Structural and functional classification
of joints
Joints in the human body can be classified based on
their structure and function. Let's take a look at both classifications:
Structural Classification of Joints:
·
Fibrous Joints: These joints are
held together by fibrous connective tissue and allow little to no movement.
There are three types of fibrous joints:
a) Suture Joints:
Found only in the skull, these joints have very short, interconnecting fibers
and provide minimal movement.
b) Syndesmosis Joints:
These joints have longer connective tissue fibers than suture joints, allowing
for slight movement. An example is the joint between the tibia and fibula in
the lower leg.
c) Gomphosis Joints:
These joints occur between the teeth and their sockets in the jawbone. They are
held firmly in place by periodontal ligaments and have no movement.
·
Cartilaginous Joints: These
joints are connected by cartilage and allow limited movement. There are two
types of cartilaginous joints:
a)
Synchondroses
Joints:
These joints have hyaline cartilage between the bones and provide very little
movement, if any. An example is the epiphyseal plate in growing long bones.
b) Symphyses Joints:
These joints have a fibrocartilaginous pad between the bones, which provides
slight movement and acts as a shock absorber. The pubic symphysis and
intervertebral discs are examples of symphyses joints.
·
Synovial Joints: These joints are
the most common type in the body and are characterized by the presence of a
synovial cavity. Synovial joints allow for a wide range of movement. They
consist of the following structures:
a) Articular Cartilage:
Covers the articulating surfaces of the bones to reduce friction and absorb
shock.
b) Synovial Cavity:
A fluid-filled space between the bones that allows for smooth movement.
c) Synovial Fluid:
Lubricates the joint and provides nutrients to the articular cartilage.
d) Joint Capsule:
Surrounds the joint and provides stability. It is composed of an outer fibrous
layer and an inner synovial membrane.
e) Ligaments: Connect bones
and reinforce the joint capsule, providing additional stability.
Functional classification of joints
The functional classification of joints is based on
the amount of movement they allow. There are three types of functional joints:
1) Synarthroses
(immovable joints)
2) Amphiarthroses
(slightly movable joints)
3) Diarthroses
(freely movable joints)
· Synarthroses
are immovable joints. They are held together by dense fibrous connective
tissue, which prevents any movement between the bones. Examples of synarthroses
include:
a) Sutures: These are found
between the bones of the skull.
b) Gomphoses: These are found
between the roots of teeth and the sockets in the jawbone.
· Amphiarthroses
are slightly movable joints. They are held together by cartilage, which allows
for a limited range of movement. Examples of amphiarthroses include:
a) Synchondroses:
These are found between the bones of the ribs and the sternum.
b) Symphyses: These are found
between the pubic bones of the pelvis.
· Diarthroses
are
freely movable joints. They are held together by a fibrous capsule that
contains a synovial fluid. The synovial fluid lubricates the joint and helps to
reduce friction during movement. Examples of diarthroses include:
a) Ball-and-socket joints:
These are found at the shoulder and hip. They allow for a wide range of motion,
including rotation.
b) Hinge joints: These are found
at the elbow and knee. They allow for movement in one plane, such as flexion
and extension.
c) Pivot joints: These are found
at the neck. They allow for rotation of the head.The functional classification
of joints is closely related to the structural classification. For example,
fibrous joints are always synarthroses, cartilaginous joints are usually
amphiarthroses, and synovial joints are always diarthroses.
Here is a table summarizing the functional
classification of joints:
|
Functional Classification |
Structure |
Movement |
Examples |
|
Synarthroses |
Dense fibrous
connective tissue |
No movement |
Sutures,
gomphoses |
|
Amphiarthroses |
Cartilage |
Limited
movement |
Synchondroses,
symphyses |
|
Diarthroses |
Fibrous
capsule with synovial fluid |
Free movement |
Ball-and-socket
joints, hinge joints, pivot joints |
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