Development of pharyngeal arches, clefts and pouches.pptx

The development of pharyngeal arches is meticulously orchestrated process crucial for the formation of essential structures in the head and neck region. This slideshow shows the development of pharyngeal arches, derivatives of each arches, pouches and clefts with clinical significance. it includes some of the recent research papers associated with pharyngeal arches and its anomalies.
This slideshow effectively summarizes the key aspects of pharyngeal arches and leaves the student with a clear understanding of its importance and implications.

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2. Development of Pharyngeal Arches GUIDED BY: PROF. DR. RABINDRA MAN SHRESTHA ASSO. PROF. DR. JYOTI DHAKAL PRESENTED BY: Dr. KAJAL MEHTA PG RESIDENT 2 DEPARTMENT OF ORTHODONTICS, KANTIPUR DENTAL COLLEGE

3. Contents Introduction Neural crest cells Rhombomeres Development of Pharyngeal Apparatus -Pharyngeal arches -Pharyngeal pouches -Pharyngeal grooves Clinical significance Summary Conclusion References 3

4. Objectives To know components of pharyngeal apparatus To discuss components and derivatives of pharyngeal arches To study components and derivatives of pharyngeal clefts To learn components and derivatives of pharyngeal pouches To discuss clinical syndromes 4

5. Introduction During the late somite period (4th week post conception), mesoderm of ventral foregut region becomes segmented to form a series of five distinct bilateral mesenchyme swellings, called pharyngeal (branchial) arches Pharyngeal arches appear in 4th week of embryological development when neural crest cells migrate into future head and neck region 5

6. 6 A. Lateral view of a embryo [approximately 25 days]. The bulging in the first and second pharyngeal arches. B. The left side of a embryo approximately 28 days old. The first three pharyngeal arches are visible.

7. Introduction ( Contd..) Development of pharyngeal arches is complex It involves a number of disparate embryonic cell types: ectoderm, endoderm, neural crest and mesoderm 7

8. Neural crest cells Are ectomesenchymal tissues arising from neural folds Lies along the lateral edges of neural plate Possesses great migratory propensities, following natural cleavage planes between mesoderm, ectoderm, and endoderm Translocated neural crest cells, upon reaching their predetermined destinations (genetically predetermined/specified by local environmental influences), undergo cytodifferentiation into a wide variety of diverse cell types 8

9. Fig:- Formation and migration of neural crest cells. Crest cells form at the tips of neural folds and do not migrate away from this region until neural tube closure is complete.

10. Rhombomeres 10 Is a transiently divided segment of the developing neural tube within the hindbrain region. Eight of these segments in the hindbrain(R1-R8) Neural crest cells arises from these segments Fig: shows the pathways of neural crest cell migration from cranial neural folds into face and pharyngeal arches.

11. Pharyngeal Apparatus Pharyngeal arches - neural crest & mesoderm Pharyngeal grooves/clefts - ectoderm Pharyngeal pouches - endoderm Pharyngeal membrane 11

12. 2023 Oct;243(4):564-569.   Epub 2023 A revised terminology for the pharyngeal arches and the arch arteries Anthony Graham   1 ,  Jill P J M Hikspoors   2 ,  Robert H Anderson   3 ,  Wouter H Lamers   2 ,  Simon D Bamforth   3 Abstract The pharyngeal arches are a series of bulges found on the lateral surface of the head of vertebrate embryos. In humans, and other amniotes, there are five pharyngeal arches and traditionally these have been labelled from cranial to caudal-1, 2, 3, 4 and 6. This numbering is odd-there is no '5'. Two reasons have been given for this. One is that during development, a 'fifth' arch forms transiently but is not fully realised . The second is that this numbering fits with the evolutionary history of the pharyngeal arches. Recent studies, however, have shown that neither of these justifications have basis. The traditional labelling is problematic as it causes confusion to those trying to understand the development of the pharyngeal arches. In particular, it creates difficulties in the field of congenital cardiac malformations, where it is common to find congenital cardiac lesions interpreted on the basis of persistence of the postulated arteries of the fifth arch. To resolve these problems and to take account of the recent studies that have clarified pharyngeal arch development, we propose a new terminology for the pharyngeal arches . In this revised scheme, the pharyngeal arches are to be labelled as follows-the first, most cranial, the mandibular (M), the second, the hyoid (H), the third, the carotid (C), the fourth, the aortic (A) and the last, most caudal, the pulmonary (P) 12

13. Pharyngeal arch (Brachial arch) Begin to develop early in 4 th week as neural crest cells migrate into head and neck region. Each pharyngeal arch consists, mesenchyme derived from lateral plate of mesoderm. Soon neural crest cell migrate into the arches and surround the central core of mesenchymal cells. Migration of neural crest cells into the arches produce discrete swelling demarcating each of the pharyngeal arch. 13

