Areolar Tissue – Tutorial

Please read Unit 2 – Introduction to Connective Tissues prior to completing the activities in this chapter.

Introduction to Areolar Tissue

Areolar tissue is the least specialized type of connective tissue proper with a matrix containing interwoven yet loosely arranged (widely spaced) elastic and collagen fibers in a thick ground substance that fills most of the extracellular space.  Due to the open flexible jelly-like consistency of the matrix, areolar tissue is sometimes referred to as loose connective tissue.  Areolar tissue can contain a variety of cellular components including fibroblasts, fibrocytes, adipocytes, mesenchymal cells (connective tissue stem cells), and a variety of immune system cells such as mast cells and free and fixed macrophages.  Areolar tissue is widely distributed throughout the human body, and it can appear different in various locations depending on the prevalence of different cell types and the density and arrangement of extracellular protein fibers.

Since the matrix of areolar tissue is generally comprised of extremely flexible elastic fibers and strong yet flexible collagen fibers in a viscous ground substance, it is strong enough hold tissues together yet flexible enough to absorb shock and provide cushioning between organs and tissues.  Furthermore, due to the elasticity of areolar tissue, it is often located between adjacent tissues or organs that must slide independently with body movement.  Because of these properties, areolar tissue is found in both the dermis and hypodermis where it serves to anchor skin while allowing it to float over underlying tissues as they move.  Areolar tissue is also found in the connective tissue sheath surrounding nerves and blood vessels, allowing muscle, tendon, and bone to glide past nerves and blood vessels as the body moves.  Areolar tissue is also found in thin layers under epithelial tissues (known as the lamina propria) where its open matrix allows for gas exchange and free movement of immune cells in the extracellular space between capillaries and epithelial cells (recall that epithelial tissues are avascular).

It should also be noted that the number and size of adipocytes within areolar tissue greatly influences how it appears under a microscope.  Individual adipocytes can change size as they store or release fats, and mesenchymal cells can divide to create new adipocytes if the body takes in more calories on a regular basis than what it metabolizes.  Since adipocytes can be present in areolar tissue, at times areolar tissue will simply appear as adipose tissue in the locations described in the previous paragraph.

Tutorial:  Use the image slider below to learn more about the characteristics of areolar tissue. 

Microscopy:  Use the image slider below to learn how to use a microscope to identify and study areolar tissue on a microscope slide of mesentery (visceral peritoneum).

Tutorial:  Use the hotspot image below to learn more about the characteristics of areolar tissue. 

Tutorial:  Use the hotspot image below to learn more about the characteristics of areolar tissue. 

Tutorial:  Use the image slider below to study numerous examples of areolar tissue.