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Development of the palate, nasal cavity, and tongue

Q: What does the secondary palate do in relation to the hard and soft palate?

The secondary palate forms the primordium (earliest structure of development) of the hard palate and the anchor point of the soft palate .

Q: What are palatine shelves?

Palatine shelves are structures that form the roof of the oral cavity and floor of nasal cavity and is established from maxillary prominences

Q: How is the right and left nasal cavity established?

Merging of palatine shelves with nasal septum establishes the right and left nasal cavity

Q: When does the formation of nasal cavities happen in relation to the formation of secondary palate?

The formation of nasal cavities happens almost simultaneously to the formation of secondary palate

Q: What is the incisive foramen ?

A passageway for nerves and blood vessels at the junction of the primary palate and secondary palate (two palatine shelves) that forms at week 10.

Q: What is the significance of incisive foramen in embryonic development?

The incisive foramen is a landmark that indicates proper embryonic development of the palate

Q: Which parts of the palate ossify as part of palate development?

Primary palate and anterior part of secondary palate - posterior part of secondary palate doesn't ossify

Q: What initiates nasal cavity development?

Thickening of surface ectoderm on the frontonasal prominence (in skyblue), forming the nasal placodes .

43 important questions on Development of the palate, nasal cavity, and tongue

Which weeks of embryonic development does the development of palate happen?

5th to 12th week

What is the critical period of palate development?

6th to 9th week

When and how is the primary palate formed?

The primary palate is formed early in 6th week by merging of the two medial nasal prominences, which also continue to extend posteriorly to the intermaxilliary process.

What does the secondary palate do in relation to the hard and soft palate?

The secondary palate forms the primordium (earliest structure of development) of the hard palate and the anchor point of the soft palate.

What are palatine shelves?

Palatine shelves are structures that form the roof of the oral cavity and floor of nasal cavity and is established from maxillary prominences

How do palatine shelves merge with each other?

Maxillary prominences (which are later established as palatine shelves) extend medially and merge with each other on the median plane, merge with the nasal septum above that is growing inferiorly, and merge anteriorly with primary palate to establish fused palatine shelves.

How is the right and left nasal cavity established?

Merging of palatine shelves with nasal septum establishes the right and left nasal cavity

When does the formation of nasal cavities happen in relation to the formation of secondary palate?

The formation of nasal cavities happens almost simultaneously to the formation of secondary palate

What is the incisive foramen ?

A passageway for nerves and blood vessels at the junction of the primary palate and secondary palate (two palatine shelves) that forms at week 10.

What is the significance of incisive foramen in embryonic development?

The incisive foramen is a landmark that indicates proper embryonic development of the palate

Which parts of the palate ossify as part of palate development?

Primary palate and anterior part of secondary palate
- posterior part of secondary palate doesn't ossify

What initiates nasal cavity development?

Thickening of surface ectoderm on the frontonasal prominence (in skyblue), forming the nasal placodes.

What happens to the nasal placodes as development proceeds?

The nasal placodes become depressions called nasal pits with medial and lateral nasal processes around due to proliferation of underlying mesenchyme.

How does a nasal pit develop to a nasal sac?

Growth of medial and lateral nasal processes deepen the nasal pit and ultimately closes it forming the nasal sac with a surface opening called the nostril

What initially separates the nasal cavity from the oral cavity?

oronasalmembrane

When and why does the oronasal membrane disappear?

It ruptures around the 7th week, allowing communication between the nasal and oral cavities through a temporary opening.

How is the definitive separation between the nasal and oral cavities established?

1. The formation and fusion of the primary palate begins the separation
2. Later, fusion of the palatine shelves completes it.

Which structures fuse to form the secondary palate?

Palatine shelves

Which structures fuse to form the primary palate?

intermaxillary segment

What is closed and what still remains open when the palatine shelves fuse with each other?

The palatal shelves close off the nasal cavity from the mouth (anteriorly),
but the nasopharynx remains open posteriorly

What structure grows downward to fuse with developing palate and separate the right and left nasal cavities?

The nasal septum, formed by the fusion of the frontonasal prominence with the medial nasal processes.

Summarise the steps in the formation of the nasal cavity.

