HUMAN BIOLOGY

96 Chapter 5

fibrous joint

attaches

tooth to

jawbone

synovial joint (ball

and socket) between

humerus and scapula

cartilaginous joint

between rib and

sternum

cartilaginous joint

between adjacent

vertebrae

synovial joint (hinge

type) between

humerus and radius

synovial joint (ball

and socket) between

pelvic girdle and

femur

What is a Joint?

• A joint connects one bone to another.


• In all joints, connective tissue bridges the gap between bones.


• Synovial (freely movable) joints include the hinge-like knee
  joint and the ball-and-socket joints at the hips.


• Cartilaginous joints have cartilage in the space between bones.
  They allow only slight movement. In fibrous joints, fibrous
  connective tissue joins the bones.

taKe-hoMe Message

cartilaginous joint Joint
in which cartilage fills the
space between bones.

fibrous joint Joint consist‑
ing of fibrous connective
tissue that connects the
bones. The joint has no
cavity.

synovial joint Joint in
which a fluid‑filled cavity
separates the linked bones;
the most common type of
joint in the human body.

Joints: Connections between bones

n    Joints are areas of contact or near contact between bones.

All joints have some form of connective tissue that bridges

the gap between bones.

n    Link to synovial membranes 4.7

There are three main types of joints

in the skeletal system (Figure 5.9A).

In the most common type of joint,

called a synovial joint, adjoining

bones are separated by a cavity

(Figure 5.9B). The articulating ends

of the bones are covered with a

cushioning layer of cartilage, and

they are stabilized by ligaments. A

capsule of dense connective tissue

surrounds the bones of a synovial

joint. The synovial membrane that

lines the inner surface of the capsule

contains cells that secrete a lubricating synovial fluid into

the joint cavity.

Figure 5.9 The three main types of joints between bones are synovial joints, cartilaginous joints, and fibrous joints. A shows

locations of the different types of joints. B shows the knee joint, a synovial joint that is the largest and most complex joint in the

body. (© Cengage Learning)

femur

patella

cartilage

ligaments

menisci

tibia

fibula

B

5.5

Synovial joints are built to allow movement. In hinge-

like synovial joints such as the knee and elbow, the motion

is limited to simple flexing and extending (straightening).

The ball-and-socket joints at the hips are known as freely

movable joints because they are capable of a wider range

of movements: They can rotate and move in different

planes—for instance, up-down or side-to-side. Figure 5.10

shows these and some other ways body parts can move

at joints.

In a cartilaginous joint, cartilage fills the space between

bones, so only slight movement is possible. The interverte-

bral disks between vertebrae are examples. Similar joints

occur between the breastbone and some of the ribs.

There is no cavity in a fibrous joint, and fibrous connec-

tive tissue unites the bones. An adult’s fibrous joints gener-

ally don’t allow movement. Examples are the fibrous joints

that hold your teeth in their sockets. In a fetus, fibrous

joints loosely connect the flat skull bones. During child-

birth, these loose connections allow the bones to slide over

each other, preventing skull fractures. A newborn baby’s

skull still has fibrous joints and soft areas called fontanels.

With time the joints harden into sutures. Much later in life

the skull bones may fuse completely.

A

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