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.
What is formed by the viscerocranium?
The viscerocranium is composed of the 5 pharyngeal arches. These go on to form the facial skeleton and various other structures of the face and pharynx
What structure forms the palatine tonsils?
Pharyngeal pouch 2
What evolutionary cranium is associated with development of the brain and sense organs?
Chrondocranium (originates from cartilage)
Describe the mechanism of Treacher Collins syndrome.
An autosomal dominant condition that results in mutation of TCOF1. This mutation affects survival of neural crest cells, leaving fewer cells to migrate and form arch 1 structures.
The external ear originates from arches 1 and 2. What structure forms directly from the arches to later form the ears?
Auricular hillocks
What CN is associated with the first pharyngeal arch?
CNV3 - Mandibular division of the trigeminal
The fourth pharyngeal arch contains what nerve?
Vagus nerve - superior laryngeal
True/False. Intrinsicly patterned cells are assigned an identity early in development and will not change throughout migration.
True. Conversely, cells that are inductive patterned migrate and change identity based on signals from nearby cells.
The root of the tongue is formed from what structure?
Arches 3 & 4
What causes preauricular fistulas?
Persistent cleft between preauricular hillocks
The facial nerve is associated with which pharyngeal arch?
2nd arch
The vagus nerve is associated with what pharyngeal arch?
Arches 4 & 6
Describe the mechanism of Treacher Collins syndrome.
An autosomal dominant condition that results in mutation of TCOF1. This mutation affects survival of neural crest cells, leaving fewer cells to migrate and form arch 1 structures.
True/False. Both the anterior and posterior neuropores close at the same time.
False. The anterior neuropore closes before the posterior. Both should close by day 27/28.
The meninges arise from what germ layer?
Mesoderm
What genes are expressed in the dorsal spinal cord and prevent development of motorneurons?
BMB & Pax
What are the three parts of the early brain?
Prosencephalon, mesencephalon, rhombencephalon
The prosencephalon develops into what two parts during brain development?
Diencephalon & telencephalon
The rhombencephalon develops into what two parts during brain development?
Metencephalon & myelencephalon
From what early brain structure do the caudal & rostral medulla arise?
Myelencephalon
From what early brain structure does the pons arise?
Metencephalon
What structure arises from the metencephalon?
Pons & cerebellum
What structure arises from the diencephalon?
Thalamus & hypothalamus
From what early structure does the cerebral cortex arise?
Telencephalon
What portion of the pituitary gland arises from the diencephalon?
Posterior pituitary
What early structure forms the eye?
Diencephalon
What disorder is caused by a buildup of CSF in the brain due to cerebral aqueduct stenosis?
Hydrocephaly
From what early brain structures do the lateral and third ventricles arise, respectively?
Lateral - telencephalon
Third - Diencephalon
