Development of Orofacial Structures Flashcards
What structure forms the forehead and dorsum+apex of the nose?
Frontal nasal prominence
What structure forms the alae of the nose?
Lateral nasal prominences
What structure forms the nasal septum, ethmoid bone, and cribriform plate?
Medial nasal prominences
What structure forms the upper cheek regions and lip?
Maxillary prominences
What structure forms the chin, lower lip, and cheek regions?
Mandibular prominences
Facial development depends on inductive interactions of what 3 areas?
Forebrain
Frontonasal region
Developing eye
The five facial primordia appear early in the ____ week as prominences around the ______
4th
Stomodeum
What are the 5 facial primordia?
2 maxillary prominences
2 mandibular prominences
1 frontonasal prominence
The facial primordia are separated from the cavity of the primordial pharynx by a bilaminar ____ _____ which ruptures at ~26 days
Oropharyngeal membrane
Facial development occurs during the 4th-8th weeks. _______ contains active growth centers. Pharyngeal arch 1 splits to form the maxillary and mandibular prominences.
The maxillary prominences form the lateral boundaries of the _______, which come from ____ and _____ neural crest cells. The mandibular prominences form the _____ boundary of the above structure.
Mesenchyme
Stomodeum; midbrain; hindbrain; caudal
What are the first parts of the face to form?
Lower jaw
Lower lip
The lower jaw and lower lip form as the ____ ____ disintegrates and there is extension and fusion of the ____ ____ toward/at the midline
Oropharyngeal membrane
Mandibular prominences
By the end of the 4th week, _____ ____ form on the inferolateral parts of the frontonasal prominence, characterized by bilateral oval thickenings of surface _____ that are primordia of the nasal epithelium
Nasal placodes; ectoderm
The nasal placodal edges proliferate, producing medial and lateral _____ _____
Nasal prominences
The nasal placodes remain in place as the medial and lateral nasal prominences grow, resulting in the formation of _____ _____
Nasal pits
The nasal placodes remain in place as the medial and lateral nasal prominences grow, resulting in the formation of nasal pits. The pits will form the ____ and ____ ___
Nostrils; nasal cavities
What do the lateral nasal prominences form?
The alae (sides) of the nose
The _____ ______ grow medially toward each other and the median nasal prominences which results in the median nasal prominences becoming more midline
Maxillary prominences
The lateral nasal prominence is separated from the maxillary prominence by a cleft called the ____ _____
Nasolacrimal groove
By the end of the 6th week, each maxillary prominence merges with the ____ ____ at the nasolacrimal groove; this establishes continuity between the sides of the nose and cheek region
Lateral nasal prominence
The primordia of the _____ (external part of the ears) develop by the end of the ____ week
Auricles; 5th
During ear development, 6 ____ _____ form around the first pharyngeal groove and the ____ ____ ___, consisting of 3 mesenchymal swellings on each side
Auricular hillocks; external acoustic meatus
T/F: Initially, the external ears are located in the neck region.
True; As the mandible develops, they become located on the side of the head at the level of the eyes
Between the 7th-10th weeks, the medial nasal prominences merge with what 2 structures?
Maxillary nasal prominences
Lateral nasal prominences
Merging of the medial nasal prominences with the maxillary and lateral nasal prominences results in the continuity of the upper jaw an dlip, and separation of the nasal pits from the _______.
As the medial nasal prominences merge, they form the ______ _____ which will become the ______ of the upper lip, premaxillary part of the maxilla, and the primary palate
Stomodeum
Intermaxillary segment; philtrum
Most of the upper lip, maxilla, and secondary palate form from the ____ _____, whih will merge laterally with the ____ ____
Maxillary prominences; mandibular prominences
Mesenchyme in pharyngeal arch ____ forms the facial muscles, innervated by the ______ nerve
2; facial
Mesenchyme in pharyngeal arch ____ forms the muscles of mastication (among others), and is innervated by ____ n.
1; trigeminal
Facial development occurs slowly during fetal period, including changes in proportion and relative positions of facial components. The nose is initially flat and the mandible is underdeveloped, reaching characteristic form by ____ weeks.
