The function of the Haversian canal is:

Haversian canals are found in

Bone-forming cells are known as

Refer to the given figure and identify the correct characteristic features.
$(i)$ It is a type of loose connective tissue.
$(ii)$ It contains fibroblasts,macrophages,collagen fibres,and mast cells.
$(iii)$ The cells of this tissue are specialized to store fats.
$(iv)$ It forms the inner lining of blood vessels,stomach,and intestine.

Identify cells $P$ and $Q$ in the given areolar connective tissue diagram.

The mast cells secrete the following substance: