5. Embryology Of Head And Neck

Question 1

What does the endoderm tube develop into?

Answer 1

Glandular development:

• parathyroid
• thymus
• palatine tonsils
• thyroid

Question 2

What are the pharyngeal arches?

Answer 2

Comprised of a system of mesenchymal proliferations in the neck region
5 in total (1-6, 5 does not form)
Together will frontonasal prominence constitute the building blocks for the head and neck region

Question 3

What does each pharyngeal arch have?

Answer 3

An associated artery, nerve (cranial nerve) and cartilage bar

Question 4

Which cranial nerves are associated with pharyngeal apparatus?

Answer 4

CNV, VII, IX, X

Question 5

Where do muscles of mastication originate from?

Answer 5

Pharyngeal arch 1 derivatives

Question 6

Where do muscles of facial expression originate from?

Answer 6

Pharyngeal arch 2 derivatives

Question 7

What muscles derives from the third pharyngeal arch?

Answer 7

Stylopharyngeus

Question 8

What muscles derive from the 4th pharyngeal arch?

Answer 8

Cricothyroid
Levator palatini
Constrictors of the pharynx

Question 9

What muscle derives from the 6th pharyngeal arch?

Answer 9

Intrinsic muscles of the larynx

Question 10

What do the cartilages of first pharyngeal arch become?

Answer 10

Malleus and incus plus a template for formation of the mandible

Question 11

What do the cartilages for the second pharyngeal arch become?

Answer 11

Stapes plus upper part of hyoid bone

Question 12

What do the cartilages of the third pharyngeal arch become?

Answer 12

Remainder of thyroid bone

Question 13

What do the cartilages of the 4th and 6th pharyngeal arches become?

Answer 13

Cartilages of the larynx

Question 14

What happens to the 1st and 2nd arch arteries?

Answer 14

Disappear

Question 15

What does the 3rd arch artery become?

Answer 15

Internal carotid artery

Question 16

What does the 4th arch artery become?

Answer 16

Arch of aorta (L) and brachiocephalic (R)

Question 17

What does the 6th arch artery become?

Answer 17

Pulmonary arch

Question 18

What are pharyngeal pouches?

Answer 18

Endoderm lined pockets in the pharynx

Question 19

What does the first pharyngeal pouch become?

Answer 19

Tympanic cavity

Question 20

What does development of the pharyngeal pouches result in?

Answer 20

Formation of palatine tonsils and parathyroid glands and the thymus

Question 21

Which is the only pharyngeal cleft that remains and what does it become?

Answer 21

1st cleft

Becomes external acoustic meatus

Question 22

What happens to most of the pharyngeal clefts?

Answer 22

2nd arch grows down to cover them, obliterating them

Question 23

What happens if the 2nd arch does not develop normally and does not cover all clefts?

Answer 23

Branchial cyst may form

Branchial fistula may form

Question 24

What drives development of the face?

Answer 24

Expansion of the cranial neural tube
Appearance of a complex tissue system
Development of the sense organs and the need to separate respiratory tract from GI tract

Question 25

What forms the facial primordia?

Answer 25

1st pharyngeal arch | Frontonasal prominence

Question 26

What are the components of the face embryologically?

Answer 26

Stomatodeum - buccopharyngeal membrane Frontonasal prominence 1st pharyngeal arch - maxillary and mandibular prominences

Question 27

What does the frontonasal prominence develop into?

Answer 27

Forehead Bridge of nose Nose Philtrum

Question 28

What does the maxillary prominence develop into?

Answer 28

Cheeks Lateral upper lip Lateral upper jaw

Question 29

What does the mandibular prominence develop into?

Answer 29

Lower lip and jaw

Question 30

How does the nose develop?

Answer 30

- Nasal placodes appear on frontonasal prominence - Then sink to become the nasal pits - Medial and lateral nasal prominences form on either side of the pits - Maxillary prominences grow medially, pushing the nasal prominences closer together in the midline - Maxillary prominences fuse with medial nasal prominences - medial nasal prominences then fuse in midline

Question 31

How are the nasal and oral cavities separated?

Answer 31

Fusion of medial nasal prominences creates the intermaxillary segment - labial component: philtrum - upper jaw: 4 incisors - palate: primary palate

Question 32

What is a lateral cleft lip?

Answer 32

Failure of fusion of medial nasal prominence and maxillary prominence

Question 33

What is a cleft lip and cleft palate?

Answer 33

Combined failure of palatal shelves to meet in midline

Question 34

What component of the ear develops from the 1st pharyngeal cleft?

Answer 34

External auditory meatus

Question 35

What do the middle ear cavity and ossicles develop from?

Answer 35

1st pharyngeal pouch and cartilages of 1st and 2nd arches

Question 36

What do auricles develop from?

Answer 36

Proliferation within the 1st and 2nd pharyngeal arches surrounding the meatus

Question 37

Where does the tongue lie?

Answer 37

Partly in the oral cavity and partly in the pharynx

Question 38

What attaches the tongue to the floor of the mouth?

Answer 38

Lingual frenulum

Question 39

What separates the anterior 2/3 from the posterior 1/3 of the tongue?

Answer 39

Sulcus terminalis

Question 40

What is the point of the sulcus terminalis called?

Answer 40

Foramen cecum

Question 41

When do the primordia of the tongue appear?

Answer 41

At same time as palate begins to form

Question 42

Which pharyngeal arch contributes to the tongue?

Answer 42

All of them

Question 43

What do the 2 lateral lingual swellings develop from?

Answer 43

Pharyngeal arch 1

Question 44

What do the 3 median lingual swellings develop from?

Answer 44

Pharyngeal arch 1 - tuberculum impar Pharyngeal arch 2,3,4 - cupola Pharyngeal arch 4 - epiglottal swelling

Question 45

How is the lingual frenulum formed?

Answer 45

Extensive degeneration occurs, freeing tongue from the floor of the oral cavity

Question 46

Where does the primordium of the thyroid gland appear?

Answer 46

In floor of pharynx between the tuberculum impar and cupola

Question 47

Where is the point of origin for the descent of the thyroid?

Answer 47

Marked y the foramen cecum

Question 48

What happens in the descent of the thyroid?

Answer 48

Bifurcated and descendsas a bi-lobed diverticulum connected by the isthmus

Question 49

How does the thyroid gland remain connected to the tongue?

Answer 49

By the thyroglossal duct

Question 50

What are some thyroid abnormalities?

Answer 50

Thyroglossal cysts and fistulae | Ectopic thyroid tissue

Question 51

What structures in the developing face must rise to form the upper lip and jaw?

Answer 51

Maxillary prominence and medial nasal prominences

Question 52

To what structures in the head and neck do neural crest cells contribute?

Answer 52

Cartilage bars in each of the pharyngeal arches leading to development of the skeleton of the face

Question 53

What structures develop from the 3rd and 4th pouches?

Answer 53

Parathyroid glands and thymus