Areolar (loose) connective tissue
Textus connectivus laxus
Also known as: loose connective tissue, areolar connective tissue, lamina propria
The most widespread connective tissue: a loose, gel-rich meshwork of all three fibre types and many cell types that packages organs, underlies epithelia and surrounds vessels and nerves.
Overview
Areolar tissue has relatively few, loosely interwoven collagen, elastic and reticular fibres in a large volume of viscous ground substance rich in hyaluronan, with abundant interstitial fluid. Its spaces ("areolae") give it its name. It contains the full cast of connective-tissue cells: fibroblasts, macrophages, mast cells, plasma cells, lymphocytes, other leukocytes and a few adipocytes.
Because it is soft, pliable and richly supplied with capillaries, it is the tissue in which most inflammatory and immune reactions take place, and it acts as a reservoir of water and salts for surrounding tissues. It forms the lamina propria of mucous membranes, the papillary layer of the dermis, the subcutaneous tissue (together with adipose tissue), and the packing around blood vessels, nerves, glands and muscle fibres (endomysium).
- Location
Lamina propria of mucosae; papillary dermis; hypodermis; around vessels, nerves and organs; between muscles; serous membranes.
Anatomy
- Histology
Loose, randomly oriented pink collagen fibres, thin dark elastic fibres (special stains), scattered nuclei of varied cell types, much "empty" space (ground substance extracted in processing).
Function
- Cushions and binds organs; permits movement.
- Site of inflammation and immune defence.
- Holds tissue fluid (oedema accumulates here).
- Supports epithelia and supplies them by diffusion.
Clinical significance
Spread of infection
Some bacteria (e.g. Streptococcus pyogenes) secrete hyaluronidase and streptokinase, letting infection spread rapidly through loose connective tissue — cellulitis and necrotising fasciitis.
Compiled from standard anatomy and physiology references — see the Cells & Tissues sources. For education only; not medical advice.