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SA head and neck > S6) Development of the Head, Neck and Face > Flashcards

S6) Development of the Head, Neck and Face Flashcards

1
Q

Describe the structure of the pharyngeal arches

A

Pharyngeal arches are comprised of a system of mesenchymal proliferations in the neck region of the embryo

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2
Q

How many pharyngeal arches are there?

A

5 in total, numbered 1 to 6 (5th does not form in humans)

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3
Q

Identify the components which constitute the building blocks for the head and neck region

A
  • Pharyngeal arches
  • Frontonasal prominence (FNP)
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4
Q

Describe the association of the cranial nerves with the pharyngeal apparatus

A
  • Cranial nerves – CN V, CN VII, CN IX & CN X
  • Functions:

I. Mixed sensory & motor functions

II. Supply the derivatives of the pharyngeal arches

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5
Q

Describe how the muscles of the face are derived from the pharyngeal arches

A
  • Ph Arch 1: muscles of mastication
  • Ph Arch 2: muscles of facial expression
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6
Q

State the 3 muscles derived from the 4th pharyngeal arch

A

Ph Arch 4:

  • Cricothyroid
  • Levator palatini
  • Constrictors of the pharynx
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7
Q

State the muscles derived from the 3rd and 6th pharyngeal arches

A
  • Ph Arch 3: stylopharyngeus
  • Ph Arch 6: intrinsic muscles of the larynx
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8
Q

Each of the pharyngeal arches develops a neural crest.

Identify the cartilages of the 1st & 2nd pharyngeal arches

A

- Ph Arch 1 – Meckel’s cartilage: malleus, incus + a template for formation of the mandible

- Ph Arch 2 – Reichert’s cartilage: stapes + upper part hyoid bone

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9
Q

Each of the pharyngeal arches develops a neural crest.

Identify the cartilages of the 3rd, 4th & 6th pharyngeal arches

A

- Ph Arch 3 – remainder of hyoid bone

- Ph Arch 4 & 6 – cartilages of the larynx

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10
Q

The aortic sac lies in floor of the pharynx.

Hence, in light of this describe the derivatives of the pharyngeal arch arteries

A

- Ph arch 1&2 arteries disappear

- Ph arch 3 artery = internal carotid artery

- Ph arch 4 artery = arch of aorta (L) & subclavian artery (R)

- Ph arch 6 artery = pulmonary arteries

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11
Q

What is a pharyngeal pouch?

A

Pharyngeal pouches are endoderm lined pockets in the pharynx

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12
Q

The first pharyngeal pouch is the largest.

What is its derivative?

A

Pharyngotympanic tube and middle ear cavity

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13
Q

What is the derivative of the second pharyngeal pouch?

A

Palatine tonsils

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14
Q

What are the derivatives of the third pharyngeal pouch?

A
  • Inferior parathyroid
  • Thymus gland
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15
Q

What are the derivatives of the fourth pharyngeal pouch?

A
  • Superior parathyroid gland
  • C cells of thyroid gland
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16
Q

What is a pharyngeal cleft?

A

Pharyngeal clefts are grooves which form in the lateral ectodermal surface of the neck region to separate the arches

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17
Q

Describe the fate of the first pharyngeal cleft

A

1st pharyngeal cleft is remains and becomes the external acoustic meatus

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18
Q

What happens to the other pharyngeal clefts (besides 1)?

A

Ph arch 2 grows down to cover others, obliterating all other clefts

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19
Q

Which conditions can occur if there are remnants of other pharyngeal clefts?

A

Branchial cysts or fistulae can occur

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20
Q

Identify 5 muscular derivatives of pharyngeal arch 1

A
  • Muscles of mastication
  • Mylohyoid
  • Anterior belly of digastric
  • Tensor tympani
  • Tensor veli palatine (soft palate)
21
Q

Identify 5 skeletal derivatives of pharyngeal arch 1

A
  • Maxilla
  • Zygoma
  • Meckel’s cartilage: mandible, malleus, incus
22
Q

Identify 4 muscular derivatives of pharyngeal arch 2

A
  • Muscles of facial expression
  • Stapedius
  • Stylohyoid
  • Posterior belly of digastric
23
Q

Identify 4 skeletal derivatives of pharyngeal 2

A

Reichert’s cartilage:

  • Superior part of hyoid
  • Stapes
  • Styloid process
  • Stylohyoid ligament
24
Q

What is the muscular derivative of pharyngeal arch 3?

