Embryology 2 (TQ)

poxidicu's version from 2016-06-08 19:25

Aortic Arch Derivative

Question Answer
1stPart of maxillary artery (branch of external carotid)
Mn: 1st arch is maximal.
2nd (1)Stapedial artery and hyoid artery.
Second = Stapedial
3rd (2)Common Carotid artery and proximal part of internal Carotid artery
C is 3rd letter of alphabet.
4th (2)Left→ aortic arch
Right → proximal part of right subclavian artery
4th arch (4 limbs) = systemic.
6th (2)Proximal part of pulmonary arteries and (on left only) ductus arteriosus.
6th arch = pulmonary and the pulmonary-to- systemic shunt (ductus arteriosus).
What do the aortic arches become?Develop into the arterial system.
Path of Left/Right reccurent laryngeal nerve nerveR: under right subclavian
L: under ductus arteriosus

Neural Tube defects

Question Answer
Spina Bifida OccultaTuft of hair
Spina Bifida occulta MOAFailure of bony spinal canal to close but NO HERNIATION
MeningoceleMeninges herniate through spinal canal defect
MeningomyeloceleMeninges and spinal cord herniate through spinal canal defect

Fetal Post natal derivatives

Question Answer
Umblical VeinLigamentum teres Hepatis
UmbliLical arteriesmediaL umblical Ligament
Ductus arteriosusLigamentum arteriosum
Ductus venosusLigamentum venosum
Foramen ovaleFossa ovalis
AllaNtoisUrachus mediaN umblical ligament
NotochordNucleus pulposus of intervertebral disc

Urine from wrong places

Question Answer Column 3
Failure of urachus to obliteratePatent urachusUrine discharge from umblicus
Failure of urachus to obliterateVesicourachal diverticulumoutpouching of bladder
Failure of Vitelline duct to obliterateVitelline fistula meconium discharge from umblicus
Failure of Vitelline duct to obliterateMeckel diverticulumAttached to ileum with ectopic gastric mucosa leading to melena & periumbilical pain

Brachial Apparatus

Question Answer
Brachial cleftsEctoderm.
- Also called branchial grooves.
Brachial archesMesoderm (muscles, arteries) and
neural crest (bones, cartilage) → this is why bones of skull are neural crest
Brachial pouchesEndoderm
MnCAP covers outside to inside:
Clefts = ectoderm
Arches = mesoderm
Pouches = endoderm
What is the branchial apparatus?Composed of branchial clefts, arches, and pouches
- Also called pharyngeal apparatus.

Branchial Cleft Derivatives

Question Answer
1st clefExternal auditory meatus.
2nd thru 4th cleftTemporary cervical sinuses, which are obliterated by proliferation of 2nd arch mesenchyme
What does a persistent cervical sinus indicate?Persistent cervical sinus Ž branchial cleft cyst within lateral neck.

Branchial Pouch derivatives

Question Answer
1st pouch (3)Develops into middle ear cavity, eustachian tube, mastoid air cells.
1st pouch contributes to endoderm-lined structures of ear.
2nd pouch (1)Eithelial lining of palatine tonsil.
3rd pouch (3)Dorsal wings—develops into inferior parathyroids.
Ventral wings—develops into thymus
3rd pouch contributes to 3 structures (thymus, left andright inferior parathyroids).
4th pouchDorsal wings—develops into superior parathyroids
Mn (5)Ear, tonsils, bottom-to-top
1 (ear),
2 (tonsils),
3 dorsal (bottom for inferior parathyroids),
3 ventral (to = thymus),
4 (top = superior parathyroids)
Lowest pouch structures?3rd-pouch structures end up below 4th-pouch structures
DiGeorgeAberrant development of 3rd and 4th pouches → T-cell deficiency (thymic aplasia) and hypocalcemia (failure of parathyroid development)


Question Answer
Failure of fusion of the maxillary and medial nasal processeCleft Lip (formation of 1° palate)
Failure of fusion of the two lateral palatine processesCleft Palate (formation of 2° palate).
Failure of fusion of lateral palatine processes with the nasal septum and/or median palatine procesCleft palate (formation of 2° palate).


Question Answer
Foramen cecumNormal remnant of thyroglossal duct and common ectopic thyroid tissue site is the tongue
Thyroglossal duct cyst midline neckMove with swallowing
Persistent cervical sinus ->Branchial cleft cyst lateral neckDoes not move with swallowing


Question Answer
palpable olive mass in epigastric region with non bilious vomitingCongenital pyloric stenosis
Unicate process formed byVentral bud
body, tail, isthmus andaccessory pancreatic duct formed byDorsal pancreatic bud
Ventral and dorsal parts fail to fuse at 8 weeksPancreas divisum
Ventral pancreatic bud encircles 2nd part of duodenum forming a ring of pancreatic tissue causing duodenal narrowingAnnular pancreas


Question Answer
Rostral fold closureSternal Defects
Lateral fold closureOmphalocele, gastrochisis
Persistence of herniation of abdominal contents into umblical cord COVERED by peritoneumOmphalocele
Extrusion of adbominal contents through abdominal folds NOT COVERED by peritoneumGastrochisis
Caudall fold closureBladder extrophy
Failure to recanalize (eg trisomy 21)Duodenal Atresia
Due to vascular accident (apple peel atresia)Jejunal, ileal, colonic atresia
Midgut herniates through umblical ring6thweek
Returns to abdominal cavity +rotates around SMA10thweek


