The pharyngeal apparatus in a 4 week old human embryo consists of pharyngeal arches and pouches. There are initially 4 pairs of pharyngeal arches which give rise to important structures in the head and neck region. The first pharyngeal arch forms parts of the jaw and middle ear bones. The second arch forms the stapes and structures associated with the hyoid bone. The third and fourth arches contribute to parts of the larynx and thyroid cartilage. Between the arches are 4 pairs of pharyngeal pouches which form other structures like the tonsils, parathyroid and thyroid glands, and thymus gland. Abnormal development of these pouches can lead to conditions like DiGeorge

1. Pharyngeal Arches
& Pouches
-Bharanidharan S

2. Pharangeal apparatus
•The head and neck region of four
week human embryo somewhat
resemble these regions of a fish
embryo of comparable stage
•This explains the former use of
designation branchial apparatus

3. Pharyngeal apparatus consists of
Pharyngeal arches
Pharyngeal pouches
Pharyngeal grooves/clefts
Pharyngeal membrane

4. Pharyngeal pouchPharyngeal groove
Pharyngeal
membrane
Pharyngeal arch

5. Pharyngeal Arches
Definition
Mesenchymal condensation on either side
of the pharynx are known as pharangeal
arches.

6. •Pharyngeal arches
begin to develop
early in the fourth
week as neural
crest cells migrate
into the head and
neck region

7. Pharyngeal Arches
• By the end of the fourth week, four pairs of
pharyngeal arches are visible externally
• The fifth and sixth arches are rudimentary
and are not visible on the surface of the
embryo
• The pharyngeal arches are separated from
each other by fissures called pharyngeal
grooves
• They are numbered in craniocaudal sequence

8. •Each pharyngeal arch consists of a core of
mesenchyme
•Is covered externally by ectoderm and internally by
endoderm
Pharyngeal Arch Components

9. Ist Pharangeal Arch Derivatives
Ist pharangeal arch consists of 2 swellings.
The swellings are:
1.Maxillary Swelling
2.Mandibular Swelling

10. Maxillary
Swelling
Mandibular
Swelling

11. Maxillary process
(palatopterygoquadrate cartilage):
Maxillary process gives rise to
•Incus
The incus or anvil is a bone in
the middle ear.The anvil
shaped small bone is one of
the 3 ossicles in the middle
ear.

12. Mandibular process
Mandibular process give rise
to:
•Most of the Mandible
•Malleus
• Anterior ligament of malleus
•Sphenomandibular ligament

14. Muscles of 1st arch:
Musculature of 1st pharangeal arch
includes:
•Muscles of mastication i.e
temporalis,masseter,lateral and medial
pterygoid
•Anterior belly of digastric muscle
•mylohyoid
•Tensor tympani
•Tensor veli palatini

15. Nerve supply to the 1st arch
•Nerve supply to 1 st arch is provided
by Mandibular division of V nerve.
•Maxillary Artery
Note
•By intramembranous ossification
of mesenchyme of 1 st
arch,maxilla,zygomatic,squamous
part of temporal are developed.

17. as2nd Pharangeal Arch
2nd
pharangeal arch gives rise to
•Stapes
•Styloid process
•Stylohyoid ligament
•Lesser cornua
•Upper half of body of hyoid.
2nd pharangeal arch is also known a hyoid arch or
rechiert’s cartilage.
skeletal component

19. Musculature of 2nd arch
Musculature of 2nd arch includes
•Occipotofrontalis
•Auricular muscles
•Posterior belly of digastric muscle
•Platysma
•Muscles of facial expression
•Stylohyoid.

20. Nerve supply
•2nd arch is innervated by facial nerve
and Stapedial Artery(temporary)

21. 3rd Pharangeal Arch
Skeletal component
3rd arch includes
•Lower Half of hyoid bone
•Greater cornua of the hyoid bone.
Musculature
Musculature is limited to stylopharangeus
muscle

23. Nerve supply
It is innervated by
glossopharangeal
nerve,Internal
carotid Artery.

24. 4th and 6th Pharangeal Arch
Skeletal component
Cartilage of 4th and 6th arch fuse together to form
•Thyroid
•Cricoid
•Aretenoid
• Corniculate cartilages
• Cunieform.

25. Musculature:
It includes
•Cricothyroid
•Constrictors of pharynx
•And other muscles of Larynx.
Nerve supply:
External laryngeal and recurrent
laryngeal,branches of vago
accessory complex,arch of
aorta,right subclavian
artery,pulmonary arteries,ductus
arteriosus.

28. Pharangeal pouches
•The pharyngeal pouches are balloon like
diverticula that formed on the endodermal
side between the pharyngeal arches
•The pairs of pouches develop in a
craniocaudal sequence between the arches

30. •There are four well defined pairs of pharyngeal
pouches
•The fifth pair is absent or rudimentary
•The first pair of pouches lies between the first
and second pharyngeal arches

31. •The first pharyngeal pouch forms stalk like
diverticulum called tubotympanic recess
•The proximal part forms the
pharhyngotympanic tube.
•The distal part forms the tymmpanic
cavity,lining of tympanic membrane and
mastoid antrum.
Ist Pharangeal Pouch

33. •Dorsal part of this pouch takes part in
formation of tubo-tympanic recess.
•The ventral part forms palatine tonsil.
•The epithelial lining of pouch prolifierates and
forms buds that penetrates the surrounding
mesenchyme.
•Part of the pouch remains and is found in the
adult as tonsillar fossa.
Second Pharyngeal Pouch

34. Derivatives of 2nd pharangeal pouch

35. Third Pharyngeal Pouch
•Epithelium of dorsal region of 3rd pouch
differntiates into inferior thyroid gland
•.While ventral region differntiates into
thymus.
•Both inferior parathyroid and thymus gland
primordial lose their connection with
pharyngeal wall.

36. 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

37. Fourth Pharyngeal Pouch:
•Each dorsal part develops into a
superior parathyroid gland
•It migrates caudally and lies on the posterior
surface of the thyroid gland as superior
parathyroid gland.

38. Fifth Pharyngeal Pouch:
•The fifth pouch is the last of the
pharyngeal pouches to develop.It gets
incorpated in the 4th pouch.
•It forms ultimobranchial body in some
species;which gives rise to Parafollicular or C
cells of the thyroid gland.These cells secrete
calcitonin a hormone involved in calcium
regulation in the blood.

39. Anomalies of Pharyngeal pouches:
•Digeorge syndrome-This syndrome occurs due to
the failure of development of 3rd and 4th
pouches.This syndrome is characterised by
Thymic hypoplasia which causes selective T-cell
deficiency and greatly reduced cell-mediated
immunity.
•Nezelof’s syndrome-It results from the failure
of development of only the 3rd pharyngeal
pouch.In this case superior parathyroid glands are
present but both inferior parathyroid glands and
thymus are absent