus looks like a baby
What occurs during week 10 of embryogenesis?
genitalia have male/female characteristics
The alar plate and the basal plate are responsible for which type of functions?
- alar (dorsal) = sensory
- basal (ventral) = motor
describe the steps of neural development.
1. notochord induces overlying ectoderm to differentiate into neuroectoderm and form the neural plate
2. neural plate gives rise to the neural tube and neural crest cells
3. notochord becomes nucleus pulposus of the intervertebral disk in adults
What is the rule of 2's for early development?
2nd week
- 2 germ layers (bilaminar disk): epiblast, hypoblast
- 2 cavities: amniotic cavity, yolk sac
- 2 components to placenta: cytotrophoblast, syncytiotrophblast
What is the rule of 3's for early development?
3rd week
- 3 germ layers (gastrula): ectoderm, mesoderm, endoderm
What is the rule of 4's for early development?
4th week
- 4 heart chambers
- 4 limb buds grow
Name the embryologic derivatives of surface ectoderm.
- adenohypophysis (from Rathke's pouch)
- lens of eye
- epithelial linings of oral cavity
- sensory organs of ear and olfactory epithelium
- epidermis
- salivary, sweat and mammary glands
-
Name the embryologic derivatives of neuroectoderm.
- brain (neurohypophysis, CNS neurons, oligodendrocytes, astrocytes, ependymal cells, pineal gland)
- retina
- spinal cord
Name the embryologic derivatives of neural crest cells
- ANS, DRG, cranial nerves, celiac ganglion, melanocytes
- chromaffin cells of adrenal medulla, parafollicular (C) cells of thyroid
- Schwann cells, pia and arachnoid, bones of the skull
- odontoblasts, aorticopulmonary septum
What is craniopharyngioma?
benign Rathke's pouch tumor with cholesterol crystals, calcifications
What are the embryologic derivatives of endoderm?
- gut tube epithelium and derivatives (i.e. lungs, liver, pancreas, thymus, parathyroid, thyroid follicular cells)
What are the embryologic derivatives of mesoderm?
- muscle, bone, connective tissue
- serous linings of body cavities (i.e. peritoneum)
- spleen (derived from foregut mesentery)
- cardiovascular structures, lymphatics, blood
- bladder, urethra, kidneys
- vagina, testes, ovaries
- eustachian tube, adrenal cortex
- skin dermis
What are some mesodermal defects?
- VACTERL:
- Vertebral defects
- Anal atresia
- Cardiac defects
- Tracheo-Esophageal fistula
- Renal defects
- Limb defects (bone and muscle)
What is a malformation?
intrinsic disruption; occurs during the embryonic period (weeks 3-8)
What is a deformation?
extrinsic disruption; occurs after the embryonic period
What is agenesis?
absent organ due to absent primordial tissue
What is hypoplasia?
incomplete organ development; primordial tissue present
What is aplasia?
absent organ despite present primordial tissue
What are the effects of teratogens before week 3 of embryogenesis, week 3-8 (embryonic period), and after week 8?
- before week 3: all-or-none effects
- week 3-8: embryonic period
- after week 8: growth and function affected
What are the effects of ACE inhibitors on the fetus?
renal damage
What are the effects of Alcohol on the fetus?
leading cause of birth defects and mental retardation --> fetal alcohol syndrome
What are the effects of Alkylating agents on the fetus?
- absence of digits
- multiple anomalies
What are the effects of aminoglycosides on the fetus?
CN VIII toxicity
What are the effects of cocaine on the fetus?
- abnormal fetal development and fetal addiction
- placental abruption
What are the effects of diethylstilbestrol (DES) on the fetus?
vaginal clear cell adenocarcinoma
What are the effects of folate antagonists on the fetus?
neural tube defects
What are the effects of iodide (lack or excess) on the fetus?
congenital goiter or hypothyrodism
What are the effects of lithium on the fetus?
Ebstein's anomaly (atrialized right ventricle)
What are the effects of maternal diabetes on the fetus?
caudal regression syndrome (anal atresia to sirenomelia)
Does the chorion form before the amnion? what days of fetal development do the chorion and amnion form?
chorion (day 3)
amnion (day 8)
Describe the characteristics of fetal development for dizygotic twins.
- monozygotes that split to develop 2 placentas (separate/fused), chorions and amniotic sacs
-dizygotes develop individual placentas, chorions, and amniotic sacs
Describe the characteristics of fetal development of monozygotic twins.
