1. Pharyngeal arches

2. The pharyngeal (Branchial)
apparatus :
 It consists of :
1-pharyngeal arches.
2-pharyngeal pouches.
3-pharyngeal grooves.
4-pharyngeal membranes.
 These embryonic structures contribute to
the development of the head & neck
regions.

3. Drawings illustrating the
human pharyngeal apparatus.
A, dorsal view of cranial part of an
embryo.
B to D, lateral views showing later
development of pharyngeal arches.
E to G, ventral or facial views,
illustrating the relationship of the first
pharyngeal arch to the stomodeum.
-Maxillary prominence of 1st arch lies
lateral to stomodeum.
-Mandibular prominence of
1st arch lies caudal to stomodeum.
H,horizontal S.of cranial part of emb.
I, horizontal S. illustrating the arch
components + floor of pharynx.
J, sagittal S.illustrating the openings
of pharyngeal pouches in the lateral
wall of the primordial pharynx.

4. Pharyngeal arches
They begin to develop early in the
4th week as neural crest cells migrate
into the future head & neck regions.
By the end of 4th week, 4 pairs of
pharyngeal arches are visible externally
The 5th & 6th arches are rudimentary
and not visible on surface of embryo.
Fronto-nasal
prominence
Pharyngeal arches are separated
externally by fissures- the pharyngeal
grooves, which numbered craniocaudally as the arches.
The arches appear along lateral wall
of primordial pharynx.
The primordial mouth (stomodeum)
is temporarily closed by oropharyngeal
bilaminar membrane (ectoderm &
endoderm), which ruptures at about 26
th

5. Pharyngeal arches
1st pharyngeal arch (mandibular
arch), the primordium of jaws
consists of :
1- A dorsal portion, the
maxillary process, which gives rise to
the maxilla (upper jaw), zygomatic
bone, and squamous part of temporal
bone.
2- A ventral portion, the mandibular
process, which gives rise the mandible
( lower jaw).
-1st pair of pharyngeal arches plays a
major role in facial development.
2nd pharyngeal arch (hyoid arch) :
contributes to the formation of hyoid
bone.

6. Pharyngeal Arches
A, By the end of the 4th week (28days),
4 pairs of pharyngeal arches are developed.
B, Drawing showing pharyngeal pouches
+ aortic arches, that supplies the
pharyngeal arches and arise from truncus
arteriosus, then enter the dorsal aorta.
The derivatives of aortic arches : are the
adult arteries of head & neck.
C, Horizontal section showing the floor
of primordial pharynx and germ layer
derivatives of the pharyngeal arch
components : each arch consists of
a core of mesenchyme, which is covered
externally by ectoderm and internally by
endoderm.

7. Pharyngeal Arch
Components arch consists of a core of mesenchyme that is
Each
covered externally by ectoderm and internally by
endoderm.
A core of mesenchyme derived from the original
mesenchyme - mesoderm during 3rd week + neural
crest cells (neuroecto-dermal origin) during 4th week
that migrate into the arches.
Skeletal musculature & vascular endothelia are
derived from the original mesenchyme in the
arches.
A typical pharyngeal arch contains :
1-an aortic arch artery : arises from
truncus arteriosus of primordial heart to enter the
dorsal aorta.
2-a cartilaginous rod : that forms the skeleton of arch.
3-a muscular components : to give ms. of head
& neck.

8. Fate of Pharyngeal
Arches
A, lateral view of embryo at 5
week
(32 days) showing pharyngreal arches
+ cervical sinus.
th
B, section illustrating growth of 2nd
arch over 3rd & 4rth arches.
C, embryo of about 33 days.
D, section illustrating early closure
of the cervical sinus during 5th week.
E, embryo of 41 days (end of 6th w.).
F, section showing the transitory
cystic remnant of cervical sinus.
G, drawing of 20-week fetus
illustrating the area of face derived
from the 1st pair of pharyngeal arches.

9. Fate of Pharyngeal
Arches
They contribute to the development of
face, nasal cavities, mouth,larynx, pharynx,
and neck.
During 5th week, 2nd arch enlarges to
overgrow the 3rd & 4th arches, forming
ectodermal depression- the cervical sinus.
B,D
By the end of 7th week, 2nd to 4th
pharyngeal grooves + the cervical sinus
have disappeared, giving the smooth
contour to the neck

10. Derivatives of Pharyngeal
Arch Cartilages :
A, lateral view of 4-week embryo, illustrating location of cartilages in pharyngeal arches.
B, 24-week fetus illustrating adult dreivatives of arch cartilages :
1-Note development of mandible by intramembranous ossification of
mesenchymal tissue surrounding the ventral part of 1st arch cartilage (Meckel’s
cartilage) + development of malleus & incus (middle ear bones) dorsally + anterior
ligament of malleus & sphenomandibular ligament in the middle part. 2-Note, the 2nd
arch cartilage (hyoid or Reichert’s cartilage) gives rise dorsally stapes & styloid
process, in the middle stylohyoid ligament, and ventrally lesser cornu + upper part of

11. Derivatives of Pharyngeal
Arch Cartilages :
B, 3- Note also derivatives of the 3rd arch cartilage which ossifies to form :
greater cornu (horn) + inferior part of the body of hyoid bone.
4- Cartilaginous components of 4th & 6th pharyngeal arches fuse to
form most of laryngeal cartilages (thyroid + cricoid + arytenoid + corniculate +
cuneiform), EXCEPT the cartilage of epiglottis which develops from the mesenchyme
of the caudal part of hypopharyngeal eminence lying in the floor of primordial
pharynx and derived from 3rd & 4th pharyngeal arches.
The 5th arch is often absent, if present it is rudimentary and has No derivatives.

12. Derivatives of Pharyngeal
Arch Muscles :
A, lateral view of 4-week embryo showing the muscles derived from the
pharyngeal arches, the arrow showing the pathway of myoblasts from the occipital
myotomes to form the muscles of tongue.
B, sketch of head & neck of 20-week fetus, showing the 1st pharyngeal arch
forms ms. of mastication & other ms./ 2nd arch forms ms. of facial expression,
post.belly of digastric & other ms. / 3rd arch forms stylopharyngeus./ 4th arch forms
cricothyroid, levator veli palatini + constrictors of pharynx. / 6th arch forms
interinsic ms. of larynx + striated ms of esophagus.

13. Derivatives of Pharyngeal
Arches

14. Derivatives of Pharyngeal Arch
Nerves
A, lateral view of head &neck and thorax of
4-week embryo showing the cranial nerves :
Trigeminal N.(V), Facial N.(VII),
Glossopharyngeal N.(IX), and Vagus N.(X)—
supplying 1st ,2nd , 3rd & caudal (4th + 6th )
pharyngeal arches, respectively.
B, sketch of head & neck of 20-week fetus
showing the 2 branches of 1st arch nerve (CNV),
maxillary & mandibular branches of trigeminal N
C, Sagittal section of fetal head & neck
showing the sensory nerves of trigeminal N.,
which is the principal sensory N. of head & neck
supplying face, teeth & m.m. of nasal cavity,
palate, mouth & tongue, and is the motor N. for
ms. of mastication.
C, The nerves from 2nd to 6th pharyngeal arches
have little sensory nerves, however, they
innervate m.m. of post.tongue, pharynx & larynx.