Development of pharyngeal apparatus


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Development of Pharyngeal apparatus
by Prof. Mohamed A. Autifi
Professor of Anatomy and Embryology
Al-Azhar Faculty of Medicine

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Development of pharyngeal apparatus

  1. 1. And Lower Extremity Bones of the Pelvic Girdle
  2. 2. Introduction After folding, the 2ry yolk sac inside the embryo .gives rise to : Fore gut -Mid gut – hind gut Oral membrane : The fore gut is divided into  Amniotic cavity Gut Before folding a. Cranial part : extends from oral . membrane to the laryngo-tracheal groove : It gives rise to  Part of mouth cavity  Salivary glands  Pharyngeal apparatus  Respiratory system Cloacal membrane Yolk sac Amniotic cavity Foregut Midgut Hindgut Stomodeum Vitello-intestinal duct Allantois Cloacal membrane Connecting stalk After folding .b. Caudal part : begins distal to the laryngotracheal groove It gives rise to: esophagus-stomach- part of duodenumliver-biliary system –pancreas. Prof. Mohamed A. Autifi
  3. 3. The pharyngeal arches They are 6 curved cylindrical mesenchymal thickening on each side of the primitive pharynx.  They develop in the head & neck similar in origin & structure to gills of the fish.  Gill = Branchia  Each arch consists of : 1. Outer ectodermal covering 2. Inner endodermal lining 3. Mesodermal core  Prof. Mohamed A. Autifi
  4. 4.      Each pharyngeal arch consists, at first of mesenchyme derived from the lateral plate mesoderm. Soon, neural crest cells migrate into the pharyngeal 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. NB. Mesenchyme =connective tissue of embryo The mesenchyme derived from neural crest cells is called (ectomesenchyme) to differentiate it from mesenchyme derived from mesoderm. Prof. Mohamed A. Autifi
  5. 5. A typical pharyngeal arch contains: 1- A cartilaginous rod that forms the skeleton of the arch. 2- A muscular component that differentiates into muscles in the head and neck. 3- An aortic arch , an artery that arises from the truncus arteriosus of the primordial heart. 4- A nerve that supplies the mucosa and muscles derived from the arch. Prof. Mohamed A. Autifi
  6. 6. Nerve supply of the pharyngeal arches  It is derived from the hindbrain (pons and M.O)  Each arch receives mixed nerve. Its motor branch supplies muscles derived from the arch. Its sensory branch supplies skin and mucous membrane of the arch.   Prof. Mohamed A. Autifi
  7. 7. Development of Pharyngeal arches •By the end of the 4th week, 4 well defined pairs of pharyngeal arches are visible externally. •The 5th and 6th arches are small and cannot be seen on the surface of the embryo. Prof. Mohamed A. Autifi
  8. 8. Development of Pharyngeal arches Prof. Mohamed A. Autifi
  9. 9. Cartilages    Most of the cartilages that form within the pharyngeal arches develop from the neural crest of the midbrain and hindbrain regions, although the cartilages of arches 4 and 6 apparently develop from lateral plate mesoderm. The first pharyngeal arch is remodeled to form a cranial maxillary process (swelling) and a caudal mandibular process (swelling). Each process contains a central cartilaginous element (the maxillary known as palato-pterygo-quadrate cartilage and the mandibular known as Meckel's cartilage) surrounded by a mesenchymatic tissue. Prof. Mohamed A. Autifi
  10. 10. Development of Pharyngeal arches Prof. Mohamed A. Autifi
