Skeletal and Muscular Systems

MULTIPLE CHOICE

Directions: Each group of questions below consists of a numbered list of descriptive words or phrases accompanied by a diagram with certain parts indicated by letters or by a list of lettered headings. For each numbered word or phrase, select the lettered part or heading that matches it correctly and then insert the letter in the space to the right of the appropriate number. Sometimes more than one numbered word or phrase may be correctly matched to the same lettered part or heading.

        1.   ________ Closes during the second year

a.
Centrum
b.
Epiphysial plate
c.
Frontal bone
d.
Anterior fontanelle
e.
Cartilaginous viscerocranium

ANS:   D

The anterior fontanelle, located where the two parietal bones and the halves of the frontal bone meet, usually closes about the middle of the second year. Palpation of this fontanelle during infancy gives information about ossification of the cranium and intracranial pressure.

        2.   ________ Forms by intramembranous ossification

a.
Centrum
b.
Epiphysial plate
c.
Frontal bone
d.
Anterior fontanelle
e.
Cartilaginous viscerocranium

ANS:   C

The frontal bone, part of the membranous neurocranium, develops by intramembranous ossification from two primary centers. The halves of the frontal bone begin to fuse during the second year, and the frontal (metopic) suture usually is obliterated by the eighth year.

        3.   ________ Partly within the pharyngeal arches

a.
Centrum
b.
Epiphysial plate
c.
Frontal bone
d.
Anterior fontanelle
e.
Cartilaginous viscerocranium

ANS:   E

The ends of the cartilaginous rods in the first and second pairs of pharyngeal arches reach the ventral surface of the neurocranium in the region of the developing ears. Later, they undergo endochondral ossification to form the lesser horns and the superior part of the body of the hyoid bone.

        4.   ________ Growth of long bones

a.
Centrum
b.
Epiphysial plate
c.
Frontal bone
d.
Anterior fontanelle
e.
Cartilaginous viscerocranium

ANS:   B

During the later stages of postnatal bone growth, the mass of cartilage between the diaphysis and epiphysis decreases in thickness to form a comparatively thin cartilage, the epiphysial cartilage plate. This plate is of importance for growth of long bones. At the termination of growth in the bone, the epiphysial plate disappears and the epiphysis unites with the diaphysis.

        5.   ________ Primary ossification center

a.
Centrum
b.
Epiphysial plate
c.
Frontal bone
d.
Anterior fontanelle
e.
Cartilaginous viscerocranium

ANS:   A

Most of the body of a typical vertebra (thoracic and lumbar) is ossified from a primary center, the centrum, which appears during the eighth week. At birth, the bone of the centrum is separated from the separate halves of the vertebral arch of cartilage by the neurocentral joints.

        6.   ________ Styloid process

a.
Centrum
b.
Epiphysial plate
c.
Frontal bone
d.
Anterior fontanelle
e.
Cartilaginous viscerocranium

ANS:   E

The styloid process of the temporal bone develops by endochondral ossification of part of the dorsal end of the cartilage of the second pharyngeal arch. The cartilages of the first two pairs of pharyngeal arches constitute the cartilaginous viscerocranium.

        7.  

________ Associated with the first pharyngeal arch cartilage

a.
A
b.
B
c.
C
d.
D
e.
E

ANS:   A

Development of the mandible is associated with the cartilage of the first pharyngeal arch. As this cartilage degenerates, the condensed mesenchyme near it undergoes intramembranous ossification to form the mandible.

        8.  

________ Part of the cartilaginous viscerocranium

a.
A
b.
B
c.
C
d.
D
e.
E

ANS:   E

The styloid process of the temporal bone and the malleus, incus, and stapes are derived from the cartilaginous viscerocranium.

        9.  

________ Forms in the maxillary prominence of the first pharyngeal arch

a.
A
b.
B
c.
C
d.
D
e.
E

ANS:   B

The maxilla forms in the maxillary prominence of the first pharyngeal arch by intramembranous ossification. It is part of the membranous viscerocranium, as are the mandible, zygomatic, and squamous temporal bones.

      10.  

________ Part of the cartilaginous neurocranium

a.
A
b.
B
c.
C
d.
D
e.
E

ANS:   D

The occipital bone ossifies partly by endochondral ossification of the posterior part of the cartilaginous neurocranium. This plate of cartilage forms in the base of the developing cranium (skull) by the fusion of several paired cartilages.

      11.  

________ Forms in the mandibular prominence of the first pharyngeal arch

a.
A
b.
B
c.
C
d.
D
e.
E

ANS:   A

The mandible is the part of the membranous viscerocranium that develops mainly by intramembranous ossification around the degenerating cartilage of the first pharyngeal arch.

      12.  

