1. DEVELOPMENT OF HEAD AND
NECK
PHARYNGEAL APPARATUS

2. PHARYNGEAL APPARATUS
• CONSISTS OF---
• 1 PHARYNGEAL/BRANCHIAL ARCHES
• 2 PHARYNGEAL/BRANCHIAL POUCHES
• 3 PHARYNGEAL/BRANCHIAL GROOVES
• 4 PHARYNGEAL/BRANCHIAL MEMBRANES
• THESE PRIMITIVE EMBRYONIC STRUCTURES
CONTRIBUTE GREATLY TO THE FORMATION OF
HEAD & NECK

3. PHARYNGEAL APPARATUS
• PHARYNGEAL ANOMALIES RESULT FROM
PERSISTENCE OF PARTS OF PHARYNGEAL
APPARATUS THAT NORMALLY DISAPPEAR
• OROPHARYNGEAL MEMBRANE ,FORMED
DURING THE THIRD WEEK,SEPARATES THE
STOMODEUM FROM PRIMITIVE PHARYNX
• OROPHARYNGEAL MEMBRANE RUPTURES ON
ABOUT DAY 26

6. PHARYNGEAL ARCHES
• BEGIN TO DEVELOP EARLY IN THE 4th WEEK
WHEN NEURAL CREST CELLS MIGRATE INTO
FUTURE HEAD & NECK REGION
• INITIALLY EACH ARCH CONSISTS OF A CORE OF
MESENCHYME COVERED EXTERNALLY BY
ECTODERM AND INTERNALLY BY ENDODERM
• THE MESENCHYME IS DERIVED FROM---
• 1 PARAXIAL MESODERM
• 2 LATERAL MESODERM
• 3 NEURAL CREST CELLS

7. PHARYNGEAL ARCHES
• THE ARCHES SUPPORT THE LATERAL WALLS OF
THE CRANIAL PART OF THE FOREGUT [ THE
PRIMITIVE PHAYRYNX ]
• STOMODEUM [PRIMTIVE MOUTH ] APPEARS AS A
SLIGHT DEPRESSION OF SURFACE ECTODERM
• STOMODEUM COVERED BY OROPHARNGEAL
MEMBRANE
• PHARYNX COMMUNICATES WITH THE AMNIOTIC
CAVITY WHEN OROPHARYNGEAL MEMBRANE
RUPTURES

8. PHARYNGEAL ARCHES
• FIRST PAIR APPEARS LATERAL TO THE
DEVELOPING PHARYNX
• OTHER ARCHES APPEAR AS ROUNDED
ELEVATIONS ON EACH SIDE OF THE PHARYNX
• BY THE END OF THE 4th WEEK 4 WELL
DEFINED PAIRS OF ARCHES ARE VISIBLE
EXTERNALLY
• 5th & 6th PAIR OF ARCHES ARE RUDIMENTARY
AND NOT VISIBLE EXTERNALLY

9. PHARYNGEAL ARCHES
• ARCHES ARE SEPARATED FROM EACH OTHER BY
GROOVES
• ARCHES AND GROOVES ARE NUMBERED
CRANIOCAUDALLY
• PHARYNGEAL ARCH COMPONENTS
• 1 SKELETAL COMPONENT
• 2 MUSCULAR COMPONENT
• 3 ARTERIAL COMPONENT
• 4 NERVE COMPONENT

21. PHARYNGEAL POUCHES
• PRIMITIVE PHARYNX WIDENS CRANIALLY
WHERE IT JOINS THE MOUTH
• NARROWS CAUDALLY AS IT JOINS THE
OESOPHAGUS
• ENDODERM OF PHARYNX LINES THE
INTERNAL ASPECT OF ARCHES
• THE ENDODERM PASSES INTO BALLOON LIKE
DIVERTICULA ---THE POUCHES

27. PHARYNGEAL POUCHES
• PAIRS OF ARCHES DEVELOP IN A CRANIOCAUDAL
SEQUENCE
• THE 1st PAIR OF POUCHES LIES B/W 1st & 2nd ARCHES
• FATE OF PHARYNGEAL POUCHES
• FIRST POUCH
• EXPANDS INTO TUBOTYMPANIC RECESS WHICH GIVES
RISE TO---
• 1 TYMPANIC CAVITY
• 2 MASTOID ANTRUM
• 3 AUDITORY TUBE WHICH CONNECTS THE TYMPANIC
CAVITY WITH THE PHARYNX

28. PHARYNGEAL POUCHES
• FATE OF POUCHES
• SECOND POUCH
• LARGELY OBLITERATES AS PALATINE TONSIL
DEVELOPS
• PART OF THE CAVITY REMAINS AS
INTRATONSILLAR CLEFT
• ENDODERM PROLIFERATES AND GROWS INTO
THE SURROUNDING MESENCHYME WHICH LATER
DIFFERENTIATES INTO LYMPHOID TISSUE

29. PHARYNGEAL POUCHES
• FATE OF POUCHES
• THIRD POUCH
• EXPANDS AND FORMS---
• 1 SOLID DORSAL BULBAR PORTION---FORMS
INFERIOR PARATHYROID GLAND
• 2 HOLLOW ELOGATE VENTRAL
PORTION---FORMS THYMUS

30. PHARYNGEAL POUCHES
• FATE OF POUCHES
• FOURTH POUCH
• EXPANDS AND FORMS---
• 1 DORSAL BULBAR PORTION---FORMS SUPERIOR
PARATHYROID
• 2 VENTRAL ELONGATE PORTION---FORMS
ULTIMOBRANCHIAL BODY WHICH FUSES WITH THYROID
GLAND AND GIVES RISE TO PARAFOLLICULAR CELLS
• FIFTH POUCH
• RUDIMENTARY AND BECOMES PART OF FOURTH POUCH

31. PHARYNGEAL GROOVES
• FOUR GROOVES OR CLEFTS ARE PRESENT IN
THE NECK REGION OF THE EMBRYO FROM 4th
to 6th WEEK
• ONLY 1st GROOVE EXISTS AS EXTERNAL
ACOUSTIC MEATUS
• OTHER GROOVES COME TO LIE IN A SLIT LIKE
DEPRESSION ---THE CERVICAL SINUS
• THESE GROOVES NORMALLY OBLITERATE AS
THE NECK DEVELOPS

32. PHARYNGEAL MEMBRANES
• TEMPORARY STRUCTURES
• APPEAR IN THE BOTTOM OF PHARYNGEAL
GROOVES ON EACH SIDE OF THE NECK DURING
THE 4th WEEK
• FORMED WHEN EPITHELIA OF A GROOVE
[ECTODERM] AND A POUCH [ENDODERM ]
APPROACH EACH OTHER SEPARATED BY
MESENCHYME
• ONLY 1st MEMBRANE GIVES RISE TO THE
TYMPANIC MEMBRANE