Branchial Arches Flashcards
What is the pharynx and what germ layer is it derived from?
Region behind oral and nasal cavities
Endoderm
How are the branchial arches formed?
Neural Crest cells migrate to the head and neck lateral to the rostral part of the foregut and from the arch structures
What are branchial grooves?
Ectodermal lefts between adjacent arches
What are branchial pouches?
Endodermal out pocketing from rostral foregut, between adjacent arches
What four things do each branchial arch have?
Cartilage
Nerve
Artery
Muscle
What are the four elements of the branchial apparatus?
Branchial Arch
Branchial Groove
Branchial Pouch
Branchial Membrane - site of contact of groove and pouch
What does the first arch form?
Face, has maxillary and mandibular processes
Surrounds stomodeum (primitive mouth)
What is the oropharyngeal membrane?
Boundary between the mouth and the pharynx
Location of Palatoglossal arch
What is formed from the first arch?
Skeletal - Malleus, Incus
Ligaments - Ant. ligament of the malleus, Sphenomandibular ligament
Muscles - Branchiomotor innervation of CN V
What is formed form the second arch?
Skeletal - Stapes, Styloid process, Hyoid (Lesser horn, upper half of body)
Ligaments - Stylohyoid ligament
Muscles - Branchiomotor innervation of CN VII
What is formed from the third arch?
Skeletal - hyoid bone (greater horn, lower half of body))
Muscles - stylopharengeus (IX)
What is formed from the fourth arch?
Skeletal - Cartilages of the larynx
Muscles - branchiomotor innervation of CN X
What is formed from the sixth arch?
Muscles - Sternocleidomastoid, Trapezius (CN XI)
What forms the external auditory meatus?
First branchial groove
What forms the tympanic membrane?
First branchial membrane
What does the first branchial pouch form?
Auditory tube and tympanic cavity
Clinical: First branchial cleft cyst - tract linked to external auditory meatus
What does the second branchial pouch form?
Lining of palantine tonsils
Clinical: Second branchial cleft cyst - tract linked to tonssilar fossa
What does the third branchial pouch form?
Inferior parathyroid gland, Thymus
Clinical: Third Branchial Cleft cyst - tract at thyrohyoid membrane or piriform recess
What does the fourth branchial pouch form?
Superior parathyroid gland, C-cells of thyroid
Clinical: does not form
What do branchial grooves 2-6 form?
Cervical sinus
What is a branchial sinus?
Anomaly that results in blind pouch from pharynx
What is a branchial fistula?
Anomaly
Channel, often connecting pharynx to skin of neck; usually passes anterior to sternocleidomastoid between int. and ext. carotid A.
How does the thyroid develop?
Starts as median endodermal thickening on floor of pharynx
Elongates to form thyroid diverticulum; descends anterior to hyoid bone and larynx
Thyroglossal duct connects diverticulum to foramen cecum
What is a lingual thyroid?
The thyroid gland does not migrate and lies within the tongue
