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PHARYNGEAL APPARATUS. Branchial apparatus “GILL”, (Greek)

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Presentation on theme: "PHARYNGEAL APPARATUS. Branchial apparatus “GILL”, (Greek)"— Presentation transcript:

1 PHARYNGEAL APPARATUS

2 Branchial apparatus “GILL”, (Greek)

3 Pharyngeal apparatus consists of : Pharyngeal arch Pharyngeal pouch Pharyngeal membrane Pharyngeal groove

4 PHARYNGEAL APPARATUS PHARYNGEAL ARCHES

5 The pharyngeal arches contribute exclusively in the formation of the : Face Nasal cavities Mouth Larynx Pharynx Neck

6 The first pair of pharyngeal arches appears as an elevation on the surface, lateral to the developing pharynx

7 By the end of the fourth week 4 pairs of pharyngeal arches are visible externally The fifth and sixth arches are not visible externally The pharyngeal arches are separated by a depression called pharyngeal groove or cleft externally, and pharyngeal pouch internally Numbered in craniocaudal sequence

8 Each pharyngeal arch consist of a core of mesenchyme That is covered externally by ectoderm and internally by endoderm mesenchyme

9 3 rd week mesenchyme - derived from mesoderm 4 th week mesenchyme - derived from neural crest cells that migrate into the pharyngeal arches

10 During the 5 th week, the second pharyngeal arch enlarges and overgrows the 4 th and the 3 rd arches forming an ectodermal depression called cervical sinus by the end of 7 th week, the 2 nd to the 4 th pharyngeal grooves and the cervical sinus are disappeared, giving the neck a smooth surface 2 nd arch

11 A typical pharyngeal arch contains: 1- An aortic arch 2- A cartilaginous rod 3- A muscular component 4- A nerve

12 PHARYNGEAL APPARATUS PHARYNGEAL ARCH DERIVATIVES

13 Derivatives of The First Pharyngeal Arch Cartilage The dorsal end of first arch cartilage ( Meckel’s cartilage ) ossifies to form malleus and incus The middle part of cartilage forms anterior ligament of malleus and sphenomandibular ligament Ventral part of the first arch cartilages form primordium of the mandible ] The cartilage disappears as mandible develops around it [

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15 The first pharyngeal arch gives a rise to maxillary and mandibular process Major role in facial development Mandibular process Maxillary process

16 Derivatives of second pharyngeal arch The dorsal end of second arch cartilage (Reichert cartilage) ossifies to form the stapes and styloid process The ventral end of second arch cartilage ossifies to form the lesser cornu and superior part of the body of the hyoid bone Its perichondrium forms the stylohyoid ligament

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18 The second pharyngeal arch ( hyoid arch ) contributes to the formation of hyoid bone

19 Derivatives of The Third Pharyngeal Arch Cartilage The third arch cartilage ossifies to form the greater cornu and the inferior part of the body of the hyoid bone

20 The fourth and sixth arch cartilages fuse to form the laryngeal cartilages except epiglottis which develops from hypopharyngeal eminence The fifth pharyngeal arch is rudimentary ( disappear later) and has no derivatives Derivatives of fourth pharyngeal arch cartilages

21 Derivatives of Pharyngeal Arch Muscles The muscles of the first pharyngeal arch forms the muscles of mastication

22 Derivatives of 2 nd Pharyngeal arch muscles The second pharyngeal arch forms the : 1 - stapedius 2 - stylohyoid 3 - posterior belly of digastric 4 - auricular 5 - muscles of facial expression

23 Derivatives of 3 rd pharyngeal arch muscles The third arch forms the : stylopharyngeus

24 Derivatives of 4 th pharyngeal arch muscles The fourth arch forms : 1 - cricothyroid muscle 2 - levator veli palatini 3 - constrictors of pharynx

25 Derivatives of 6 th pharyngeal arch muscles The sixth pharyngeal arch forms the intrinsic muscles of the larynx

26 Derivatives of Pharyngeal Arch Nerves The trigeminal nerve ( the fifth cranial nerve ) supply derivatives of the first pharyngeal arch by it’s caudal two branches 1 - maxillary branch 2- mandibular branch

