development of the muscular system Flashcards
Ventromedial part of paraxial mesoderm
sclerotome
Dorsolateral part of paraxial mesoderm
» Dermatome
» Myotome
Mesenchyme
embryonic connective tissue
-from Sclerotome
Intramembranous ossification
Mesenchyme → bone
Endochondral ossification
Mesenchyme → cartilage
→bone
Hyaline cartilage
Chondrification centers →
prechondrocytes → chondroblasts →
chondrocytes
process of forming vertebral column
Caudal 1⁄2 of sclerotome “A”
fuses with the cephalic 1⁄2 of
sclerotome “B”
what are the vertebra components?
– Caudal dense part
– Cephalic loose part
Nucleus pulposus
– Notochord expands to form the
nucleus pulposus
– Mucoid substance
Annulus fibrosus
– Fibrous tissue from sclerotome
– Fibrocartilage
ribs
– Sclerotome cells that grow out from costal processes of thoracic vertebrae • Costal cartilage also from sclerotome
sternum
– Develops in the somatic
lateral plate mesoderm
thoracic outlet syndrome
presence of a cervical rib
-brachial plexus can be compressed and subclavian artery can compress blood flow
pectus carinatum
- sternum protrusion
- “pigeon chest”
pectus excavatum
“funnel chest”
sternum depression
- can compress and shift heart
- have exercise intolerance
hox genes
• Group of related
genes that control
the body plan along a cranio-
caudal axis
hox genes- gain of function
– Caudalization
-vertebrae more similar to those beneath it
hox genes loss of function
- Cranialization
- vertebrae look more similar to those above it
epimere
-myotome
-• Epaxial muscles
• Innervated by
dorsal rami
true muscles of back
hypomere
-mytome • Hypaxial muscles • Innervated by ventral rami all other muscles with exception of eye
epaxial divisions
– Form extensor muscles of neck and vertebral column
hypaxial divisions
– 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
poland syndrome
– 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
prune-belly syndrome
• 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
