1. PHARYNGEAL APPARATUS

2. Branchial apparatus
“GILL” , (Greek)

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

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

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

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

12. PHARYNGEAL ARCH DERIVATIVES
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 [

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

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

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. Derivatives of fourth pharyngeal arch cartilages
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

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

22. Derivatives of 2nd 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 3rd pharyngeal arch muscles
The third arch forms the :
stylopharyngeus

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

25. Derivatives of 6th 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 4th
2 - recurrent laryngeal branch supply the 6th

28. PHARYNGEAL APPARATUS
PHARYNGEAL POUCHES

29. 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
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
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
These bilateral primordia of thymus come together in the median plane to form thymus
It descends into the superior mediastenum
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

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
By the sixth week, each dorsal part develops into a superior parathyroid gland
Its connection with the pharynx is reduced to a narrow duct that soon degenerates

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 – 11th edition
CHAPTER 16 – Head and Neck Pgs. 265 – 278