Chapter 10 Flashcards
In general, the skeletal system develops from
A. paraxial
B. lateral plate (parietal layer) mesoderm
C. neural crest
AOTA
These are segmented series of tissue blocks on each side of the neural tube
Somitomeres (head region) and
somites (occipital region)
Somites differentiate into a ventromedial part the _____________, and a dorsolateral part the _____________
sclerotome; dermomyotome
At the end of the fourth week, sclerotome cells become polymorphous and form loosely organized tissue called
Mesenchyme
These cells may become fibroblasts, chondroblasts, or osteoblasts (bone-forming cells).
Mesenchyme cells
The process of bone differentiation among flat bones (e.g flat bones on the skull)
intramembranous ossification
hyaline cartilage models is ossified thru
a. intramembranous ossification
b. endochondral ossification
endochondral ossification
It forms the protective case around the brain
Neurocranium
Forms the skeleton of the face
Viscerocranium
The two portions of the neurocranium
- the membranous part, consisting of flat bones, which surround the brain as a vault
- the cartilaginous part, or chondrocranium, which forms bones of the base of the skull.
The membranous portion of the skull is derived from
- neural crest cells and
- paraxial mesoderm
Narrow seams of connective tissue that separate the flat bones of the skull at birth
Sutures
At points where more than two bones meet, sutures are wide and are called _______
Fontanelle
It is found where the two parietal and two frontal bones meet
Fontanelle
In most cases, the anterior fontanelle closes by ___ months of age, and the posterior fontanelle closes by _____ months of age.
18;
1 to 2
Those that lie in front of the rostral limit of the notochord, which ends at the level of the pituitary gland in the center of the sella turcica, are derived from neural crest cells. They form the _________________.
a. prechordal chondrocranium
b. chordal chondrocranium
prechordal chondrocranium
Those that lie posterior to arise from occipital sclerotomes formed by paraxial mesoderm and form the _____________
chordal chondrocranium
It consists of the bones of the face, and is formed mainly from the first two pharyngeal arches
Viscerocranium
The first pharyngeal arch of the viscerocranium gives rise to a dorsal portion, called the _______________.
maxillary process
The maxillary process give rise to the (3)
- maxilla
- the zygomatic bone, and
- part of the temporal bone
The ventral portion of the pharyngeal arch
Mandibular process
Mesenchyme around the Meckel cartilage condenses and ossifies by intramembranous ossification to give rise to the
a. mandible
b. maxilla
mandible
The Meckel cartilage disappears except in the _____________ ligament.
sphenomandibular
The dorsal tip of the mandibular process, along with that of the second pharyngeal arch, later gives rise to the _________, _________, and ________
incus, the malleus, and the stapes
Ossification of the three ossicle begins in the ________ month
fourth
The small appearance of the face is caused by
- virtual absence of the paranasal air sinuses
- the small size of the bones, particularly
the jaws.
These cells are often target for teratogens
Neural Crest Cells
This defect arises when the cranial vault fails to form
cranioschisis
the cranial vault fails to form and brain tissue exposed to amniotic fluid degenerates, results to
Anencephaly
Cranioschisis is caused by
failure of the cranial neuropore to close
caused by premature closure of one
or more sutures
Craniosypnostosis
crest cells form the ____________.
paraxial mesoderm forms the _______ and the loose mesenchyme in the ________
frontal bones; parietal bones; coronal sutures
It encodes ephrin—B1, a ligand for EphB receptors that causes cells to repel each other
EFNB1
Loss of function mutations in EFNB1 causes
craniofrontonasal syndrome
This syndrome is characterized by coronal suture synostosis and hypertelorism
craniofrontonasal syndrome
these two transcription factors regulates the proliferation of neural crest cells in the frontal bones
MSX2 and TWIST1
Boston-type craniosynostosis is caused due to mutations in _______
MSX2
Mutations in TWIST1 cause ______ that is characterized by coronal suture synstosis and polydactyly
Saethre-Chotzen syndrom
these receptors has three extracellular immunoglobulin domains and a cytoplasmic tyrosine kinase that mediates signaling
Transmembrane tyrosine kinase receptors
these receptors are coexpressed in prebone and precartilage regions, including craniofacial structures
FGFR1 and FGFR2
This receptor is expressed in the cartilage growth plates of long bones and in the occipital region
Fibroblast growth factor receptor 3 (FGFR3)
This receptor increases proliferation
FGFR2
Which receptor promotes osteogenic differentiation
a. FGFR1
b. FGFR2
c. FGFR3
FGFR1
This is caused by early closure of the sagittal suture [57% of cases], resulting in frontal and occipital expansion, and the skull becomes long and narrow
Scaphocephaly
Premature closure of the coronal sutures (20% to 25% of cases) results in a short skull called
Brachycephaly
the coronal sutures close prematurely on one side only, resulting to an asymmetric flattening of the skull called
Plagiocephaly
The most common cause of craniosynostosis are
genetic
Other causes of craniosynostosis
- vitamin D deficiency;
- exposure to teratogens (DRVMC)(diphenylhydantoin, retinoids, valproic acid, methotrexate, and cyclophosphamide)
- intrauterine factors that
constrain the fetus (oligohydramnios and multiple birth pregnancies)
The most common form of skeletal dysplasia (1/20,000 live births) primarily affecting the long bones
Achondroplasia (ACH)
Skeletal defects of Achondroplasia includes:
A. small skull
B. small midface
C. short fingers
D. accentuated spinal culrvature
B,C and D are correct plus large skull or megalocephaly
ACH is inherited as an
a. autosomal dominant
b. autosomal recessive
A
The most common neonatal lethal form of skeltal dysplasia (1/40,000 live births)
Thanatophoric dysplasia
Thanatophoric dysplasia is
a. autosomal recessive
b. autosomal dominant
B. autosomal dominant for the two types of Thanatophoric dysplasia
a type of Thanatophoric dysplasia that is characterized by short, curved femurs with or without cloverleaf skull
Type I
Which type of Thanatophoric dysplasia is cahracterized by straight, relatively long femurs and severe cloverleaf skull caused by craniosynostosis
type II
Another term for cloverleaf skull
kleeblattschadel
K-L-E-E-B-L-A-T-T-S-C-H-A-D-E-L
It occurs when all of the sutures close prematurely, resulting in the brain growing through the anterior and sphenoid fontanelles
cloverleaf skull
another autosomal dominant form of skeletal dysplasia, appears to be a milder type of ACH.
