Provide definitions/explanations for the following terms:
$(i)$ Perichondrium
$(ii)$ Serum

(N/A) $(i)$ Perichondrium: It is a layer of dense irregular connective tissue that surrounds the cartilage of developing bone.
$(ii)$ Serum: It is the clear,yellowish fluid part of blood that remains after the coagulation factors (like fibrinogen) have been removed from the blood plasma.