Pharyngeal (Branchial) Apparatus

(Page 59)

Dr. Sherif Fahmy

Dr. Sherif Fahmy

Dr. Sherif Fahmy

Pharyngeal (Branchial) Arches• They are 6 mesodermal thickenings on both sides of

pharynx.• They appear in the 4th and 5th weeks.• Arches are covered with ectoderm (externally) and

lined with endoderm (internally).• Arches are separated from each other by 4 clefts on

outer surface which is covered with ectodermal cells.

• Arches are separated from each other by 5 pouches on inner aspect (cavity of pharynx) which are lined with endodermal cells.

Dr. Sherif Fahmy

Dr. Sherif Fahmy

Dr. Sherif Fahmy

Processes of the 1st archFirst arch has 2 processes:1- Maxillary process.2- Mandibular process.

Dr. Sherif Fahmy

Dr. Sherif Fahmy

Mandibular process

Maxillary process

Dr. Sherif Fahmy

Maxillary process

Mandibular process

Dr. Sherif Fahmy

Maxillary process

Mandibular process

2nd arch Dr. Sherif Fahmy

Maxillary process

Mandibular process

Dr. Sherif Fahmy

Structure of each arch• Each arch is composed of

mesodermal (mesenchymal) cells that give rise to bones, cartilages and muscles.• Each arch has an arterial supply

which is called aortic arch.• Each arch has a cranial nerve.

Dr. Sherif Fahmy

Cranial Nerve Related to Pharyngeal Arches

Dr. Sherif Fahmy

Dr. Sherif Fahmy

Each arch has a nerve supply:-Mandibular & Maxillary n. supplies derivatives of 1st arch.-Facial n. supplies derivatives of 2nd arch.-Glossopharyngeal n. supplies derivatives of 3rd arch.-Superior laryngeal br. of vagus supplies derivatives of 4th arch.-Recurrent laryngeal n. supplies derivatives of 6th arch.N.B. Pre-trematic nerve crosses from one arch to other, e.g. chorda tympani n.(branch of facial n.) supplies anterior 2/3 of tongue.

Dr. Sherif Fahmy

Dr. Sherif Fahmy

EctodermEndoderm

Cleft

Pouch

Cartilage

Aortic arch

Nerve supply

Floor of pharynx

Coronal section of neck showing structure of pharyngeal arches

Thickened mesoderm

Dr. Sherif Fahmy

Cleft

Pouch

Cartilage

Nerve supply of the arch

Aortic arch

Pretrematic nerve

Dr. Sherif Fahmy

Derivatives of Pharyngeal Arches

Dr. Sherif Fahmy

Fate of Pharyngeal Clefts• Clefts are present on outer surface between

the arches, covered with ectoderm.• Dorsal part of first cleft forms external

auditory meatus and outer layer of ear drum.• Downward growth of 2nd arch will cover the

other clefts with a space inbetween called cervical sinus.

• Cervical sinus becomes smaller till it is completely obilterated. Dr. Sherif Fahmy

Dr. Sherif Fahmy

Fate of Pharyngeal PouchesArch Ventral partVentral part Dorsal partDorsal part

First pouch Occupied by developing tongue.

Tubo-tympanic recess that gives rise to midlle ear & Eustachian tube

Second pouch Occupied by developing tongue

Palatine tonsile

Third pouch Thymus gland Inferior parathyroid gland

Fourth pouch Unknown Superior parathyroid gland

Fifth pouch Ultimo-branchial body which form parafollicular cells in thyroid

Dr. Sherif Fahmy

Congenital Anomalies• Ectopic thymic present in neck• Ectopic parathyroid tissue especially inferior

parathyroid gland.• Branchial cyst: Remenant of cervical sinus.• Branchial fistula: Remenant of cervical sinus

that communicates with skin through extenal fistula, while if it communicates with pharynx it forms internal fistula.

Dr. Sherif Fahmy