development of the muscular system

Question 1

Ventromedial part of paraxial mesoderm

Answer 1

sclerotome

Question 2

Dorsolateral part of paraxial mesoderm

Answer 2

» Dermatome

» Myotome

Question 3

Mesenchyme

Answer 3

embryonic connective tissue

-from Sclerotome

Question 4

Intramembranous ossification

Answer 4

Mesenchyme → bone

Question 5

Endochondral ossification

Answer 5

Mesenchyme → cartilage

→bone

Question 6

Hyaline cartilage

Answer 6

Chondrification centers →
prechondrocytes → chondroblasts →
chondrocytes

Question 7

process of forming vertebral column

Answer 7

Caudal 1⁄2 of sclerotome “A”
fuses with the cephalic 1⁄2 of
sclerotome “B”

Question 8

what are the vertebra components?

Answer 8

– Caudal dense part

– Cephalic loose part

Question 9

Nucleus pulposus

Answer 9

– Notochord expands to form the
nucleus pulposus
– Mucoid substance

Question 10

Annulus fibrosus

Answer 10

– Fibrous tissue from sclerotome

– Fibrocartilage

Question 11

ribs

Answer 11

– Sclerotome cells that
grow out from costal
processes of thoracic
vertebrae
• Costal cartilage also
from sclerotome

Question 12

sternum

Answer 12

– Develops in the somatic

lateral plate mesoderm

Question 13

thoracic outlet syndrome

Answer 13

presence of a cervical rib

-brachial plexus can be compressed and subclavian artery can compress blood flow

Question 14

pectus carinatum

Answer 14

• sternum protrusion

- “pigeon chest”

Question 15

pectus excavatum

“funnel chest”

Answer 15

sternum depression

• can compress and shift heart
• have exercise intolerance

Question 16

hox genes

Answer 16

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

Question 17

hox genes- gain of function

Answer 17

– Caudalization

-vertebrae more similar to those beneath it

Question 18

hox genes loss of function

Answer 18

• Cranialization

- vertebrae look more similar to those above it

Question 19

epimere

Answer 19

-myotome
-• Epaxial muscles
• Innervated by
dorsal rami
true muscles of back

Question 20

hypomere

Answer 20

-mytome
• Hypaxial
muscles
• Innervated by
ventral rami
all other muscles with exception of eye

Question 21

epaxial divisions

Answer 21

– Form extensor muscles of neck and vertebral column

Question 22

hypaxial divisions

Answer 22

– Cervical myotomes: form scalene, prevertebral, geniohyoid, and
infrahyoid muscles – Thoracic myotome: form the lateral and ventral flexor muscles of the
vertebral column – Lumbar myotome: form quadratus lumborum – Sacrococcygeal myotome: form muscles of pelvic diaphragm

Question 23

poland syndrome

Answer 23

– Associated with syndactyly
– Absence of pectoralis major and minor
– Ipsilateral breast hypoplasia
– Absence of 2 to 4 ribs
-absence of migration of cells of hypomere

Question 24

prune-belly syndrome

Answer 24

• Partial or complete
absence of abdominal
musculature
• Primarily affects males
• Associated with:
– Cryptorchidism (failure
of one or both testes to
descend)
– Malformation of
urinary tract and
bladder
• Urethral obstruction
-abnormal migration of cells of hypomere into abdominal wall