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81 Cards in this Set

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What are the olfactory placodes
paired disks of thickened surface ectoderm associated with the telecephalon, they will form the olfactory epithelium of the nasal cavity
What do the epipharyngeal placodes give rise to
The seonsory ganglia of CN 5,7,9, and 10 (the cranial nn. associated with the pharyngeal arches)
Describe the frontonasal promience
-crainial to forebrain between optic vesicles
-filled with condensed mesenchyme
-olfactory placodes are located on surface
Describe the Pharyngeal arches (in general)
-5 paired elevations on either side of the embryo at the level of the pharynx
-filled with condensed mesenchyme
Describe the PHaryngeal grooves (in general)
-3 visible externally
-located between the PAs
-floor of groove is outser sruface ecotoderm layer of pharyngeal membrane/ closing plate
The lining of the pharyx is dervied from
endoderm
Describe the pharyngeal pouches
-outpouchings of the pharynx that endent laterally between the PAs
-laterall wall of pouch is adjacent ot medial wall of groove
-groove and pouch interface at pharyngeal membrane/ clsoing plate
What are the three layers of the Pharyngeal membrane/ closing plate
Outer=Floor of pharyngeal groove, surface ectoderm
middle=intervening mesenchyme from neural crest
Inner-lateral wall of pharyngeal pouch, endoderm
The oral cavity (stomadeum) is the result of growth from which structures
PA 1 and frontonasal prominence
What are the boundries of the oral caivty
Caudal-cardiac bulder
Cranial-frontal prominenece
Lateral-1st PA
Posterior-oral membrane
What structure gives rise to the pituitary gland
The anterior pituitary is "from the mouth" and the posterior is "from the brain"

. The Anterior Lobe originates from an evagination of the Oral Ectoderm from the roof of the oral cavity. This diverticulum, called Hypophysial Diverticulum (Rathke’s pouch), is located near the junction of the oral cavity and pharynx. The hypophyseal diverticulum extends superiorly towards the forebrain. At the same time, a group of cells called the Neurohypophysial Diverticulum (infundibulum) grows inferiorly from the floor of the Diencephalon. The two diverticula eventually fuse to form the pituitary gland and the infundibulum.
What precursors supply the mesenchyme of the pharyngeal arches?
1.Mesoderm
1a. Paraxial Mesoderm (head mesoderm)
1b.occipital somites (1-4)
1c. Lateral plate

2. Neural Crest (ectomesenchyme)

2.
Mesoderm (paraxial, occipital somites, lateral plate) is one of the precursors that contributes to the pharyngeal arches. What will this tissue give rise to
skeletal muscle and vascular endothelium
Neural Crest tissue is one of the precursos that contributes to the pharyngeal arches. What will this tissue give rise to?
Skeletal tissue, FCT, vascular smooth muscle, components of the peripheral nerous system
Neural crest tissue migrates into the pharyngeal arches and frontalnasal prominence under the guidence of signals from which centers.
Forebrain-Prosencephalon
Hindbrain-Rhombencephalon
The mesenchyem of each pharyngeal arch rearranges and forms four structures. What are these
1. Cartilage
2. Muscle
3. Vascular
4. Nervous (cranial n.)
Condensed mesenchyme within the pharyngeal arches will form
cartilage
Loose mesenchyme within the pharyngeal arches will form
connetive tissue
Paraxial mesoderm within the pharyngeal arches will form
Sketeal muscle
How does the type of origin tissue in the pharyngeal arch determine how the resulting bones will ossify?
Pharyngeal cartilage-endochondrial ossification
Pharyngeal mesenchyme-intramembranous ossification
What is the fate of PA1 mandibular portion cartilage
Meckel's Cartilage, becomes the sphenomandibular ligmanet, the malleus, and the incus
What is the fate of PA 2 cartilage
Reichart's Cartilage
Becomes the stylohyoid ligmanent, Styloid process, Upper 1/2 and lesser horns of the hyoid bone, stapes
What is the fate of PA 3 cartiagle
Lower 1/2 and greater horns of hyoid bone
What is the fate o the cartilage of PA 4 an 6
Laryngeal Cartilages
What are the bones derived from PA 1. WHat tissue do they come from and how do they ossify
Crest derived, intramembranous ossification

maxillary portion=maxilla, zygomatic, squama of temporal bone, nasal, lacrimal, palatine, omer, ala, greater wing, and pterygoid plates of sphenoid

mandibular portion=mandible

Dentin and teeth of maxilla and mandible are formed form crest derived mesenchyme
What are the skeletal muscle components derived from PA 1. What tissue to they come from
Skeletal muscle comes from paraxial mesoderm

