PHARYNGEAL APPARATUS.pptx concise and descriptive
- 1. PHARYNGEAL/BRANCHIAL APPARATUS BY DR OBASIKENE CATHERINE CONSULTANT RADIOLOGIST
- 2. Outline • Introduction • Normal anatomical structures • Anomalies of the pharyngeal apparatus • Role of radiology • conclusion
- 3. INTRODUCTION • The pharyngeal apparatus contains cells from all three germ cell layers (endoderm, mesoderm and ectoderm) and from the neural crest. • Pharyngeal apparatus components are • Pharyngeal arches • Pharyngeal pouches • Pharyngeal clefts • Pharyngeal membrane
- 4. EMBRYOLOGY • The pharyngeal arches develop at fourth and fifth week of embryonic life • At the beginning of 4th week of embryonic life, a pair of curved elevation, develops in the neck region at the anterior lateral aspect of the neck which is the first pharyngeal arch. • Subsequently four more pharyngeal arches develop in the craniocaudal direction • The pharyngeal arches are numbered 1,2,3,4,6.The fifth does not develop in humans
- 5. • The pharyngeal arches are cores of mesenchyme which develops around the cranial part of the foregut(pharynx). • The pharyngeal arch is located between the inner covering of the endoderm and an outer covering of the ectoderm • Each pharyngeal arch has a cartilaginous, muscular, nervous and arterial components • These will subsequently give rise to structures of the developing fetus • The cartilaginous part will form the skeleton of each arch • The muscular part will differentiate into muscles of the head and neck. • Each pharyngeal arch will develop its own motor and sensory innervation supplied by the cranial nerves.
- 6. • On a molecular basis, the formation and development of each branchial arch will depend on the adequate expression of several genes. • Hox genes, which are dependent of retinoic acid and key for an adequate growth and division along the anterior- posterior axis in vertebrates, serve to enable proper segmentation of arches 2 through 6. • Dlx genes establish the pattern and polarity of pharyngeal arch 1. In addition, Dlx genes are paramount for the development of the upper and lower jaw.
- 7. Pharyngeal clefts and pouches • Each pharyngeal arch is separated from the other on the external surface by a groove known as the pharyngeal grooves or clefts. • The pharyngeal clefts are invagination of the ectoderm. • It is seen on the external surface. • There are four pairs of pharyngeal clefts separating the five pairs of pharyngeal arches. • The endodermal outpouchings of the developing pharynx (pharyngeal pouches ) separates the pharyngeal arches from each other. The pharyngeal pouches are also four pairs in number.
- 8. • pharyngeal membranes are formed between the pharyngeal pouch and groove
- 10. Derivatives of the pharyngeal arches
- 11. • The cartilage of the first pharyngeal arch (Meckel’s cartilage) is related to the development of the ear. • The proximal part of this cartilage form the malleus and incus. • The rest forms the sphenomandibular ligament and the anterior ligament of the malleus.
- 12. First arch (mandibular) • The first pharyngeal arch separates into maxillary (dorsal) and mandibular (ventral) prominences. • The maxillary prominence forms the maxilla, zygomatic bone, part of the vomer and short limb of the incus. • The mandibular prominence gives rise to the temporal bone, the malleus and the mandible.
- 13. • Muscles: Muscles of mastication, mylohyoid muscle, anterior belly of digastric muscle, tensor tympani, tensor veli palatine • Artery derivates: Maxillary artery Cranial nerve: Trigeminal nerve (CN V) • Its sensory field is that of the trigeminal nerve - skin of the face, the lining of the mouth and nose, and general sensation to the anterior 2/3 of the tongue.
