Joints attach bones and allow for movement. They are classified by their structure as fibrous, cartilaginous, or synovial joints, and by their function as synarthroses, amphiarthroses, or diarthroses. Synovial joints contain articular cartilage, a joint cavity filled with synovial fluid, a fibrous capsule, and often ligaments. The synovial fluid and articular cartilage help reduce friction within the joint to allow for its movement.

1. Section 25: Joints – Structure
and Function
25-1

2. Joints
Joints attach bones,
provide support and
protection, and allow
for body movement
for body movement.
Joints are
categorized by their
categorized by their
structural
classification and
their functional
classification.
25-2 From: Ames
Chapter 5 – The Skeletal System

3. Joints
Joints
• Provide necessary range of motion
Provide necessary range of motion
• Classification based on structure: fibrous,
cartilagenous synovial
cartilagenous, synovial
• Classification based on function:
th (i bl ) hi th
synarthroses (immovable), amphiarthroses
(slightly movable), diarthoses (freely
bl )
movable)
25-3 From: Arora

4. JOINTS
JOINTS
• Joints are where two or more bones articulate
( )
(move).
• Joints are classified according to how much
movement they allow
movement they allow.
1. Fibrous – these are fixed or immovable joints
such as the cranium sacrum and the coccyx
such as the cranium, sacrum and the coccyx.
2. Cartilaginous – these are slightly movable
joints such as the vertebrae
joints such as the vertebrae.
3. Synovial – these are freely movable joints such
as the shoulder and hip
25-4 From: Essex
as the shoulder and hip.

5. Cartilaginous joints
Cartilaginous joints
• Articulating bones are united by cartilage
Articulating bones are united by cartilage
• Lack a joint cavity
T t h d d
• Two types – synchondroses and
symphyses
25-5 From: Mathis

6. Cartilaginous joints: synchondroses
Cartilaginous joints: synchondroses
• A bar or plate of hyaline cartilage unites
A bar or plate of hyaline cartilage unites
the bones
• All synchondroses are synarthrotic
• All synchondroses are synarthrotic
• Examples include:
– Epiphyseal plates of children
– Joint between the costal cartilage of the first
rib and the sternum
25-6 From: Mathis

7. 25-7 From: Mathis

8. Cartilaginous joints: symphyses
Cartilaginous joints: symphyses
• Hyaline cartilage covers the articulating
Hyaline cartilage covers the articulating
surface of the bone and is fused to an
intervening pad of fibrocartilage
intervening pad of fibrocartilage
• Amphiarthrotic joints designed for strength
and flexibility
and flexibility
• Examples include intervertebral joints and
th bi h i f th l i
the pubic symphysis of the pelvis
25-8 From: Mathis

9. 25-9 From: Mathis

10. Synovial Joints
Synovial Joints
• Bone ends separated by a joint cavity
Bone ends separated by a joint cavity
containing synovial fluid
• Most joints of the limbs
• Most joints of the limbs
• Full range of motion available in most
j i t
joints
25-10 From: Arora

11. Synovial joints
Synovial joints
• Those joints in which the articulating
Those joints in which the articulating
bones are separated by a fluid-containing
joint cavity
joint cavity
• All are freely movable diarthroses
E l ll li b j i t d t j i t
• Examples – all limb joints, and most joints
of the body
25-11 From: Mathis

12. Components of synovial joints
Components of synovial joints
• A joint capsule consists of two layers
j p y
– Fibrous capsule holds the ends of the bones
together and allows movement of the joint
Synovial membrane which consists of connective
– Synovial membrane which consists of connective
tissue
• Synovial fluid: combination of materials filtered
y
from blood and secreted by cells of the synovial
membrane
C t i h l i id hi h k th fl id
– Contains hyaluronic acid, which makes the fluid very
slippery
– Lubricant to reduce friction within the joint
25-12 From: Hoxha

13. • Articular (hyaline) cartilage covers ends
Articular (hyaline) cartilage covers ends
of the bones. Smooth and resilient.
• Joint cavity is a small space bounded by
• Joint cavity is a small space bounded by
the synovial membrane and the articular
cartilages It is filled with synovial fluid
cartilages. It is filled with synovial fluid
25-13 From: Hoxha

14. Structure of synovial joints
Structure of synovial joints
• Articular cartilage – hyaline
Articular cartilage hyaline
• Fibrous capsule
J i t it t i i l fl id
• Joint cavity, contains synovial fluid
• Reinforcing ligaments
25-14 From: Arora

15. Synovial joints: general structure
Synovial joints: general structure
• Synovial joints all have the following
Synovial joints all have the following
– Articular cartilage
Joint (synovial) cavity
– Joint (synovial) cavity
– Articular capsule
Synovial fluid
– Synovial fluid
– Reinforcing ligaments
25-15 From: Mathis

16. 25-16 From: Mathis

17. Synovial joints: friction-reducing
d
and extra structures
• Bursae – flattened fibrous sacs lined with
Bursae flattened, fibrous sacs lined with
synovial membranes and containing
synovial fluid
synovial fluid
– Common where ligaments, muscles, skin,
tendons or bones rub together
tendons, or bones rub together
• Tendon sheath – elongated bursa that
wraps completely around a tendon
wraps completely around a tendon
• Fat pads
25-17 From: Mathis

18. 25-18 From: Mathis