- 1 zygote splits evenly to develop 2 amniotic sacs with a single common chorion and placenta
- conjoined twins have 1 chorion, 1 amniotic sac
Describe the fetal component of placental development
- primary site of nutrient and gas exchange between mother and fetus
- cytotrophoblast - inner layer of chorionic villi. (Cyto makes cells)
- Syncytiotrophoblast - outer layer of chorionic villi; secretes hCG (structurally similiar to LH; simulates corpus luteum to secrete progesterone during first trimester)
Describe the maternal component of placental development
decidua basalis - derived from the endometrium. Maternal blood in lacunae
What is the purpose of umbilical arteries? How many are there?
- return deoxygenated blood from fetal internal iliac arteries to placenta
- there are two (2)
What is the purpose of umbilical vein? How many are there?
- supplies oxygenated blood from placenta to fetus; drains into IVC
- there is one (1)
What is the origin of the umbilical arteries and veins?
allantois
What is the urachus?
duct between bladder and yolk sac
What are the consequences of failure of urachus to obliterate?
1. patent urachus - urine discharge from umbilicus
2. vesicourachal diverticulum - outpouching of bladder
When does the urachal duct form?
usually during the 3rd week, yolk sac from allantois, which extends into urogenital sinus
When does the vitelline duct obliterate?
7th week,obliteration of vitelline duct (omphalomesenteric duct), which connects yolk sac to midgut lumen
What is a vitelline fistula?
failure of duct to close resulting to meconium discharge from umbilicus
What is Meckel's diverticulum?
partial closure, with patent portion attached to ileum. May have ectopic gastric mucosa (melena and periumbilical pain)
What does the truncus arteriosus give rise to?
ascending aorta and pulmonary trunk
What does the bulbus cordis give rise to?
right ventricle and smooth parts (outflow tract) of left and right ventricle
What does the primitive ventricle give rise to?
portion of the left ventricle
What does the primitive atria give rise to?
trabeculated left and right atrium
What does the left horn of the sinus venosus give rise to?
coronary sinus
What does the right horn of sinus venosus give rise to?
smooth part of right atrium
What does the right common cardinal vein and right anterior cardinal vein give rise to?
superior vena cava
What is the embryogenesis of the truncus arteriosus?
neural crest migration --> truncal and bulbar ridges that spiral and fuse to form the aorticopulmonary septum --> ascending aorta and pulmonary trunk
What types of pathology is associated with the truncus arteriosus?
- transposition of great vessels (failure to spiral
- tetralogy of fallot (skewed AP septum development)
- persistent TA (partial AP septum development)
Describe the steps of interventricular septum development
1. muscular ventricular septum forms. Opening = interventricular foramen
2. Aorticopulmonary septum meets and fuses with muscular ventricular septum to form membranous interventricular septum, closing interventricular foramen
3. growth of endocardial cushions separates atria from ventricles and contributes to both atrial separation and membranous portion of the interventricular septum
What are some pathologies related with the development of the interventricular septum?
- membranous septal defects causes initial Left-to-right shunting, which then becomes right-to left shunting (Eisenmenger complex)
Describe the steps of interatrial septum development.
1. foramen primum narrows as septum primum grows toward endocardial cushions
2. perforations in septum primum form foramen secundum (foramen primum disappears)
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 the atrial septum
8. foramen ovale usually closes soon after birth because of increased left atrium pressure
What are some pathologies associated with interatrial septum development?
- patent foramen ovale, caused by excessive resorption of septum primum and/or secundum
In which tissues (and during which weeks) does fetal erythropoiesis occur?
1. Yolk sac (3-8 weeks)
2. Liver (6-30 weeks)
3. Spleen (9-28 weeks)
4. bone marrow (28 weeks onward)
What is the composition of fetal and adult hemoglobin?
- fetal = alpha(2)gamma(2)
- adult = alpha(2)beta(2)
What is the composition of saturated oxygen in blood in umbilical vein and arteries?
- vein = 80% saturated oxygen
- arteries = low oxygen saturation
Name the three important shunts in fetal blood cirulation.
1. ductus venous
2. foramen ovale
3. ductus arteriosus
Describe the ductus venous shunt.
- blood entering the fetus through the umbilical vein is conducted via the ductus venousus into the IVC to bypass the hepatic ciruclation
Describe the foramen ovale shunt.
Most oxygenated blood reaching the heart via the IVC is diverted through the foramen ovale and pumped out the aorta to the head and body.
Describe the ductus arteriosus shunt.
Deoxygenated blood from the SVC is expelled into the pulmonary artery and ductus arteriosus to the lower body of the fetus
What occurs at birth in relation to the shunts in fetal ciruclation?