A

Stylopharyngeus muscle

25
Q

What is the skeletal derivative of pharyngeal arches 3 and 4?

A

Epiglottis

26
Q

Identify the 3 muscular derivatives of pharyngeal arches 4-6?

A
  • Constrictor muscles of pharynx and muscles of soft palate (levator veli palatine)
  • Muscles of the larynx
  • Striated muscle of upper oesophagus
27
Q

What is the skeletal derivative of pharyngeal arches 4-6?

A

Cartilages of the larynx

28
Q

Which 4 events drive the development of the face?

A
  • The expansion of the cranial neural tube
  • The appearance of a complex tissue system
  • The development of the sense organs
  • The need to separate the respiratory tract from the GI tract
29
Q

What is associated with the appearance of a complex tissue system in the development of the face?

A
  • The cranial gut tube
  • The outflow of the developing heart
30
Q

Identify and describe 2 structures which form in the early development of the face

A
  • Facial primordia

I. Derived from Ph arch 1

II. Contains FNP

  • Primordia of eyes
31
Q

What does the FNP do in the facial primordia?

A

Frontonasal prominence surrounds ventro-lateral part of the forebrain

32
Q

Identify the 4 components of the developing face

A
  • Frontonasal prominence
  • Maxillary prominence (PhA 1)
  • Mandibular prominence (PhA 1)
  • Stomatodeum (depression in buccopharyngeal membrane)
33
Q

Identify 4 major facial features

A
  • Palpebral fissures
  • Oral fissure
  • Nares
  • Philtrum
34
Q

Identify the 4 components of the frontonasal prominence

A
  • Forehead
  • Bridge of nose
  • Nose
  • Philtrum
35
Q

Identify the 3 components of the maxillary prominence

A
  • Cheeks
  • Lateral upper lip
  • Lateral upper jaw
36
Q

Identify 2 components of the mandibular prominence

A
  • Lower lip
  • Lower jaw
37
Q

In 5 steps, describe the embryological development of the nose

A

⇒ Nasal placodes appear on the FNP & 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 the midline

38
Q

In 2 steps, describe the development of palatal shelves

A

⇒ Maxillary prominence give rise to two palatal shelves

⇒ These grow vertically downwards into the oral cavity on each side of developing tongue

39
Q

In 2 steps, explain how the oral and nasal cavities are separated

A

⇒ Fusion of medial nasal prominences creates the intermaxillary segment

⇒ The secondary palate is derived from palatal shelves

40
Q

State the 3 components of the intermaxillary segment

A
  • Labial component: philtrum
  • Upper jaw: 4 incisors
  • Palate: primary palate
41
Q

In 3 steps, explain how the nasal septum is formed

A

⇒ The mandible grows large enough to allow the tongue to “drop”

⇒ The palatal shelves then grow towards each other and fuse in the midline

⇒ The nasal septum develops as a midline down-growth & ultimately fuses with palatal shelves

42
Q

How does a cleft lip occur?

A

Lateral cleft lips are due to the failure of fusion of the medial nasal prominence with the maxillary prominence

43
Q

How does a cleft lip and cleft palate occur?

A
  • Failure of fusion of medial nasal prominence & maxillary prominence
  • Failure of palatal shelves to meet in midline
44
Q

Describe the development of the following structures in the ear:

  • External auditory meatus
  • Middle ear cavity
  • Ossicles
  • Auricles
A
  • External auditory meatus develops from the 1st Ph cleft
  • Middle ear cavity develops from 1st pharyngeal pouch
  • Ossicles develop from cartilages of 1st and 2nd arches respectively
  • Auricles develop from proliferation within the Ph Arches 1&2
45
Q

Explain how the ears are positioned

A
  • Initially, external ears develop in the neck
  • As the mandible grows, the ears ascend to the side of the head to lie in line with the eyes
46
Q

Explain the effect of alcohol on embryological development

A
  • The facial skeleton is derived from neural crest cells in the Ph arches
  • Neural crest migration as well as development of the brain are known to be extremely sensitive to alcohol
47
Q

What is the incidence of Foetal Alcohol Syndrome?

A

Incidence of FAS = 1 / 100 births

48
Q

Describe the effects of Foetal Alcohol Syndrome on the development of the face:

A
49
Q

What is ARND?

A

Alcohol-related neurodevelopmental delay

SA head and neck (18 decks)

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