Develpment Of The Muscular And Skeletal Systems

Question 1

The Myotome forms _______

Answer 1

All the muscles of the body except the constrictor and dilater papillae in the eye

Question 2

The somite divides into what two parts

Answer 2

Ventromedial part and dorsolateral part

Question 3

The ventromedial part of the somite develops into what

Answer 3

Sclerotome

Question 4

The dorsolateral part of the somite develops into what

Answer 4

Dermatomes and myotome

Question 5

The sclerotome gives rise to

Answer 5

The mesenchyme - embryonic connective tissue

Question 6

The mesenchyme gives rise to what three things

Answer 6

Hyaline cartilage
Endochondral ossification
Intramembranous ossification

Question 7

Intramembranous ossification

Answer 7

Mesenchyme —> bone

• the mesenchyme forms in the shape of the bone you want first
• clavicle, flat bones of skull, face bones

Question 8

Endochondral ossification

Answer 8

Mesenchyme —> cartilage —> bone

• the mesenchyme forms cartilage in the shape of the bone first
• most bones in the body

Question 9

How is hyaline cartilage formed (4 steps)

Answer 9

Chondrification centers —> prechondrocytes —> chondroblasts —> chondrocytes

Question 10

Two parts of the sclerotome

Answer 10

Caudal dense part

Cephalic loose part

Question 11

What two parts fuse to form the vertebrae

Answer 11

Casual dense part and cephalic loose part of the sclerotome

Question 12

Two parts of the intervertebral discs

Answer 12

Nucleus pulposus and annulus fibrosus

Question 13

Annulus fibrosus

Answer 13

Part of the intervertebral disc; consist of fibrous tissue from the sclerotome and fibrocartilage

Question 14

Nucleus pulposus

Answer 14

Part of the intervertebral discs; made of mucous substance and notochord cells
- it’s the only remaining part left over from the notochord at this point

Question 15

How do ribs form

Answer 15

Sclerotome cells grow out from costal processes of thoracic vertebrae; the costal cartilage is also from the sclerotome

Question 16

How does the sternum form

Answer 16

It develops in the somatic lateral plate mesoderm; mesenchymal condensations chondrify and fuse together

Question 17

Cervical rib formation

Answer 17

An abnormality in rib formation; causes the brachial plexus to compress against the rib and compresses the subclavian
- one of the causes of thoracic outlet syndrome

Question 18

Pectus carinatum

Answer 18

Abnormality in rib/sternum formation; causes a protrusion of the sternum called “pigeon chest”

• unknown what causes this
• patients are otherwise normal

Question 19

Pectus excavatum

Answer 19

Abnormality in rib/sternum formation; causes steal depression “funnel chest”

• can compress the heart and/or shift the heart to the side
• sx include SOB, fatigue with exercise
• can need surgical correction
• cause is unknown

Question 20

Hox genes

Answer 20

Group of genes that control the body plan along a cranio-caudal axis

Question 21

Caudalization

Answer 21

Gain of function via hox gene defect; upper vertebrae appear like lower vertebrae

Question 22

cranialization

Answer 22

loss of function via hox gene defect; lower vertebrae appear like upper vertebrae

Question 23

gain of function (caudalization) in Hox6 in cervical vertebrae

Answer 23

those vertebrae start to look more similar to vertebrae that are lower (thoracic)

Hox 6 is normally found in upper thoracic region; cervical vertebrae can over express Hox 6 and they will now look like thoracic vertebrae

Question 24

gain of function (caudalization) of Hox 10

- normally found in lumbar region

Answer 24

expressed in thoracic region; the thoracic vertebrae will then look like lumbar vertebrae

Question 25

loss of function (cranialization) of Hox 4

Answer 25

C2, C3, C4

those vertebrae will look like the vertebrae above them (C1)

Question 26

loss of function (cranialization) of Hox 5

Answer 26

the vertebrae that lost Hox 5 will appear like C2

- Hox 5 normally found C3-T2

Question 27

loss of function (cranialization) of Hox 6

Answer 27

Hox 6 normally found in C6-T6; those thoracic vertebrae would look like cervical vertebrae and we wouldn’t have ribs attached

Question 28

loss of function (cranialization) of Hox 10

Answer 28

hox 10 normally found L1-S4; the lumbar vertebrae that aren’t expressing hox 10 will look thoracic

Question 29

Hox 9 function

Answer 29

gene that encodes for floating ribs

Question 30

loss of function (cranialization) of hox 9

Answer 30

normally T8-L4

- won’t have floating ribs with cranialization

Question 31

Hox 11 location

Answer 31

S1-coccyx

Question 32

epimere

Answer 32

derived from the myotome; develops into the epiaxial muscles

Question 33

epaxial muscles

Answer 33

true muscles of the back (erector spinae muscles, splenius capitus, etc)
- innervated by the dorsal rami

Question 34

hypomere

Answer 34

derived from the myotome; develops into the hypaxial muscles

Question 35

hypaxial muscles

Answer 35

all other muscles of the body except the true muscles of the back (epaxial muscles) and the constrictor and dilator of pupils
- innervated by ventral rami

Question 36

cervical myotomes form:

Answer 36

scalene, prevertebral, geniohyoid, and infrahydoid muscles

Question 37

thoracic myotomes form:

Answer 37

later and ventral flexor muscles of the vertebral column

Question 38

lumbar myotomes form:

Answer 38

quadratus lumborum

Question 39

sacrococcygeal myotomes form:

Answer 39

muscles of the pelvic diaphragm

Question 40

4 hypaxial divisions of the muscles

Answer 40

• cervical myotomes
• thoracic myotomes
• lumbar myotomes
• sacrococcygeal myotomes

Question 41

poland syndrome

Answer 41

a result of absence of migration of hypomere cells into the chest; patient’s do not have pectoralis major and/or minor; patients have ipsilateral breast hypoplasia associated with syndactyly and sometimes loss of 2-4 ribs

Question 42

prune-belly syndrome

Answer 42

partial or complete absence of abdominal musculature as a result of absence or abnormal migration of hypomere cells into the abdominal wall

• primarily affects males
• associated with crytorchidism and malformation of urinary tract and bladder