14. Pharyngeal arch ( Contd..) Initially it consist of mesodermal tissue deep clefts ectoderm dips ectodermal or pharyngeal clefts With the development of arches and cleft out pocketing which is endodermal or pharyngeal pouches 14

15. 15 Fig:- Drawing shows the pharyngeal arches cut in cross section

16. Fate of Pharyngeal Arches A typical pharyngeal arch contains: An aortic arch , an artery that arises from truncus arteriosus of the primordial heart. A cartiliginous rod that forms the skeleton of the arch. A muscular component that differentiates into muscles in the head and neck. A nerve that supplies the mucosa and muscles derived from the arch. 16

17. First pharyngeal arch 1st pharyngeal arch is the precursor of both maxillary and mandibular jaws and appropriately bounds the lateral aspects of stomodeum. Cartilage of 1 st arches – meckel’s cartilage Provides template for subsequent development of the mandible. 17

18. First pharyngeal arch (Contd.) First pharyngeal arch is comprised of two parts: Maxillary prominence  (dorsal portion) – becomes future maxilla, zygomatic bone and part of temporal bone Is associated with maxillary cartilage ,  which gives rise to the incus Mandibular prominence  (ventral portion) – becomes future mandible Is associated with Meckel’s cartilage, which gives rise to malleus and sphenomandibular ligament 18

19. 19 Fig: Lateral view of the head region demonstrating the cartilages of the pharyngeal arches

20. First pharyngeal arch ( contd …) Musculature of mandibular arch form: Muscles of mastication Anterior belly of digastric Tensor tympani Tensor veli palitini muscle 20

21. First pharyngeal arch(Contd..) Nerve : Mandibular branch of trigeminal nerve(post trematic nerve) Artery : Maxillary artery The nerve of the arch itself runs along the cranial side of the arch. (post- trematic nerve of the arch) Each arch also receives a branch from the nerve of the succeeding arch. This runs along the caudal border of the arch and called pre- trematic nerve of the arch 21

22. Second pharyngeal arch Also called hyoid arch Cartilage- Reichert’s cartilage which gives rise to - stapes, styloid process stylohyoid ligament lesser horn and upper part of the body of hyoid bone. 22

23. Second pharyngeal arch (Contd..) T wo arteries associated : Stapedial artery  – connects the embryonic precursors of the internal carotid, internal maxillary and middle meningeal arteries. It regresses before birth Hyoid artery  – gives rise to the cortico tympanic artery in the adult 23

24. Second pharyngeal arch (Contd..) Muscles of 2 nd arches- stylohyoid Stapedius post. belly of digastric auricular muscles Platysma muscles of facial expression Nerve – Facial nerve 24

25. Third pharyngeal arch Cartilage of the 3 rd arch produces lower part of body and greater horn of hyoid bone. Nerve -Glossopharyngeal nerve(CN IX) Muscle of 3 rd arch forms stylopharyngeus muscle 25

26. Fourth pharyngeal arch Vascular derivatives of 4 th pharyngeal arch differ between left and right: Right  – proximal portion of subclavian artery Left  – aortic arch Fourth arch gives rise to  laryngeal cartilages  – namely thyroid, corniculate and cuneiform cartilages 26

27. Fourth pharyngeal arch (cont ..) Nerve - Superior laryngeal branch of vagus nerve Muscles- Constrictors muscles of pharynx levator palatini and cricothyroid 27

28. Sixth pharyngeal arch Vascular derivatives of the sixth pharyngeal arch differ between the left and right: Right  – proximal portion of the pulmonary arteries Left  – ductus arteriosus  Associated nerve is the  recurrent laryngeal branch  of the  vagus nerve (CN X), innervates intrinsic muscles of l arynx(Except:- Cricothyroid) 28

29. Pharyngeal pouches are balloon-like diverticula that formed on the endodermal side between the pharyngeal arches Four pairs of pharyngeal pouches Fifth pouch is rudimentary 29

30. First pharyngeal pouch Its ventral part is obliterated by the formation of tongue Dorsal part gives rise to tubotympanic recess which forms: 1)Tympanic Cavity 2)Auditory tube 30

31. Second pharyngeal pouch Its ventral portion is also obliterated by developing tongue D orsal portion of this pouch persists in an attenuated form as the tonsillar fossa, E ndodermal lining of which covers the underlying mesodermal lymphatic tissue to form palatine tonsil (Note - neither pharyngeal nor lingual tonsils originate from pharyngeal pouch) 31

32. Second pharyngeal pouch (Contd..) 32

33. Third pharyngeal pouch Ventral diverticulum endoderm proliferates and migrates from each side to form thymus gland Dorsal diverticulum endoderm differentiates and then migrates to form inferior parathyroid gland 33

34. Fourth pharyngeal pouches D orsal diverticulum endoderm differentiates into superior parathyroid gland Ventral region gives rise to ultimobranchial body, which later incorporated into thyroid gland Cells of ultimobranchial body gives rise parafollicular cells or C cells which secretes calcitonin(hormone involved in regulation of calcium level in blood) 34

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36. Pharyngeal cleft 1 st pharyngeal groove persists, and while its ventral end is obliterated, its dorsal end deepens to form external acoustic meatus. The 2 nd , 3 rd and 4 th pharyngeal grooves become obliterated by the caudal overgrowth of 2 nd pharyngeal arch (hyoid operculum). At the end of 5th week post conception,3 rd and 4 th pharyngeal arches are collectively sunk into a retro hyoid depression, the cervical sinus. 36 Fig: Remnants of third and fourth cleft form cervical sinus , which is normally obliterated.

