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1
Q

Cardiac looping

A

heart beats at week 4

primary heart tube establishes L-R polarity through dynein movement (Kartagener’s = dextrocardia)

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2
Q

Atria formation

A

Septum primum forms, then detaches at each end to stay in the middle (top hole = foramen secundum, bottom = foramen primum)
Septum secundum first covers most of foramen secundum, then all of foramen primum
Remaining hole of foramen secundum is the foramen ovale (septum primum serves as valve)

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3
Q

Ventricle formation

A

interventricular foramen is closed by the fusion of muscular septum and aorticopulmonary septum (comes from neural crest!)

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4
Q

Outflow tract

A

neural crest cells and endocardial cell migrations allow for travel and bulbar ridges that form aorticopulmonary septum

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5
Q

Valve development

A
  • aortic/pulmonary valves: endocardial cushion of outflow tract
  • mitral/tricuspid: endocardial cushion of AV canals
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6
Q

Fetal erythropoiesis locations

A

3-8 wks: yolk sac
6 wks - birth: liver***
10-28 weeks: spleen
18 weeks - birth: bone marrow

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7
Q

Fetal circulations (give 3 shunts)

A

Ductus venosus: umbilical vein to IVC (bypass portal system)
Foramen ovale: RA to LA (bypass cardiopulmonary system)
Ductus arteriosus: Left PA to descending aorta (bypass lungs)

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8
Q

How can the closure of the DA be manipulated? (accel closure, prevent closure)

A

Accel closure: indomethacin, NSAIDs (block PGs)

Prevent closure: prostaglandins E1, E2

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9
Q

Notable vessels to ligaments

A

Allantois - urachus: median umbilical ligament
Notochord: nucleus pulposus
Umbilical arteries: medial umbilical ligaments
Umbilical vein: ligamentum teres hepatis (falciform ligament)

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10
Q

Thyroid diverticulum

A

primitive pharynx –> descends to neck
(connected to tongue by thyroglossal duct - if duct persists, become pyramidal lobe of thyroid)
most common site of ectopic thyroid tissue: tongue

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11
Q

Thyroglossal duct cyst

A

Anterior midline neck mass, moves with swallowing

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12
Q

Anterior abdominal wall defects

A

rostral (head) folds: sternal defects
lateral folds: omphalocele (sealed by peritoneum), gastroschisis
caudal (butt) folds: bladder exstrophy

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13
Q

Duodenal atresia is seen with what genetic condition?

A

Trisomy 21! Arises due to failure of recanalization. Look for double bubble sign and bilious vomiting (or polyhydramnios)

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14
Q

A vascular accident early in development causes what abdominal abnormality?

A

Jejunal/ileal/colonic atresia
Can be complete obliteration of intestine
Look for polyhydramnios

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15
Q

Midgut development (ampulla of Vader to proximal 2/3 of transverse colon)

A

6th week: herniates through umbilical ring

10th week: returns to abdominal cavity, rotates around SMA

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16
Q

Pancreas development

A

Ventral bud = uncinate process and main duct
encircles duodenum in annular pancreas, can cause obstructive symptoms
Dorsal bud: body, tail, isthmus, accessory duct

Pancreatic divisum: failure of fusion of buds (which normally occurs at 8 weeks), can be a cause of pancreatitis

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17
Q

Notochord function and development

A

induces overlying ectoderm to become neuroectoderm –> neural plate –> neural tube and neural crest cells

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18
Q

Regional specification of developing brain (3 regions become 5 regions)

A

Forebrain:
telencephalon: hemispheres/lateral ventricle
diencephalon: thalamus/third ventricle
Midbrain:
mesencephalon: midbrain/aqueduct
Hindbrain:
metencephalon: pons/cerebellum/4th ventricle
myelencephalon: medulla/lower 4th ventricle

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19
Q

CNS/PNS progenitors

A

neuroectoderm –> CNS, glial cells (ependymal, oligodendroglial, astrocytes)
neural crest –> PNS neurons, Schwann cells
mesoderm –> microglia (come from macrophages!)