As the brain enlarges, the ____ ____ expands bilaterally, causing the _____ (oriented laterally) to assume a forward-facing orientation
Small appearance of the face prenatally results from rudimentary upper and lower jaws, un-erupted deciduous teeth, and small nasal cavities and maxillary sinuses
14
Cranial cavity; orbits
As the face develops, nasal placodes are depressed, forming ____ _____.
Expansion of median nasal prominences and lateral nasal prominence mesenchyme causes these to deepen, forming the right and left ____ ____ ___
Nasal pits
Primordial nasal sacs
Primordial nasal sacs grow dorsally and ventrally to the developing forebrain, separated from the oral cavity by the _____ _____, which ruptures by the end of the 6th week
Oronasal membrane
Continuous between the nasal and oral cavities are the _____ ____, which are openings from the nasal cavity into the nasal pharynx
Primordial choanae
The primordial choanae are relocated to nasal cavity/pharynx junction after the _____ _____ develops.
Superior, middle, and inferior ____ ____ are developing simultaneously
Secondary palate
Nasal conchae
Epithelium lining the roof of each nasal cavity specializes, forming the ______epithelium, where cells will differentiate into the olfactory _____
Olfactory; neurons
Palatogenesis begins in the ____ week and is completed by the beginning of the____ week (if not complete by this point there is high likelihood of palate malformation) = critical period
6th; 9th
Palatogenesis occurs beginning with merging of the medial nasal prominences to form the ____ ____ ___, or primary palate. This is made up of a wedge-shaped mass of mesenchyme between the _____ prominences, forming the _______ part of the maxilla
Median palatine process; maxillary; premaxillary
The ‘______ palate’ is the primordium of the hard and soft parts of the palate
Definitive
The secondary palate develops early in the 6th week from lateral palatine processes, or _____ ______, which are mesenchymal projections extending from internal aspects of the _______ prominences
These will project inferomedially on each side of the ______
Palatal shelves; maxillary
Tongue
As the jaws elongate, the tongue is pulled away from its root, moving inferiorly in the mouth. This allows the _____ ____ to assume a horizontal position above the tongue around the 7th-8th week
Palatal shelves (aka lateral palatine processes)
Bone gradually develops in the primary palate, forming the ______ part of the maxilla, which houses the incisor teeth. Bone extends from the maxillae and palatine bones into the lateral palatine processes to form the _____ ______.
The posterior portions do not ossify, but instead extend posteriorly and fuse, forming the ____ ____ and ______. The line of fusion is indicated by the ________
Premaxillary; hard palate
Soft palate; uvula; palatine raphe
Once the hard and soft palates have formed, the ____ _____ persists in the median plane, represented in the adult hard palate by the ______ fossa
Nasopalatine canal; incisive
Formation of a cleft palate has multifactorial causes, including the participation of _______ cells. It can be classified as anterior or posterior, and the anatomical landmark delineating the two is the ____ _____
Neural crest; incisive foramen
Anterior cleft palate occurs with failure of what 2 structures to fuse?
Palatine shelves fail to fuse with primary palate
Posterior cleft palate occurs with failure of what structures to fuse?
Palatine shelves fail to fuse with each other and with the nasal septum
[note that anteroposterior cleft palate is a combination of both anterior and posterior defects]
What is th emost common malformation of the head/neck?
Unilateral cleft lip
Unilateral cleft lip results from:
_____ _____ fails to fuse with th emedial nasal prominence.
Underlying somitomeric mesoderm and neural crest fail to expand, resulting in persistent ____ ____
Maxillary prominence
Labial groove
The ______ _____ develops as a downgrowth from the internal parts of merged medial nasal prominences. Fusion of this structure with the palatine processes begins anteriorly (9th week) and is completed posteriorly (12th week)
Nasal septum
Tongue development begins with a ____ _____ ____ that appears at the end of the 4th week, this is the first indication of tongue development as a triangular elevation in the floor of the primordial _______
Median lingual swelling; pharynx
Two _____ _____ ____ develop on each side of the median lingual swelling, these rapidly proliferate, merge, and overgrow the median lingual swelling
Lateral lingual swellings
All tongue buds result from proliferation of mesenchyme in ventromedial parts of pharyngeal arch ____
1
Merged lateral lingual swellings form the _____ part of the tongue, which is the ______ 2/3s
Oral; anterior
Once the oral part of the tongue develops, the ______ part forms
Pharyngeal
Formation of the pharyngeal part of the tongue begins when the ventromedial parts of pharyngeal arch 2 fuse, forming the _______.