muscles of mastication, digastric anterior belly, mylohyoid, tensor tympani, tensor palati
Which skeletal muscles are derived from PA 2? What tissue do they come from?
Paraxial mesoderm
muscles of facial expression, stapedius, stylohoid, digastric posterior belly
WHich skeletal muscles are derived from PA III
Paraxial mesoderm
stylopharyngeus
(explains why this muscle is the only muscle of the pharynx innervated by the glossopharyngeal N. and all the others are by the vagus)
which skeletal muscles are drived form PA's 4 and 6
what tissue do they come from
Mesoderm-occipital somite myotomes
laryngeal muscles, pharyngeal constrictors, palatoglossus, palatopharyngeus, slapingopharyngeus, levator palati, muslces of the upper 1/3 of the esophagus
Which cranial nn. associated with each of the pharyngeal arches
1= CN V (trigeminal, mastication)
2= CN VII (facial, facial expression)
3= CN IX (glossopharyngeal, stylopharyngeous)
4= X, Superior laryngeal
6= X, Inferior lyaringeal
What is the normal fate of the pharyngeal grooves
-all except the first disappear
-First becomes External auditory meatus
-Second becomes the cervical sinus which overgroes the 3rd and fuses with the cardiac prominence. THis eventually disappears
In general, Abnormal development of the pharyngeal grooves will lead to defects in what location?
lateral side of the neck, ventral to the SCM
Duplication of the 1st pharyngeal groove can lead to
Blind pouch or fistula tha ttracks from the external auditory meatus to the side of the cheek
A persistent cervical sinus from the second pharyngeal groove can lead to
-Cervical cysts, Cervical fistula (2nd groove=tracts to tonsilar fossa through carotid bifurcation, if 3rd, tracks to the supeior part of the laynx where it piereces the thyrohyoid membrane)
What type of signaling sets up the plan for the axial location of head and neck structures? How do the signals get there
nested expression of Hox genes
-pattern first established in midline derived structures like the neural crest
-carried lateryally into the pharyngeal arches by cell migration
-cells that become CT carry the pattern information other cells read the pattern and differentiate
What signaling center sets up the plan for arrangment of structures in the uuper face, eye, and iner ear
Prosencephalic Center (precordal plate)
What type of signaling sets up differential growth zone sin the surface ectoderm over the forebrain
Sonic hedgehog, Shh result in patterning of the frontonasal prominence
What are the mesenchyme primorida of the tongue
Which PAs do they come from
-paried lateral lingual swellings and unparied tuberculum impar from PA 1
-hypoharyngeal swelling from PA III and IV
Which PAs contribute to tongue formation
PA1=lateral lingual swellings and tuberculum impar
PA III and IV=hypopharyngeal swelling
What are the precursors of the intrinsic and externisic skeletal muscles of the tongue?
Occipital somites (except palatoglossus)
How is the tongue innervated?
body sensory=CN V
root sensory= CN IX
Motor (except palatoglossus)=CN XII
taset=CN VII, IX, X
Describe ankyloglossia
Tongue tied, retention of an abonrmally short lingual frenulum
Bifid Tongue results form
incomplete fusion of the tongue primorida (lateral sweelings, tuberculum lmpar, hypopharyngeal swelling)
What are the 5 primorida of the face
1. Frontal Prominence
2-3. Paired Maxillary Processes
4-5. Paired Mandibular processes
Decribe the differences between merging and fusion in terms of formation of the face
mergeing-between incompletely separated adjacent processes, the groove is closed
Fusion-between completely separate processes, invovles epitthelial disintegration
When does the majority of facial changes occur
weeks 5-7
Describe the formation of the nasal pit
Regional growth withing the frontonasal promience results in U shaped elevations that surrond the olfactory placodes-LNP and MNP. The growth of these prominences around the olfactory placodes changes then inot the nasal pit
Explain how the nasolacrimal duct is formed
-the maxillary prominence fused with the free edge of teh lateral nasal prominence
-MaxP merges with lateral edge of the adjacent FNP
-a line forms in the base of the groove between the FNP and Maxillary prominence, it becomes a solid rod of cells which obtains a lumen and becomes the duct
Failure of the Nasolacrimal duct to canalize can result in
Dacryostenosis
How is the intermaxillary segemetn formed?What ?structures arise form this
Adjacent medial nasal prominences fuse
forms philtrum, incisor bridge, and primary palate
this completes the upper jaw
How is the nasal fin formed
The maxillary prominence fuses with the lateral free edge of the medial nasal process, the line of fusion fors the nasal fin that separaes the nasal pit from the oral cavity
How are each of the following nose structures formed?
sides (ala)
bridge, tip, and collumella
sides-lateral nasal prominences
bridge, tip and collumella-medial nasal prominence
How do the cheeks form/ oral cavity narrows
Merger of the maxiallry prominenece with adjacen tmandibular promience
How are the primitive choanae formed
Elongation of the nasal cavity streches the oronasal membrane which eventually ruptures forming the prmitive choanae
How might abnormal growth of the ethmoid bone affect the orbits
Responsible for normal orbital separatoin. Abnormal ethmoid=> hypotelorism or hypertelorism
When is the human facial form acheived
week 8
What causes the auricles to move into the proper position
elongation and hypertroph of PA 1
also moves eyes to the midline
How is the primary palate formed
Merger of the medial nasal prominences (forming the intermaxillary segment) forms the primary palate.
How is the secondary palate formed
Merge of the palatine processes, the shelf like projections of the forming maxillary and palatine bone
What is the role of "shelf force" in the formatino of the palate
It elevates the palatal processes for horizontal apposition and fusion.
generated by the hydration of hyaluronic acid (a large carbohydrate containing polymer) surrounding the mesenchymal cells within the palatal processes


