PHARYNGEAL APPARATUS

Dr. G.Prabavathy

Assistant Professor

Pharyngea

l

apparatus

Clinical syndromes

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

Pharyngeal arches

Pharyngeal clefts

Pharyngeal pouches

Pharyngeal membranes

PHARYNGEAL APPARATUS

PHARYNGEAL / BRANCHIAL

APPARATUS

4th week of intrauterine development

PHARNGEAL ARCHES

In fourth week of development – series of surface

elevations appear in the lateral wall of primitive pharynx

caudal to stomodeum

PHARYNGEAL ARCHES

Initially there are six arches. Fifth arch is small

and rudimentary and soon disappears

Only five pharyngeal arches remain

6th arch

Arch 6

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

Arrangement of post-trematic and pre-trematic

nerves

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

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

SKELETAL ELEMENTS

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

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

PIERRE ROBIN SYNDROME

Autosomal recessive

disorder

Micrognathia

Cleft palate

glossoptosis (posteriorly

placed tongue)

PHARYNGEAL CLEFTS

PHARYNGEAL CLEFTS

• Invagination of surface ectoderm between the

pharngeal arches

• Four pharyngeal clefts

Second arch grows rapidly downward overlaps

the second,third and fourth pharyngeal clefts –

cervical sinus

Only first pharyngeal cleft – external auditory

meatus, whereas other clefts are obliterated

Pharyngeal

Membrane

Adult derivatives

First Tympanic membrane

Second

Third

fourth

Obliterate/disappear

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

BRACHIAL CYST AND BRANCHIAL FISTULA

BRANCHIAL FISTULA

When branchial cyst ruptures – branchial fistula

Open along ant border of sternocleidomastoid

Internal branchial fistula

External branchial fistula

LATERAL CERVICAL FISTULA

PHARNYGEAL POUCHES

PHARNYGEAL POUCHES Four pairs of pouches – evaginations of endoderm,

lining between two arches

FIRST PHARYNGEAL POUCH

First pharyngeal pouch – tubotympanic recess

Distal part of tubotympanic recess – middle ear

cavity and mastoid antrum

Proximal part – eustachian/auditory tube

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)

THIRD PHARYNGEAL POUCH

Dorsal bulbar part – parathyroid III or inferior

parathyroid gland

Ventral tubular part - thymus

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

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

Enumerate the Derivatives of second pharyngeal

arch

Name the Derivatives of first pharyngeal arch

Explain Cervical sinus

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