Pharyngeal Arches, Pouches and Cysts Flashcards
When do the pharyngeal arches begin developing?
4th week
Most skeletal and connective tissues of head and neck are made of?
neural crest cells
How are the pharyngeal arches numbered?
cranial > caudal
Describe the pharyngeal system?
6 pairs of pharyngeal arches separated by endodermally lined pouches and ectodermally lined clefts (grooves)
> Four well-defined pairs visible externally
> Fifth and sixth rudimentary
Each pharyngeal arch consists of?
nerve
artery
cartilage
List the 3 components which make up the pharyngeal arches and what each component forms?
- ectoderm > pharyngeal grooves
- mesoderm > pharyngeal arches
- endoderm > pharyngeal pouches
How many pharyngeal arches develop in an embryo?
5
> 1, 2, 3, 4, and 6
Which pharyngeal arch does not give rise to any derivatives?
5
At what stage of development does the tongue develop?
4th week of intrauterine life
From which pharyngeal arch does the anterior two-thirds of the tongue develop?
1st pharyngeal arch
Which pharyngeal arches are responsible for the formation of the posterior third of the tongue?
3rd and 4th pharyngeal arches
What is derived from the first pharyngeal arch?
- Prominences
- maxilla & mandible bones
- zygomatic bone - Cartilage (meckel’s cartilage)
- malleus & incus
- anterior ligament of malleus
- sphenomandibular ligament - Muscles (of mastication)
- temporalis
- masseter
- pterygoids
- mylohyoid
- tensor tympani - Nerve
- Mandibular branch of CV 5 (Trigeminal nerve)
Which pharyngeal arches are responsible for the formation of the 3 bony ossicles of the ear?
- malleus + incus > pharyngeal arch I
- stapes > pharyngeal arch II
What is derived from the first pharyngeal pouch?
- Eustachian tube
- tympanic membrane
- Temporal bone
What is derived from the first pharyngeal groove?
Develops into the external acoustic meatus
> The remaining grooves disappear and form cervical sinus
> May form and abnormal lateral cervical cyst or fistula
What is derived from the second pharyngeal arch?
- Reichert’s cartilage
- stapes
- the upper body & lesser cornu of hyoid bone
- the styloid process of temporal bone
- stylohyoid ligament. - Muscles
- platysma
- muscles of facial expression
- stylohyoid
- stapedius - Nerve
- CV 7 (Facial nerve) - Artery
- stapedial artery
What is derived from the second pharyngeal pouch?
Lymphatic nodules - palatine tonsils
What does the tubotympanic recess contribute to?
Eustachian tube
What is derived from the third pharyngeal arch?
- Cartilage
- forms lower body of hyoid & greater cornu of hyoid bone. - Muscles
- stylopharyngeus
- superior & middle pharyngeal constrictors - Nerve
- CN 9 (Glossopharyngeal nerve) - Artery
- common carotid & proximal portions of the internal & external carotid.
What is derived from the third branchial pouch?
- Inferior parathyroids
- Thymus gland
What doe the fourth and sixth pharyngeal arches form together?
Fourth & sixth pharyngeal arch cartilages fuse to form the laryngeal cartilages
What is derived from the fourth pharyngeal arch?
- Muscles
- cricothyroid
- inferior pharyngeal constrictors - Nerve
- Superior Laryngeal branch of Vagus nerve - Artery
- Right Subclavian
- Aortic arch
What is derived from the fourth pharyngeal pouch?
- superior parathyoid glands
- parafollicular thyroid cells (ultimobranchial body)
What is derived from the fifth pharyngeal arch?
has no derivatives
> is rudimentary if present
What is derived from the sixth pharyngeal arch?
- Muscles
- remaining intrinsic laryngeal musculature - Nerve
- Recurrent laryngeal nerve branch of Vagus nerve - Artery
- Pulmonary Artery & ductus arteriosus
Which cranial nerve innervates the first branch?
trigeminal nerve
Which nerve innervates the second arch?
facial nerve
Which nerve innervates the third arch?
glossopharyngeal nerve
Which nerve innervates the fourth and sixth arches?
vagus nerve
Which cranial nerves innervate muscles derived from preotic somites?
oculomotor
trochlear
abducents
Which nerve innervates muscles derived from occipital somites?
hypoglossal nerve
Describe branchial cysts?
Develop along anterior border of sternocleidomastoid
Most found inferior to angle of mandible
Often present in adulthood
Remnants of cervical sinus and/or second pharyngeal groove
Describe branchial vestiges?
Cartilaginous or bony remnants
Usually anterior to inferior third of sternocleidomastoid
Describe first arch syndrome?
results in various congenital anomalies of eyes, ear, mandible, palate
- migration of neural crest cells into first pharyngeal arch implicated
What are the 2 main manifestations of first arch syndrome?
- Treacher Collins syndrome
- Underdevelopment of zygomatic bones of face, defects of lower eyelids, external ear deformations - Pierre Robin syndrome
- Hypoplasia of the mandible, cleft palate & eye and ear defects present
What does first branchial arch syndrome look like on a person?
- The right corner of the mouth is extended in a cleftlike fashion
- The right auricle is severely deformed and the external acoustic meatus is absent
Describe the embryology of the thyroid gland?
Endoderm of the floor primitive pharynx between 1st & 2nd arches
Descends as a bilobed diverticulum from foramen cecum around the 4th week to rest in the neck region by 7-8th wk.
