Craniofacial Development Part 1 and 2 - Dr. BC Flashcards
the cranium develops from ________ , beginning in week ____-
mesenchyme
5
mesenchyme develops from _______ and ________-
neural crest cells
mesoderm
the developing cranium consists of 2 parts, what are they
neurocranium and viscerocranium
the neurocranium is the bony case that encloses the
brain
the neurocranium is subdivided into what 2 parts
a cartilaginous part and a membranous part
the cartilaginous part of the neurocranium forms the
cranial base
the membranous part of the neurocranium forms the
cranial vault
the membranous cranial vault is made of flat bones forming the
calvaria
the neurocranium is derived from mesoderm from _______ and _______
somites and ecto-mesenchyme
the neurocranium is derived from neural crest cells in ____________
pharyngeal arches
the viscerocranium is the facial skeleton that is derived from ____________ from ___________ in ___________
ecto-mesenchyme
neural crest cells
pharyngeal arches
neural crest cells are a vulnerable populations as they leave the
neuroectoderm
The cartilaginous neurocranium/chondrocranium of the skull initially consists of a number of separate__________
cartilages
The cartilages that lie in front of notochord, which ends in the center of the ___________, are derived from ___________
sella turcica
neural crest cells
the cartilages that lie posterior to the notochord arise from ________________ formed by ____________
occipital somites
paraxial mesoderm
The base of the skull is formed when these cartilages fuse and ossify by ______________ in the ______ period
endochondral ossification
fetal
The ossification pattern of these bones has a definite sequence _______ to ________, beginning with the ________ bone, followed by _________, and then ________ bone
anterior to posterior
occipital
sphenoid
ethmoid
the membranous neurocranium consists of ______ bones
flat
the membranous neurocranium has paired ______ and _______ bones ; part of _______ bone
frontal
parietal
occipital
The membranous portion of the skull is derived from ___________ and _________ mesoderm
neural crest cells
paraxial
Mesenchyme from neural crest cells and paraxial mesoderm invests the brain and undergoes
intramembranous ossification
the result of intramembranous ossification results in the formation of a number of
flat, membranous bones
Intramembranous ossification occurs in the ______ mesenchyme at the sides and top of the brain, forming the________
head
calvaria (skullcap)
During fetal life, the flat bones of the calvaria are separated by
dense connective tissue membranes
During fetal life, the flat bones of the calvaria are separated by dense connective tissue membranes that form
fibrous joints, thesutures of calvaria
Six _____________ are found where several sutures meet
large fibrous areas (fontanelles)
The softness of the bones and their loose connections at the sutures enable the _______ to undergo changes of
calvaria
shape during birth (molding)
After recovering from molding during birth, the neonate’s cranium is ______, and its bones are ______
round
thin
The fibrous sutures of the neonate’s calvaria permit the brain to ________ during infancy and childhood
enlarge
Because of growth of the surrounding bones, the ________ and ______ fontanelles disappear within 2 to 3 months after birth, but they remain as sutures for several years
posterior
sphenoid
The ________ fontanelles disappear by the end of the first year, and the ________ fontanelle disappears by the end of the second year
mastoid
anterior
craniosynostosis can limit or slow the growth of the baby’s
brain
anencephaly occurs no later than day _____ of development
24
encephalocele occurs no later than ____ days of development or shortly thereafter for the most severe lesions
24
The first sign of skeletal development is an _______ density in the ________ in the _______ fetal month
increased
ectomesenchyme
2nd
The first sign of skeletal development is an increased density in the ectomesenchyme in the 2nd fetal month, which differentiates into a _______ called the _________,
hyaline cartilage skeleton
chondrocranium
The first sign of skeletal development is an increased density in the ectomesenchyme in the 2nd fetal month, which differentiates into a hyaline cartilage skeleton, the chondrocranium, mainly comprising the __________ part of the _________ and the ________
anterior
cranial base
nasal capsule
The viscerocranium is formed mainly from what arches
first 2 pharyngeal arches
Most mesenchyme in the head region is derived from the
neural crest (ectomesenchyme)
Neural crest cells migrate into the ________ and form the bones and connective tissue of_________
pharyngeal arches
craniofacial structures
as the neural folds fuse to form the neural tube, neuroectodermal cells form __________ between the _________ and ________
neural crest cells
surface ectoderm
neural tube
neural crest cells form _______ and _______ cells of the sensory, sympathetic, and parasympathetic nervous system
neurons
glial
neural crest cells form epinephrine producing cells called _________ of the _________ gland
medulla
adrenal (suprarenal)
neural crest cells form _________ of the epidermis
pigment-containing cells
neural crest cells form many of the ________ and __________ components of the head
skeletal and connective tissue
the first arch gives rise to a
maxillary process
The first arch gives rise to a maxillary process, which extends _______ beneath the region of the ______
forward
eye
First arch neural crest ossify by intramembranous ossification to form what 3 things
maxilla
zygomatic bone
squamous part of the temporal bone
The first arch also gives rise to a _______ process, which contains the __________
mandibular
Meckel cartilage
Mesenchyme around the Meckel cartilage condenses and ossifies by _________ ossification to give rise to the ___________
intramembranous
body of the mandible
The Meckel cartilage disappears except in the
phenomandibularligament
what is endochondral ossification
replacement of calcified cartilage by osseous tissue
Some endochondral ossification occurs in what 4 places
condylar head
coronoid process
angle of the mandible
mental protuberance
The _________ tip of the mandibular process of arch 1 gives rise to the
dorsal
malleus and incus middle ear bones (ossicles)
The 2nd arch gives rise to the ___________ and the ___________
stapes middle ear bone (ossicle)
styloid process of the temporal bone
Ossification of the three ossicles begins in the _________ month, making these the ________ bones to become fully ossified
4th
1st
Mesenchyme for formation of the bones of the face is derived from _______ , including the ________ and ________ bones
neural crest cells
nasal
lacrimal
early in development, the face is small. This is caused by the absence of the _________ sinuses and small size of the _____ bones
paranasal air sinuses
jaws
With the appearance of _______ and development of the _________, the face loses its babyish characteristics
teeth
air sinuses
Facial development occurs mainly between weeks
4 - 8
The stomodeum is separated from the pharynx (endodermal foregut) by the
oropharyngeal (buccopharyngeal) membrane
Five facial primordia appear as prominences around the stomodeum, including what 3 things?
