Pharyngeal arches, pouches and clefts

when do the pharyngeal arches develop

Weeks 4-5 of development

How many pharyngeal arches are there?

6 (but 5th never really forms)

what germ layer are pharyngeal arches derived from?

Mesoderm

How many pharyngeal clefts are there?

4

what germ layer do clefts/grooves develop from?

Ectoderm

how many pharyngeal pouches are there?

4

what germ layer do pouches develop from?

endoderm

what is the innervation of the 1st arch?

trigeminal nerve - CNV

which bones does the 1st arch give rise to?

• maxilla

• mandible

• ear bones (incus and mallelous)

• temporal and zygomatic

which muscles does the 1st arch give rise to?

Muscles of MASTICATION:

• Temporalis

• masseter

• pterygoids

• mylohyoid

• anterior belly of digastric

what is the innervation of the 2nd arch?

Facial nerve - CNVII

Bones of the 2nd arch?

• Hyoid (lesser horns, upper portion)

• Styloid process

• stapes bone in the ear

Muscles of the 2nd arch?

Muscles of FACIAL EXPRESSION:

• posterior belly of digastric

• stylohyoid

• stapes muscle

Innervation of 3rd arch?

Glossopharyngeal - CNIX

Bones of the 3rd arch?

Remainder of hyoid bone

Muscles of the 3rd arch?

stylopharyngeus

Innervation of the 4th arch

Vagus - CNX: Superior laryngeal branch

Bones of the 4th/6th arches?

No bones - but work together to form laryngeal cartilages

Muscles of the 4th arch?

• levator palatini

• pharyngeal constrictors

• cricothyroid

Innervation of the 6th arch?

Vagus - CNX: recurrent laryngeal branch

Muscles of 6th arch?

• rest of larynx muscles

which arch does the anterior 2/3 of the tongue originate form?

1st arch

which arch does the posterior 1/3 of the tongue originate from?

3rd/4th archs

Which cleft does the external auditory meatus and eardrum develop from?

1st cleft

what does the 2nd, 3rd and 4th cleft/groove develop onto?

Nothing - fade away in early development

what does the internal auditory meatus & Eustachian tube develop from?

1st pharyngeal pouch

which pouch gives rise to the primitive tonsils?

2nd pouch

what gives rise to the inferior parathyroid?

Dorsal part of the 3rd pouch

what does the ventral part of the 3rd arch give rise to?

primitive thymus

what gives rise to the superior parathyroid gland?

dorsal portion of the 4th pouch

what does the ventral portion of the 4th pouch develop into?

The ultimo pharyngeal body - forms the parafollicular C cells of the thyroid gland