Comparison between tract and nerve

  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...

Difference between monozygotic and dizygotic twin


Difference between monozygotic and dizygotic twin 

Topics
Monozygotic twin
Dizygotic twin
Origin
Single ovum fertilized by a single sperm (they are developed from one embryo splitting  into two embryos .
They are developed from two different eggs, which are fertilized by sperms separately
Fetal membrane
1.     monochorionic and diamniotic
2.     monochorionic and monochorionic
3.     dichorionic and diamniotic
Always dichorionic and diamniotic
Placenta
One or two (usually one )
Two placenta
Chorion
One or two (usually one )
Usually two
Amnion
One or two (usually one )
Usually two
Sex
Same
(two girls or two boys)
Same or different
(two girls or two boys or one girl and one boy )
Physical appearance
Usually Identical
Different
Cause
Unknown
Cuase by IVF, certain fertility drugs or hereditary predisposition
Blood types
Same
different
Percentage
1/3 of twins are monozygotic
2/3 of twins are dizygotic
Proportion of genes in common
100
50
Twin to twin transfusion syndrome
High risk of twin to twin transfusion syndrome
Low risk of twin to twin transfusion syndrome
Incidence
Incidence is independent of age, rage and parity
Incidence is dependent of age, rage, parity and ovulation inducing drugs
Similarity
Finger print
Different
Different

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