BIO 135 Virtual Labs

Identification Guide to
Connective Tissue Proper

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	Areolar (or Loose) C.T. Identification: Loose arrangement of thin (elastic and reticular) and thick (collagen) fibers that criss-cross haphazardly. Features to Know: collagen fibers (1), elastic fibers (2), fibroblasts (3). Fibers Present: collagen fibers, elastic fibers, reticular fibers. Where Located: surrounding most organs, underneath epithelia. Functions: wraps, cushions, holds defensive cells, holds fluids.
	Reticular C.T. Identification: Dark-staining reticular fibers (2) present, but may be obscured by the numerous nuclei of lymphoblasts and other cells (1). Overall brownish color is also distinctive. Features to Know: lymphoblasts (1). Fibers Present: reticular fibers (2). Where Located: spleen (also bone marrow, lymph nodes). Function: forms scaffolding to support loose cells.
	Adipose Tissue Identification: Virtually no extracellular matrix visible due to greatly enlarged cells, nearly the entire volume of which is a fat vacuole (appears empty on slide). Most likely to be confused with simple squamous epithelium: note that the "open" areas are surrounded by narrow bands of cytoplasm, not multiple, nucleated cells. Few nuclei will be visible (arrow). Features to Know: adipocyte, nucleus. Fibers Present: none visible. Where Located: underneath skin, breasts, surrounding eyes & kidneys. Functions: energy storage, cushioning, insulation.
	Dense Regular C.T. Identification: Densely packed parallel fibers. Note scattered cells (lack of lacunae distinguish this tissue from cartilages; compare especially to fibrocartilage). Features to Know: fibroblast (1). Fibers Present: collagen fibers. Where Located: ligaments and tendons. Function: attaches bone to bone or muscle; resists tensile (pulling) forces in single direction.
	Dense Irregular C.T. Identification: The collagen fibers are in distinct bundles, separated by space, giving an overall patchy or blocky appearance very dissimilar to other tissues. Features to Know: fibroblasts, if visible. Fibers Present: collagen fibers. Where Located: dermis of skin. Functions: provides strength; can withstand tensile forces in many directions.
	Elastic C.T. Identification: Similar to dense regular CT (densely packed collagen fibers), but with distinct dark, usually zigzagging, lines of elastic fibers (arrow). Although it has a similar name to Elastic Cartilage, these two tissues are not that similar (note the more parallel fibers and lack of lacunae here). Features to Know: fibroblasts. Fibers Present: collagen fibers, elastic fibers. Where Located: aorta. Function: elasticity (can stretch and return to original shape).