Fate of Pharyngeal Arches

Fate of Pharyngeal Arches
Upper Respiratory System
The pharyngeal apparatus contributes to formation of head and neck structures.
The pharyngeal apparatus consists of:
Pharyngeal arches
(1-6)
Pharyngeal
membranes
Pharyngeal
pouches
Pharyngeal
grooves
Upper Respiratory System
Pharyngeal Arches:
The pharyngeal arches begin to develop early in the fourth week as neural
crest cells (cranial ectomesenchyme) migrate into the future head and neck
regions.
Upper Respiratory System
Pharyngeal Arches:
The primordial jaws – first pair of pharyngeal arches – appear as surface
elevations lateral to the developing pharynx.
1st pair
Developing
Pharynx
Primordial
Jaws
Primordial Jaws = Maxillary Prominence (green) & Mandibular Prominence (red)
Upper Respiratory System
Pharyngeal Arches:
By the end of the fourth week, four pairs of pharyngeal arches are visible
externally.
Upper Respiratory System
Pharyngeal Arches:
The forming pharyngeal arches are separated from each other by fissures –
pharyngeal grooves.
Pharyngeal
grooves
Pharyngeal Arches
Fate of Pharyngeal Arches
The pharyngeal arches contribute extensively to the formation of the face, nasal
cavities, mouth, larynx, pharynx, and neck.
A typical pharyngeal arch contains:
1. An aortic arch – an artery that arises from the aortic sac and connects with
the truncus ateriosus of the primordial heart.
Each Pharyngeal Arch Contains:
1.An aortic arch
2.A cartilaginous rod of tissue
3.A muscular component
4.A nerve
Pharyngeal Arch: Aortic Arches (Cardiology Phase)
1st Aortic Arch
Maxillary artery
2nd Aortic Arch
Stapedial artery
3rd Aortic Arch
Carotid arteries: Common, Internal & External
4th left Aortic Arch
4th right Aortic Arch
Arch of the Aorta
Right proximal Subclavian artery
5th Aortic Arch
Degenerates
6th Aortic Arch, proximal portion Pulmonary arteries
6th Aortic Arch, distal portions
left side
Ligamentum arteriosum
right side
Degenerates
Pharyngeal Arches
Fate of Pharyngeal Arches
A typical pharyngeal arch contains:
2. A cartilaginous rod – that forms the skeletal structures of the arch
Pharyngeal Arch: Cartilaginous Rod (Pulmonology & GI Phases)
1st Arch
Meckel’s cartilage (maxillary & mandibular prominences,
malleus, and incus
2nd Arch
Stapes, Styloid process, Lesser cornu (horn) of hyoid bone,
Superior part of body of hyoid bone
3rd Arch
Greater cornu (horn) of hyoid, Inferior body of hyoid bone
4th Arch
Thyroid cartilage, Cricoid cartilage, Arytenoid cartilages,
Corniculate cartilages, Cuneiform cartilages, Triticeal cartilages
Pharyngeal Arches
Fate of Pharyngeal Arches
A typical pharyngeal arch contains:
3. A muscular component – that differentiates into the muscles in the head
and neck
Pharyngeal Arches: Muscular Component (Musculo-skeletal, GI, Neuroscience)
1st Arch
Muscles of mastication: temporalis, masseter, medial and lateral
pterygoids; mylohyoid; anterior belly of digastric muscle
2nd Arch
Muscles of facial expression: buccinator, auricularis, frontalis,
platysma, orbiculais oris, obicularis occuli; stapedius, stylohyoid,
posterior belly of digastric
3rd Arch
Stylopharyngeus
4th & 6th
Cricothyroid, Levator veli palatini, Constrictors of pharynx (superior,
middle, inferior), Intrinsic muscles of larynx (oblique arytenoid,
transverse arytenoid, posterior crico-arytenoid, lateral cricoarytenoid, thyro-arytenoid), Striated muscle of esophagus
Pharyngeal Arches
Fate of Pharyngeal Arches
A typical pharyngeal arch contains:
4. A nerve – that supplies the mucosa (epithelial lining) and muscles derived
from the arch
Pharyngeal Arches: Nerve Supply (Neuroscience Phase)
1st Arch
Trigeminal nerve (V1, V2, V3)
2nd Arch
Facial nerve (VII)
3rd Arch
Glossopharyngeal nerve (IX)
4th Arch
Vagus nerve (X): Superior laryngeal branch of vagus (CN X)
[External laryngeal nerve & Internal laryngeal nerve],
Recurrent laryngeal branch of vagus nerve (CN X)
Fate of Pharyngeal Arches
First Arch – Mandibular Arch
1. First aortic arch – maxillary artery.
2. Skeletal structures –
a. Maxillary prominence – gives rise to the maxilla (upper jaw), zygomatic
bone, and squamous part of temporal bone
b. Mandibular prominence – forms the mandible (lower jaw)
c. Malleus
d. Incus
e. Anterior ligament of malleus
f. Sphenomandibular ligament
3. Muscles – muscles of mastication: temporalis, masseter, medial and later
pterygoids; mylohyoid; anterior belly of digastric muscle
4. Nerve – trigeminal nerve (CN V)
The first pair of pharyngeal arches plays a major role in facial
development.
