Musculoskeletal Embryology I Flashcards
Intraembryonic mesoderm lateral to notochhord and neural tube thickens to form two longitudinal columns of ___ ____
paraxial mesoderm
By the end of the third week, the paraxial mesoderm becomes segmented into blocks - the ____ (42-44 pairs)
somites
Each somite differentiates into two parts. What is the ventromedial part that form the vertebrae and ribs called?
Sclerotome
Each somite differentiates into two parts. What is the dorsolateral part called?
dermomyotome
The myotome region of the dermomyotome forms ____
myoblasts
The dermatome region of the dermomyotome forms the ____
dermis
Mesodermal cells give rise to loosely organized embryonic connective tissue called the ___
mesenchyme
in this process, mesenchymal cells from membranous sheaths, and the bone is formed by osteoblasts and osteoclasts within the membranous model
intramembranous bone formation
in this process, the model of bone is formed by chondrocytes and osteoblasts within the cartilage form bone
endochondral bone formation
Vertebrae develop by ___ bone formation
endochondral
At week ___, the sclerotomes appear as paired condensations of mesenchymal cells, migrate around the notochord and neural tube to merge from the opposing somite
4
The body of each vertebra is formed by ____. The densely packed caudal half of one sclerotome grows and fuses with the loosely arranged cephalic half of the next caudal sclerotome to form the mesenchymal ____, the primordium of vertebral body.
resegmentation; centrum
The _____ surrounds the notochord and serves as bony floor for the spinal cord
centrum
The dorsal mesenchymal cells that surround the neural tube form the ___ ___, which is the primordium of the vertebral arch
neural arch
The notochord degenerates where the developing bodies are formed but persists between adjacent vertebral bodes to become the ___ ___ of intervertebral discs
nucleus pulposus
This outer part of the intervertebral discs is formed by original sclerotomal cells that migrate into that site
annulus fibrosus
At six weeks, ____ centers appear in each vertebra and ____ begins during the eight week
chondrificaiton; ossification
In normal circumstances, the developing vertebral bodies are formed from migration sclerotomal cells around the neural tube and appearance of chondrification centers that soon unite. If this migration and differentiation fails on one side, results in the failure of half of vertebra to form. These vertebral defects produce ____ of the vertebral column
scoliosis
some lateral mesenchymal condensations called ___ processes develop in association with vertebral arches of all the developing neck and trunk vertebrae
costal
In cervical vertebrae, the costal and transverse process give rise to lateral and medial boundaries of ___ foramen.
transverse
At birth, each vertebra consists of three bony parts connected by cartilage. The bony halves of the vertebral arches fuse during __ to ___ years of life.
3; 5
Imperfect fusion of vertebral arches can lead to a condition called ___ __, which leaves the spinal cord, spinal nerves and meninges vulnerable to injury
spina bifida
This type of spina bifida is the failure of formation of the vertebral arch in lumbar vertebrae, although the spinal cord, spinal nerves, and meninges are normal. The defect is often marked by a tuft of overlying hair.
spina bifida occulta
This type of spina bifida is more severe. The neural tube fails to close, and involves the protrusion of the spinal cord, the meninges, or both through the defects in vertebral arches. These defects are usually associated with significant neurological deficits.
spina bifida cystica
True or false? Ribs are cartilaginous during the embryonic period but begin to ossify during fetal development.
true
The lower 5 ribs have no connection to the ___
sternum
The sternum develops independenttly from mesenchymal condensations called ___ ___, that are located in the ventrolateral body wall
sternal bars
Each myotome splits into two structures, the dorsal epimere and ventral hypomere, which forms ___ and ____ muscles respectively
epaxial; hypaxial
_____ divisions of the myotomes form the segmental muscles of the main body axis, the extensor muscles of neck, and the vertebral column (deep back muscles)
epaxial
What happens to the embryonic extensor muscles that are derived from sacral and coccygeal myotomes?
they degenerate
note: their adult derivatives are the dorsal and sacrococcygeal ligaments
____ divisions of cervical myotomes form the scalene, prevertebral geniohyoid, and infra hyoid muscles
hypaxial
The ____ myotomes form the lateral and ventral flexor muscles of the vertebral column (rectus abdominus, external abdominal oblique, transverse abdominus)
throacic
The intercostal muscles are derived from the ___ myotome
hypaxial
At limb forming levels, the hypaxial ___ also invade the developing limb buds and give rise to limb musculature
myoblasts
The ___ myotomes form the quadratus lumborum muscle
lumbar
Dermatome will become the dermis of the ___ and ___
neck; trunk
As the somites develop, each is associated with a corresponding ___ ___ growing out from the neural tube.
spinal nerve
each circumferential band of skin on the trunk receives sensory innervation from a single pair of ___ ___ spinal nerves
segmentally related
