The document discusses the pharyngeal apparatus, which develops in the human embryo between the head and thorax. It has 6 arches that facilitate respiration and feeding. Each arch contributes to the development of specific anatomic structures of the head, face, palate and neck. The arches give rise to cartilages, muscles, nerves, arteries, and endodermal pouches that develop into important structures like the ears, tongue, tonsils, and thyroid gland. Understanding the development and derivatives of the pharyngeal arches explains the anatomy of many craniofacial and neck regions.

1. THE PHARYNGEAL APPARATUS
By Professor Samuel Asala

2. Pharyngeal (Branchial) Apparatus: Introduction
• Branchial (or pharyngeal) apparatus is the equivalent of the gill (respiratory apparatus) in fish and
amphibians. Pharyngeal apparatus is preferred
• Develops as a complex structure in human embryo between the head and thorax
• Facilitates the dual functions of respiration and feeding
• Development begins in 4th week
• Bilateral ridges and grooves that develop into numerous anatomic structures of the head, face, palate
and anterior part of neck.
• Understanding the apparatus explains the distribution of cranial nerves in parts of head and neck

3. PHARYNGEAL APPARATUS: COMPONENTS
• Location & appearance
• Position of future head & neck
• Lateral to cranial part of future gut (pharynx)
• 6, later 5 arches
• Presence of 3 embryonic layers
• Ectoderm, Mesoderm, Endoderm
• External grooves
• Internal Pouches
• Membrane

4. Components of
Pharyngeal Arches
Arches
• Disappearance of 5th
arch
• Clefts or Grooves
• Pouches

5. 32-week
embryo

6. Embryonic structure of pharyngeal development
From superficial to deep:
• Ectoderm
• Pharyngeal groove/cleft
• Mesoderm
• Muscle
• Cartilage
• Nerve
• Artery
• Endoderm
• Pharyngeal pouch

7. Components of pharyngeal arches

8. Derivatives of
Pharyngeal Arches
• Ear
• Tongue
• Palatine Tonsil
• Parathyroid
glands
• Thyroid:
Ultimobranchial
body
• Thymus gland

9. Model of Developing Pharyngeal Arches
Early Pharyngeal Arch Components Further Development of Pharyngeal Pouches

10. Ectodermal derivatives of Pharyngeal Arches
• Pharyngeal Clefts (Grooves)
• 1st Cleft – External auditory meatus, Tympanic Membrane
• 2nd, 3rd & 4th arch clefts – Cervical sinuses – obliterated by expanding 6th arch

11. Cartilage-based derivatives of pharyngeal arches

13. Mesenchymal Derivatives of the Pharyngeal arches: Cartilages
Pharyngeal arches
1 Premaxilla; maxilla; zygoma; part of temporal bone; Meckel’s cartilage; mandible; malleus;
incus; anterior ligament of malleus; sphenomandibular ligament
2 Stapes (Reichert’s cartilage) ; styloid process; stylohyoid ligament; lesser horn and upper
part of body of hyoid bone
3 Greater horn and lower part of body of hyoid bone
4
Laryngeal cartilages (thyroid, cricoid, arytenoid, corniculate, cuneiform)
6

14. Mesenchymal Derivatives of Pharyngeal arches: Muscles
Pharyngeal Arches Muscles
1 Muscles of mastication (temporalis, masseter, medial & lateral pterygoids), mylohyoid,
anterior belly of digastric, tensor palatini, tensor tympani
2 Muscles of facial expression (buccinator, auricularis, frontalis, platysma, orbicularis oris,
orbicularis oculi), posterior belly of digastric, stylohyoid, stapedius
3 Stylopharyngeus
4 Cricothyroid, levator palatine, superior inferior constrictors of pharynx, intrinsic muscles
of larynx
6

15. Mesenchymal Derivatives of Pharyngeal arches: Nerves
Pharyngeal Arches Nerves
1 Trigeminal nerve (Maxillary and Mandibular)
2 Facial nerve
3 Glossopharyngeal nerve
4 Superior laryngeal nerve (Branch of vagus nerve)
6 Recurrent laryngeal nerve (Branch of vagus nerve)

16. Mesenchymal Derivatives of Pharyngeal arches: Arteries
Pharyngeal Arches Arteries
1 Maxillary artery (degenerates)
2 Hyoid artery; Stapedial artery (degenerates)
3 Internal carotid artery; Common carotid artery
4 Proximal part of right subclavian artery
6 Proximal part of pulmonary arteries

17. Endodermal Derivatives of Pharyngeal Pouches
Pharyngeal Pouches Derivatives
1 Tympanic (middle ear) cavity; Auditory (Eustachian) tube
2 Palatine tonsils; Tonsillar fossa
3 Inferior parathyroid gland; Thymus
4 Superior parathyroid gland; ultimobranchial body (parafollicular [C] cells of the thyroid
gland)

18. Derivatives of Pharyngeal Arches

19. Developmental abnormalities