Chapter 10

Question 1

In general, the skeletal system develops from

A. paraxial
B. lateral plate (parietal layer) mesoderm
C. neural crest

Answer 1

AOTA

Question 2

These are segmented series of tissue blocks on each side of the neural tube

Answer 2

Somitomeres (head region) and
somites (occipital region)

Question 3

Somites differentiate into a ventromedial part the _____________, and a dorsolateral part the _____________

Answer 3

sclerotome; dermomyotome

Question 4

At the end of the fourth week, sclerotome cells become polymorphous and form loosely organized tissue called

Answer 4

Mesenchyme

Question 5

These cells may become fibroblasts, chondroblasts, or osteoblasts (bone-forming cells).

Answer 5

Mesenchyme cells

Question 6

The process of bone differentiation among flat bones (e.g flat bones on the skull)

Answer 6

intramembranous ossification

Question 7

hyaline cartilage models is ossified thru

a. intramembranous ossification
b. endochondral ossification

Answer 7

endochondral ossification

Question 8

It forms the protective case around the brain

Answer 8

Neurocranium

Question 9

Forms the skeleton of the face

Answer 9

Viscerocranium

Question 10

The two portions of the neurocranium

Answer 10

1. the membranous part, consisting of flat bones, which surround the brain as a vault
2. the cartilaginous part, or chondrocranium, which forms bones of the base of the skull.

Question 11

The membranous portion of the skull is derived from

Answer 11

1. neural crest cells and
2. paraxial mesoderm

Question 12

Narrow seams of connective tissue that separate the flat bones of the skull at birth

Answer 12

Sutures

Question 13

At points where more than two bones meet, sutures are wide and are called _______

Answer 13

Fontanelle

Question 14

It is found where the two parietal and two frontal bones meet

Answer 14

Fontanelle

Question 15

In most cases, the anterior fontanelle closes by ___ months of age, and the posterior fontanelle closes by _____ months of age.

Answer 15

18;
1 to 2

Question 16

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

Answer 16

prechordal chondrocranium

Question 17

Those that lie posterior to arise from occipital sclerotomes formed by paraxial mesoderm and form the _____________

Answer 17

chordal chondrocranium

Question 18

It consists of the bones of the face, and is formed mainly from the first two pharyngeal arches

Answer 18

Viscerocranium

Question 19

The first pharyngeal arch of the viscerocranium gives rise to a dorsal portion, called the _______________.

Answer 19

maxillary process

Question 20

The maxillary process give rise to the (3)

Answer 20

1. maxilla
2. the zygomatic bone, and
3. part of the temporal bone

Question 21

The ventral portion of the pharyngeal arch

Answer 21

Mandibular process

Question 22

Mesenchyme around the Meckel cartilage condenses and ossifies by intramembranous ossification to give rise to the

a. mandible
b. maxilla

Answer 22

mandible

Question 23

The Meckel cartilage disappears except in the _____________ ligament.

Answer 23

sphenomandibular

Question 24

The dorsal tip of the mandibular process, along with that of the second pharyngeal arch, later gives rise to the _________, _________, and ________

Answer 24

incus, the malleus, and the stapes

Question 25

Ossification of the three ossicle begins in the ________ month

Answer 25

fourth

Question 26

The small appearance of the face is caused by

Answer 26

1. virtual absence of the paranasal air sinuses 2. the small size of the bones, particularly the jaws.