37. Pharyngeal cleft(Contd.) Failure of these pharyngeal grooves to be obliterated completely results in a pharyngeal fistula leading from pharynx to the outside or in a pharyngeal (cervical) sinus or cyst, forming a closed sac If derived from pharyngeal pouch, they are lined by columnar or ciliated epithelium; If from pharyngeal groove, they are lined by squamous epithelium 37

38. Congenital anomalies Brachial cyst: Cervical Sinus persists as cyst along anterior border of sternomastoid muscle. If ruptures -: brachial sinus Branchial sinus : It can be external or internal. External: if the cyst opens outside, usually anterior to sternomastoid. Internal: cyst opens into pharynx, usually in the tonsillar region. Branchial/Cervical fistula : The cyst opens both externally and internally. Connects pharynx with outside. 39

39. First arch syndrome Due to lack of migration of neural crest cells into first pharyngeal arch. They usually produce facial anomaly . agnathia, synotia , and microstomia . 40

40. Treacher Collins syndrome: Inherited autosomal dominant trait -Malar hypoplasia -Mandibular hypoplasia -down slanting palpebral fissures -deformed external ears Genetic defect: Mutation of TCOF1 (Treacle) gene located on chromosome 5 41

41. 42 Fig: Patient with Bird like appearance due to pronounced retrognathia and a relatively normal nasal projection.

42. Pierre Robin Syndrome Autosomal recessive discorder -Micrognathia -Cleft palate - Glossoptosis Genetic cause—anomalies in chromosomes 2, 11 or 17 . Genetic dysregulation of SOX9 gene that controls development of face. 43

43. Eagles syndrome 44 Elongated styloid process compress carotid artery Difficulty swallowing Sensation of having something in throat Pain on turning neck or touching back of throat

44. Summary Pharyngeal arches- Five in numbers, present in lateral wall and floor of the primitive pharynx. Pharyngeal clefts- Four in numbers, present externally between the arches, lined by ectoderm. Pharyngeal pouches- Four in numbers, present internally between arches, lined by endoderm. 45

45. Table-1 Major structures of the Brachial Apparatus Arch Nerve Muscular skeletal First (Mandibular) Trigeminal nerve Muscles of mastication Malleus Incus Mandible Second (Hyoid) Facial nerve Muscles of facial expressions Stapes Styloid Process Lesser horn of hyoid Third Glossopharyngeal nerve Superior constrictor Greater horn of hyoid Fourth Superior laryngeal branch Cricothyroid, Levator veli palatini, constrictors of pharynx Laryngeal cartilages [thyroid, corniculate, cuneiform] Sixth Recurrent laryngeal branch All intrinsic muscle of larynx (except cricothyroid) Cricoid , Arytenoid 46

46. Table-2 The Fate of pharyngeal arch arteries Arch artery Derivatives First arch artery Maxillary artery Second arch artery Hyoid and Stapedial arteries Third arch artery Common carotid artery Internal Carotid artery Fourth arch artery Aortic arch (on the left side) Subclavian artery(on the right side) Sixth arch artery Ductus arteriorus (on the left side) Pulmonary artery (on the right side) 47

47. Table-3 Derivatives of the Pharyngeal Pouches Pharyngeal Pouch Derivatives 1 st pouch Tympanic [middle ear] cavity Auditory [eustachian] tube 2 nd pouch Palatine tonsils Tonsillar fossa 3 rd pouch Inferior parathyroid gland Thymus 4 th pouch Superior parathyroid gland ultimobranchial body [parafollicular [C] cells of the thyroid gland] 48

48. Conclusion P haryngeal arches form the cornerstone of the complex anatomy of the face and neck. These embryonic structures are the foundation of face and neck development, and anomalous growth can result in craniofacial abnormalities. 49

49. References: 1.Sadler TW. Langman's medical embryology. 14 th ed. China: Lippincott Williams & Wilkins. Wolters Kluwer Health; 2015. 2.Sperber GH. Craniofacial embryology. London: Wright; 1989. 3.Inderbir Singhs Human Embryology 4. Graham A, Hikspoors JP, Anderson RH, Lamers WH, Bamforth SD. A revised terminology for the pharyngeal arches and the arch arteries. Journal of anatomy. 2023 Oct;243(4):564-9. 50

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