Development of the Head and Neck pt. 2 Flashcards
<p>Incomplete fusion or formation of the medial nasal prominences results in </p>
<p>Midline facial defects
-median cleft lip or synopthalmia with proboscis</p>
<p>Synopthalmia with proboscis is associated with </p>
<p>Holoprosencephaly </p>
<p>Incomplete fusion between the intermaxillary segment and the maxillary prominences results in </p>
<p>Anterior cleft deformities </p>
<p>Anterior cleft deformities are deformities anterior to the incisive foramen such as </p>
<p>Cleft lip or cleft upper jaw </p>
<p>The most common congenital malformation of the head and neck and occurs in 1/700 births </p>
<p>Cleft lip</p>
<p>Forms when a wedge of ectoderm furrows at the junction between the maxillary and lateral nasal prominences </p>
<p>Nasolacrimal groove </p>
<p>The nasolacrimal groove forms the </p>
<p>Nasolacrimal duct and lacrimal sac</p>
<p>Incomplete fusion between the maxillary and lateral nasal prominence along the nasolacrimal groove results in
-Nasolacrimal duct is exposed to surface</p>
<p>Oblique facial cleft (nasolacrimal duct is exposed to surface)</p>
<p>Form the connective tissues, cartilages, and bones associated with the cheeks, lateral upper lip, and secondary palate (posterior to incisive foramen)</p>
<p>Maxillary prominences of the 1st pharyngeal arch</p>
<p>The secondary palate is posterior to the </p>
<p>Incisive foramen </p>
<p>The secondary palate forms from midline fusion of the maxillary prominences' outgrowths called </p>
<p>Palatine shelves </p>
<p>Initially, the palatine shelves are vertically oriented around the </p>
<p>Protruding tongue </p>
<p>As the oral cavity grows and the tongue flattens, the palatine shelves become horizontally-oriented and approximate to fuse in the midline and form the </p>
<p>Secondary palate </p>
<p>The midline nasal septum (from the frontal nasal prominence) fuses with the superior midline surface of the </p>
<p>Palatine shelves</p>
<p>Incomplete midline fusion of the maxillary prominences' palatine shelves, sometimes due to micrognathia and failure of tongue to flatten, results in </p>
<p>Posterior cleft palate</p>
<p>Cleft palate without associated cleft lip occurs in </p>
<p>1/1500 births </p>
<p>Form the mandible and malleus-incus ear ossicles</p>
<p>Mandibular prominences of the first pharyngeal arch</p>
<p>Incomplete midline fusion of the mandibular prominences results in </p>
<p>Cleft chin</p>
<p>The external surfaces of the pharyngeal arches is covered by </p>
<p>Surface ectoderm</p>
<p>The surface ectoderm lines recesses between the pharyngeal arches as 4 bilateral pairs of </p>
<p>Pharyngeal clefts/grooves </p>
<p>Forms the epithelial lining of the external auditory meatus and the epithelial lining of the external surface of the tympanic membrane (ear drum)</p>
<p>The 1st pharyngeal cleft</p>
<p>Clefts 2-4 are overgrown by the 2nd pharyngeal arch and form a </p>
<p>Temporary cervical sinus </p>
<p>Remnants of the cervical sinus of clefts 2-4 may form
-located laterally along anterior border of sternocleidomastoid</p>
<p>Lateral cervical cysts</p>
<p>Not part of the structures derived from the pharyngeal region, but part of it forms from the ectoderm of the stomodeum</p>
<p>Pituitary gland (hypophysis)</p>
Arises as an ectodermal diverticulum from the stomodeum (referred to as Rathke's pouch) which detaches
Glandular anterior lobe (adenohypophysis) of pituitary
Forms as a ventral neuroectoderm envagination from the hypothalamus
Nerual posterior lobe (neurohypohpysis) of the pituitary
Neuron cell bodies located in hypothalamic nuclei produce hormones that are carried through axons in the pituitary stalk to reach the
Posterior lobe for release
The external ear epithelium is derived from ectoderm of the
First pharyngeal cleft
The middle ear is derived from mesoderm-mesenchyme of the
1st and 2nd pharyngeal arches
A thickening of surface ectoderm that invaginates to form the cochlea and vestibular apparatus of the inner ear
Otic placode
The retina, pigmented epithelia, optic nerve, isis smooth muscles, and viterous humor are all derived from
Neuroectoderm of the neural tube
The lens, conjunctival and corneal epithelia, eyelids, and lacrimal apparatus are derived from surface ectoderm that forms a
Lens placode
The remaining ocular structures form from
Mesenchyme
The same endoderm that lines the pharynx of the foregut lines the internal surface of the
Pharyngeal arches and the 4 bilateral pairs of pharyngeal pouches recessed between the arches
The first pouch forms the
Tubotympanic recess
The proximal portion of the tubotympanic recess develops into the
Auditory (Eustachin) tube
The distal portion of the tubotympanic recess develops into the
Tympanic/middle ear cavity
Develops into the epithelial-lined crypts of the palatine tonsil
2nd Pouch
Forms the epithelial glandular cells of the inferior parathyroid glands and epithelial reticular cells of the thymus
3rd pouch
The thymus is infuiltrated by
Lymphocytes
Forms epithelial glandular cells of the superior parathyroid gland
4th pouch
The 4th pouch houses migrated neural crest cells known as the
Ultimobranchial body
Neural crest-derived ultimobranchial cells of the fourth pouch become the calcitonin-producing
Parafollicular cells of the thyroid
Neural crest cells give rise to the supportive stroma surrounding ectoderm or endoderm-derived glandular cells of the
Thymus, pituitary, parathyroid, and salivary glands
Also forms from the endoderm of the pharynx
Thyroid gland
An evagination of endoderm located in the ventral midline of the floor of the pharynx near the posterior/root of the tongue
The thyroid diverticulum (foramen cecum)
The thyroid diverticulum extends and migrates caudally in the midline and temporarily maintains its attachment to the root of the tongue during its migration through the
Thyroglossal duct
The thyroglossal ducts disintegrates, but its persistence results in a midline mass that moves with the tongue protrusion known as the
Thyroglossal duct Cyst
