CFD 5 - arches 2 Flashcards
What do the pharyngeal arches consist of?
- ectoderm - outside
- endoderm - inside (except 1st arch - a continuation of the ectoderm)
- cartilage
- blood vessels and nerve
- muscle
What is the 1st pharyngeal arch called?
mandibular arch
What does the Meckel’s cartilage of the 1st pharyngeal arch give rise to?
2 bones:
- incus
- malleus
2 ligaments:
- sphenomandibular
- sphenomaleolar
What muscles does the 1st pharyngeal arch give rise to?
- body of the tongue
- muscles of mastication:
- temporalis, masseter, pterygoids
- mylohyoid, anterior body of digastric
What nerve is associated with the 1st pharyngeal arch?
CN V
What arteries are associated with the 1st pharyngeal arch?
maxillary and carotid arteries
What dental/oral anomalies can be caused by TCS?
- clefts
- tooth agenesis
- enamel deformities
- misplacement upper 6s
What is the 2nd pharyngeal arch called?
hyoid arch
What does the Reichert’s cartilage of the 2nd pharyngeal arch form?
- stapes
- lesser horn and superior hyoid body
- styloid process, stylohyoid ligament
What muscles are formed from the 2nd pharyngeal arch?
muscles of facial expression and posterior belly of digastric
What nerve is associated with the 2nd pharyngeal arch?
CN VII
What other structures are formed from the 2nd pharyngal arch?
thyroid gland and tonsil
What does the 3rd pharyngeal arch form?
- greater horn of hyoid
- inferior hyoid body
- root of the tongue
- stylopharyngeus muscle
- CN IX
What does the 4th pharyngeal arch form?
- thyroid cartilage
- pharynx and epiglottis
- muscles - pharyngeal constrictor and soft palate
- CN X - sup. laryngeal
What happens to the 5th pharyngeal arch?
rapidly disappears
What does the 6th pharyngeal arch form?
- cricoid and arytenoid cartilages
- larynx
- muscles of larynx
- CN X - inf. laryngeal
What happens to the 2nd-6th clefts?
disappear - obliterated by the proliferating 2nd arch, arch basically grows over the top
What does the 1st pouch form?
- eustacian tube
- middle ear cavity
- tympanic membrane
- ventral part obliterated by the tongue
What does the 2nd pouch form?
- tonsillar fossa
- ventral part obliterated by the tongue
What does the 3rd pouch form?
inf. parathyroid gland and thymus
What does the 4th pouch form?
sup. parathyroid gland
During the 4th and 5th weeks of head and neck region development, what clefts remain?
only the first pair of clefts remain, all the other grooves have been obliterated by the cervical sinus as the neck develops
Where do you find pharyngeal membranes?
appear in the floor of the pharyngeal grooves
What forms the pharyngeal membranes?
- these membranes form where the epithelia of the grooves and pouches approach each other
- the endoderm of the pouches and the ectoderm of the grooves are soon separated by mesenchyme
What happens to the pharyngeal membranes?
only first pharyngeal membrane becomes the tympanic membrane, others obliterate
What causes a branchial fistula/cyst?
2nd arch fails to grow down sufficiently over 2nd-4th clefts
Where would you get a branchial fistula/cyst?
along anterior border of sternocleido-mastoid muscle
What is the appearance of a branchial fistula/cyst?
will have a very thing lining where you could get almost a gill like structure on the neck
What causes ectopic thymic or parathyroid tissue?
failure to migrate completely
What does ectopic thymic or parathyroid tissue result in?
parathyroid gland ends up being closer to the mouth than it should be
