Organization of the Body
is found in the skin as the leathery
, and it forms ﬁbrous
joint capsules and the ﬁbrous coverings that surround some or-
gans (kidneys, bones, cartilages, muscles, and nerves).
Elastic Connective Tissue
A few ligaments, such as those con-
necting adjacent vertebrae, are very elastic. Te dense regular
connective tissue in those structures is called
(Figure 4.8f). Additionally, many of the larger
arteries have stretchy sheets of elastic connective tissue in
tĭ-lij), which stands up to both tension
pression, has qualities intermediate between dense connective
tissue and bone. It is tough but ﬂexible, providing a resilient
rigidity to the structures it supports.
Cartilage lacks nerve ﬁbers and is avascular. It receives its nu-
trients by diﬀusion from blood vessels located in the connective
tissue membrane (perichondrium) surrounding it. Its ground
substance contains large amounts of the GAGs chondroitin sul-
fate and hyaluronic acid, ﬁrmly bound collagen ﬁbers (and in
some cases elastic ﬁbers), and is quite ﬁrm. Cartilage matrix also
contains an exceptional amount of tissue ﬂuid. In fact, cartilage
is up to 80% water! Te movement of tissue ﬂuid in its matrix
enables cartilage to rebound a±er being compressed and also
helps to nourish the cartilage cells.
with great resistance to tension (pulling forces) where the ten-
sion is exerted in a single direction. Crowded between the colla-
gen ﬁbers are rows of ﬁbroblasts that continuously manufacture
the ﬁbers and scant ground substance.
Collagen ﬁbers are slightly wavy (see Figure 4.8d). Tis al-
lows the tissue to stretch a little, but once the ﬁbers straighten
out, there is no further “give” to this tissue. Unlike our model
(areolar) connective tissue, this tissue has few cells other than
ﬁbroblasts and is poorly vascularized.
With its enormous tensile strength, dense regular connec-
tive tissue forms
, which are cords that attach muscles
to bones; ﬂat, sheetlike tendons called
sēz) that attach muscles to other muscles or to bones; and the
that bind bones together at joints. Ligaments contain
more elastic ﬁbers than tendons and are slightly more stretchy.
Dense regular connective tissue also forms fascia (fash
bond”), a ﬁbrous membrane that wraps around muscles, groups
of muscles, blood vessels, and nerves, binding them together
like plastic sandwich wrap.
Dense Irregular Connective Tissue
Dense irregular connec-
has the same structural elements as the regular va-
riety. However, the bundles of collagen ﬁbers are much thicker
and they are arranged irregularly; that is, they run in more than
one plane (Figure 4.8e). Tis type of tissue forms sheets in body
areas where tension is exerted from many diﬀerent directions. It
Connective tissues. (c)
Connective tissue proper. (For a related
A Brief Atlas of the Human Body
, Plate 13.)
Connective tissue proper: loose connective tissue, reticular
Network of reticular fibers in a
typical loose ground substance; reticular cells
lie on the network.
Fibers form a soft internal skeleton
(stroma) that supports other cell types
including white blood cells, mast cells, and
Lymphoid organs (lymph nodes,
bone marrow, and spleen).
Dark-staining network of reticular connective
tissue fibers forming the internal skeleton of the spleen (350
White blood cell