Topic # 7 DEVELOPMENT OF THE MUSCULOSKELETAL SYSTEM

Question 1

comprises 40 – 45 % of the total body weight.

➢ Long and cylindrical w/ many nuclei located at the periphery of the cell.

Answer 1

Skeletal or striated or voluntary myocyte

Question 2

is found in the walls of tubular and visceral organs.

➢ Spindle-shaped w/ one nucleus located in the middle of the cell

Answer 2

Smooth or visceral or involuntary myocyte

Question 3

comprises the myocardium of the heart.

➢ Branched w/ many nuclei located in the middle of the cell.

Answer 3

Cardiac myocyte

Question 4

Muscle development requires

Answer 4

innervations

Question 5

by delamination forms mesenchymal cells that elongate to form myoblasts.

Answer 5

Splanchnic mesoderm

Question 6

Cardiac muscle cells are joined together by intercellular
connections called

Answer 6

intercalated discs.

Question 7

Types of Connective Tissues

Answer 7

1. Loose connective tissue - mesenchymal, mucoid, areolar adipose tissue, etc.
2. Dense connective tissue - tendons, ligaments.
3. Cartilage
4. Bone

Question 8

two types of fibers secreted by fibroblasts:

Answer 8

collagenous and elastic

Question 9

originates from paraxial mesoderm, somatic mesoderm or ectomesenchyme

Answer 9

Bone

Question 10

occurs in most bones of the axial skeleton and appendicular skeleton. This occurs by ossification of a cartilage model.

Answer 10

Endochondral Bone Development

Question 11

occurs in bones of calvaria (roof of skull) and face.
Mesenchymal (osteogenic) cells from mesoderm or ectoderm proliferate and aggregate;
become round and enlarged and are now termed osteoblasts.

Answer 11

Intramembranous Bone Development

Question 12

Common Malformations of the Vertebra Alignment Defects

Answer 12

1. Scoliosis
2. Kyphosis
3. Lordosis
4. Torticolis or wry neck
5. spina bifida
6. Rachischisis
7. Spina bifida occulta

Question 13

lateral deviation of vertebral column.

Answer 13

Scoliosis

Question 14

sagittal deviation of vertebral column in a fixed position.

Answer 14

Kyphosis

Question 15

sagittal deviation of vertebral column in a fixed extended position.

Answer 15

Lordosis

Question 16

abnormal twisting of the cervical vertebral column.

Answer 16

Torticolis or wry neck

Question 17

absence of vertebral arch (failure of vertebral arch to form dorsally
over the vertebral foramen).

Answer 17

Spina bifida

Question 18

spina bifida of several adjacent vertebrae.

Answer 18

Rachischisis

Question 19

spina bifida covered by skin and subcutis.

Answer 19

Spina bifida occulta

Question 20

develops from outward growth of ectomesenchymal tissue located rostral to the cranium and pharynx.

Answer 20

face

Question 21

cleft lip caused by failure of fusion of medial nasal and maxillary
processes.

Answer 21

Cheiloschisis

Question 22

cleft palate caused by failure of medial palatine processes to fuse.

Answer 22

Palatoschisis

Question 23

Primordia of enamel organs
escape to the exterior and develop tooth structures anchored on the parietal bone or
base of the ear.

Answer 23

Heterotropic polyodontia

Question 24

loss of a specific part of a limb. It is usually named using the defect
as prefix and the phrase “melia” (melos=limb) or dactyl (Gr. dactylos= digit) as suffix.

Answer 24

Limb Reduction

Question 25

inherited; systemic premature
ossification of physes of extremeties.

Answer 25

Achondroplasia (dwarfism; Dachshund)

Question 26

complete absence of a limb.

Answer 26

amelia

Question 27

absence of a part of a limb.

Answer 27

Meroromelia

Question 28

complete absence of limb.

Answer 28

Acromelia

Question 29

absence of half or one or more segments of a limb.

Answer 29

Hemimelia

Question 30

reduced size of a limb.

Answer 30

Micromelia

Question 31

absence of one or more proximal segments, a consequence of
pregnant women taking thalidomide in the late 1950’s.

Answer 31

Phocomelia

Question 32

fused digits.

Answer 32

Syndactyly

Question 33

shortened or stumpy digits.

Answer 33

Brachydactyly

Question 34

absence of one or more digits.

Answer 34

Ectrodactyly

Question 35

presence of one or more extra digits. This is common in pig and cat.

Answer 35

Limb Duplication

Question 36

one or more extra digits.

Answer 36

Polydactyly

Question 37

partial or complete duplication of one limb.

Answer 37

Bimelia

Question 38

limb growing from the back of the animal.

Answer 38

Notomelia (noto=back)

Question 39

can results from malformed joints, denervation, abnormal muscle tension, or impaired mobility in utero.

Answer 39

Arthrogryposis

Question 40

abnormal maturation of the hip joint that results in formation
of a shadow acetabulum and flattened femoral head. Inherited and associated w/ large, muscular breeds of dog. Onset of signs may occur at 3 – 5 months of age.

Answer 40

Hip Dysplasia

Question 41

permanent fixation of a joint caused by immobility of the fetus in utero.

Answer 41

Ankylosis