Embryology Flashcards
Remnants of the thyroglossal duct, which connects the lobes of the premature thyroid, causes what disorder?
Midline cyst
The interior portion of the pharyngeal arch is called…?
Pharyngeal pouch
What does the first pharyngeal pouch form?
Tubotympanic recess
What structure develops into the external auditory meatus?
First pharyngeal pouch
The tympanic membrane originates from what germ layer?
All three germ layers!
A woman comes to the clinic with her newborn child. The child was diagnosed with a cleft lip shortly after birth. How did this happen?
The maxillary and intermaxillary prominences failed to fuse.
What tissue composes the paryngeal pouch, arch, and cleft, respectively?
Pouch - Endodern
Arch - Mesoderm
Cleft - Ectoderm
The sixth pharyngeal arch contains what nerve?
Vagus nerve - recurrent laryngeal
What is the newest part of the skull, evolutionarily?
Neurocranium
What cranial bones arise from the Pharyngeal arch?
Maxilla, mandible, temporal, zygomatic bones
Where does the thyroid bud before moving anteriorly and causally?
Between pharyngeal pouches 1 & 2
Parafollicular cells of the thyroid are formed from what structure?
Pharyngeal pouch 4
Where are pharyngeal clefts found?
Exterior to the pharyngeal arch
The intrinsic muscles of the larynx that assist with speech production originate from what arch?
Pharyngeal arch 6
What muscle originates from pharyngeal arch 3?
Stylopharyngeus
What bones arise from the 2nd arch?
Styloid process, hyoid, stapes
What nerve is associated with the 3rd arch?
Glosspharyngeal nerve
What muscles arise from Arch 1?
Chewing - Temporalis, pterygoid, masseter
Block sound - tensor tympani
Swallowing - Tensor veli palantini, anterior belly of the digastric, mylohyoid muscles
Pharyngeal grooves 3, 4, 6, fuse to form temporary lateral cervical sinuses. Failure of these sinuses to properly form or regress causes what disorders?
Lateral cervical cyst - cyst due to persistent sinus
Cervical fistula - external sinus openings
The parathyroid and thymus originate from what structure?
Pharyngeal pouch 3
True/False. Knocking out the gene that encodes the identity of a pharyngeal arch does not affect development.
False. Knocking out a gene will result in duplication of the above arch. These are inductive cells so they migrate to the correct location, but were not assigned the correct identity.
What conductive ear structures arise from Arch 1?
Malleus, Incus
What arch forms the digastric muscle?
The digastric if formed by two arches. The anterior portion arises from the first pharyngeal arch and the posterior portion arises from arch 2.
Describe the development of the mouth, lips, and palate.
Medial nasal processes, lateral nasal processes, maxillary prominence, and mandibular prominence develop from the first pharyngeal arch.
The medial nasal process and maxillary prominence fuse to form the upper lip and jaw.
The fused medial nasal processes form the intermaxillary prominence, which becomes the tip of the lip, other upper jaw structures, and the palate.
The mandibular prominences fuse to form the lower jaw.