Fundamentals of Anatomy and Physiology

100

Specialized Connective Tissue

A number of types of connective tissue have specialized
functions. Cartilage is one of these special kinds of tis-sues.
The three types of cartilage found in the body are hyaline,
fibrous, and elastic. Cells of cartilage are called
chondrocytes (KON-droh-sightz); they are large round
cells with spherical nuclei. When we view cartilage un-der
the microscope, these chondrocytes are found in cavities
called lacunae (lah-KOO-nee). The lacunae are cavities
in a firm matrix composed of protein and poly-saccharides.
Depending on the type of cartilage, various amounts of
collagen and elastin fibers are embedded in the matrix,
causing the cartilage to be either flexible or very strong and
resistant.
Hyaline cartilage, when viewed under the micro-
scope, has a matrix with no visible fibers in it, hence the
name hyaline, which means clear (Figure 5-8). As the fetus
forms in the womb, the skeletal system is made entirely of
hyaline cartilage and is visible after the first 3 months of
pregnancy. Most of this hyaline cartilage is gradually
replaced by bone over the next 6 months through a process
called ossification. However, some hyaline cartilage
remains as a covering on the surfaces of the bones at joints.
In our bodies, the costal cartilages that attach the anterior
ends of our upper seven pair of ribs to the sternum are
hyaline cartilage. The trachea

Chapter 5

and bronchi are kept open by incomplete rings of hya-line

cartilage. The septum of our nose is also made of hyaline

cartilage.

Fibrocartilage has a majority of tough collagenous

-fibers embedded in the matrix (Figure 5-9). These fibers

make this type of cartilage dense and very resistant to

stretching. The intervertebral disks that surround our spinal

cord and act as shock absorbers between our ver-tebrae are

made of this strong cartilage. It also connects our two

pelvic bones at the pubic symphysis. Thus, we can flex our

vertebral column and bend within a particu-lar range of

movement. During delivery, a minimal range of expansion

of the birth canal can occur at the pubic symphysis due to

the fibrocartilage.

The third type of cartilage is elastic cartilage. This

type of cartilage has a predominance of elastin fibers

embedded in the matrix. These fibers must be specially

stained to view under a microscope (Figure 5-10). These

fibers permit this type of cartilage to be easily stretched and

flexible while being capable of returning to its origi-nal

shape. Elastic cartilage makes up our external ear or

auricle, our ear canals or auditory tubes, and our epiglottis.

Bone is very firm specialized connective tissue. Bone

is covered in great detail in Chapter 7. If we section a bone,

we see that it is composed of two types of bone tis-sue:

compact bone, which forms the dense outer layer of

Function Characteristics and Location (^)
Cartilage Hyaline cartilage is found on (^)
Provides firm but flexible support articular bone surfaces and also (^)
for the embryonic skeleton and at the nose tip, bronchi, and (^)
part of the adult skeleton. bronchial tubes. Ribs are joined (^)
Hyaline
to the sternum (breastbone) by (^)
the costal cartilage. It is also (^)
Forms the skeleton of the embryo. found in the larynx and the rings (^)
in the trachea. (^) (A)

(B)

Morphology

Cells

(chondrocytes)^

Matrix

Lacuna

(space^

enclosing

cells)

Source

Associates/Science Biophoto ©

(B) Photo

(^) ,
® Learning
Cengage
© (A)
Figure 5- 8 The anatomy of hyaline
cartilage.