- at birth, infant takes a breath --> decrease resistance in pulmonary vasculature causes increase in left atrial pressure vs. right atrial pressure --> foramen ovale closes (now called fossa ovalis)
- increase in oxygen leads to decrease in prostaglandins, causing closure of ductus arteriosus
Name the three components of the three-stage vesicles of the developing brain.
- prosencephalon
- mesencephalon
- rhombencephalon
Name the components of the five-stage vesicles of the developing brain.
- telencephalon
- diencephalon
- mesencephalon
- metencephalon
- myelencephalon
What are the adult derivatives and origins of the developing brain? and their associated cavities
- telencephalon --> cerebral hemispheres (lateral ventricle)
- diencephalon --> thalami, etc (3rd ventricle)
- mesencephalon --> midbrain
- metencephalon --> pons, cerebellum (aqueduct)
- myelencephalon --> medulla, spinal cord (4th ventricle)
What are the consequences of neuropores failure to fuse?
- occurs usually in the 4th week
- persistent connection between amniotic cavity and spinal canal
- assoicated with low folic acid intake during pregnancy
- elevated alpha-fetoprotein (AFP) in amniotic fluid and maternal serum
- increase in AFP + acetylcholinesterase in CSF
What is spina bifida occulta?
- failure of bony spinal canal to close, but no structural herniation.
- usually seen at lower vertebral levels
- dura is intact
What is meningocele?
meninges herniate through spinal canal defect
What is myelomeningocele?
meninges and spinal cord herniate through spinal canal defect
What is anencephaly?
malformation of anterior end of neural tube; no brain/calvarium, elevated AFP, polyhydramnios (no swallowing center in brain)
What is holoprosencephaly?
- decrease in separation of hemispheres across midline --> results in cyclopia
- associated with Patau's syndrome, severe fetal alcohol syndrome, and cleft lip/palate
What is a Chiari II malformation?
- cerebellar tonsillar herniation through foramen magnum with aqueductal stenosis and hydrocephaly
- often present with syringomyelia, thoracolumbar myelomeningocele
What is a Dandy-Walker malformation?
- large posterior fossa
- absent cerebellar vermis with cystic enlargement of 4th ventricle
- can lead to hydrocephalus and spina bifida
What is syringomyelia?
- enlargement of the central canal of spinal cord
- crossing fibers of spinothalamic tract are typically damaged first
- "cape-like" bilateral loss of pain and temperature sensation in upper extremities with preservation of touch sensation
- most common at C8-T1
- associated with Chiari II malformations
What are the derivatives of the aortic arches?
- they 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 artery
4th - on left, aortic arch; on right, proximal part of right subclavian artery --> [4 limbs = systemic]
6th - proximal part of pulmonary arteries and (on left only) ductus arterious [pulmonary and the pulmonary-to-systemic shunt - ductus arteriosus]
What are brancial appartus composed of?
- branchial clefts, arches and pouches
What is the order of clefts, arches and pouches?
"CAP covers outside from inside"
- Clefts = ectoderm
- Arches = mesoderm
- Pouches = endoderm
From what are branchial clefts derived?
- derived from ectoderm
- also called branchial grooves
From what are brancial arches derived?
- derived from mesoderm (muscles, arteries) and neural crests (bones, cartilages)
From what are branchial pouches dervied?
derived from endoderm
What does the 1st branchial cleft develop into?
external auditory meatus
What does the 2nd thorugh 4th branchial clefts form?
temoprary cervical sinuses, which are obliterated by proliferation of 2nd arch mesenchyme
What is a cause of persistent cervical sinus?
branchial cleft cyst within lateral neck
What are the cartilage derivatives of branchial arch 1?
- Meckel's cartilage (Mandible, malleus, incus, sphenomandibular ligament)
What are the muscle derivatives of branchial arch 1?
- muscles of mastication (temporalis, masseter, lateral and medial pterygoids), mylohyoid, anterior belly of digastric, tensor tympani, tensor veli palatini, anterior 2/3 of tongue
What is the nerve derivative of branchial arch 1?
CN V2 and V3 (chewing)
What types of abnormalities may be seen with branchial arch 1 malformations?
- treacher Collins syndrome: 1st arch neural crest fails to migrate --> mandibular hypoplasia, facial abnormalities
What are the cartilage derivatives of branchial arch 2?
Reichert's cartilage
- stapes, styloid process, lesser horn of hyoid, stylohyoid ligament
What are the muscle derivatives of branchial arch 2?
muscles of facial expression --> stapedius, stylohyoid, posterior belly of digastric
What is the nerve derivative of branchial arch 2?
