In the

embryonic development In developmental biology, animal embryonic development, also known as animal embryogenesis, is the developmental stage of an animal embryo. Embryonic development starts with the fertilization of an egg cell (ovum) by a sperm, sperm cell (spermat ...

vertebrate Vertebrates () are animals with a vertebral column (backbone or spine), and a cranium, or skull. The vertebral column surrounds and protects the spinal cord, while the cranium protects the brain. The vertebrates make up the subphylum Vertebra ...

s, pharyngeal pouches form on the endodermal side between the

pharyngeal arch The pharyngeal arches, also known as visceral arches'','' are transient structures seen in the Animal embryonic development, embryonic development of humans and other vertebrates, that are recognisable precursors for many structures. In fish, t ...

es. The

pharyngeal groove A pharyngeal groove (or branchial groove, or pharyngeal cleft) is made up of ectoderm unlike its counterpart the pharyngeal pouch on the endodermal side. The first pharyngeal groove produces the external auditory meatus The ear canal (external ...

s (or clefts) form the lateral ectodermal surface of the neck region to separate the arches.

Specific pouches

First pouch

The

endoderm Endoderm is the innermost of the three primary germ layers in the very early embryo. The other two layers are the ectoderm (outside layer) and mesoderm (middle layer). Cells migrating inward along the archenteron form the inner layer of the gastr ...

lines the future

auditory tube The Eustachian tube (), also called the auditory tube or pharyngotympanic tube, is a tube that links the nasopharynx to the middle ear, of which it is also a part. In adult humans, the Eustachian tube is approximately long and in diameter. It ...

(pharyngotympanic Eustachian tube),

middle ear The middle ear is the portion of the ear medial to the eardrum, and distal to the oval window of the cochlea (of the inner ear). The mammalian middle ear contains three ossicles (malleus, incus, and stapes), which transfer the vibrations ...

, mastoid antrum, and inner layer of the tympanic membrane. Derivatives of this pouch are supplied by Mandibular nerve.

Second pouch

* Contributes the

, palatine tonsils, supplied by the

facial nerve The facial nerve, also known as the seventh cranial nerve, cranial nerve VII, or simply CN VII, is a cranial nerve that emerges from the pons of the brainstem, controls the muscles of facial expression, and functions in the conveyance of ta ...

Third pouch

* The third pouch possesses dorsal and ventral wings. Derivatives of the dorsal wings include the inferior

parathyroid gland Parathyroid glands are small endocrine glands in the neck of humans and other tetrapods. Humans usually have four parathyroid glands, located on the back of the thyroid gland in variable locations. The parathyroid gland produces and secretes par ...

s, while the ventral wings fuse to form the cytoreticular cells of the

thymus The thymus (: thymuses or thymi) is a specialized primary lymphoid organ of the immune system. Within the thymus, T cells mature. T cells are critical to the adaptive immune system, where the body adapts to specific foreign invaders. The thymus ...

. The main nerve supply to the derivatives of this pouch is cranial nerve IX,

glossopharyngeal nerve The glossopharyngeal nerve (), also known as the ninth cranial nerve, cranial nerve IX, or simply CN IX, is a cranial nerve that exits the brainstem from the sides of the upper Medulla oblongata, medulla, just anterior (closer to the nose) to t ...

Fourth pouch

Derivatives include: * superior

s and ultimobranchial body which forms the parafollicular C-Cells of the

thyroid gland The thyroid, or thyroid gland, is an endocrine gland in vertebrates. In humans, it is a butterfly-shaped gland located in the neck below the Adam's apple. It consists of two connected lobes. The lower two thirds of the lobes are connected by ...

. * Musculature and cartilage of larynx (along with the sixth pharyngeal arch). * Nerve supplying these derivatives is Superior laryngeal nerve.

Fifth pouch

* Rudimentary structure, becomes part of the fourth pouch contributing to thyroid C-cells.Endocrine Glands

Sixth pouch

* The fourth and sixth pouches contribute to the formation of the musculature and cartilage of the larynx. Nerve supply is by the recurrent laryngeal nerve.

Additional images

File:Kiemenbogen.jpg, Pattern of the branchial arches. I-IV branchial arches, 1–4 pharyngeal pouches (inside) and/or

pharyngeal grooves A pharyngeal groove (or branchial groove, or pharyngeal cleft) is made up of ectoderm unlike its counterpart the pharyngeal pouch on the endodermal side. The first pharyngeal groove produces the external auditory meatus The ear canal (external ...

(outside)
a

Tuberculum laterale The tongue is a muscular organ in the mouth of a typical tetrapod. It manipulates food for chewing and swallowing as part of the digestive process, and is the primary organ of taste. The tongue's upper surface (dorsum) is covered by taste buds ...

Tuberculum impar The median tongue bud (also tuberculum impar) marks the beginning of the development of the tongue. It appears as a midline swelling from the first pharyngeal arch late in the fourth week of embryogenesis. In the fifth week, a pair of lateral l ...

c Foramen cecum
d

Ductus thyreoglossus The thyroglossal duct is an embryological anatomical structure forming an open connection between the initial area of development of the thyroid gland and its final position. It is located exactly mid-line, between the anterior 2/3 and posterior 1 ...

Sinus cervicalis The cervical sinus is a structure formed during embryonic development. It is a deep depression found on each side of the neck. It is formed as the second pharyngeal arch (hyoid arch) grows faster than the other pharyngeal arches, so they become ...

File:Gray979.png, Floor of pharynx of human embryo about twenty-six days old.

References

External links

* (Item #1 at Fig. 14) * * *
Outline at howard.edu (scroll down to "III. THE PHARYNGEAL POUCHES")
{{Authority control Animal developmental biology Pharyngeal arches Human head and neck