  11. 11. Arch First arch (mandibular arch) Consists of maxillary process and mandibular process Skeletal Muscular Derivatives Derivatives Maxillary 1.Muscles of process Mastication gives rise to: 1.Maxilla 2.Tensor 2.Zygomatic bone palati 3.Squamous part of temporal bone 3.Tensor Mandibular tympani process differentiates into : 4. Mylohoid 1.Malleus 2.Incus 5. Anterior 3.Anterior belly of ligament of digastric malleus 4.Sphenomandibular Prof. Mohamed. A. Autifi ligament Vascular Element 1. Maxillary artery Nereve Mandibular nerve (V)
  12. 12. Arch Second arch (Hyoid arch) Skeletal Derivatives Muscular Derivatives Reichert’s cartilage: Differentiates into: 1.Stapes 2.Styloid process 3.Stylohyoid ligament 4.Lesser horn of the hyoid bone 5.Upper part of body of hyoid bone Vascular Element 1. Muscles of Stapedial the scalp artery and face (caroticotympanic br. 2. Platysma of ICA) 3. Stylohyoid 4. Stapedius 5. Posterior belly of digastric Prof. Mohamed. A. Autifi Prof. Mohamed. A. Autifi Prof. Mohamed A. Autifi Nereve Facial nerve (VII)
  13. 13. Arch Third arch Skeletal derivatives 1. Greater horn of Stylopharyngeus hyoid bone 2. Lower part of body of hyoid bone Fourth arch Thyroid cartilage Sixth arch Muscular derivatives Cricothyroid Rest of Cartilages 1. Other intrensic of the larynx muscles of larynx except epiglottis: 2. Constrector -Cricoid, muscles of pharynx -Arytenoid, except -Corniculate Stylopharyngeus and -Cuneiform. 3. Muscles of NB. The epiglottis palate except develops from tensor palati mesenchyme in Prof. Mohamed A. Autifi hypobrancheal Vascular Element Nereve 1. I.C.A 2. C.C.A Glossopharyngeal nerve (IX) 1. Arch of aorta on left side 2. Subclavian A on right side Superior laryngeal nerve (X) 1. Pulmonary A on each sides 2. Ductus arteriosus on left side Recurrent laryngeal nerve (X)
  14. 14. More details about cartilages Derivatives of Cartilages of First Pharyngeal Arch The ventral part of the first arch cartilage ( Meckel cartilage ) form primordium of the mandible The middle part of cartilage forms anterior ligament of malleus and sphenomandibular ligament Prof. Mohamed A. Autifi The dorsal end of first arch cartilage ossifies to form malleus and incus
  15. 15. Derivatives of Cartilage of second Pharyngeal Arch The ventral end of second arch cartilage (Reichert cartilage) ossifies to form the lesser cornu and upper part of the body of the hyoid bone Prof. Mohamed A. Autifi The dorsal end of second arch cartilage (Reichert cartilage) ossifies to form the stapes, styloid process and stylohyoid ligament
  16. 16. Derivatives of Third Pharyngeal Arch Cartilage The third arch cartilage ossifies to form the greater cornu and the lower part of the body of the hyoid bone Prof. Mohamed A. Autifi
  17. 17. Derivatives of The fourth and sixth Pharyngeal Arch Cartilages • The fourth and sixth arch cartilages fuse to form the laryngeal cartilages except epiglottis which develops from hypobrancheal eminence • The fifth pharyngeal arch is rudimentary and disappear later and has no derivatives Prof. Mohamed A. Autifi
  18. 18. Muscular component Prof. Mohamed A. Autifi
  19. 19. Pharyngeal Pouches and clefts
  20. 20. Development of Pharyngeal pouches and clefts Prof. Mohamed A. Autifi
  21. 21. Pharyngeal pouches  The pharyngeal pouches are balloon-like diverticula that formed on the endodermal side between the pharyngeal arches  The pairs of pouches develop in a craniocaudal sequence between the arches.  The first pair of pouches lies between the first and second pharyngeal arches.  There are four well defined pairs of pharyngeal pouches  The fifth pair is absent or rudimentary • Prof. Mohamed A. Autifi