27 Derivatives of Pharyngeal Arch Nerves The facial nerve ( VII ( supply the second arch The glossopharyngeal nerve (IX) supply the third arch The vagus nerve (X) supply the fourth and sixth arches by : 1 - superior laryngeal branch supply the 4 th 2 - recurrent laryngeal branch supply the 6 th

28 PHARYNGEAL APPARATUS PHARYNGEAL POUCHES

29 The primordial pharynx The primordial pharynx, derived from the foregut widens cranially where it joins the primordial mouth or stomodeum It narrows caudally where it joins the esophagus pharyngeal arches The pharyngeal pouches are balloonlike diverticula that formed on the endodermal side between the pharyngeal arches The pairs of pouches develop in a craniocaudal sequence between the arches

30 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

31 Derivatives of First Pharyngeal Pouch The first pharyngeal pouch expands into an elongate tubotympanic recess

32 Derivatives of First Pharyngeal Pouch first pharyngeal groove The expanded distal part of this recess contacts the first pharyngeal groove, where it contributes to the formation of the tympanic membrane (eardrum) The cavity of the tubotympanic recess gives rise to the tympanic cavity and mastoid antrum

33 Derivatives of Second Pharyngeal Pouch The second pharyngeal pouch is largely obliterated (disappear) as the palatine tonsils develop Part of the cavity of this pouch remains as the tonsillar sinus or fossa

34 Derivatives of Second Pharyngeal Pouch The endoderm of the pouch grows into the underlying mesenchyme. the central parts of these buds form crypts

35 Derivatives of Second Pharyngeal Pouch At about 20 weeks the mesenchyme around the crypts differentiates into lymphoid tissue These tissues soon organize into the lymphatic nodules of the palatine tonsil

36 Derivatives of Third Pharyngeal Pouch The third pharyngeal pouch expands and develops a : 1- solid dorsal part 2- hollow ventral part Its connection with the pharynx is reduced to a narrow duct that soon degenerates By the sixth week the epithelium of : 1- each dorsal part begins to differentiate into inferior parathyroid gland 2 – each ventral parts begins to differentiate into primordia of thymus These bilateral primordia of thymus come together in the median plane to form thymus It descends into the superior mediastenum

37 Derivatives of Third Pharyngeal Pouch The primordia of thymus and inferior parathyroid glands lose their connections with the pharynx and migrate into the neck Later the inferior parathyroid glands separate from the thymus and lie on the dorsal surface of the thyroid gland superior inferior

38 Derivatives of Fourth Pharyngeal Pouch The fourth pharyngeal pouch also expands into 1- dorsal part 2- ventral parts Its connection with the pharynx is reduced to a narrow duct that soon degenerates By the sixth week, each dorsal part develops into a superior parathyroid gland

39 Derivatives of Fourth Pharyngeal Pouch The parathyroid glands derived from the third pouches descend with the thymus and are carried to a more inferior position than the parathyroid derived from the fourth pouches This explains why the parathyroid glands derived from the third pair of pouches are located inferior to those from the fourth pouches

40 The Fifth Pharyngeal Pouch When this develops, this rudimentary pouch becomes part of the fourth pharyngeal pouch and helps to form the ultimopharyngeal body

41 PHARYNGEAL APPARATUS PHARYNGEAL GROOVES

42 During the fourth and fifth weeks, head and neck region of the human embryo exhibit four pharyngeal grooves or clefts on each side These grooves separate the pharyngeal arches externally Only first pair persists as the external acoustic meatus ( external auditory canal ) The other grooves normally obliterated ( disappear ) with the cervical sinus as the neck develops

43 Pharyngeal Membranes Pharyngeal membranes appear in the floor of the pharyngeal grooves These membranes formed where the epithelia of the grooves and pouches approach each other The endoderm of the pouches and ectoderm of the grooves are soon separated by mesenchyme Only first pharyngeal membrane becomes the tympanic membrane, others obliterate ( disappear )

44 RECOMMENDED READING LANGMAN’S MEDICAL EMBRYOLOGY – 11 th edition CHAPTER 16 – Head and Neck Pgs. 265 – 278


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