________ Part of the membranous neurocranium

a.
A
b.
B
c.
C
d.
D
e.
E

ANS:   C

The parietal and other flat bones of the cranium are parts of the membranous neurocranium that develop by intramembranous ossification. At birth, they are separated by connective tissue sutures.

      13.  

________ Articulates with the centrum

a.
A
b.
B
c.
C
d.
D
e.
E

ANS:   D

Each half of the vertebral arch (a lamina), is ossified from a primary ossification center. At birth, the laminae are separated from each other dorsally by cartilage and from the centrum by the cartilaginous neurocentral joints. These joints disappear when the vertebral arch fuses with the centrum (usually about the fifth year). The laminae of the vertebral arch fuse during the first year; failure of this fusion to occur results in spina bifida occulta.

      14.  

________ Neurocentral joint

a.
A
b.
B
c.
C
d.
D
e.
E

ANS:   B

As stated above, the neurocentral joints are located between the centrum and the vertebral arch. In the superior cervical vertebrae, the centra unite with the vertebral arches about the third year, but in the inferior lumbar vertebrae, union is not completed until the sixth year.

      15.  

________ Replaced by a synovial joint

a.
A
b.
B
c.
C
d.
D
e.
E

ANS:   E

The ribs are connected to the costal processes of thoracic vertebrae at costovertebral joints; these are the plain type of synovial joint. As the ribs and vertebrae ossify, joints develop between the tubercles of the ribs and the transverse processes of the vertebrae.

      16.  

________ Centrum

a.
A
b.
B
c.
C
d.
D
e.
E

ANS:   A

The major part of the body of a typical vertebra is formed by the centrum. It is ossified from a primary center that appears dorsal to the notochord. The centrum occasionally is ossified from bilateral primary centers.

      17.  

________ Its cartilage is ossified during infancy

a.
A
b.
B
c.
C
d.
D
e.
E

ANS:   C

The vertebrae form by the ossification of cartilaginous bone models. Primary centers appear during the early fetal period—one in each half of the vertebral arch and one in the centrum. At birth, the ossified halves of the vertebral arch are still separated from each other by cartilage. This cartilage is ossified during the first year.

      18.  

________ Disappears during childhood

a.
A
b.
B
c.
C
d.
D
e.
E

ANS:   B

The vertebral arch during infancy and early childhood is separated from the bone of the centrum by persistent bilateral zones of cartilage (neurocentral joints). These two lateral zones are ossified during the fifth and sixth years.

      19.  

________ Form the tongue muscles

a.
A
b.
B
c.
C
d.
D
e.
E

ANS:   B

The first pair of four occipital myotomes degenerate. Myoblasts from the remaining three myotomes migrate from the occipital region to the floor of the pharynx and form the striated muscles of the tongue, with the exception of the palatoglossus muscle. The hypoglossal nerve (CN XII) supplies all the muscles of the tongue except for the palatoglossus muscle, which is supplied by the pharyngeal branch of the vagus nerve (CN X).

      20.  

________ Normally regress during the eighth week

a.
A
b.
B
c.
C
d.
D
e.
E

ANS:   E

The paired somites begin to differentiate from the paraxial mesoderm in a craniocaudal sequence during the third week. By the end of the fifth week, 42 to 44 pairs of somites are present. The coccygeal somites regress with the tail-like caudal eminence during the eighth week.

      21.  

________ Form the scalene muscles

a.
A
b.
B
c.
C
d.
D
e.
E

ANS:   C

Myoblasts from the cervical myotomes form the scalene muscles, as well as the prevertebral, geniohyoid, and infrahyoid muscles.

      22.  

________ Give rise to the muscles of mastication

a.
A
b.
B
c.
C
d.
D
e.
E

ANS:   A

Myoblasts from the pharyngeal arches migrate to form the muscles of mastication (temporal, masseter, and medial and lateral pterygoids). The muscles of facial expression, as well as those of the pharynx and larynx, are also formed from the myoblasts of the pharyngeal arches. Muscles derived from any one of the pharyngeal arches retain the nerve supply of that particular arch; that is, the trigeminal nerve (CN V) innervates the muscles of mastication, as well as other muscles (mylohyoid, anterior belly of digastric, tensor tympani, tensor veli palatini) that are derived from the first pharyngeal arch. The facial nerve (CN VII), which is the second pharyngeal arch nerve, innervates the muscles of facial expression.

      23.  

________ Muscles originate from somites

a.
A
b.
B
c.
C
d.
D
e.
E

ANS:   D

The limb muscles are derived from the somites. Grafting and gene targeting studies in mammals indicate that the precursor myogenic cells in limb buds originate from the somites. These cells are first located in the ventral part of the dermomyotome and are epithelial in nature. Following mesenchymal-epithelial transformation, the cells then migrate into the primordium of the limb.