1. Thickening of surface ectoderm on frontonasal prominence forming nasal placodes

2. Nasal placodes become nasal pits bordered by medial and lateral nasal processes

3. Medial and lateral nasal processes grow, deepening the nasal pit = formation of nasal sac

4. Oronasal membrane forms between nasal sacs and oral cavity

5. Oronasal membrane ruptures, forming temporary opening

6. Primary palate forms, starting separation of nasal and oral cavities.

7. Palatine shelves fuse (secondary palate) = complete anterior separation of oral and nasal cavities.

8. Nasal septum grows downward = divides nasal cavity into right and left sides with nasopharynx and oropharynx open posteriorly

When does the development of the tongue start?

4th week, on the floor of the pharyngeal arches.

Why can the tongue formation only initiate once the pharyngeal arches are formed?

Because tongue develops on the floor of pharyngeal arches

What forms on the floor of the first pharyngeal arch at the start of tongue development?

The median tongue bud

What forms on the floor of the second pharyngeal arch?

copula

What forms on the floor of the third and fourth pharyngeal arches?

hypopharyngeal eminence

When does the formation of initial swellings (median tongue bud, copula, and hypopharyngeal eminence) occur?

4th week

What new swellings appear in the 5th week anterior to the median tongue bud?

Two distal tongue buds (lateral lingual swellings) — from the 1st pharyngeal arch

What happens to the distal tongue buds/lateral lingual swellings in week 6?

They overgrow the median tongue and fuse in the midline, forming the anterior two-thirds (oral part) of the tongue.

Which swelling overgrows the copula, and what does it form?

The hypopharyngeal eminence starts to overgrow the copula in week 5. Then, it continues to expand in week 6, forming the posterior 1/3 of the tongue.

What is the foramen cecum and where does it form?

A small pit at the junction between the median tongue bud and hypopharyngeal eminence that appears in week 5.

What significance does the lingual septum have for tongue development?

lingual septum marks the fusion of the lingual swellings into a singular oral part of the tongue

What marks the boundary between the oral and pharyngeal parts of the tongue?

The terminal sulcus, a groove located just anterior to the foramen cecum.

How is the tongue’s innervation determined?

The tongue’s innervation is determined by the pharyngeal arch of origin because each arch carries its corresponding cranial nerve.

Which cranial nerves innervate the tongue?

CN V (trigeminal) - 1st pharyngeal arch
CN VII (facial) - 2nd pharyngeal arch
IX (glossophrayngeal) - 3rd pharyngeal arch
X (vagus) - 4th pharyngeal arch

From where is the tongue’s musculature derived?

From invading myoblasts from occipital somites and head mesenchyme

Explain the development of pharyngeal arch 1 with corresponding innervations to the developed structures.

Pharyngeal arch 1 --> median tongue bud --> median tongue bud overgrown by lateral lingual swellings innervated by lingual (sensory) branch of mandibular division of trigeminal nerve CN V --> lateral lingual swellings fuse to anterior 2/3 of tongue innervated by chorda tympani of facial nerve CN VII (from 2nd pharyngeal arch) + lingual branch of CN V (inherited from lateral lingual swellings)

Explain the development of pharyngeal arch 2 with corresponding innervations to the developed structures.

Pharyngeal arch 2 innervated by chorda tympani from of facial nerve CN VII --> copula --> copula overgrown by hypopharyngeal eminence from 3rd pharyngeal arch

Explain the development of pharyngeal arch 3 with corresponding innervations to the developed structures.

Pharyngeal arch 3 --> large, ventral part of hypopharyngeal eminence --> most of posterior 1/3 of tongue innervated by sensory branch of glossopharyngeal nerve CN IX

Explain the development of pharyngeal arch 4 with corresponding innervations to the developed structures.

Pharyngeal arch 4 --> small dorsal part of hypopharyngeal eminence --> small dorsal region of posterior 1/3 of tongue innervated by sensory superior laryngeal branch of vagus nerve CN X

Explain the development of occipital somites with corresponding innervations to the developed structures.

Occipital somites --> myoblasts --> intrinsic muscles of tongue innervated by hypoglossal nerve CN XII

Explain the development of head mesoderm with corresponding innervations to the developed structures.

Head mesoderm --> myoblasts --> palatoglossus muscle innervated by pharyngeal plexus of vagus nerve CN X

The question on the page originate from the summary of the following study material:

Embryology

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