CN VII (facial expression)
What are the cartilage derivatives of branchial arch 3?
greater horn of hyoid
What are the muscle derivatives of branchial arch 3?
Stylopharyngeus
What is the nerve derivative of branchial arch 3?
CN IX (stylopharyngeus)
What types of abnormalities can be seen with branchial arch 3 malformations?
congenital pharyngocutaneous fistula --> persistence of cleft and pouch --> fistula between tonsillar area, cleft in lateral neck
What are the cartilage derivatives of branchial arches 4-6?
thyroid, cricoid, arytenoids, corniculate, cuneiform
What are the muscle derivatives of branchial arches 4-6?
4th arch: most pharyngeal constrictors; cricothyroid, levator veli palatini
6th arch: all intrinsic muscles of larynx except cricothyroid
What are the nerve derivatives of branchial arches 4-6?
4th arch: CN X (superior laryngeal branch -> swallowing)
6th arch: CN X (recurrent laryngeal branch -> speaking)
Which arches form the posterior 1/3 of the tongue?
arches 3 and 4
Which arch makes no major developmental contributions?
brancial arch 5
What does the 1st branchial pouch develop into?
- middle ear cavity, eustachian tube, mastoid air cells
- contribues to endoderm-lined structures of ear
What does the 2nd branchial pouch develop into?
- epithelial lining of palatine tonsil
What does the 3rd branchial pouch (dorsal wings) develop into?
- inferior parathyroids
- contributes to 3 structures (thymus, left and right inferior parathyroids)
What does the 3rd branchial pouch (ventral wings) develop into?
- thymus
What does the 4th branchial pouch develop into?
- superior parathyroids
What is a consequence of abberant development of 3rd and 4th pouches?
- DiGeorge syndrome --> leads to T-cell deficiency (thymic aplasia) and hypocalcemia (failure of parathyroid development)
What is MEN 2A?
Multpile endocrine neoplasia type 2
- adrenal medulla (pheochromocytoma)
- parathyroid (tumor): 3rd/4th pharygneal pouch
- parafollicular cells (medullary thryoid cancer); derived from neural crest cells; associated with 4th/5th pharyngeal pouches
Which cranial nerves are involved in taste? Which nucleus do they project to?
- CN VII, IX, X
- solitary nucleus
Which cranial nerves are involved in the sensation of pain in the tongue?
- CN V3, IX, X
Which cranial nerve is involved in motor of the tongue?
CN XII
Which branhcial arch forms the anterior 2/3 of the tongue?
posterior 13 of tongue?
- anterior 2/3 = 1st (CN VII)
- posterior 1/3 = 3rd (CN IX) and 4th (CN X)
From which myotomes are muscles of the tongue derived?
occipital myotomes
Describe the process of thryoid development.
- thyroid diverticulum arises from floor of primitive pharynx, descends into neck
- connected to tongue by thyroglossal duct, which normally disappears but may persist as pyramidal lobo f thyroid
- foramen cecum is normal remnant of thyroglossal duct
most common ectopic thyroid tissue site is the tongue
- thyroglossal duct cyst in midline neck and will move with swallowing (vs. persistent cervical sinus leading to branchial cleft cyst in lateral neck)
Describe a cleft lip
failure of fusion of the maxillary and medial nasal processes (formation of primary palate)
Describe a cleft palate
failure of fusion of the lateral palatine process, the nasal septum and/or the median palatine process (formation of secondary palate)
Describe the locations of the foregut, midgut and hindgut.
- foregut: pharynx to duodenum
- midgut: duodenum to transverse colon
- hindgut: transverse colon to rectum
What are the developmental defects of the anterior abdominal wall due to failure of the following:
- rostral fold closure:
- lateral fold closure:
- caudal fold closure:
- rostral fold closure: sternal defects
- lateral fold closure: omphalocele, gastroschisis
- caudal fold closure: bladder exstrophy
What is gastroschisis?
extrusion of abdominal contents through abdominal folds; not covered by peritoneum
What is omphalocele?
persistence of herniation of abdominal contents into umbilical cord, covered by peritoneum
What is dudoenal atresia?
failure of recanalize (trisomy 21)
- recanalization: the process of restoring flow to or reuniting an interrupted channel of a bodily tube
What is jejunal, ileal, colonic atresia?
due to vascular accident (apple peel atresia)
Describe the development of the midgut.
6th week - midgut herniates through umbilical ring

10th week - midgut returns to abdominal cavity and rotates around superior mesenteric artery
Describe tracheoesophageal fistula.
- abnormal connection between esophagus and trachea
- most common subtype is blind upper esophagus with lower esophagus connected to trachea.