- 14. Second arch(hyoid) • Cartilage of the 2nd arch the Reichert’s cartilage forms the Stapes, long limb of incus, styloid process, lesser horn and upper part of body of hyoid bone; stylohyoid ligament • Muscles: Muscles of facial expression, stylohyoid muscle, posterior belly of digastric muscle, stapedius • Artery derivates: Stapedial artery( which connects the embryonic precursors of the internal carotid, internal maxillary and middle meningeal arteries. It regresses before birth), caroticotympanic arteries • Cranial nerve: Facial nerve (CN VII) providing anterior 2/3rd of the tongue with taste sensation
- 15. Third arch • The 3rd arch cartilage: Greater cornu, lower part of body of hyoid bone • Muscles: stylopharyngeus muscle • Artery derivates: Common carotid artery, internal carotid artery (proximal portion) • Cranial nerve: Glossopharyngeal nerve (CN IX) providing taste and sensation to the posterior 1/3rd of the tongue.
- 16. Fourth pharyngeal arch • Fourth pharyngeal arch : Laryngeal cartilages (thyroid and cunieform) • There are no skeletal structures in the fourth arch • Muscles: Cricothyroid muscle, levator veli palatini, constrictors of pharynx • Artery derivates: Aortic arch, subclavian artery (proximal portion) • Cranial nerve: Superior laryngeal branch of vagus nerve (CN X)
- 17. • The fourth and sixth pharyngeal arches cartilages merge to give rise to the laryngeal cartilages. by differentiating into the cricoid, arytenoid, and corniculate cartilages • Muscles: Intrinsic muscles of larynx, striated muscles of esophagus • Artery derivates: Ductus arteriosus, pulmonary arteries (proximal portion) • Cranial nerve: Recurrent laryngeal branch of vagus nerve (CN X)
- 18. Pharyngeal cleft derivatives • The first pharyngeal cleft forms the external auditory meatus • The 2nd ,3rd ,4th pharyngeal clefts form the cervical sinus temporarily which is obliterated later by the rapidly developing 2nd pharyngeal arch
- 19. Pharyngeal pouches • Pouch Derivatives • 1st Eustachian tube and middle ear cavity • 2nd lining of palatine tonsil • 3rd dorsal-Inferior parathyroid gland ventral-thymus • 4th dorsal-superior parathyroid glands ventral-ultimobranchial bodies which give rise to the parafollicular cells (C cells) of the thyroid gland, which are responsible for the secretion of calcitonin
- 20. • the first pharyngeal membrane forms the tympanic membrane
- 21. Anomalies of the pharyngeal arches • Anomalies of pharyngeal arches occur when the neural crest cells fail to migrate to the arch, leading to structural anomalies of the derivatives of the arch
- 22. 1st pharyngeal arch anomaly • Treacher Collins syndrome or mandibulofacial dysostosis (autosomal dominant) Features :hypoplasia of facial bones – mandible, maxilla, zygomatic bone, cleft palate Ear defects • Pierre Robin syndrome • Features: migrognathia, cleft palate, ear defects.
- 23. 3rd pharyngeal arch anomaly • DiGeorge syndrome features hypoplasia of or agenesis of thymus, parathyroid gland, facial and cardiovascular anomalies
- 24. Anomalies of the pharyngeal clefts • Persistent cervical sinus causes the formation of branchial cysts. • It can also cause formation of branchial sinus or fistula
- 25. Anomalies of the pharyngeal pouches • Ectopic parathyroid glands and thymus
- 26. ROLE OF RADIOLOGY • Make diagnosis • Confirm diagnosis • Follow up treatment/complications
- 27. 2nd branchial cleft cysts usually located below the angle of the mandile,anterior to sternomastoid muscle usually rounded or spheric, sharply circumscribed fluid density centrally Thin hyperdense wall
- 28. Treacher collins sydrome Hypoplastic zygomatic arches Atresia of the external auditory canal and middle ear cavity with dysplastic ossicles
- 29. • micro gnath ia
- 31. REFRENCES 1.Kenhub.com/en/library/anatomy/pharyngeal arches 2.Teach me anatomy/pharyngeal arches 3.Radiopeadia .org 4.Paediatic imaging 5.Brijesh Kumar in Embryology Text and Atlas
- 32. THANK YOU FOR LISTENING