Editing Loose connective tissue (section)

{{More citations needed|date=May 2015}}
{{Short description|Type of connective tissue in animals}}
{{Redirect|Areolar|other uses|areola (disambiguation)}}
{{Distinguish|Areola}}
{{Infobox anatomy
| Name        = Loose connective tissue
| Latin       = textus connectivus laxus
| Image       =Normal Epidermis and Dermis with Intradermal Nevus 10x.JPG
| Caption     =Section of dermis. The papillary dermis consists of loose connective tissue.
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| Lymph       =
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'''Loose connective tissue''', also known as '''areolar tissue''', is a cellular [[connective tissue]] with thin and relatively sparse [[collagen fiber]]s. They have a semi-fluid matrix with lesser proportions of fibers. Its [[ground substance]] occupies more volume than the fibers do. It has a viscous to gel-like consistency and plays an important role in the diffusion of oxygen and nutrients from the capillaries that course through this connective tissue as well as in the diffusion of carbon dioxide and [[metabolic wastes]] back to the vessels. Moreover, loose connective tissue is primarily located beneath the [[epithelium|epithelia]] that cover the body surfaces and line the internal surfaces of the body. It is also associated with the epithelium of glands and surrounds the smallest blood vessels. This tissue is thus the initial site where pathogenic agents, such as bacteria that have breached an epithelial surface, are challenged and destroyed by cells of the immune system.<ref name="Foot01">{{cite book |last1=Pawlina |first1=Wojciech |last2=Ross |first2=Michael |title=Histology : a text and atlas : with correlated cell and molecular biology |date=2020 |publisher=Wolters Kluwer Health |location=Philadelphia |isbn=9781496383426 |edition=Eighth}}</ref>

In the past, the designations areolar tissue, [[adipose tissue]], and [[reticular tissue]] have been listed as subsets of loose connective tissue. However, they are no longer considered subsets of loose connective tissue. Loose connective tissue is a subset of [[Connective tissue#Types|connective tissue proper]]. Furthermore, areolar tissue is the same as loose connective tissue, adipose tissue is a subset of [[connective tissue#Types| specialized connective tissue]], and reticular tissue is the presence of reticular fibers and reticular cells together forming the stroma of hemopoietic tissue (specifically the red bone marrow) and lymphatic tissue organs (lymph nodes and spleen but not the thymus).<ref name="Foot01" />

Most cell types in loose connective tissue are transient wandering cells that migrate from local blood vessels in response to specific stimuli. Loose connective tissue, therefore, is a site of [[Inflammation|inflammatory]] and immune reactions. In areas of the body where foreign substances are continually present, large populations of immune cells are maintained. For example, the lamina propria, the loose connective tissue of mucous membranes, such as those of the respiratory and alimentary systems, contains large numbers of these cells.<ref name="Foot01" />