Embryology

Question 1

Sonic hedgehog

Answer 1

Produced at base of limbs in zone of polarizing activity

Patterning along AP axis and CNS development

Mutation can cause holoprosencephaly

Question 2

Wnt-7

Answer 2

Produced at apical ectodermal ridge at distal end of each developing limb

Needed for proper organization on dorsal ventral axis

Question 3

FGF gene

Answer 3

Produced at apical ectodermal ridge

Stimulates mitosis of underlying mesoderm for limb lengthening

Question 4

Hox genes

Answer 4

Segmental organization of embryo in cranial caudal axis

Codes for transcription factors

Mutations lead to appendages in wrong location

Question 5

When does blastocyst implant?

Answer 5

6 days

This is when hCG secretion begins

Question 6

Week 2

Answer 6

Bilaminar disc - epiblast and hypoblast layers

Question 7

Week 3

Answer 7

Gastrulation - 3 germ layers

Epiblast invaginates and cells go thru primitive steak to form three layers

Original epiblast becomes ectoderm

Question 8

Week 4

Answer 8

Heart beats

Upper and lower limb buds form

4 limbs and 4 heart chambers

Question 9

Week 6

Answer 9

Can hear fetal heart activity on ultrasound

Midgut herniated thru umbilical ring to keep growing

Question 10

Week 8

Answer 10

Fetal movements start

8= gait

Question 11

Week 10

Answer 11

Genitalia can be seen

“Ten- italia”

Also when midgut returns to abdomen and rotates 270 degrees counterclockwise on SMA

Question 12

What are the fetal and maternal components of placenta?

Answer 12

Cytotrophoblasts - inner layer of chorionic villi

Syncytiotrophoblasts - outer layer of chorionic villi that make hormones (hCG) and has no MHC expression to dec chance of immune attack

Mom - deciduous basalis from endometrium

Question 13

What is the most common configuration of monozygotic twins?

Answer 13

Monochorionic diamniotic

Split between morula and blastocyst stages before implantation

Question 14

Urachus

Answer 14

Connects fetal bladder to umbilicus

Forms from the allantois

Question 15

Vitellius duct

Answer 15

Connects yolk sac to midgut lumen

Obliterated in 7th week

Question 16

Stages of Lung Development

Answer 16

1- embryonic (4-7 wks) - bud, trachea, bronchi

2- pseudoglandular (5-17 wks) - terminal bronchioles form from endodermal tubules and modest capillary network

3- canalicular (16-25 wks) - respiratory bronchioles and alveolar plus more prominent capillary network

**can breath at 25 wks

4- saccular (26 to birth) - alveolar sacs with only primary septation, surfactant at 26 wks

5- alveolar (36 wks to 8 yo) - secondary septation and increased number of alveoli

Question 17

Cleft Lip v Cleft Palate

Answer 17

Lip- failure of maxillary and medial nasal processes to fuse

Palate - failure of two lateral palatine shelves to fuse OR palatine shelves do not fuse with nasal septum / median palatine shelf