Embryology

Question 1

When does the face begin to develop? What are the parts of the developing face? What are those parts derived from?

Answer 1

4th week

• Facial prominences begin to form (5 prominences)
• Max and mandibular processes (4) and a single frontonasal process
• they are derived from the 1st branchial arch
• Mandibular processes merge eventually > mand, lower face and tongue
• Meckel’s cartilage malleus and incus (1st arch)
• 2nd arch (reickerts cartilage) > stapes and styloid process

Question 2

What is the number 1 branchial cleft anomaly?

Answer 2

Persistent remnants of the 2nd branchial cleft&raquo_space; cysts (90-95% of branchial arch anomalies)

Question 3

Brain, eyes, nose when do they begin to emerge? Describe the process

Answer 3

4th week - Brain lobes are clearly delineated, optic cups form. The frontonasal process intervenes so basic eyes are still 180 degrees apart
5th week - nasal placodes and olfactory grooves form, also 1st arch > m of mastication and 2nd > m of facial expression

Question 4

At what point does bone formation begin? What does this mark?

Answer 4

8th week, marks the end of the embryonic period

- the fetus is now less susceptible to teratogenic insults