Page 305 - Fundamentals of anatomy physiology

292 Unit 2 Support and Movement

Checkpoint the synovial membrane. p. 165 Now let’s consider the major
features of synovial joints.
1. Name and describe the three types of joints as classified
by their range of motion. Articular Cartilage

2. What characteristics do typical synarthrotic and Under normal conditions, the bony surfaces at a synovial joint
amphiarthrotic joints share? cannot contact one another, because special articular cartilage
covers the articulating surfaces. Articular cartilage resembles hya-
3. In a newborn, the large bones of the skull are joined line cartilage elsewhere in the body. p. 160 However, articular
by fibrous connective tissue. The bones later grow, cartilage has no perichondrium (the fibrous sheath described
interlock, and form immovable joints. Structurally, in Chapter 4), and the matrix contains more water than that of
which type of joints are these? other cartilage.

See the blue Answers tab at the back of the book. The surface of articular cartilage is slick and smooth. This
feature alone can reduce friction during movement at the joint.
9 9-2 Synovial joints are freely However, even when pressure is applied across a joint, the
smooth articular cartilages do not touch one another because
movable joints containing synovial fluid a thin film of synovial fluid within the joint cavity separates
them (Figure 9–1a). This fluid acts as a lubricant, minimizing
Learning Outcome Describe the basic structure of a synovial joint, and friction.
describe common synovial joint accessory structures and their functions.
Synovial joints cannot function normally if the articular
Synovial joints are freely movable and classified as diarthroses. cartilages are damaged. When such damage occurs, the matrix
A two-layered joint capsule, also called an articular capsule, may begin to break down. The exposed surface will then change
surrounds the synovial joint (Figure 9–1). The joint capsule from a slick, smooth-gliding surface to a rough abrasive surface
contains an inner synovial membrane and an outer fibrous capsule. of bristly collagen fibers. This abrasive surface drastically in-
This membrane does not cover the articulating surfaces within creases friction at the joint.
the joint. Recall that a synovial membrane consists of areolar
tissue covered by an incomplete epithelial layer. The synovial
fluid that fills the joint cavity originates in the areolar tissue of

Figure 9–1 The Structure of a Synovial Joint.

Medullary cavity Quadriceps Femur Accessory Structures
tendon Tibia of a Knee Joint
Spongy bone
Periosteum Patella Bursa
Fat pad
Components of Joint capsule
Synovial Joints Synovial Meniscus

Joint capsule membrane Ligaments
Synovial membrane Joint cavity Extracapsular
Articular cartilages ligament (patellar)
Articular Intracapsular
Joint cavity containing cartilage ligament (cruciate)
synovial fluid

Metaphysis
Compact bone

a Synovial joint, sagittal section b Knee joint, sagittal section