Important genes of embryogenesis/Early Fetal Devo EC

Question 1

Produced at the base of limbs in zone of polarizing activity. Involved in patterning along anterior-posterior axis. Involved in CNS development; mutation can cause holoprosencephaly.

Answer 1

Sonic hedgehog gene

Question 2

Produced at apical ectodermal ridge (thickened ectoderm at distal end of each developing limb). Necessary for proper organization along dorsal-ventral axis.

Answer 2

Wnt-7 gene

Question 3

Produced at apical ectodermal ridge. Stimulates mitosis of underlying mesoderm, providing for lengthening of limbs.

Answer 3

FGF gene

Question 4

Involved in segmental organization of embry in craniocaudal direction. Mutations cause appendages in wrong locations.

Answer 4

Homeobox (Hox) genes

Question 5

Week 1 of embryogenesis

Answer 5

Zygote (day 2), Morula (day 3), Blastocyst (day 5), Implantation (day 6)

hCG secretion begins after implantation (+ pregnancy test)

Question 6

Week 2 of embryogenesis

Answer 6

Bilaminar disc (Epiblast [will become 3 layers] and Hypoblast [becomes yolk sac])

“2 weeks=2 layers”

Question 7

Week 3 of embryogenesis

Answer 7

Trilaminar disc/Gastrulation

Primitive streak, Notochord, Mesoderm organization, Neural plate begin to form

“3 weeks=3 layers”

Question 8

Embryonic period (weeks 3-8)

Answer 8

Neural tube formed by neuroectoderm and closes by week 4

Organogenesis

Extremely susceptible to teratogens

Question 9

Week 4 of embryogenesis

Answer 9

Heart begins to beat

Limb buds begin to form

“4 weeks=4 limbs”

Question 10

Week 8 of embryogenesis

Answer 10

Start of fetal period

Fetal movement/looks like a baby

Question 11

Week 10 of embryogenesis

Answer 11

Genitalia have male/female characteristics

Question 12

Process that forms trilaminar embryonic disc. Establishes the ectoderm, mesoderm, and endoderm germ layers. Starts with the epiblast invaginating to form the primitive streak.

Answer 12

Gastrulation

Question 13

What are the three divisions of the ectoderm?

Answer 13

Surface ectoderm
Neuroectoderm
Neural crest

Question 14

Adenohypophysis (from Rathke’s pouch), lens, epithelial lining of oral cavity, sensory organs of ear, olfactory epithelium. Epidermis, anal canal below pectinate line, parotid, sweat, and mammary glands.

Answer 14

Surface ectoderm

Question 15

Craniopharyngioma

Answer 15

Benign Rathke’s pouch tumor with cholesterol crystals and calcifications

Question 16

Brain, retina/optic nerve, and spinal cord

Answer 16

Neuroectoderm

Question 17

PNS, Melanocytes, Chromaffin cells of adrenal medulla, Parafollicular cells of thyroid, Pia and Arachnoid, Bones of skull, odontoblasts, aorticopulmonary septum.

Answer 17

Neural crest

Question 18

Muscle, bone, CT, Serous lining of body cavities, spleen, CV structures, Lymphatics, Blood, Wall of gut tube, Wall of bladder, Urethra, Vagina, Kidneys, Adrenal cortex, Dermis, Gonads

Answer 18

Mesoderm

Question 19

Mesoderm defects

Answer 19

VACTERL

Vertebral defects
Anal atresia
Cardiac defects
T-E fistula
Renal defects
Limb defects (bone and muscle)

Question 20

Induces ectoderm to form neuroectoderm (neural plate). It’s only postnatal derivative is the nucleus pulposus.

Answer 20

Notochord (mesoderm)

Question 21

Gut tube epithelium (including anal canal above pectinate line), lungs, liver, gallbladder, pancreas, eustachian tube, thymus, parathyroid, thyroid follicular cells)

Answer 21

Endoderm

Question 22

Absent organ due to absent primordial tissue

Answer 22

Agenesis

Question 23

Absent organ despite primordial tissue

Answer 23

Aplasia

Question 24

Extrinsic disruption; occurs after the embryonic period

Answer 24

Deformation

Question 25

Incomplete organ development; primordial tissue present.

Answer 25

Hypoplasia

Question 26

Intrinsic disruption; occurs during embryonic period (weeks 3-8)

Answer 26

Malformation