Embryology*

Question 1

When is the pre embryonic period?

Answer 1

0-2.5 weeks

Question 2

When is the Embryonic period?

Answer 2

2.5-8 weeks

Question 3

When is the fetal period?

Answer 3

8 weeks - 9 months

Question 4

what period does gastrulation and neurulation take place?

Answer 4

Pre embryonic period.

Question 5

What is gastrulation?

Answer 5

When the 3rd Germ layer is established.

Epiblast cells move and displace the hypoblast cells.

Question 6

What are the three embryonic layers?

Answer 6

Ectoderm, Mesoderm, Endoderm.

Question 7

What is neurulation?

Answer 7

It is the first major event in organogenesis.

Results in the formation of the neural tube. which gives rise to the CNS. Another germ layer develops.

Question 8

What is the process of neurulation?

Answer 8

The ectoderm thickens in the midline above the notochord (neural plate)

A crease develops along the axis (neural groove).

Neural folds move together. Fusing to form a neural tube. Cells on the crest if the groove are called neural crest cells.

Question 9

What does gastrulation do?

Answer 9

It lays down the basic structural framework of the embryo and sets the stage for organogenesis.

By the end of the embryonic period, all adult organ systems are recognizable.

Question 10

What are neural crest cells?

Answer 10

They differentiate into craniofacial cartilage and bones.

Question 11

How many pharyngeal arches are there in the neck region?

Answer 11

There are 6 pairs of pharyngeal arches in the neck region.

Question 12

What does each arch have?

Answer 12

• Cartilage
• Artery
• Mesoderm component
• Cranial Nerve (arch-specific)
• Skeletal component.

Question 13

Name the nerves of each Pharyngeal Arch.

Answer 13

Arch 1 = trigeminal nerve (CN V)

Arch 2 = facial nerve (CN VII)

Arch 3 = Glossopharyngeal nerve (CN IX)

Arch 4 = vagus nerve (CN X)

Question 14

Name the muscles of each pharyngeal arch.

Answer 14

Arch 1 = Muscles of mastication

Arch 2 = Muscles of facial expression

Arch 3 = Stylopharyngeus

Arch 4 = Pharyngeal constrictors, soft palate & intrinsic muscles of the larynx.

Question 15

Explain the development of the tongue.

Answer 15

The mucosa of the anterior 2/3rd of the tongue formed from lateral lingual swellings of 1st arch.

Tuberculum impar of 2nd arch forms taste buds of anterior 2/3rds.

The hypobranchial eminence of 3rd arch forms posts 1/3rd mucosa.