Embyological Basis Of Head And Neck

Question 1

When does the blastocyst implantation occurs.

Answer 1

Week 2.

They also form the bilaminar disc (epiblast + hypoblast)

Question 2

What is gastrulation? And whin does it happen?

Answer 2

Formation of endoderm and mesoderm as a result of epiblast migration.
This happen in week 3

Question 3

Appearance of the branchial (pharyngeal) arches occur during.

Answer 3

4-5th week

Question 4

This arch in human neither never formed or regressed early.

Answer 4

5th arch

Question 5

What does the arch apparatus consist of?

Answer 5

• branchial arches.
• branchial clefts.
• branchial membrane.
• pharyngeal pouches.

Question 6

The mesencymal core consist of.

Answer 6

Mesoderm + Neural crest cells

Question 7

What is the mesenchymal derivatives of cartilages?

Answer 7

• neural crest cells (1 - 3).

- lateral plate mesoderm (4 and 6)

Question 8

Develops from paraxial mesoderm.

Answer 8

Skeletal muscles

Question 9

What is the derivative of external acoustic meatus?

Answer 9

The 1st branchial cleft

Question 10

What forms the neck contour?

Answer 10

Formed when the 2nd arch overgrow the 3rd and 4th arches

Question 11

A defect when 2nd arch fails to overgrow the 3rd and 4th completely.

Answer 11

Lateral cervical cyst

Question 12

The 1st branchial membrane gives rise to.

Answer 12

Eardrums

Question 13

1st pouch forms.

Answer 13

auditory tube and middle ear.

Question 14

Pouches are lined by.

Answer 14

Endoderm

Question 15

2nd pouch forms.

Answer 15

The palatine tonsils

Question 16

3rd pouch forms.

Answer 16

Thymus lobules (ventral wing) and inferior parathyroid (dorsal wing) glands

Question 17

4th pouch forms.

Answer 17

Superior parathyroid (dorsal wing) + parafollicular cells of thyroid (ventral wing) glands

Question 18

Failure of 3rd and 4th pouches to differentiate.

Answer 18

DiGeorge syndrome (also small deletion of ch.22)

Question 19

What are the derivatives of cartilage of 2nd pharyngeal arch?

Answer 19

The ventral end: the lesser cornu and the upper part of the body of the hyoid bone.
The dorsal end: the stapes, styloid process and stylohyoid ligament

Question 20

What are the 5 facial processes that form by end of week 5?

Answer 20

• unpaired frontonasal process.
• 2 maxillary processes.
• 2 mandibular processes.

Question 21

Maxillary and mandibular processes derived from.

Answer 21

The 1st arch

Question 22

Dorsum and apex of the nose formed from.

Answer 22

Frontonasal process

Question 23

Ectodermal thickenings

Answer 23

Nasal placodes

Question 24

What is frontonasal dysplasia?

Answer 24

Facial congenital anomaly caused by excess of tissue in frontonasal process. (Widely spaced eyes, broad nose, vertical midline groove)

Question 25

Results from failure of merging of maxillary and nasal processes.

Answer 25

Cleft lip

Question 26

Defect suppressing the growth of the hillocks.

Answer 26

Microtia

Question 27

Accessory appendages.

Answer 27

Auricular appendages

Question 28

Tongue buds form from which arch?

Answer 28

1st arch

Question 29

Embryologically, skull consist of.

Answer 29

• neurocranium.

- viscerocranium.

Question 30

Skull base formed from.

Answer 30

Fusion of cartilagenous plate

Question 31

Premature closure of skull sutures.

Answer 31

Craniosynostosis

Question 32

The cartilagenous viscerocranium derived from.

Answer 32

The first and second arch cartilages

Question 33

The maxillary process give raise to.

Answer 33

Maxilla - zygoma - squamous temporal

Question 34

What is treacher collins syndrome?

Answer 34

Characterized by malar and mandibular hypoplasia, slanting palpebral fissures, malformed ears