20
Q

Neural tube defects

A

Failure of cranial neuropore to close: anencephaly
Failure of caudal neuropore to close: spina bifidas
Spina bifida occulta: bones don’t close, no herniation, intact dura (normal AFP)
Meningocele: meninges herniates (can be caused by teratoma)
Myelomeningocele: meninges and neural tissue herniate

21
Q

Posterior fossa malformations

A

Chiari Arnold II: herniation of cerebellar tonsils through the foramen magnum, often seen myelomeningocele

Dandy-Walker: agenesis of vermis with cystic enlargement of 4th ventricle, seen with hydrocephalus and spina bifida

22
Q

Synringomyelia

A

cystic cavity within spinal cord, leads to damage of anterior commisures and subsequent cape-like distribution of pain/temp loss
Most often occurs at C8-T1

23
Q

Tongue development

A

1st/2nd arches: anterior 2/3 (CN V3, CN VII)
3rd/4th arches: posterior 1/3 (CN IX, CN X)

Motor: CN XII (except CN X to palatoglossus)

24
Q

Renal development

A

Pronephros: week 4, then degenerates (turns into nothing!)
Mesonephros: interim kidney for 1st trimester (then, contributes to male genitals)
Metanephros: appears in Wk 5, forms permanent kidney
- ureteric bud: caudal (butt) end of metanephros, becomes ureter, pelvises, calyces, CDs
- metanephric mesenchyme: glomerulus through DCT

Ureteropelvic junction = last to canalize, most common site of obstruction (hydronephrosis)

