HUMAN BIOLOGY

70 Chapter 4

Connective tissue: binding, support, and other roles

n    Connective tissue connects, supports, and anchors the

body’s parts.

n    Links to Lipids 2.10, Structural proteins 2.11

Connective tissue provides support and protection for

cells, tissues, and organs. It makes up more of your body

than any other tissue. In most kinds of connective tissue,

the cells secrete fiberlike structural proteins and a “ground

substance” of polysaccharides. These ingredients form a

matrix around the cell. The matrix can range from hard to

liquid, and it gives each kind of connective tissue its spe-

cialized properties (Table 4.2).

Fibrous connective tissues

are strong and stretchy

The various kinds of fibrous connective tissue all have

cells and fibers in a matrix, but in different proportions that

make each kind of fibrous connective tissue well suited to

perform its special function.

The different forms of loose connective tissue have few

fibers and cells that are loosely arranged in a jellylike

ground substance. This structure makes loose connective

tissue flexible. The example in Figure 4.3A wraps many

organs and helps support the skin. A “reticular” (netlike)

form of loose connective tissue is the framework for soft

organs such as the liver, spleen, and lymph nodes.

Fibrous Connective Tissues

Loose Collagen and elastin loosely arranged in ground

substance; quite flexible and fairly strong

Dense Mainly collagen; strong and somewhat flexible.

Its collagen fibers are aligned in parallel in

tendons and ligaments

Elastic Mainly elastin; easily stretches and recoils

Special Connective Tissues

Cartilage Mainly collagen in a watery matrix; resists

compression

Bone Very strong, mineral-hardened matrix

Adipose Mainly cells filled with fat; soft matrix

tissue

Blood Matrix is the fluid blood plasma, which contains

blood cells and other substances

Table 4.2 Connective Tissues at a Glance

Figure 4.3 Animated! Connective tissues connect, support, and anchor. (A–C: Ed Reschke/Peter Arnold; D: Science Photo Library/Science Source)

collagenous fiber

fibroblast

elastic fiber

collagenous

fibers

collagenous

fibers

fibroblast

ground substance

with very fine

collagen fibers

cartilage cell

(chondrocyte)

Type Loose connective tissue
Description Fibroblasts, other
cells, plus fibers loosely arranged
in semifluid matrix
Common Locations Under the
skin and most epithelia
Function Elasticity, diffusion

Type Dense, irregular

connective tissue

Description Collagenous

fibers, fibroblasts, less matrix

Common Locations In skin and

capsules around some organs

Function Support

Type Dense, regular

connective tissue

Description Collagen fibers in

parallel bundles, long rows of

fibroblasts, little matrix

Common Locations Tendons,

ligaments

Function Strength, elasticity

Type Cartilage

Description Cells embedded in

pliable, solid matrix

Common Locations Ends of long

bones, nose, parts of airways,

skeleton of embryos

Function Support, flexibility, low-

friction surface for joint movement

ABC D

4.2

Dense connective tissue has more collagen than does loose

connective tissue, so it is less flexible but much stronger.

The form pictured in Figure 4.3B helps support the skin’s

lower layer, the dermis. It also wraps around muscles and

organs that do not need to stretch much, such as kidneys.

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