- results in cyanosis, choking and vomiting with feeding, air bubblei n stomach on CXR, polyhydramnios, failure to pass NG tube into stomach, and pneumonitis
What is congenital pyloric stenosis?
- hypertrophy of the pylorus causes obstruction
-palpable "olive" mass in epigastric region and nonbilious projectile vomitting at ~2 weeks of age
- treatment is surgical incision
- occurs in 1/600 live births,o ften in 1st born males
Describe the embryology of the pancreas.
- derived from foregut
- dorsal and ventral pancreatic buds contribute to the pancreatic head, uncinate proecess (lower half of head), and main pancreatic duct
- doresal pancreatic bud becomes everything else (body, tail, isthmus, and accessory pancreatic duct)
Describe the embryology of the annular pancreas.
- ventral pancreatic bud abnormally encircles 2nd part of duodenum; forms a ring of pancreatic tissue that may cause duodenal narrowing
What is pancreas divisum?
ventral and dorsal parts fail to fuse at 8 weeks
What is the embryology of the spleen?
arises from dorsal mesentery (mesodermal) but is supplied by artery of foregut (celiac artery)
Describe the embryology of the kidney
1. proneprhos - week 4, then degenerates
2. mesoneprhos - functions as interim kidney for 1st trimester; later contributes to male genital system
3. metanephros - permanent; beginning first appear during 5th week of gestation' nephrogenesis continues through 32-36 weeks of gestation
Describe the embryology of ureteric bud.
derived from caudal end of mesonephros; gives rise to ureter, pelivises, and, through branching, calyces and collecting ducts; fully canalized by 10th week.
Describe the embryology of metanephric mesenchyme.
ureteric bud interacts with this tisue; interaction induces differentiation and formation of glomerulus and renal tubules to distal convoluted tubule
Which site is the last to canalize in the kidney?
uteropelvic juntion with kidney.
- most common site of obstruction (hydronephrosis) in fetus
What is Potter's syndrome?
bilateral renal agenesis --> oligohydramnios --> limb deformities, facial deformities, pulmonary hypoplasia
- caused by malformation of ureteric bud

* babies who can't "Pee" in utero develop Potter's"
What is a horeshoe kidney?
- inferior poles of both kidneys fuse
- as they ascend from pelvis during fetal development, horseshoe kidneys get trapped under inferior mesenteric artery and remain low in the abdomen
- kidney functions normally
Describe the embryology of females.
default development. mesonephric duct degenerates and paramesonephric duct develops
- mesonephric duct must be induced to remian; default program for embryo development is for paramesonephric duct to develop into female
Describe the embryology of males.
- SRY gene on Y chromosome - produces testis-determining factor (testes development)
- Mullerian inhibitory factor from Sertoli cells - supresses development of paramesonephric ducts
- increase adnrogens from Leydig cells - stimulates development of mesonephric ducts
What are the derivatives of mesonephric (wolffian) ducts?
- develops into male internal structures (escept prostate)
- seminal vesicles, epididymis, ejaculatory duct, and ductus deferens
What are the derivatives of paramesonephic (mullerian) ducts?
- develops into femal internal structures - fallopian tube, uterus, and upper 1/3 of vagina (lower 2/3 from urogenital sinus)
What is a bicornuate uterus?
- results from incoplete fusion of the paramesonephric ducts
- associated with urinary tract abnormalities and infertility
What are the male/female genital homologues for the genital tubercle?
male: female

-glans penis --> glans clitoris
- corpus cavernosum and spongiosum --> vestibular bulbs
what are the male/female genital homologues for the urogenital sinus?
male: female

- bulbourethral glands (of Cowper) --> greater vestibular glands (of Bartholin)
- prostate gland --> urethral and paraurethral glands (of Skene)
what are the male/female genital homologues for the urogenital folds?
male:female
- ventral shaft of penis (penile urethra)--> labia minora
what are the male/female genital homologues for the labioscortal swelling?
male:female
- scrotum --> labia majora
What is hypospadias?
abnomal opening of penile urethra on inferior (ventral) side of penis due to failure of urethral folds to close
- more common than epispadias, fix to prevent UTIs
What is epispadias?
abnormal opening of penile urethra on superior (dorsal) side of penis due to faulty positioning of genital tubercle
- exstrophy of the bladder is associated with epispadias
What are the female and male remnants of the gubernaculum (band of fibrous tissue)?
female: ovarian ligament and round ligament of uterus

male: anchors testes within scrotum
What are the female and male remnants of the processus vaginalis (evagination of peritoneum)?
- female: obliterates
- male: forms tunica vaginalis