Ventromedial parts of pharyngeal arch 3 and 4 develop the ____ _____
Copula
Hypopharyngeal eminence
During formation of the pharyngeal part of the tongue, the hypopharyngeal eminence overgrows the copula, forming what part of the tongue?
Posterior 1/3 of tongue
The line of fusion anterior and posterior parts of the pharyngeal part tongue = ____ _____
Terminal sulcus
Tongue musculature is derived from myoblasts of the _______ myotomes, accompanied by the _____ n. to innervate the tongue
Occipital; hypoglossal
What are the 3 most common tongue abnormalities?
Glossoschissis = bifid tongue
Ankyloglossia = “tongue-tied”
Macroglossia = large tongue
4 nerves that supply the anterior 2/3 of the tongue
Lingual branch of V3: sensory innervation of mucosa
Chorda tympani branch of CN VII: taste
CN IX: circumvallate/vallate papilla
CN XII: motor of intrinsic skeletal mm
4 nerves supplying posterior 1/3 of tongue
CN IX: Sensory innervation of mucosa and taste
CN XII: motor of intrinsic skeletal m
CN X: sensory of posterior tongue and pharynx; taste (epiglottis)
CN X: motor to palatoglossus m.
What type of ossification involves mesenchymal production of osseous tissue without cartilage formation?
Intramembranous ossification
With intramembranous ossification, mesenchyme condenses and becomes highly vascular, differentiating into ________ which deposit osteoid to form bone. These cells then become trapped and become ______
Osteoblasts; osteocytes
What type of ossification involves bone formation in preexisting cartilaginous models (i.e., long bones)?
Endochondral ossification
With endochondral ossification, primary ossification centers appear in the ________.
_______ hypertrophy and the matrix becomes calcified, at which point the cells die
Diaphysis
Chondrocytes
The cranium develops from mesenchyme around the developing brain.
The _____ is the bony case enclosing the brain, and the _______ are the bones comprising the facial skeleton
Neurocranium; viscerocranium
Both the neurocranium and the viscerocranium are made up of 2 primary components, what are they?
Cartilaginous
Membranous
The cartilaginous portion of the neurocranium develops as several cartilages fuse, forming the _____ of the cranium via _______ ossification
Base; endochondral
In what order do the 4 parts of the cartilaginous neurocranium form?
- Occipital bone (base)
- Body of sphenoid
- Ethmoid bone
- Temporal bone (petrous and mastoid parts)
The membranous neurocranium consists of head mesenchyme at the sides and top of the brain, which will form the ________ via ________ ossification
Calvaria; intramembranous
Calvaria = _____ and _____bones of the skull
Frontal; parietal
The calvaria of the skull are formed by intramembranous ossification and will be interconnected via ______
Sutures
The cartilaginous viscerocranium consists of _______ ____ cells that form bones as well as the _______ ______ of craniofacial structures
Neural crest; connective tissue
What pharyngeal arches contribute to the cartilaginous viscerocranium?
1
2
3
4
Pharyngeal arches 1, 2, 3, and 4 contribute to the cartilaginous viscerocranium. What are their bony contributions?
PA1: malleus + incus
PA2: stapes, styloid process of temporal bone; lesser horn of hyoid
PA3: greater horns of the hyoid bone
PA4: cartilages fuse —> laryngeal cartilages (except epiglottis)
The membranous viscerocranium develops via intramembranous ossification within the _____ prominence to form the ________, ________, and _______ bones
Maxillary; squamous temporal; maxillary; zygomatic
[note that the squamous temporal bone will become part of the neurocranium]
During development of the membranous viscerocranium, cells of the mandibular prominence form the _______
Mandible
Umbrella term for a condition characterized by premature fusion of cranial sutures, often associated with other skeletal defects
Craniosynostosis
The cause of craniosynostosis is unclear, and it is more common in ______
Boys
Condition characterized by premature closure of the sagittal suture, so the cranium becomes long, narrow, and wedge shaped
Scaphocephaly
Condition characterized by premature closure of the coronal suture on one side, so the cranium is twisted and asymmetric
Plagiocephaly
Condition characterized by premature closure of the coronal suture, leading to a high, tower-like cranium
Brachycephaly
Condition characterized by premature closure of the frontal (metopic) suture leading to deformities of frontal and orbital bones in addition to other anomalies
Trigonocephaly
Which 2 types of craniosynostosis are most common?
