Pharyngeal Apparatus and Derivatives Flashcards
What are the components of the pharyngeal apparatus?
The pharyngeal apparatus consists of:
Pharyngeal (branchial) arches (mesoderm/mesenchyme)
Pharyngeal clefts (ectoderm)
Pharyngeal pouches (endoderm)
How many pharyngeal arches are there, and how many give rise to permanent structures?
There are 6 pharyngeal arches, but only 5 give rise to permanent structures. The 5th pharyngeal arch obliterates completely.
What are the derivatives of the 1st pharyngeal arch?
The 1st pharyngeal arch gives rise to:
Bones: Maxilla, mandible, zygomatic arch, temporal bone, incus, and malleus
Muscles: Muscles of mastication, mylohyoid, anterior belly of the digastric, tensor tympani, and tensor veli palatini
Nerve: CN V (Trigeminal nerve)
Artery: Maxillary artery (from the 1st aortic arch)
What are the malformations associated with the 1st pharyngeal arch?
First arch syndrome: Limited migration of neural crest cells into the 1st pharyngeal arch
Manifestations: Treacher Collins syndrome and Pierre Robin sequence
What are the derivatives of the 2nd pharyngeal arch?
Bones: Stapes, styloid process of the temporal bone, and part of the hyoid bone (lesser horn and body)
Muscles: Facial muscles, stapedius, stylohyoid, posterior belly of the digastric, and auricular muscles
Nerve: CN VII (Facial nerve)
Artery: Hyoid and stapedial arteries (from the 2nd aortic arch)
What are the derivatives of the 3rd pharyngeal arch?
Bones: Hyoid bone (Greater horn and lower part of the body)
Muscles: Stylopharyngeus
Nerve: CN IX (Glossopharyngeal nerve)
Artery: Common carotid and part of the internal carotid (from the 3rd aortic arch)
What are the derivatives of the 4th pharyngeal arch?
Cartilages: Thyroid, cricoid, arytenoid, corniculate, and cuneiform (laryngeal cartilages)
Muscles: Cricothyroid, levator palatini, and pharyngeal constrictors
Nerve: CN X (Vagus nerve, superior laryngeal branch)
Artery: Left side gives rise to the aortic arch, and the right side gives rise to the proximal portion of the right subclavian artery (from the 4th aortic arch)
What are the derivatives of the 6th pharyngeal arch?
Cartilages: Thyroid, cricoid, arytenoid, corniculate, and cuneiform (laryngeal cartilages)
Muscles: Intrinsic muscles of the larynx
Nerve: CN X (Vagus nerve, recurrent laryngeal branch)
Artery: Left side gives rise to the left pulmonary artery and the ductus arteriosus, and the right side gives rise to the right pulmonary artery (from the 6th aortic arch)
What are the derivatives of the 1st pharyngeal pouch?
Tubotympanic recess
Primitive tympanic (middle ear) cavity
Auditory (Eustachian) tube
Tympanic membrane/eardrum
What are the derivatives of the 2nd pharyngeal pouch?
Palatine tonsil primordium
Tonsillar fossa
What are the derivatives of the 3rd pharyngeal pouch?
Dorsal wing: Inferior parathyroid glands
Ventral wing: Thymus
What are the derivatives of the 4th pharyngeal pouch?
Dorsal wing: Superior parathyroid glands
Ventral wing: Ultimobranchial body (which gives rise to parafollicular cells in the thyroid gland)
What is the fate of the 1st pharyngeal cleft?
The 1st pharyngeal cleft forms the external auditory meatus.
What happens to the 2nd-4th pharyngeal clefts?
The 2nd-4th pharyngeal clefts merge and are incorporated into the cervical sinus.
What are some congenital anomalies associated with the pharyngeal apparatus?
First arch syndrome: Treacher Collins syndrome and Pierre Robin sequence
Branchial fistulas: Abnormal openings due to incomplete closure of pharyngeal clefts
Ectopic thymic tissue
Ectopic parathyroid glands
What role do neural crest cells play in the development of the pharyngeal arches?
Neural crest cells contribute to the formation of skeletal muscles of the face and migrate from rhombomeres in the hindbrain to the branchial arches.
What controls the migration of neural crest cells from rhombomeres in the hind brain in the developing fetus
HOX genes
What is the nerve associated with each pharyngeal arch?
1st arch: CN V (Trigeminal nerve)
2nd arch: CN VII (Facial nerve)
3rd arch: CN IX (Glossopharyngeal nerve)
4th arch: CN X (Vagus nerve, superior laryngeal branch)
6th arch: CN X (Vagus nerve, recurrent laryngeal branch)
What are the aortic arch derivatives for each pharyngeal arch?
1st aortic arch: Maxillary artery
2nd aortic arch: Hyoid and stapedial arteries
3rd aortic arch: Common carotid and part of the internal carotid
4th aortic arch: Left side gives rise to the aortic arch, right side gives rise to the proximal portion of the right subclavian artery
6th aortic arch: Left side gives rise to the left pulmonary artery and ductus arteriosus, right side gives rise to the right pulmonary artery
What are the cartilage derivatives of the 1st pharyngeal arch?
The 1st pharyngeal arch gives rise to Meckel’s cartilage, which forms the incus and malleus.
What are the cartilage derivatives of the 2nd pharyngeal arch?
The 2nd pharyngeal arch gives rise to Reichert’s cartilage, which forms the stapes, styloid process, and part of the hyoid bone.
What are the cartilage derivatives of the 3rd pharyngeal arch?
The 3rd pharyngeal arch gives rise to the hyoid bone (lesser horn and lower part of the body).
What are the cartilage derivatives of the 4th-6th pharyngeal arches?
The 4th-6th pharyngeal arches give rise to the laryngeal cartilages: thyroid, cricoid, arytenoid, corniculate, and cuneiform.
