Connective tissues are one of the four main tissue types in humans that are extensively present in the body. They are characterized by cells embedded in an extracellular matrix (ECM) composed of a ground substance and three main types of protein fibers— collagen, elastic, and reticular fibers. The ground substance of connective tissues can range from a watery and jelly-like consistency to mineralized and hard. The wide variety of cells in the connective tissues include fibroblasts, osteocytes,...

Connective tissue develops from the mesoderm of a developing embryo and consists of cells, fibers, and ground substance: a gel-like material containing large complexes of carbohydrates and proteins. Connective tissue was first identified as a separate tissue family in the 18th century, and Johannes Peter Muller coined the term connective tissue.
Fat cells (adipocytes), smooth muscle cells (myoblasts), and bone cells (osteoblasts) are some connective tissue cell types. Some immune system cells...

Connective tissues perform a broad range of functions in the body. Their primary function is to connect and link different tissues in the body and act as packaging material between tissues. The areolar tissue, a connective tissue prototype, commonly cements various tissue types in diverse body organs. In contrast, adipose tissue cushions internal organs while insulating the body from heat loss.
Hard connective tissues, such as bones and cartilage, provide structure and support to the body.

The connective tissues have different properties and functions in the human body. They are broadly categorized into proper, supporting, or fluid connective tissues.
Connective Tissue Proper
Connective tissue proper is the most abundant class of connective tissues. As its name implies, it predominantly connects different tissues in the body. Depending on the cell types, ground substance, viscosity, and fiber types in the ECM, connective tissue proper is further categorized into loose and dense.

Blood and lymph are fluid connective tissues. They contain cells, also known as formed elements, circulating in a liquid extracellular matrix, the plasma. The formed elements are derived from hematopoietic stem cells in the bone marrow. Blood and lymph connect all vital parts and carry nutrients, oxygen, and other essential molecules like antibodies.
Blood
The blood flows through blood vessels— arteries, capillaries, and veins. Blood plasma is primarily made of proteins, solutes, and water.

Connective tissue proper is a class of connective tissue that encompasses all mature connective tissues except bone, cartilage, blood, and lymph. This extensive class of tissues has two subclasses — loose and dense connective tissues — classified based on the protein fiber arrangement and the amount of ground substance. 
The loose connective tissues have a meshwork of thin collagen and elastin fibers, which provide tensile strength for support and enough elasticity to move cells. They have...