1 frontonasal prominence
Paired max. prominences (from pharyngeal arch 1)
Paired mand. prominences (from pharyngeal arch 1)
The ___________ forms the forehead; the upper boundary of the stomodeum (mouth) and the nose
frontonasal prominence
The ________ form the lateral boundaries of the stomodeum (mouth)
maxillary prominences
The _________ constitute the caudal boundary of the stomodeum (mouth) constitute the caudal boundary of the stomodeum (mouth)
mandibular prominences
The lower ____ and lower _____ are the first parts of
the face to form
jaw and lip
During weeks ______, the mandibular prominences gradually enlarge and merge in the midline
4 -5
Between weeks 5-8, neural crest cells of the first pharyngeal arch give rise to left and right cartilaginous rods called the ________ cartilages
Meckel
The _______ form the lower lip, the lower jaw, and the
lower cheek regions
mandibular prominences
The _________ of the mandible marks the site where the 2 mandibular processes merge in the midline
mentum or genu
What contains the line of fusion of the two separate halves of the mandible (mental symphysis)
mentum or genu
The line of fusion in the mentum or genu that divides inferiorly to enclose a triangular area is called the
mental protuberance
A partial or incomplete merger of the mandibular processes forms the common midline ____________
chin dimple or cleft
Until the end of the _____ week, the primordial jaws comprise only masses of _________ tissue with no differentiation of the lips and gingivae
6th
mesenchymal
At the end of week 6, a curvy thickening of ectoderm, the _________, grows into the underlying mesenchyme
labio-gingival lamina
Most of this lamina degenerates, creating a __________ between the lips and gingivae
labio-gingival groove or sulcus
A small midline remnant of the labio-gingival lamina persists as the ______ of the lower lip
frenulum
Later in the sixth week, a
second lamina, the _______, arises in the more
buccal margin of the
developing gingiva of both
jaws
dental lamina
The dental lamina eventually will give rise to _______ that penetrate the mesenchyme of both jaws and will form the deciduous and permanent teeth
tooth buds
The margins of the placodes proliferate, producing horseshoe- shaped elevations, the _______ and _______ nasal prominences
medial ; lateral
the nasal pits become anterior _______
and _______
nares (nostrils)
nasal cavities
the lateral nasal prominences form the ______ of the nose.
alae (sides)
Merging the ________ and _______ results in continuity of the upper jaw and lip and separation of the nasal pits from the stomodeum
medial nasal and
maxillary prominences
Each lateral nasal prominence is initially separated from the maxillary prominence by a
cleft, the
nasolacrimal groove
By the end of the sixth week, each maxillary prominence has begun to merge with the lateral nasal prominence along the line of the
nasolacrimal groove
By the end of the sixth week, when each maxillary
prominence has begun to merge with the
lateral nasal prominence along the line of the
nasolacrimal groove, continuity has been established between the side of the nose which is formed by the _________________ prominence, and the cheek region formed by the __________ prominence
lateral nasal prominence
maxillary prominence
The nasolacrimal duct develops in the floor of the
nasolacrimal groove
The superior end of the nasolacrimal duct expands to form the
lacrimal sac
By the late fetal period, the
nasolacrimal duct drains into the ________ in the lateral wall of the nasal cavity.
inferior meatus
By the end of the ____ week, the primordia of the auricles (external
part of ears) have begun to develop
5th
Six auricular hillocks form around the ____ pharyngeal groove, the primordia of the _____, and the _____ meatus
1st
auricle
external acoustic
Initially, the external ears are located in the ______ region; however, as the ______ develops, they become located on the side of the _____ at the level of the ______
neck
mandible
head
eye
Small ___________ are usually located
anterior to the auricle of the external ear; however, they may occur in other sites around the auricle or
in the lobule (earlobe)
auricular sinuses and
cysts