Question Answer
PronephrosWeek 4 and then degenerates
MesonephrosIst trimister kidney which later makes male genital system
MetanephrosPermanent 5th week which has ureteric bud & metanephric mesenchyme
Ureteric BudUreter, pelvcises calyces and collecting duct
Metanephric mesenchymeGlomerulus and renal tubules to distal convoluted tubule
Ureterpelvic JunctionLast to canalize & most common site of obstruction in fetus(eg Hydronephrosis)
Potters syndromeMalformationof ureteric Bud
Horse shoe kidneyGets trapped under inferior mesenteric artery (eg turner syndrome)

Genital embryo

SRY gene maketestis determining factor leading to mullerian inhibitory factor which STOP Paramesonephric ductsDEFAULT girls have paramesonephric duct
Mesonephric ducts develops male internal structuresParamesonephric ducts develop female internal structures(eg Bicornuate uterus - incomplete fusion of paramesonephric ducts)
SEED Seminal vesicles, Epididymis, Ejaculatory duct, ductus deferensFallopian tube, uterus, uppper 1/3 of vagina

Male/Female Homologs

Note: Main external structures are genital tubercle and urogenital sinus
Genital tubercleGlans penisGlans clitoris
Genital tubercle #2Corpus cavernosum and spongiosumVestibular bulbs
Urogenital sinusBulbourethral glands (of Cowper)Greater vestibular glands (of Bartholin)
Urogenital sinus #2Prostate glandUrethral and paraurethral glands (of Skene)
Urogenital foldsVentral shaft of penis (penile urethra)Labia minora
Labioscrotal swellingScrotumLabia majora
Gubernaculum (band of fibrous tissue) (remnant)Anchors testes within scrotum.Ovarian ligament + round ligament of uterus.
Processus vaginalis (evagination of peritoneum) (remnant)Forms tunica vaginalis.Obliterated HYDROCELE & INdirect Hernia
What stimulates differentiation into female/male structures?DHT (male)Estrogen (female)

Female Histology

Question Answer
VaginaStratified squamous epithelium, nonkeratinized
EctocervixStratified squamous epithelium, nonkeratinized
Endocervix Simple columnar epithelium
Transformation zoneSquamocolumnar junction (most common area for cervical cancer)
UterusSimple columnar epithelium with long tubular glands
Fallopian tubeSimple columnar epithelium, many ciliated cells, a few secretory (peg) cells
Ovary, outer surfaceSimple cuboidal epithelium (germinal epithelium covering surface of ovary)

Ovarian Cysts

Question Answer
Follicular cyst?
Asscs (2)
Distention of unruptured graafian follicle.
May be associated with hyperestrogenism and endometrial hyperplasia.
Most common ovarian mass in young women.
Corpus luteum cystHemorrhage into persistent corpus luteum.
Commonly regresses spontaneously.
Theca-lutein cyst
Cause? Assc (2)
Often bilateral/multiple. Due to gonadotropin stimulation.
Associated with choriocarcinoma and moles.
Hemorrhagic cystBlood vessel rupture in cyst wall. Cyst grows with ↑ blood retention;
Usually self-resolves.
Dermoid cystMature teratoma. Cystic growths filled with various types of tissue such as fat, hair, teeth, bits of bone, and cartilage.
Endometrioid cystEndometriosis within ovary with cyst formation. Varies with menstrual cycle.
When filled with dark, reddish-brown blood it is called a “chocolate cyst.
"Chocolate cyst"Endometrioid cyst
Most common ovarian cyst?Follicular cyst
EpispadiasFaultypositioning of genital tubercle
HypospadiasFailure of urethral folds to close

SRY gene

Question Answer
Y chromsome hasSRY GENE
Sry gene makesTestis determining factor
Testis determining factor simulatesTestes
Testes stimulateSertoli cells & Leydig cells
Sertoli cell makesAnti-mullerian hormone which causes degenration of paramesonephric duct which are female internal genitalia.(Anti-mullerian hormone deficiency)
Leydig cell makesTestosterone which leads to male internal genetalia formation
Tesosterone to DHT makesMale external genitalia & prostate (5a-reductase deficiency)
5a-reductase deficiencymale internal genitalia, ambiguous external genitalia until puberty
Anti-mullerian hormone deficiencyPt presents with both male and female internal genitalia and male external genitalia


Question Answer
Weber Lateralizes Left & Rinne both ears AC > BCsenorinerual loss Right ear
Weber Lateralizes Right & Rinne both ears AC > BCsensorineural loss Left ear
Rinne Left BC>AC & Weber's lateralized to the leftconductive loss on the left
Rinne Right BC>AC & Weber's lateralized to the rightconductive loss on the right


SyphilisTreponema PallidiumSingle Painless ulcer at innoculation site with heaped up border and clean baseVDRL/RPR/ Darkfield microscopy
HerpesHerpes SimplexMultiple painful superficial vesicles or ulcerations with erythematous baseTzanck Smear/PCR
ChancroidHaemophilus DucreyiDeep purulent painful ulcers with matted suppurative lymphadenitisGram Stain/PCR
Granuloma InguinaleKlebsiella GranulomatisPainless progressive red serpiginous ulcerative lesions without lymphadenopathyGram Stain culture/Biopsy-Donovan bodies