Chapter 8
Joints
251
8
Gomphoses
A
gomphosis
(gom-fo
9
sis) is a peg-in-socket fibrous joint (Fig-
ure 8.1c). Te only example is the articulation of a tooth with
its bony alveolar socket. Te term
gomphosis
comes from the
Greek
gompho
, meaning “nail” or “bolt,” and refers to the way
teeth are embedded in their sockets (as if hammered in). Te fi-
brous connection in this case is the short
periodontal ligament
(Figure 23.11, p. 860).
Cartilaginous Joints
Describe the general structure of cartilaginous joints. Name
and give an example of each of the two common types of
cartilaginous joints.
In
cartilaginous joints
(kar
0
tĭ-laj
9
ĭ-nus), the articulating bones
are united by cartilage. Like fibrous joints, they lack a joint cav-
ity and are not highly movable. Te two types of cartilaginous
joints are
synchondroses
and
symphyses
.
Synchondroses
A bar or plate of
hyaline cartilage
unites the bones at a
syn-
chondrosis
(sin
0
kon-dro
9
sis; “junction of cartilage”). Virtually
all synchondroses are synarthrotic.
Te most common examples of synchondroses are the epi-
physeal plates in long bones of children
(Figure 8.2a)
. Epi-
physeal plates are temporary joints and eventually become
synostoses. Another example of a synchondrosis is the immov-
able joint between the costal cartilage of the first rib and the
manubrium of the sternum (Figure 8.2a).
Symphyses
A joint where
fibrocartilage
unites the bone is a
symphysis
(sim
9
fih-sis; “growing together”). Since fibrocartilage is compressible
and resilient, it acts as a shock absorber and permits a limited
amount of movement at the joint. Even though fibrocartilage is
the main element of a symphysis, hyaline cartilage is also present
in the form of articular cartilages on the bony surfaces. Symphy-
ses are amphiarthrotic joints designed for strength with flexibility.
Epiphyseal
plate (temporary
hyaline cartilage
joint)
Sternum (manubrium)
Joint between first rib
and sternum (immovable)
Pubic symphysis
Body of vertebra
Fibrocartilaginous
intervertebral disc
(sandwiched between
hyaline cartilage)
(a)
Synchondroses
Bones united by hyaline cartilage
(b)
Symphyses
Bones united by fibrocartilage
Figure 8.2
Cartilaginous joints.
previous page 285 Human Anatomy and Physiology (9th ed ) 2012 read online next page 287 Human Anatomy and Physiology (9th ed ) 2012 read online Home Toggle text on/off