Scaphocephaly (50% of cases)
Brachycephaly (30% of cases)
_____ = development of teeth
Odontogenesis
Teeth develop from reciprocal inductions between what 2 things?
Neural crest-induced mesenchyme + overlying oral epithelium (ectoderm)
U-shaped bands of oral epithelium that follow the curves of the primitive jaws
Dental laminae
_____ ____ form in each dental laminae during their respective stage (10 on top, 10 on bottom to make 20 primary teeth)
Tooth buds
The first teeth develop in the _____ _____ region, followed by the ____ _____region, then they continue posteriorly by the 6th week
Anterior mandibular; anterior maxillary
During the Cap Stage, the tooth bud is invested by mesenchyme and becomes cap-shaped. At this point it consists of what 3 components?
Enamel organ
Dental papilla
Dental sac
The enamel organ of the tooth bud consists of ______ cells from the dental lamina, its function is to produce ______
Ectodermal; enamel
What are the 3 cell layers of the enamel organ during the cap stage of tooth development?
Outer cell layer = outer enamel epithelium (OEE)
Inner cell layer lining the papilla = inner enamel epithelium (IEE)
Stellate reticulum
____ ___ = internal part of each tooth (mesenchyme)
Dental papilla
The dental papilla is responsible for formation of what 2 substances?
Dentin
Pulp
What part of the tooth bud consists of mesenchyme surrounding the dental papilla and enamel organ?
Dental follicle/sac
The dental follicle/sac is responsible for the formation of what 2 things?
Periodontal ligament
Cementum
The bell stage of tooth development begins when differentiation of the ____ ____ results in a bell shape.
The dental papilla cells adjacent to the inner enamel epithelium (IEE) form ________
Enamel organ
Odontoblasts
During the bell stage of tooth development, the dental papilla cells adjacent to the IEE form odontoblasts which produce _______, which calcifies and becomes ______.
The IEE differentiates into _______ in response to dentin production, these cells produce enamel
Predentin; dentin
Ameloblasts
Enamel and dentin formation begins at the ____ of the tooth and progresses toward the future ____
Cusps; root
What part of tooth development begins after dentin and enamel formation?
Root development
During root development, a _____ ____ ____ forms as a fusion of IEE and OEE, growing into mesenchyme and initiating root formation. ______produce root dentin
Epithelial root sheath; odontoblasts
During tooth root development, central dental papilla cells form the ____ of the tooth.
The inner cells of the dental sac form ______ which produce cementum around the root(s)
Outer cells of the dental sac form the _______ which is a collagen ligament that anchors the tooth to bone
Pulp
Cementoblasts
Periodontal ligament
Tooth eruption consists of emergence of the tooth from the dental follicle in the jaw and its functional position in the mouth. The root of the tooth grows and the crown gradually erupts through the ____ _____
Oral epithelium
T/F: maxillary teeth typically erupt before mandibular teeth
False, other way around
____ = part of the oral mucosa around the erupted crown
Gingiva
As a permanent tooth grows, the deciduous root is resorbed by _______; only the crown and uppermost part of the root are shed
Permanent teeth usually begin to erupt at 6 yrs
Osteoclasts (odontoclasts)
Permanent dentition consists of ____ teeth, which develop in stages similar to deciduous teeth.
Tooth buds for permanent teeth (with deciduous precursors) start to appear at 10 wks from extensions of the ____ _____. They develop ______ to the deciduous tooth buds
32
Dental lamina; lingual (next to the tongue)
The tooth buds for permanent teeth appear at different times, but mostly during the _____ period. Buds for 2nd/3rd permanent molars develop after birth
Fetal
Deciduous teeth begin to erupt around 6 months. In what order do they tend to erupt?
Medial incisor Lateral incisor Canine First molar Second molar
[teeth are typically shed in the same order]
