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Embryology helpful because
a tool for anatomy. There are common developmental schemes, nearly all of modern clinical research is based on non human animal models.
ontogeny recapitulates phylogeny. Growth from a zygote to a multicellular adult mimics evolution.
Embryos do not evolve so this doesn't work well
Von Baer's Law
Each stage of embryologic development resembles the embryos of phylogenetically related species.
The closer the relationship the longer the resemblence is in development
Stages of development
4.Bilaminar Germ Disk (Still Technically a Blastocyst)
5b. Trilaminar Germ Disk
7.Bill, or George, or Henry, or anything but Sue!
food stuffs live off of if you were an egg developing critter
lining of the sac develops into the germ cells of the next generation
failed closure of a caudal neuropore (relatively benign condition sometimes hair above butt. Can be insignificant and can be life threatening
Lateral plate mesoderm
most distant from the notochord
develops into the body wall and limb skeletons, smooth muscle of the gut, and coelomic cavity
1.) with completion of neurulation each somite pair becomes associated with the mixed spinal nerve that stems off the neural tube
2.) Every structure from that somie recieves innervation from that spinal level
3.) enlargements of paraxial mesoderm
what is significant about timing of somites
they develop and first appera on the cranial end of the embryo so by the time the final somites appear on the tail end the first somites have already differentiated into other structures
dermomyotome differentiates into
dermatome and myotome
Dermatome (sensory component of the skin)
myotome (most of the voluntary musculature of the body)-motor problems
1.) starts with a mesenchymal model that transforms directly into bone
2.) More common in flat bones (skull frontal etc)
3.) creates very dense bone
4.) Adult mechanism of bone repair
1.) Starts with a mesenchymal model
2.) Gradually this is replaced by cartilage which is usually hyline
3.) Associated more with long bones
4.) normal consequence of vascularization of cartilage
5.) Can be a pathological process (bone spurs)
contains large amounts of collagen fibers and is an important structural cartilage (intervertebral disks)
contains large amounts of elastin, and is thus capable of being stretched and distorted and will regain its shape (ears and sides of nose)
favors stability of structure. movement occurs only during extreme stress or in special physiolocial circumstances
Highly moveable joints
favors free movement between the bones. Stability occurs through restrictive ligaments or muscular action.
slightly moveable joints
compromise between the movement and stability. Movement generally occurs only over small and specialized range
Osseous joints (bone on bone), fibrous joints (two bones with ligament linking them togethers), Cartilaginous joints
Synovial joints (things always present)
1.) Capsular ligaments
2.) Articular cavity
3.) Articular (hyaline) cartilage
4.) Synovium (synovial fluid)
Synovial sometimes present
1.) Intrinsic ligaments
3.) Fat pads
4.) Fibrocartilaginous disks
Bone spins along vertical axis-rotation
anterior-posterior directed axis-abduction/adduction
Disk Herniation Least likely
to go through the posterior side because of the posterior longitudinal ligament
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