  22. 22. First pouch It gives rise to tubotympanic recess which forms: 1.Tympanic cavity 2.Auditory tube. (pharyngotympanic tube or Eustachian tube) Prof. Mohamed A. Autifi
  23. 23. Second pouch Gives rise to palatine tonsils -Early in 3rd month, its lining epithelium proliferates ➪ solid tonsillar buds which grow into underlying mesoderm. -Their central cells degenerate➪ hollow tonsillar crypts. -Crypts & surrounding mesoderm ➪ palatine tonsils. -Lymphatic tissue infiltrates its mesoderm during 3-5 Month -Tonsillar capsule formed by condensed mesoderm. -Remnants of pouch ➪ intratonsillar cleft Prof. Mohamed A. Autifi
  24. 24. Third pouch Gives rise to: -inferior parathyroid glands. -thymus gland. At 6th week, they lose connection to pharyngeal wall. -Thymus gland migrates caudally & medially, pulling the parathyroid. The two thymic rudiments descend into thorax. Gland is large at time of birth, ➚ up to 2nd year, little ➚ until 7th year, rapid growth to 11th year, then ➘ to adult weight (12-15 gm) -Inferior parathyroid glands descends to lower pole of thyroid gland Prof. Mohamed A. Autifi
  25. 25. Fourth pouch It gives rise to: 1.Superior parathyroid glands. It migrates with the thyroid gland. 2. Ultimo-branchial body. It incorporates into the thyroid gland. It gives parafollicular or C cells of thyroid gland Prof. Mohamed A. Autifi
  26. 26. PHARYNGEAL GROOVES (CLEFTS): In the 5th week: 4 clefts seen. The first cleft gives: external auditory meatus. The epithelium of the bottom forms outer layer of eardrum NB. Active growth of 2nd arch mesoderm overlaps 3rd & 4th arches. Temporarily, clefts ➪ectodermal cavity, cervical sinus, which disappears later. Prof. Mohamed A. Autifi
  27. 27. Development of Pharyngeal pouches and clefts Prof. Mohamed A. Autifi
  28. 28. Prof. Mohamed. A. Autifi
  29. 29. Prof. Mohamed A. Autifi
  30. 30. Congenital anomalies Lateral cervical cysts and fistulas ( (Branchial cyst & Branchial fistula Prof. Mohamed A. Autifi
  31. 31. Congenital anomalies 1. Branchial Cyst: Sinus persists as cyst along ant border of sternomastoid muscle. If ruptures ➪ branchial sinus 2. Branchial Sinus: a) External: Cyst opens outside, usually anterior to sternomastoid. b) Internal: Cyst opens into pharynx,usually in the tonsillar region. 3. Cervical Fistula: Sinus opens externally & internally, connects pharynx with outside. Prof. Mohamed A. Autifi
  32. 32. Congenital anomalies 4. 1st Arch Syndrome (Mandibulofacial dystosis) Maldevelopment of components of 1st pharyngeal arch results in various congenital malformations of eyes, ears, mandible and palate. This is due to failures of Proper neural crest migration into the 1st branchial arches. 5. DiGeorge Syndrome. Improper migration of neural crest cells into the 3rd and 4th branchial arches. It is characterized by: 1.Minor deformations of the lower face. 2.Thymic and parathyroid aplasia (i.e., no thymus and no parathyroids). The absence of a thymus has a very deleterious effect on the development of the immune system. The absence of parathyroids leads to hypocalcemia. 3.Problems with aorticopulmonary septation. Prof. Mohamed A. Autifi
  33. 33. Congenital anomalies 6. Ectopic Thymic Tissue: Thymus gland lies in the neck. 7. Ectopic Parathyroid: Inferior parathyroid may present at bifurcation of Common carotid artery. Prof. Mohamed A. Autifi
  34. 34. Thank you for attention Prof. Mohamed A. Autifi
  35. 35. Derivatives of pharyngeal floor
  36. 36. The pharyngeal floor is formed by fusion of ventral parts of the arches & pouches: It gives rise to: A. Thyroid gland. B. Tongue. C. Lower respiratory system. Prof. Mohamed A. Autifi