Question 27

These cells are often target for teratogens

Answer 27

Neural Crest Cells

Question 28

This defect arises when the cranial vault fails to form

Answer 28

cranioschisis

Question 29

the cranial vault fails to form and brain tissue exposed to amniotic fluid degenerates, results to

Answer 29

Anencephaly

Question 30

Cranioschisis is caused by

Answer 30

failure of the cranial neuropore to close

Question 31

caused by premature closure of one or more sutures

Answer 31

Craniosypnostosis

Question 32

crest cells form the ____________. paraxial mesoderm forms the _______ and the loose mesenchyme in the ________

Answer 32

frontal bones; parietal bones; coronal sutures

Question 33

It encodes ephrin—B1, a ligand for EphB receptors that causes cells to repel each other

Answer 33

EFNB1

Question 34

Loss of function mutations in EFNB1 causes

Answer 34

craniofrontonasal syndrome

Question 35

This syndrome is characterized by coronal suture synostosis and hypertelorism

Answer 35

craniofrontonasal syndrome

Question 36

these two transcription factors regulates the proliferation of neural crest cells in the frontal bones

Answer 36

MSX2 and TWIST1

Question 37

Boston-type craniosynostosis is caused due to mutations in _______

Answer 37

MSX2

Question 38

Mutations in TWIST1 cause ______ that is characterized by coronal suture synstosis and polydactyly

Answer 38

Saethre-Chotzen syndrom

Question 39

these receptors has three extracellular immunoglobulin domains and a cytoplasmic tyrosine kinase that mediates signaling

Answer 39

Transmembrane tyrosine kinase receptors

Question 40

these receptors are coexpressed in prebone and precartilage regions, including craniofacial structures

Answer 40

FGFR1 and FGFR2

Question 41

This receptor is expressed in the cartilage growth plates of long bones and in the occipital region

Answer 41

Fibroblast growth factor receptor 3 (FGFR3)

Question 42

This receptor increases proliferation

Answer 42

FGFR2

Question 43

Which receptor promotes osteogenic differentiation a. FGFR1 b. FGFR2 c. FGFR3

Answer 43

FGFR1

Question 44

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

Answer 44

Scaphocephaly

Question 45

Premature closure of the coronal sutures (20% to 25% of cases) results in a short skull called

Answer 45

Brachycephaly

Question 46

the coronal sutures close prematurely on one side only, resulting to an asymmetric flattening of the skull called

Answer 46

Plagiocephaly

Question 47

The most common cause of craniosynostosis are

Answer 47

genetic

Question 48

Other causes of craniosynostosis

Answer 48

1. vitamin D deficiency; 2. exposure to teratogens (DRVMC)(diphenylhydantoin, retinoids, valproic acid, methotrexate, and cyclophosphamide) 3. intrauterine factors that constrain the fetus (oligohydramnios and multiple birth pregnancies)

Question 49

The most common form of skeletal dysplasia (1/20,000 live births) primarily affecting the long bones

Answer 49

Achondroplasia (ACH)

Question 50

Skeletal defects of Achondroplasia includes: A. small skull B. small midface C. short fingers D. accentuated spinal culrvature

Answer 50

B,C and D are correct plus large skull or megalocephaly

Question 51

ACH is inherited as an a. autosomal dominant b. autosomal recessive

Answer 51

A

Question 52

The most common neonatal lethal form of skeltal dysplasia (1/40,000 live births)

Answer 52

Thanatophoric dysplasia

Question 53

Thanatophoric dysplasia is a. autosomal recessive b. autosomal dominant

Answer 53

B. autosomal dominant for the two types of Thanatophoric dysplasia

Question 54

a type of Thanatophoric dysplasia that is characterized by short, curved femurs with or without cloverleaf skull

Answer 54

Type I

Question 55

Which type of Thanatophoric dysplasia is cahracterized by straight, relatively long femurs and severe cloverleaf skull caused by craniosynostosis

Answer 55

type II

Question 56

Another term for cloverleaf skull

Answer 56

kleeblattschadel K-L-E-E-B-L-A-T-T-S-C-H-A-D-E-L

Question 57

It occurs when all of the sutures close prematurely, resulting in the brain growing through the anterior and sphenoid fontanelles

Answer 57

cloverleaf skull

Question 58

another autosomal dominant form of skeletal dysplasia, appears to be a milder type of ACH.

