Comparison between tract and nerve

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  Comparison between tract and nerve Nerve Nerve contain bundle of axons (nerve fibers) in the peripheral nervous system (PNS) that transmits signals between the central nervous system (CNS) and other parts of the body. It is the most important part of peripheral nervous system Location: Peripheral nervous system. Structure: Made of axons, connective tissue layers (endoneurium: axon is surrounded by it , perineurium: bundle of axons are surrounded by it, epineurium: whole nerve trunk is surrounded by it), and blood vessels. It gets myelination by Schwann cell   Function: Carries sensory signals to the CNS (afferent) from peripheral part of body or motor signals carry from from the CNS (efferent) to target organs like skeletal muscle, cardiac muscle, smooth muscle or glands Example: Sciatic nerve, median nerve, except optic nerve (though optic nerve is technically part of CNS in develop...
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Difference between primary and secondary ossification

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Difference between primary and secondary ossification centre
Primary ossification center

Secondary ossification centre:
1.      It is the first area of a bone which starts to ossify.
1.      These are the areas of ossification that appear after the appearance of the primary ossification center.
2.      It usually appears during intra-uterine life in the central part of each developing bone
3.      Exception: carpal bones of hand
2.      Most of which appear during the postnatal and adolescent years.
3.      Exception : lower end of femur (this secondary ossification centre appear before birth)
4.      In long bones the primary ossification centers appear in the diaphysis/shaft and in irregular bones the primary centers appear usually in the body of the bone.
4.      In long bones, the secondary ossification centers appear in the epiphyses (upper and lower end).
5.      All long bones have only one primary ossification center (except clavicle: which has two primary ossification centre) and  some irregular bones such as the hip bone and vertebrae have multiple primary centers.
5.      Most bones have more than one secondary ossification center.


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