Fate of Pharyngeal Arches
Second Arch – Hyoid Arch
1. Second aortic arch – stapedial artery.
2. Skeletal structures
a. Stapes
b. Styloid process
c. Lesser cornu (horn) of hyoid bone
d. Superior part of body of hyoid bone
e. Stylohyoid ligament
3. Muscles – muscles of facial expression: buccinator, auricularis, frontalis,
platysma, orbiculais oris, obicularis occuli; stapedius, stylohyoid,
posterior belly of digastric
4. Nerve – facial nerve (CN VII)
Fate of Pharyngeal Arches
Third Arch
1. Third aortic arch – common and proximal portions of the internal &
external carotid arteries.
2. Skeletal structures –
a. Greater cornu (horn) of hyoid
b. Inferior body of hyoid bone
3. Muscles – stylopharyngeus
4. Nerve – glossopharyngeal nerve (CN IX)
Fate of Pharyngeal Arches
Fourth & Sixth Arches
1. A. Fourth Aortic Arch
1. Left 4th – arch of the aorta
2. Right 4th – proximal portion of right subclavian artery
1. B. Sixth Aortic Arch
• Left 6th distal – ductus arteriorsus
• Left 6th proximal – left pulmonary artery
• Right 6th distal – degenerates
• Right 6th proximal – right pulmonary artery
2. Skeletal structures
a. Thyroid cartilage
b. Cricoid cartilage
c. Triticeal cartilages (paired)
d. Arytenoid cartilages (paired)
e. Corniculate cartilages (paired)
f. Cuneiform cartilages (paired)
Fate of Pharyngeal Arches
Fourth & Sixth Arch
3. Muscles –
a. Cricothyroid
b. Levator veli palatini
c. Constrictors of pharynx (superior, middle, inferior)
d. Intrinsic muscles of larynx (oblique arytenoid, transverse arytenoid,
posterior crico-arytenoid, lateral crico-arytenoid, thyro-arytenoid)
e. Striated muscle of esophagus
4. Nerves
a. Superior laryngeal branch of vagus (CN X) (a & b, above)
b. Recurrent laryngeal branch of vagus nerve (CN X) (c - e, above)
Fate of Pharyngeal Arches
First Arch – Mandibular Arch
1. First aortic arch – maxillary artery.
2. Skeletal structures –
a. Maxillary prominence – gives rise to the maxilla (upper jaw), zygomatic bone,
and squamous part of temporal bone
b. Mandibular prominence – forms the mandible (lower jaw)
c. Malleus
d. Incus
e. Anterior ligament of malleus
f. Sphenomandibular ligament
3. Muscles – muscles of mastication: temporalis, masseter, medial and later
pterygoids; mylohyoid; anterior belly of digastric muscle
4. Nerve – trigeminal nerve (CN V)
The first pair of pharyngeal arches plays a major role in facial development.
Fate of Pharyngeal Arches
Second Arch – Hyoid Arch
1. Second aortic arch – stapedial artery.
2. Skeletal structures
a. Stapes
b. Styloid process
c. Lesser cornu (horn) of hyoid bone
d. Superior part of body of hyoid bone
e. Stylohyoid ligament
3. Muscles – muscles of facial expression: buccinator, auricularis, frontalis, platysma,
orbiculais oris, obicularis occuli; stapedius, stylohyoid, posterior belly of digastric
4. Nerve – facial nerve (CN VII)
Fate of Pharyngeal Arches
Third Arch
1. Third aortic arch – common carotid artery and proximal portions of the internal
and external carotid arteries.
2. Skeletal structures –
a. Greater cornu (horn) of hyoid
b. Inferior body of hyoid bone
3. Muscles – stylopharyngeus
4. Nerve – glossopharyngeal nerve (CN IX)
Fate of Pharyngeal Arches
Fourth & Sixth Arches
1. A. Fourth Aortic Arch
1. Left 4th – arch of the aorta
2. Right 4th – proximal portion of right subclavian artery
1. B. Sixth Aortic Arch
• Left 6th distal – ductus arteriorsus
• Left 6th proximal – left pulmonary artery
• Right 6th distal – degenerates
• Right 6th proximal – right pulmonary artery
2. Skeletal structures
a. Thyroid cartilage
b. Cricoid cartilage
c. Triticeal cartilages (paired)
d. Arytenoid cartilages (paired)
e. Corniculate cartilages (paired)
f. Cuneiform cartilages (paired)
Fate of Pharyngeal Arches
Fourth & Sixth Arch
3. Muscles –
a. Cricothyroid
b. Levator veli palatini
c. Constrictors of pharynx (superior, middle, inferior)
d. Intrinsic muscles of larynx (oblique arytenoid, transverse arytenoid, posterior
crico-arytenoid, lateral crico-arytenoid, thyro-arytenoid)
e. Striated muscle of esophagus
4. Nerves
a. Superior laryngeal branch of vagus (CN X) (a & b, above)
b. Recurrent laryngeal branch of vagus nerve (CN X) (c - e, above)
Pharyngeal Pouch Derivatives
2nd pouch: palatine tonsil
3rd pouch: inferior parathyroid gland (dorsally)
3rd pouch: thymus (ventrally)
4th pouch: superior parathyroid gland (dorsally)
4th pouch: thymus (ventrally)
“5th pouch”: area for migrating neural crest cells from the head mesenchyme, i.e.,
cranioectomesenchyme: forms parafollicular-C cells (calcitonin
secreting cells) in the thyroid; “connective tissue” portions of the heart,
i.e., cardiac skeleton, atrial septa, valves, chorda tendinea,
interventricular membranous septum, aortico-pulmonary septum and
outflow tract (future ascending aorta and pulmonary trunk)
Floor of the Mouth
Foramen Cecum leads to Thyroglossal duct leads to formation of
Thyroid gland