are thin collagenous f
bers. They are
highly branched and Form delicate supporting networks in
a variety oF tissues, including those oF the spleen.
summarizes the components oF connective tissue.
What are the general characteristics of connective tissue?
What are the major types of cells in connective tissue?
What is the primary function of F
What are the characteristics of collagen and elastin?
Categories oF Connective Tissues
Connective tissue is divided into two major categories.
Connective tissue proper
includes loose connective tissue
(areolar, adipose, reticular) and dense connective tissue
(dense regular, dense irregular, elastic). The
include cartilage, bone, and blood. The Fol-
lowing sections describe each type oF connective tissue.
Forms delicate, thin membranes
throughout the body. The cells oF this tissue, mainly f bro-
blasts, are located some distance apart and are separated by
a gel-like ground substance that contains many collagenous
and elastic f bers that f
(f g. 5.18)
Areolar tissue binds the skin to the underlying organs
and f lls spaces between muscles. It underlies most layers
oF epithelium, where its many blood vessels nourish nearby
or Fat, develops when certain cells
(adipocytes) store Fat in droplets in their cytoplasm. At f rst,
these cells resemble f broblasts, but as they accumulate Fat,
they enlarge, and their nuclei are pushed to one side
. When adipocytes become so abundant that they crowd
out other cell types, they Form adipose tissue. This tissue lies
beneath the skin, in spaces between muscles, around the kid-
neys, behind the eyeballs, in certain abdominal membranes,
Scanning electron micrograph of collagenous F
(shades of white to gray) and elastic F
bers (yellow) (4,100×).
Components of Connective Tissue
Widely distributed, large, star-shaped cells
Secrete proteins that become F
Motile cells sometimes attached to F
Clear foreign particles from tissues by phagocytosis
Large cells, usually located near blood vessels
Release substances that may help prevent
and promote in²
bers (white F
Thick, threadlike F
bers of collagen with great tensile strength
Hold structures together
bers (yellow F
Bundles of microF
brils embedded in elastin
Provide elastic quality to parts that stretch
bers of collagen
±orm supportive networks within tissues
Scanning electron micrograph of a mast cell (6,600×).