Hypochondroplasia
Mutations in ________ causes abnormal endochondral bone formation
FGF3.
Long bones and the base of the skull are adversely affected
An example of a generalized dysplasia of osseus and dental tissues that is characterized by late closure of the fontanelles and decreased mineralization of the cranial sutures resulting in bossing (enlargement) of the frontal, parietal, and occipital bones
Cleidocranial dysostosis
caused by congenital hyperpituitarism and excessive production of growth
hormone.
Acromegaly
characterized by disproportional
enlargement of the face, hands, and feet. sometimes it causes more symmetrical ex- cessive growth and gigantism
Acromegaly
usually an abnormality in which the brain fails to grow and, as a result, the skull fails to expand
microcephaly
Which part of the body form from the sclerotome portions of the somites
Vertebrae
A typical vertebrae consists of :
a. vertebral arch
b. foramen
c. body
d. transverse processes
e. spinous process
AOTA
In which week do the migration of the sclerotome cells around the spinal cord and notochord to merge with cells from the opposing somite on the other side of the neural tube occurs?
4th
A process that occurs when the caudal half of each sclerotome grows into and fuses with the cephalic half of each subjacent sclerotome
Resegmentation
Patterning of the shapes of the different vertebraae is regulated by which genes
HOX
TRUE OR FALSE.
Mesenchymal cells between cephalic and caudal parts of the original sclerotome segment proliferate and fill the space between two precartilaginous vertebral bodies.
FALSE
Mesenchymal cells between cephalic and caudal parts of the original sclerotome segment do not proliferate but fill the space between two precartilaginous vertebral bodies.
In this way, they contribute to formation of the intervertebral disc
As the vertebrae form, two primary curves of the spine are established which are the:
I. cervical curvatures
II. thoracic curvatures
III. lumbar curvatures
IV. sacral curvatures
a. I and III
b. II and III
c. III and IV
d. I and IV
e. II and IV
E
secondary curvatures established during vertebral formation
Cervical and lumbar curvatures
This curvature is established as the child learns to hold up his or her chain
Cervical curvature
This curvature is fomed as the child learns to walk
Lumbar curvature
two successive vertebrae fuse asymmetrically or have half a vertebra missing results to
Scoliosis (Lateral curving of the spine)
In this sequence,the cervical vertebrae
are fused causing reduced mobility and a
short neck.
Klippel-Feil sequence
This abnormality involves only the bony vertebral arches, leaving the spinal cord intact
cleft vertebra (spina bifida)
In these cases, the bony defect is covered by skin, and no neurological deficits occur
spina bifida occulta
A more severe abnormality in which the neural tube fails to close, vertebral arches fail to form and neural tissue is exposed
spina bifida cystica
spina bifida can be prevented by providing mothers with
Folic acid
Spina bifida can be detected prenatally by
ultrasound
If neural tissue is exposed, ____________ can detect elevated levels of alpha fetoprotein in the amniotic fluid
Amniocentesis
The bony portion of each rib is derived from
sclerotome cells
Costal cartilages are formed by sclerotome cells that migrate across the
A. lateral somitic frontier
b. medial somitic frontier
A
Which of the following statement is TRUE
A. The sternum develops independently in the parietal layer of lateral plate mesoderm in the ventral body wall.
B. The sternum develops dependently in the parietal layer of lateral plate mesoderm in the ventral body wall.
C. The sternum develops independently in the parietal layer of lateral plate mesoderm in the dorsal body wall.
D. The sternum develops independently in the parietal layer of lateral plate mesoderm in the dorsal body wall.
A
Two sternal bands are formed in the
parietal (somatic) layer of lateral plate mesoderm on either side of the midline, and these later fuse to form cartilaginous models of the
A. manubrium,
B. sternebrae
C. Xiphoid process
D. NOTA
E. AOTA
E
It occurs in approximately 1% of the population and are usually attached to the seventh cervical vertebra
Cervical ribs
What blood vessels may be impinged due to cervical ribs?
Brachial plexus or subclavian artery
a very rare defect and may be complete or located at either end of the sternum.
Cleft sternum
This defect arises when the sternal ands fail to grow together in the midline
Cleft Sternum (Spina Bifida)
Defects of the Sternum
It may also occur in infants with congenital heart defects
Hypoplastic ossification centers and premature fusion of sternal segments (20-50%)
Defects of the Sternum
It occur in 6% to 20% of all children but are especially common in those with down syndrome
multiple manubrial ossification centers
Refers to a depressed sternum that is sunken posteriorly
Pectus excavatum
refers to a flattening of the chest bilaterally with an anteriorly projecting sternum
Pectus carinatum