Note that it is also critical that the oral cavity remain constant during palatal process fusion and that the tongue moves inferiorly as mandibular arch elongates.
How does the soft platae form
Forms from caudal proliferation of the secondary plate mesenchyme and epithelium.
What causes cleft lips
medial cleft lip= failure of the MNP's to fuse
lateral cleft lip= failure of maxially and MNP to fuse
What are the two types of oblique facial clefts. What causes them
1. Oro-auricular-tracks from lateral part of mouth toward the auricle (macrostomia)
2. Oro-orbital tracks from mouth toward medial edge of orbit
Result from failure of the fusion between the maxillary and lateral nasal prominences
What causes median cleft lips
persistence of the groove between the adjacen tmedial nasal prominences
Three morphogenic factors that can lead to a cleft palate include
1. Abnormal tongue development
2. Cysts-form from epithelial remnants during fusion, reupture can reopen palatal cleft
3. Impediment of shelft force- glucocorticoids, interferance with palatal shelf elevation
Describe Mandibulofacial Dysostosis (Treacher Clooins Syndrome)
First Arch Syndrome
1. clefts of structures derived from first arch
2. Downward slanting palpebral fissues
3. Deafness and lower lid coloboma
4. Hypoplastic zygomatic and mandible bones
autosomal dominant
Describe Maxillary Hypoplasia
first arch syndrome
hypoplasia of the midface wihypertelorism and coronal suture synostosis, high arched palate, and malocclusion. Mutation of FGF receptor chormosome 10
Describe Mandibular Hypoplasia (Pierre RObin Sequence)
First arch syndrome
1. small lower jaw
2. glossoptosis
3. cleft palate
Difficulty breathing, autosomal recessive condition
Describe the CHARGE association
First Pharyngeal arch syndrome
Coloboma, Heart defects, choana Atresia, Retardation, Genital hypoplasia, Ear anomalies
Describe Aperts Syndrome
First arch syndrome
tower-shaped skull, flat midface, syndactyly, cleft palate, variable inteligence
Describe Accutane (isotretinoin) induced facial dysplasia
Accutante contains vitamin A, signaling molecule during embryo development. Characterized by first pharyngeal arch defects, ear anomlaies, skin problems ,cleft lip and palate
Describe lateral Facial Dyplasia
first pharyngeal arch defect small mouth, unilateral facial hypoplasia, microtia, heivertebrae/ hypoplastic vertebrae
Expalin how the Salivary glands are formed
The salivary glands (major and minor; they are exocrine glands) appear around 6-8 weeks as solid cords evaginating most likely from the oral ectoderm. Epithelial/mesenchymal interactions are important for branching of the primordia to form ducts and secretory portions
Describe the formation of the tyroid gland
The Thyroid Gland (an endocrine gland) begins its development as a midline diverticulum from the floor of the pharynx between pharyngeal arches 1 and 2. In the adult tongue, this site is marked by a small depression, the Foramen Cecum, located at the boundary between the body and the root (at the apex of the terminal sulcus). The connection between the floor of the oral cavity (where the tongue is forming) and the thyroid primordium is the Thyroglossal Duct. This duct eventually disappears as the thyroid primordium is displace to its definitive position in the neck.
Agenesis of the thyroid resutls in....
Results in cretinism, type of dwarfism w/ mental retardation, growth retardation, dry skin
What is the fate of the first pharyngeal pouch
Retains connection with pharynx, associated with the middle ear as the epithelial lining of the auditory tube and middle ear cavity
What is the fate of the secondary pharyngeal pouch
The epithelial linging proliferates and forms epithelial cords that extend inot underlying mesenchyme. They form the covering epithelium and crypts of the palatine tonsil.
What is the fate of the third pharygeal pouch
Dorsal wings-inferior parathyroid glands
Ventral wing- thymus gland
What is the fate of the fourth pharyngeal pouch
Dorsal wing becomes the superior parathyroid gland
ventral wing may contribute to C cells w/ 5th pouch
What is the fate of the fith pharyngeal pouch
Opens inot the caudal aspect of pouch 4 and is infiltrated by neural crest cells. The pouch detaches from the pharynx and fuses with the caudally displaced thyroid gland primorida. Neural crest derived cells become the C cells of the thyroid clang
Describe Di George Syndrome
-heart anomalies, mincor craniofacial defects ,low set ears, hypoplastic mandible, cleft paate, hytelorism, hypoparathhyroidism, thymic aplasia
-associated with alcohol ingesting, deledtions of CHromsome 22 TBX1
-associated with insufficient neural crest cell migration