The document discusses the development of the pharyngeal apparatus during the 4th week of intrauterine development. It notes that there are initially six pharyngeal arches that develop in the lateral wall of the primitive pharynx, although the 6th arch is small and disappears, leaving five arches. Between the arches are four pharyngeal clefts lined by ectoderm and four pharyngeal pouches lined by endoderm. The derivatives of the pharyngeal arches include muscles, nerves, skeletal elements, and other structures. Clinical syndromes can result from abnormalities in development of the pharyngeal arches and clefts.

1. PHARYNGEAL APPARATUS
Dr. G.Prabavathy
Assistant Professor
Pharyngea
l
apparatus

2. Clinical syndromes

3. OBJECTIVES
 Components of pharyngeal apparatus
 Components and derivatives of pharyngeal arches
 Components and derivatives of pharyngeal clefts
 Components and derivatives of pharyngeal pouches
 Clinical syndromes

4.  Pharyngeal arches
 Pharyngeal clefts
 Pharyngeal pouches
 Pharyngeal membranes
PHARYNGEAL APPARATUS

5. PHARYNGEAL / BRANCHIAL
APPARATUS
4th week of intrauterine development

6. PHARNGEAL ARCHES
In fourth week of development – series of surface
elevations appear in the lateral wall of primitive pharynx
caudal to stomodeum

7. PHARYNGEAL ARCHES
 Initially there are six arches. Fifth arch is small
and rudimentary and soon disappears
 Only five pharyngeal arches remain

10. 6th arch

11. Arch 6

12. COMPONENTS OF PHARYNGEAL ARCH
 A Core of mesoderm – derived from paraxial mesoderm
& neural crest cells
 A Cartilaginous bar – from neural crest
 A Pharyngeal arch artery – from aortic sac
 A Nerve

14. Arrangement of post-trematic and pre-trematic
nerves

15. Pharyngeal arch Nerves
First arch Maxillary and Mandibular
nerves
Chorda tympani nerve
Second arch Facial nerve
Third arch Glossopharyngeal nerve
Fourth arch Superior laryngeal branch
of vagus
Sixth arch Recurrent laryngeal branch
of vagus
DERIVATIVES OF PHARYNGEAL ARCHES
Nerves of the pharyngeal arches

16. MUSCLES OF PHARYNGEAL
ARCHES
Pharyngea
l arch
Muscles
First arch Muscles of Mastication (Temporalis,
Masseter, Medial and Lateral Pterygoid)
Anterior belly of digastric, Mylohyoid,
Tensor tympani & tensor veli palatini
Second arch Muscles of facial expression, posterior belly
of digastric, stylohyoid, stapedius
Third arch Stylopharyngeus
Fourth arch Cricothyroid, levator palati, contrictor of
pharynx and intrinsic muscles of larynx
Sixth arch

18. SKELETAL ELEMENTS

21. SKELETAL ELEMENT OF PHARYNGEAL
ARCHES
Pharynge
al arch
Skeleton Ligaments
First arch
(Meckes’s
cartilage)
Malleus, and Incus
Premaxilla, maxilla
,zygomatic bone, part of
temporal bone, mandible,
Anterior ligament of
malleus
Sphenomandibular
ligament
Second arch
(Reichert’s
cartilage)
Stapes, styloid process,
Smaller cornu of hyoid bone,
superior surface of body of the
hyoid bone
Stylohyoid ligament
Third arch Greater cornu and lower part
of body of hyoid bone
Fourth arch Laryngeal cartilages (thyroid,
cricoid, arytenoids,
corniculate, cuneiform)Sixth arch

23. I ARCH SYNDROME
 Due to lack of migration of neural crest cells into
first pharyngeal arch
Treacher collins syndrome:
Inherited autosomal dominat trait
 Malar hypoplasia
 Mandibular hypoplasia
 Down slanting palpebral fissures
 Deformed external ears

25. PIERRE ROBIN SYNDROME
Autosomal recessive
disorder
 Micrognathia
 Cleft palate
 glossoptosis (posteriorly
placed tongue)

26. PHARYNGEAL CLEFTS

27. PHARYNGEAL CLEFTS

28. • Invagination of surface ectoderm between the
pharngeal arches
• Four pharyngeal clefts

29.  Second arch grows rapidly downward overlaps
the second,third and fourth pharyngeal clefts –
cervical sinus

30.  Only first pharyngeal cleft – external auditory
meatus, whereas other clefts are obliterated

33. Pharyngeal
Membrane
Adult derivatives
First Tympanic membrane
Second
Third
fourth
Obliterate/disappear

34. BRANCHIAL CYST
 Remnants of second, third and fourth pharyngeal
clefts form cervical sinus
 Normally cavity of cervical sinus disappears as neck
develops but it fails to obliterate – branchial cyst
 Appears along ant border of sternocleidomastoid

35. BRACHIAL CYST AND BRANCHIAL FISTULA

36. BRANCHIAL FISTULA
 When branchial cyst ruptures – branchial fistula
 Open along ant border of sternocleidomastoid
 Internal branchial fistula
 External branchial fistula

37. LATERAL CERVICAL FISTULA

38. PHARNYGEAL POUCHES

39. PHARNYGEAL POUCHES
 Four pairs of pouches – evaginations of endoderm,
lining between two arches

40. FIRST PHARYNGEAL POUCH
First pharyngeal pouch – tubotympanic recess
 Distal part of tubotympanic recess – middle ear
cavity and mastoid antrum
 Proximal part – eustachian/auditory tube

41. SECOND PHARYNGEAL POUCH
• Endoderm proliferates to Form solid buds, central core of these
buds breaks down to form Tonsillar crypts
• Part of this pouch remains as intratonsillar crypt
(crypta magna)

43. THIRD PHARYNGEAL POUCH
 Dorsal bulbar part – parathyroid III or inferior
parathyroid gland
 Ventral tubular part - thymus

44. FOURTH PHARYNGEAL POUCH
 Dorsal bulbar part – superior parathyroid gland IV
 Fifth pouch incorporated with fourth pouch – caudal
pharyngeal complex – para follicular cells or c cells

47. SUMMARY
 Pharyngeal arches – five in number, present in
lateral wall and floor of the primitive pharynx
 Pharyngeal clefts- four in number, present externally
between the arches, lined by ectoderm
 Pharyngeal pouches – four in number, present
internally between the two pharyngeal arches, lined
by the endoderm
 Pharyngeal membranes – four in number and located
between adjacent arches

48.  Enumerate the Derivatives of second pharyngeal
arch
 Name the Derivatives of first pharyngeal arch
 Explain Cervical sinus

49. IMPORTANT QUESTIONS
1. Stages of development of kidney
2. explain horseshoe shaped kidney
3. Congenital polycystic kidney [dec 2002]
4. Accessory renal arteries[ may 2007]
5. Ectopia vescicae[ may 2005]
6. Ectodermal cloaca[ may 2006]
7. Gubernaculum testes[ may 2006]
8. Name the sites of Ectopic testis
9. Undescended testis(cryptorchidism)
10. Epispadias and hypospadias
11. Derivates and remnants of Mesonephric duct
12. Enumerate the derivatives of Paramesonephric duct. What
is unicornuate uterus[april 2002]
13. Development of uterus[nov 2010]
14. Duplication of uterus[ may 2007]
15. Give embryological basis of Bicornuate uterus