Embryology 1st lecture

Question 1

Anatomy of Pharyngeal Arch

Pharyngeal cleft/groove -

žPharyngeal pouch -

žPharyngeal membrane -

Answer 1

Pharyngeal cleft/groove: separates pharyngeal arches from the outside (ectoderm lined)

žPharyngeal pouch: separates pharyngeal arches from the inside ( endoderm lined )

žPharyngeal membrane: where ectoderm and endoderm come together at clefts/grooves

*Arch 1 is covered mostly by ectoderm in the inside - oral ectoderm

Question 2

žCore of each arch?

Answer 2

mesenchyme

—Neural crest – major component

Cartilage & Bone

—Mesoderm (paraxial)

Skeletal muscles

—Nerve (V, VII, IX, X)

—Blood vessel

Question 3

Pharyngeal arch 3: Mytomes that migrate in gives rise to ___ .

Answer 3

—Stylopharyngeus

Question 4

Pharyngeal arch 2: Mytomes that migrate in gives rise to ___ .

Answer 4

Muscles of facial expression, stylohoid, post belly of digastric m

Question 5

Pharyngeal arch 1: Myotomes that migrate in give rise to ____.

Answer 5

—Muscles of mastication: temporalis, masseter, mylohyoid, ant belly of diagastric m, tensor tympani

Question 6

Pharyngeal arch 4 & 6: Myotomes that migrate in give rise to ____.

Answer 6

—Pharyngeal constrictors, soft palate m., laryngeal m.

Question 7

Summary: mesoderm derivatives

Arch

• 1st = Mandibular
• 2nd = Hyoid
• 3rd
• 4th/6th

Answer 7

Muscle

1. All muscles of mastication:

E.g. Temporalis, masseter etc.

Anterior belly of the digastric

2. Muscles of facial expression

E.g. buccinator, obicularis orbis etc.

Posterior belly of the digastric

3. Stylopharyngeus

4&6. Pharyngeal constrictors, soft palate muscles, and laryngeal muscles.

Question 8

Pharyngeal arch innervation: žArch 2

Answer 8

(VII)

—Motor à muscles of facial expression, post belly of digastric, stylohyoid

—Sensory à special sensory (taste) for ant 2/3 of tongue

Question 9

Pharyngeal arch innervation: žArch 3

Answer 9

—Motor - stylopharyngeus

—Sensory - post 1/3 of tongue; both taste and somatosensory

Question 10

Pharyngeal arch innervation: žArch 1

Answer 10

ž(V)

—Motor - masticatory muscles, ant belly of digastric, tensor tympani

—Sensory - somatosensation of face, teeth, ant 2/3 tongue, palate

Question 11

Pharyngeal arch 4&6 innervation

Answer 11

—Pharyngeal constrictors, soft palate m., laryngeal m.

Question 12

Summary: innervation

Arch

• 1st = Mandibular
• 2nd = Hyoid
• 3rd
• 4th/6th

Answer 12

Cranial Nerve

1. Trigeminal (V)
2. Facial (VII)
3. Glossopharyngeal (IX)
4. Vagal (X)

Question 13

Pharyngeal arch neural crest derivatives: Arch 1

Answer 13

—Maxillary prominence à Maxillary bone, zygomatic & squamous portions of temporal bone

Question 14

Pharyngeal arch neural crest derivatives: Arch 2

Answer 14

—Lesser cornu of hyoid, stylohyoid ligament, styloid process, stapes

Question 15

Pharyngeal arch neural crest derivatives: Arch 3

Answer 15

—Body and greater cornu of hyoid

Question 16

Summary: Neural Crest Derivatives

Arch

1st = Mandibular

Maxillary prominence

Mandibular prominence

2nd = Hyoid

3rd

4th/6th

Answer 16

Cartilage/Skeleton

1.

Maxillary Prominence: Bones: maxilla, zygomatic & squamous regions of temporal bone

Mandibular Prominence: Meckel’s cartilage*(transient embryonic structure) Bones: Mandible, incus, malleus

2. Reichert cartilage*(transient embryonic structure), Bones: Styloid process of temporal bone, superior hyoid, stapes
3. Inferior hyoid

4/6. Laryngeal cartilages