Embryology

Question 1

Sonic hedgehog gene

Answer 1

BASE OF LIMBS - anterior/posterior axis, CNS development (holoprosencephaly)

Question 2

Wnt-7 gene

Answer 2

Apical ectodermal ridge — distal end of limbs – dorsal/ventral axis

Question 3

FGF gene

Answer 3

Apical ectodermal ridge — lengthening of limbs

Question 4

Homebox (hox genes)

Answer 4

Craniocaudal organization — mutations cause appendages at wrong locations (structural defects)

Question 5

Early fetal development

Answer 5

Week 1 (hCG, blastocyst) – Week 2 (bilaminar disc) – Week 3 (trilaminar disc, gastrulation) – Week 4 (heart beat, limb buds) – Week 6 (cardiac activity) – Weeks 3-8 (organogenesis, neural tube –TERATOGENS) – Week 10 (genitalia)

Question 6

Surface ectoderm

Answer 6

Epidermis, adenohypophysis, epithelial linings of mouth, lens of eye, anal canal below pectinate line, glands

Question 7

Neuroectoderm

Answer 7

CNS and retina, optic nerve, spinal cord

Question 8

Neural crest

Answer 8

Ca MOTEL PASS – Craniofacial bones, Melanocytes, Odonocytes, Tracheal cartilage, Enterochromaffin cells, Laryngeal cartilage, Parafollicular cells/Pia, All ganglia/Adrenal medulla/Arachnoid, Schwann cells, Spiral membrane

Question 9

Mesoderm

Answer 9

Middle layer - muscle, bone, CT, peritoneum, spleen, CV structures, adrenal cortex, etc. — VACTERL defects (Vertebral, Anal atresia, Cardiac, Tracheo-Esophageal fistula, Renal, Limb)

Question 10

Endoderm

Answer 10

Gut tube lining, urethra, luminal epithelial derivatives

Question 11

Agenesis

Answer 11

No organ due to no primordial tissue

Question 12

Aplasia

Answer 12

No organ but presence of primordial tissue

Question 13

Hypoplasia

Answer 13

Incomplete organ development

Question 14

Deformation

Answer 14

Extrinsic disruption after embryonic period –REVERSIBLE

Question 15

Disruption

Answer 15

Breakdown of previously normal tissue – IRREVERSIBLE

Question 16

Malformation

Answer 16

Intrinsic disruption during weeks 3-8

Question 17

Sequence

Answer 17

Abnormalities from a single embryologic event

Question 18

Dizygotic twins

Answer 18

2 eggs, 2 sperm, 2 separate amniotic sacs, 2 separate placents

Question 19

Monozygotic twins

Answer 19

1 fertilized egg that splits into 2 zygotes — days 0-4 (dichorionic diamniotic) — days 4-8 (monochorionic diamniotic) — days 8-12 (monochorionic monoamniotic) — after day 13 (conjoined)

Question 20

Placenta components

Answer 20

Cytotrophoblast (inner layer – fetal), Syncytiotrophoblast (outer layer that secretes hCG – fetal) —– Decidua basilis (from endometrium – mother)

Question 21

Umbilical cord

Answer 21

2 arteries (deoxygenated blood from fetal internal iliacs to placenta) — 1 vein (oxygenated blood from placenta to fetus) – derived from allantois

Question 22

Urachus

Answer 22

3rd week – duct between fetal bladder and yolk sac — patent (total failure of obliteation - urine from umbilicus) – urachyl cyst (partial failure, cyst between umbilicus and bladder) – veiscourachal diverticulum (slight failure - outpouching of bladder)

Question 23

Vitelline duct

Answer 23

7th week this is obliterated (conects yolk sac to midgut lumen) – vitelline fistula (duct fails to close, meconium discharge from umbilicus) – Meckel’s diverticulum (partial closure)

Question 24

Aortic arch derivatives

Answer 24

1 (maxillary artery) – 2 (stapedial and hyoid artery) – 3 (common carotid and internal carotid) – 4 (aortic arch on L and subclavian on R) – 6 (pulmonary arteries and ductus arteriosus)

Question 25

Branchial apparatus

Answer 25

CAP outside to inside -- Clefts (ectoderm), Arches (mesoderm), Pouches (endoderm)

Question 26

Branchial clefts

Answer 26

1 (external auditory meatus), 2-4 (temporal cervical sinuses)

Question 27

Branchial arches

Answer 27

CN 5 - arch 1 - M --- CN 7 - arch 2 - S --- CN 9 - arch 3 - pharyngaeal --- CN 10 - arches 4-6 - speak and swallow

Question 28

Branchial pouches

Answer 28

Ear, tonsils, bottom to top ---- 1 (ear), 2 (tonsils), 3 dorsal (bottom parathyroids) and ventral (to = thyums), 4 (top parathyroids)

Question 29

Cleft lip

Answer 29

Failure of fusion of maxillary and medial nasal processes

Question 30

Cleft palate

Answer 30

Failure of fusion of two lateral palatine processes or lateral palatine processe with nasal septum

Question 31

Congenital torticollis

Answer 31

Swelling in baby neck that doesn't move when swallowing -- baby holds head toward affect SCM and cries when neck is pushed to opposite side --- due to birth trauma or malposition of head in utero

Question 32

Female genital embryology

Answer 32

Default development -- Paramesonephric (Mullerian) duct becomes fallopian tubes, uterus, and upper 1/3 of vagina -- Mesonephric (Wolffian) duct degenerates

Question 33

Male genital embryology

Answer 33

SRY gene --> Testes determining factor --> Sertoli cells --> Mullerian inhibitory factor Testes determining factor --> Leydig cells --> androgens --> stimulate Wolffian duct --> SEED (Seminal vesicles, Epididymis, Ejaculatory duct, Ductus deferens)

Question 34

No sertoli cells or lack of MIF

Answer 34

Male and female internal genitalia and male external genitalia

Question 35

5a-reductase deficiency

Answer 35

Male internal genitalia, ambiguous external genitalia until puberty

Question 36

Mullerian duct anomalies

Answer 36

Septate uterus (incomplete resorption of septum), Bicornuate uterus (incomplete fusion of Mullerian ducts), Uterus didelphys (complete failure of fusion - double everything)

Question 37

Genital tubercule

Answer 37

``` Glans clitoris (F) -- Glans penis (M) Vestibular bulbs (F) -- Corpus cavernosum and spongiosum (M) ```

Question 38

Urogenital sinus

Answer 38

Greater vestibular glands of Bartholin (F) -- Bulbourethral glands of Cowper (M) Urethral and paraurethral glands of Skene (F) -- Prostate gland (M)

Question 39

Urogenital folds

Answer 39

Labia minora (F) -- Ventral shaft of penis/urethra (M)

Question 40

Labioscrotal swelling

Answer 40

Labia majora (F) -- Scrotum (M)

Question 41

Imperforate hymen

Answer 41

Obstruction of female genital tract -- at birth (vaginal secretions cause mucocolpos) -- at menarche (cyclic pelvic pain, hematocolpus) -- primary amenorrhea in pt with fully developed secondary sex characteristics

Question 42

Hypospadias

Answer 42

Abnormal opening on ventral penis due to failure of urethral folds to fuse -- MOST COMMON -- inguinal hernia, cryptochidism

Question 43

Epispadis

Answer 43

Abnormal opening on dorsal penis due to faulty genital tubercle -- exstrophy of bladder -- Episadis = pEE in Eye

Question 44

Gubernaculum

Answer 44

Anchors testes in male --- ovarian ligament + round ligament in female

Question 45

Processus vaginalis

Answer 45

Tunica vaginalis in males