Lecture 17: Development Of Musculoskeletal System Flashcards
Development of the musculoskeletal system occurs aorund day 33, when ______ processes appear on the vertebral bodies. The following week, in the thoracic region, these processes elongate to form ribs.
At day 40, ________ sternal bars appear and costovertebral joints begin to develop.
At day 45, ribs connect with sternal bars; sternal bars begin to fuse. By day 60, the sternal bars are completely fused.
Costal
Mesodermal
What important musculoskeletal developmental event occurs at day 40?
Myotome splits into epimere and hypomere
What important musculoskeletal developmental event occurs at day 60?
Epimere gives rise to spinal musculature
Hypomere gives rise to trunk wall muscle layers
Sacral vertebrae fuse to form sacrum
Intervertebral discs are distinct and consist of an annulus fibrosus and nucleus pulposus
What portion of the paraxial mesoderm somite becomes the muscles of the trunk?
Myotome
What does the sclerotome of the paraxial mesoderm somite become?
Vertebrae, cartilate of ribs
What are the 3 primary components derived from the paraxial mesoderm somite?
Sclerotome
Dermomyotome
Syndetome
Somite –> syndetome –> __________
Tendons
Somite –> sclerotome –> __________, _________
Vertebrae, ribs
Somite –> dermomyotome –> dermotome –> ____________
Posterior dermis
Somite –> dermomyotome –> myotome –> _______ + ________
Epimere + hypomere
What portion of the myotome forms deep epaxial muscles (erector spinae and transversospinalis mm.)?
Epimere
What portion of the myotome forms the hypaxial muscles (lateral and ventral body wall)?
Hypomere
The epimere gives rise to deep epaxial muscles like the erector spinae group and transversospinalis mm. which typically act as extensors. These are innervated by what division of the spinal nerves?
Posterior ramus
T/F: sensory nerve processes are found in all nerves to muscle in addition to cutaneous nerves
True
The ______ division of muscles = the extensor muscles of neck and vertebral column
Epaxial
What are the 4 myotomes associated with the hypaxial division of muscles?
Cervical
Thoracic
Lumbar
Sacrococcygeal
Scalenes, prevertebral, geniohyoid, and infrahyoid muscles are associated with the ___________ myotome of the hypaxial muscle division
Cervical
Quadratus lumborum m. is associated with the ___________ myotome of the hypaxial muscle division
Lumbar
Lateral and ventral flexor muscles of the vertebral column are associated with the ___________ myotome of the hypaxial muscle division
Thoracic
Pelvic floor musculature is associated with the ___________ myotome of the hypaxial muscle division
Sacrococcygeal
__________syndrome is characterized by absence of pectoralis minor and partial loss of pectoralis major, resulting in ipsilateral breast hypoplasia. May also be associated with syndactyly or brachydactyly
Poland syndrome
Is Poland syndrome more frequent in males or females?
Males (1/20,000 overall prevalence)
___________ syndrome is characterized by partial or complete absence of abdominal musculature. May also be associated with cryptochidism (failure or one/both testes to descend) and malformation of urinary tract and bladder (results in urethra obstruction and fluid accumulation in abdomen causing further muscle atrophy)
Prune-belly
The sclerotome will develop into vertebrae and ribs. Sclerotomes are regionalized into ventral, dorsal, and lateral cells.
What are the ventral cells associated with?
Vertebral body
The sclerotome will develop into vertebrae and ribs. Sclerotomes are regionalized into ventral, dorsal, and lateral cells.
What are the dorsal cells associated with?
Vertebral arch and spine
The sclerotome will develop into vertebrae and ribs. Sclerotomes are regionalized into ventral, dorsal, and lateral cells.
What are the lateral cells associated with?
Vertebral transverse processes and ribs
What is the significance of resegmentation of the sclerotome?
The sclerotome splits into cranial and caudal pieces, allowing spinal nerves to come out and make contact with their muscle targets. By the time the vertebrae fusion process is complete, the vertebral body will be derived from 2 different portions of sclerotome.
What sclerotome is found cranial to C1, and contributes along with the cranial portion of C1 to the base of the occipital bone?
O4
Normally, spinal nerves are named for the vertebrae that sits inferiorly, what is the exception to this?
C8 - cranial portion of C8 contributes to C7. Caudal portion of C8 contributes to T1. So C8 spinal nerve sits superior to C7 vertebrae
[normal example would be that C4 spinal nerve sits superior to C4 vertebrae]
At the end of the 4th week of development, sclerotome cells appear as paired condensations of mesenchyme around the _________
Some densely packed cells move cranially and form the _________ ______
Remaining densely packed cells fuse with the cells of the immediately caudal sclerotome, forming the ________
Notochord
Intervertebral disc
Centrum
Once the centrum (an intersegmental structure) develops from 2 adjacent sclerotomes, spinal nerves lying near the intervertebral discs extend from the spinal cord to innervate the __________
Intersegmental ________ also lie on each side of the vertebral bodies
Myotome; arteries
Formation of centrum from 2 adjacent sclerotomes results in trapping of portions of the notochord, leaving the _______ _____ as a remnant.
The __________ _______ is the remaining derivative of the sclerotome
Nucleus pulposus
Annulus fibrosus
Sclerotome (mesenchymal) cells that surround the neural tube form the _______ ______, which is the primordium of the vertebral arch
Neural arch
The MAIN part of the sclerotome gives rise to what portion of the vertebrae?
Transverse processes
In the formation of the intervertebral discs, the _______ expands to form the nucleus pulposus, which will become surrounded by circularly arranged fibers that form the ________ _________
Notochord
Annulus fibrosus
What type of cartilage is associated with the intervertebral discs? Does this have a perichondrium?
Fibrocartilage; does NOT have a perichondrium
What type of cartilage is associated with most structures of the developing embryo? Does this have a perichondrium?
Hyaline cartilage, yes it has a perichondrium
Ribs develop from _________ processes of the thoracic vertebrae; cartilaginous during embryonic period and ossify during fetal period
Costal
During development you have paired sternal bars that are derived from somatic ________ ________ mesoderm. They develop ventrolaterally in the body wall, then move _________.
Lateral plate
Medially
The paired sternal bars with fuse (at 10 weeks) to form cartilaginous models of the ________, _______ (segments of sternal body), and ________ process
Manubrium; sternebrae; xiphoid
What genes are responsible for specifying vertebrae identity; i.e., how do thoracic vertebrae “know” to grow ribs?
Hox genes
[boundaries correspond to changes in vertebral shape - expression alterations can cause transformations of vertebrae]
If hox10 genes are responsible for the lack of development of ribs on lumbar and sacral, what would be the result of mutation in all copies of hox10?
Development of additional ribs in thoracic and sacral vertebrae
What vertebral malformation results in additional structures attached at C7, which may impinge on the brachial plexus and/or subclavian a. (thoracic outlet syndrome)
Cervical ribs
What body wall malformation results from a depressed sternum that is sunked posteriorly?
Pectus excavatum
What body wall malformation is characterized by bilateral flattening of the chest with an anteriorly projecting sternum?
Pectus carinatum