  37. 37. Development of the thyroid gland    Thyroid primordium appears as a median endodermal proliferation in the floor of the pharynx between tuberculum impar and hypobranchial emenence (the site is indicated by foramen caecum in adult) This thickening is invaginated to form a bilobed divertaculum which descend ventral to the developing hyoid bone then ventral to the developing larynx. It remains connected to the dorsum of the tongue by the thyroglossal duct Prof. Mohamed A. Autifi
  38. 38. Development of the thyroid gland 1 3 2 4 Prof. Mohamed A. Autifi
  39. 39. Development of the thyroid gland   The thyroid gland reaches its final position by the 7th week and begins to function at the end of the 3rd month . The endodermal cells of the thyroglossal duct form the thyroid follicles which secrete thyroxine and triiodothyronine hormones.   The ultimobranchial body forms parafollicular C cells which secrete calcitonin. The mesoderm forms the true capsule and connective tissue septa. Prof. Mohamed A. Autifi
  40. 40.    Fate of the thyroglossal duct: The part of the duct between hyoid bone and isthmus of the gland gives rise to pyramidal lobe and levator glandulae thyroidae Above the hyoid bone the duct degenerate completely. Prof. Mohamed A. Autifi
  41. 41. Congenital Anomalies: 1. Agenesis:  congenital hypothyroidism 2. Ectopic (aberrant) thyroid: Lingual, sublingual, or thoracic 3. Thyroglossal cyst: In midline of neck, common at lingual, supra-, retro- or infra-hyoid sites 4. Thyroglossal sinus: Due to rupture of thyroglossal cyst Prof. Mohamed A. Autifi
  42. 42. Thyroglossal cyst Prof. Mohamed. A. Autifi
  43. 43. Development of Tongue Prof. Mohamed A. Autifi
  44. 44. Development of Tongue A. The mucous membrane  Anterior 23: arises from 3 swelling derived from the ventral parts of both 1st pharyngeal arches as follows: •2 •1   lateral lingual swellings and median swelling “tuberculum impar” Posteror 13: developed from the upper half of hypobranchial eminince” The post.13 fuses with the ant.23 along a v-shaped sulcus terminalis. Prof. Mohamed A. Autifi
  45. 45. Development of Tongue B. The muscles of the tongue  Derived from the occipital myotomes that migrate to the developing tongue taking with it their nerve supply (hypoglossal nerve)  Some of the tongue muscles are differentiated in situ.  NB. At first the tongue is fused with the floor of the pharyngeal gut. Later on linguogingival groove appears on either side and frees the tongue from the floor of the mouth Prof. Mohamed A. Autifi
  46. 46. Lingual papillae & taste buds: Vallate & foliate papillae appear first in relation to branches of IX n Fungiform & filiform papillae appear later near fibers of chorda tympani. -All papillae soon develop taste buds Lymphoid follicles aggregate under mucosa of post 1/3 of tongue ➪ lingual tonsil Prof. Mohamed A. Autifi
  47. 47. Congenital Anomalies: 1. Ankyloglossia (tongue-tie): Frenulum of tongue extends to its tip. Prevents movements & hinders proper speech 2. Macroglossia: Large tongue, due to lymphangioma or muscular hypertrophy 3. Microglossia 4. Cleft tongue: Incomplete fusion of lingual swellings ➪ median groove/cleft, does not extend to tongue tip 5. Bifid tongue: Cleft extends to tip 6. Congenital cysts & fistulae: Remnants of thyroglossal duct Prof. Mohamed A. Autifi
  48. 48. Tongue tie Microglossia Macroglossia Prof. Mohamed A. Autifi
  49. 49. Bifid Tongue Tongue tie Prof. Mohamed. A. Autifi
  50. 50. Prof. Mohamed. A. Autifi