Answer 58

Hypochondroplasia

Question 59

Mutations in ________ causes abnormal endochondral bone formation

Answer 59

FGF3. Long bones and the base of the skull are adversely affected

Question 60

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

Answer 60

Cleidocranial dysostosis

Question 61

caused by congenital hyperpituitarism and excessive production of growth hormone.

Answer 61

Acromegaly

Question 62

characterized by disproportional enlargement of the face, hands, and feet. sometimes it causes more symmetrical ex- cessive growth and gigantism

Answer 62

Acromegaly

Question 63

usually an abnormality in which the brain fails to grow and, as a result, the skull fails to expand

Answer 63

microcephaly

Question 64

Which part of the body form from the sclerotome portions of the somites

Answer 64

Vertebrae

Question 65

A typical vertebrae consists of : a. vertebral arch b. foramen c. body d. transverse processes e. spinous process

Answer 65

AOTA

Question 66

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?

Answer 66

4th

Question 67

A process that occurs when the caudal half of each sclerotome grows into and fuses with the cephalic half of each subjacent sclerotome

Answer 67

Resegmentation

Question 68

Patterning of the shapes of the different vertebraae is regulated by which genes

Answer 68

HOX

Question 69

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.

Answer 69

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

Question 70

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

Answer 70

E

Question 71

secondary curvatures established during vertebral formation

Answer 71

Cervical and lumbar curvatures

Question 72

This curvature is established as the child learns to hold up his or her chain

Answer 72

Cervical curvature

Question 73

This curvature is fomed as the child learns to walk

Answer 73

Lumbar curvature

Question 74

two successive vertebrae fuse asymmetrically or have half a vertebra missing results to

Answer 74

Scoliosis (Lateral curving of the spine)

Question 75

In this sequence,the cervical vertebrae are fused causing reduced mobility and a short neck.

Answer 75

Klippel-Feil sequence

Question 76

This abnormality involves only the bony vertebral arches, leaving the spinal cord intact

Answer 76

cleft vertebra (spina bifida)

Question 77

In these cases, the bony defect is covered by skin, and no neurological deficits occur

Answer 77

spina bifida occulta

Question 78

A more severe abnormality in which the neural tube fails to close, vertebral arches fail to form and neural tissue is exposed

Answer 78

spina bifida cystica

Question 79

spina bifida can be prevented by providing mothers with

Answer 79

Folic acid

Question 80

Spina bifida can be detected prenatally by

Answer 80

ultrasound

Question 81

If neural tissue is exposed, ____________ can detect elevated levels of alpha fetoprotein in the amniotic fluid

Answer 81

Amniocentesis

Question 82

The bony portion of each rib is derived from

Answer 82

sclerotome cells

Question 83

Costal cartilages are formed by sclerotome cells that migrate across the A. lateral somitic frontier b. medial somitic frontier

Answer 83

A

Question 84

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.

Answer 84

A

Question 85

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

Answer 85

E

Question 86

It occurs in approximately 1% of the population and are usually attached to the seventh cervical vertebra

Answer 86

Cervical ribs

Question 87

What blood vessels may be impinged due to cervical ribs?

Answer 87

Brachial plexus or subclavian artery

Question 88

a very rare defect and may be complete or located at either end of the sternum.

Answer 88

Cleft sternum

Question 89

This defect arises when the sternal ands fail to grow together in the midline

Answer 89

Cleft Sternum (Spina Bifida)

Question 90

Defects of the Sternum It may also occur in infants with congenital heart defects

Answer 90

Hypoplastic ossification centers and premature fusion of sternal segments (20-50%)

Question 91

Defects of the Sternum It occur in 6% to 20% of all children but are especially common in those with down syndrome

Answer 91

multiple manubrial ossification centers

Question 92

Refers to a depressed sternum that is sunken posteriorly

Answer 92

Pectus excavatum

Question 93

refers to a flattening of the chest bilaterally with an anteriorly projecting sternum

Answer 93

Pectus carinatum