The Pharyngeal Arches
The development of the head and neck begins in the 4th and 5th week.
Growth of mesenchymal tissue (connective tissue) in the cranial region of the embryo
results in the formation of arches, separated by clefts. These are the pharyngeal
arches and pharyngeal clefts.
Simultaneously, a number of outpocketings appear on the lateral wall of the pharynx
– the pharyngeal pouches. The pouches separate the arches on the internal
(endodermal) surface whilst the clefts separate the arches on the external
(ectodermal) surface.
In this article, we will explore these structures from outside to inside and discuss the
structures that arise from the pharyngeal apparatus.
, Pharyngeal Clefts
There are initially four pharyngeal clefts. However, only the 1st cleft gives rise to a
permanent structure in the adult – the external auditory meatus.
The 2nd, 3rd and 4th clefts only form temporary cervical sinuses – which are then
obliterated by the rapidly proliferating 2nd pharyngeal arch.
Pharyngeal Arches
There are six pharyngeal arches – however, the 5th regresses soon after forming.
Each arch is innervated by an arch-associated cranial nerve, and has a muscular
component, a skeletal and cartilaginous supporting element. as well as a vascular
component.
In the adult, each pharyngeal arch is associated with specific structures within the
head and neck.
First Arch
The first pharyngeal arch is comprised of two parts:
Maxillary prominence (dorsal portion) – becomes the future
maxilla, zygomatic bone and part of the temporal bone. Is
associated with the maxillary cartilage, which gives rise to
the incus.
Mandibular prominence (ventral portion) – becomes the future mandible.
Is associated with Meckel’s cartilage, which gives rise to the malleus and the
sphenomandibular ligament.
The development of the head and neck begins in the 4th and 5th week.
Growth of mesenchymal tissue (connective tissue) in the cranial region of the embryo
results in the formation of arches, separated by clefts. These are the pharyngeal
arches and pharyngeal clefts.
Simultaneously, a number of outpocketings appear on the lateral wall of the pharynx
– the pharyngeal pouches. The pouches separate the arches on the internal
(endodermal) surface whilst the clefts separate the arches on the external
(ectodermal) surface.
In this article, we will explore these structures from outside to inside and discuss the
structures that arise from the pharyngeal apparatus.
, Pharyngeal Clefts
There are initially four pharyngeal clefts. However, only the 1st cleft gives rise to a
permanent structure in the adult – the external auditory meatus.
The 2nd, 3rd and 4th clefts only form temporary cervical sinuses – which are then
obliterated by the rapidly proliferating 2nd pharyngeal arch.
Pharyngeal Arches
There are six pharyngeal arches – however, the 5th regresses soon after forming.
Each arch is innervated by an arch-associated cranial nerve, and has a muscular
component, a skeletal and cartilaginous supporting element. as well as a vascular
component.
In the adult, each pharyngeal arch is associated with specific structures within the
head and neck.
First Arch
The first pharyngeal arch is comprised of two parts:
Maxillary prominence (dorsal portion) – becomes the future
maxilla, zygomatic bone and part of the temporal bone. Is
associated with the maxillary cartilage, which gives rise to
the incus.
Mandibular prominence (ventral portion) – becomes the future mandible.
Is associated with Meckel’s cartilage, which gives rise to the malleus and the
sphenomandibular ligament.
