A.
In connective tissues, extracellular matrix is abundant and carries the mechanical load. In other tissues, such as epithelia, extracellular matrix is sparse, and the cells are directly joined to one another and carry the mechanical load themselves.
B.
Animal connective tissues are enormously varied. They can be tough and flexible like tendons or the dermis of the skin; hard and dense like bone; resilient and shock-absorbing like cartilage; or soft and transparent like the jelly that fills the interior of the eye. In all these examples, the bulk of the tissue is occupied by extracellular matrix, and the cells that produce the matrix are scattered within it like raisins in a pudding; the tensile strength—whether great or small—is chiefly provided not by a polysaccharide, as it is in the cell wall of plants, but by fibrous proteins, principally collagens.
C.
The various types of connective tissues owe their specific characters to the type of collagen that they contain, to its quantity, and, most importantly, to the other molecules that are interwoven with it in varying proportions.
D.
These other molecules include the rubbery protein elastin, which gives the walls of arteries their resilience as blood pulses through them, as well as a host of specialized polysaccharide molecules.