25
Oligohydramnios/Potter sequence
ADPKD, obstructive uropathy causes decreased amniotic fluid Compression of fetus --> limb deform, facial anomalies --> compression of chest/lack of fluid in lungs --> pulmonary hypoplasia
26
Kidney abnormalities: Horseshoe kidney Multicystic dysplastic kidney Duplex collecting system
inferior poles fuse --> trapped under IMA --> kidneys remain low in abdomen (increased risk of obstruction, hydronephrosis, renal stones, infection, etc.) abnormal interaction between ureteric bud and metanephric mesenchyme --> nonfunctional kidney of cysts and connective tissue Bifurcation of ureteric bud creates Y-shaped bifid ureter. Assoc w/ vesciureteral reflux and/or ureteral obstruction (increased risk of UTIs)
27
Genes involved in early development (Shh, Wnt-7, FGF, Hox)
Shh - anterior-posterior patterning, ZPA Wnt-7 - dorsal-ventral patterning, apical ectodermal ridge FGF - stimulates mitosis of mesoderm, limb lengthening Hox - segmental organization, transcription factors
28
Early development (give events by week)
Wk 1: implantation of blastocyst, secretion of bHCG Wk 2: bilaminar disc Wk 3: trimlaminar disc (three germ layers) Wk 4: neural tube closure, heart beats Wk 4-8: organogenesis, susceptible to teratogens! Wk 6: heart visible Wk 10: sex-distinguishable genitalia
29
Ectoderm derivatives (surface ectoderm, neuroectoderm, neural crest)
Surface ectoderm: epidermis, oral cavity, ears, nose, glands (parotid, sweat, mammary), *cranipharyngioma Neuroectoderm: Brain, spinal cord, optic nerve, posterior pituitary Neural crest: PNS, melanocytes, adrenal medulla (chromaffin), skull, **aorticopulmonary system
30
Mesoderm derivatives
Muscle, bone, connective tissue, CV structures, lymph, blood, VACTERL: Vertebral defects, Anal atresia, Cardiac defects, Tracheo-Esophageal fistula, Renal defects, Limb defects
31
Endoderm derivatives
Gut tube epithelium, urethra (from urogenital sinus), lungs, liver, GB, pancreas, eustachian tube, parathyroid
32
Notable teratogens, give their effects ``` Aminoglycosides Lithium Phenytoin Tetracyclines Warfarin ```
Aminoglycosides - Cn VIII toxicity Lithium - Ebstein anomaly (atrialized R ventricle, disp of tricuspid) Phenytoin - fetal hydantoin (cleft palate, cardiac defects, fingernail hypoplasia) Tetracyclines - discolored teeth Warfarin - bone deformities, fetal hemorrhage, abortion
33
Twinning
0-4 days: Di/di 4-8 days: Mono/di 8-12 days: Mono/mono >13 days: conjoined Dizygotic (80%) - 2 eggs fertilized separately, di/di
34
Placental cells
Fetal: syncytiotrophoblasts - decreased MHC-1 reduces chance of attack by maternal immune system Maternal: decidua basalis - endometrium derivative, maternal blood flows in lacunae
35
Umbilical cord anatomy
1 vein (blood from mom to fetus) 2 arteries (1 from each internal iliac of fetus to mom) Surrounded by Wharton jelly Derived from allantois
36
Urachus
Yolk sac becomes allantois becomes urachus (duct from fetal bladder to yolk sac) Patent urachus = failure to obliterate, urine discharge from umbilicus Urachal cyst = partial failure to obliterate, fluid-filled cavity lined with uroepithelium (infection, adenocarcinoma) Vesicourachal diverticulum = slight failure of urachus to obliterate, leads to outpouching of bladder
37
Vitelline duct
Goes from midgut lumen to yolk sac Vitelline fistula = meconium discharge from umbilius Meckel diverticulum = partial closure, leads to patent portion with gastric/pancreatic tissue
38
Aortic arches (develop into arterial system)
``` 1st = maxillary artery 2nd = stapedial artery, hyoid artery 3rd = common carotid, proximal internal carotid 4th = aortic arch (left), R subclavian (right) 6th = pulmonary arteries, ductus arteriosus (left) ```
39
Branchial clefts (ectoderm!)
1st: EAM 2nd-4th = temporary cervical sinuses persistent cervical sinus become branchial cleft cyst!
40
Branchial arches
1st (mandibular) = muscles of mastication, CN V2/V3 (Treacher Collins = mandibular hypoplasia) 2nd (pharyngeal) = stapes, styloid, CN VII 3rd = stylopharyngeus, CN IX 4th-6th = cartilages of neck (thyroid, cricoid, etc.), CN X, CN X
41
Branchial pouches (endoderm!)
``` 1st = middle ear, eustachian tube 2nd = tonsils 3rd = inferior parathyroid, thymus (end up below 4th pouch structures) 4th = superior parathyroid ``` DiGeorge: abnormal 3rd and 4th MEN 2A: germline RET mutation (neural crest cells) --> medullary thyroid, pheochromocytoma (adrenal medulla) 4th pouch, parathyroid 3rd/4th pouches
42
Genital embryology
Female: mesonephric duct degenerates, paramesonephric (Mullerian ) --> internal structures Male: SRY = MIF, leads to suppression of paramesonephrics, Leydig (testosterone) stimulates mesonephric (Wolffian) to internal structures Low MIF/No Sertoli = both male/female internal, only male external 5a-reductase def (no DHT) = male internal, ambiguous external
43
Male/female homologs (male = DHT, female = estrogen)
tubercle --> glans (penis, clitoris) urogenital sinus --> Cowper/prostate or Bartholin/Skene glands urogenital folds --> ventral shaft or labia minora labioscrotal swelling --> scrotum or labia majora
44
Spadias
``` Hypo = ventral opening, failure of urethral folds to fuse Epi = faulty positioning of genital tubercle (exstrophy of bladder) ```
45
Descent of ovaries and testes
Gubernaculum (band of fibrous tissue) = anchors testes in scrotum, also forms ovarian ligament + round ligament Processus vaginalis = forms tunica vaginalis, obliterated in females

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