Anatomy lecture 7 Joints

Anatomy lecture 7
Joints
JOINTS
D r . S A A D A L S A B T I
M . B . C h . B ., P h . D .
JOINTS
A joint, also called articulation or arthrosis is the site of the junction or
union of two or more bones of the body.
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Classification of Joints
Joints are either classified structurally (according to their structure) or
functionally according to the types of movement they permit.
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Structural Classification of Joints /1
The structural classification of joints is based on:
A. the presence or absence of a space (called synovial cavity) between the
articulating bones, and
B. the type of connective tissue that binds the bones together.
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Structural Classification of Joints /2
Joints are classified structurally into three types: •
1. Fibrous joints: The bones forming the joints are held
together by fibrous connective tissue and there is no
synovial cavity.
2. Cartilaginous joints: The bones in these types of joints
are held together by cartilage, and there is no synovial cavity.
3. Synovial joints: The bones forming the joints have a
synovial cavity and are united together by an articular
capsule.
Functional Classification of Joints
This type of classification of joints relates to the degree •
of movement they permit. Functionally, the types of joints are:
Synarthrosis: An immovable joint. •
Amphiarthrosis: A slightly movable joint. •
Diarthrosis: A freely movable joint. •
All diarthroses are synovial joints. They have a variety of
shapes and permit different types of movements.
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Fibrous Joints
Fibrous joints permit little or no movement. They include
sutures, syndesmoses, and gomphoses.
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Sutures
Sutures are fibrous joints that are composed of a thin layer of •
dense fibrous connective tissue between the bones forming the
joint.
Sutures are found only in the skull. Examples are coronal, and •
sagittal sutures. Because sutures are immovable, they are
classified functionally as synarthroses.
Some sutures are replaced by bones in the adult and they are •
called synostoses.
Syndesmoses
A syndesmosis is a fibrous joint in which there is a greater
distance between the articulating bones and there is more
fibrous C.T. than in a suture.
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The distal tibiofibular joint and the interosseous membrane
between the tibia & fibula are examples of syndesmoses.
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Because it allows slight movement, a syndesmosis is classified •
functionally as an amphiarthrosis.
Gomphoses
A gomphosis is a type of fibrous joints in which a cone-shaped •
peg fits into a socket.
The only examples of gomphoses in the body are the joints •
between the roots of teeth and their sockets (alveoli) in the
mandible and maxilla.
A gomphosis is classified functionally as a synarthrosis, an •
immovable joint.
Cartilaginous Joints
Cartilaginous joints lack a synovial cavity and permit little or no
movement.
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The articulating bones in these types of joints are tightly connected
by either fibrocartilage or hyaline cartilage.
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There are two types of cartilaginous joints, synchondroses and •
symphyses.
Synchondroses
A synchondrosis is a cartilaginous joint in which the material
connecting the bones forming the joint is hyaline cartilage.
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The epiphyseal plate that connects the epiphysis and diaphysis
of a growing bone is an example of synchondroses.
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Functionally a synchondrosis is a synarthrosis. •
Symphyses
A symphysis is a type of cartilaginous joints in which the ends •
of the articulating bones are covered with hyaline cartilage,
while the bones themselves are connected to each other by a
broad, flat disc of fibrocartlage.
All symphyses are located in the midline of the body. •
The intervertebral joints, and the articulation of the two hip •
bones together anteriorly are examples of symphyses.
A symphysis is amphiarthrosis, a slightly movable joint. •
Synovial Joints /1
Synovial joints have a space called the synovial cavity •
between articulating bones.
The synovial cavity is filled with fluid called synovial fluid. •
The structure of synovial joints allow them to move freely and as •
such they are classified as diarthroses.
The articulating ends of bones in synovial joints are covered by •
articular cartilage, which provides a smooth slippery surface
for the articulating bones, but it does not bind them together.
Synovial Joints /2
A sleeve like articular capsule surrounds a synovial cavity, and •
unites the articulating bones. The articular capsule is composed
of two layers. The outer layer is referred to as the fibrous
capsule, whereas the inner layer is referred to as the synovial
membrane.
The inner layer of articular capsule, the synovial membrane, is •
a mixture of areolar connective tissue and elastic fibres.
The fibres of some fibrous capsules are arranged in parallel •
bundles of connective tissue that are highly adapted to resisting
strains and are called ligaments.
Types of Synovial Joints /1
Whereas all synovial joints have the same structure, the shapes of
their articulating surfaces vary.
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Accordingly, there are six types of synovial joints: plane (planar), •
hinge, pivot, condyloid, saddle, and ball- and socket joints.
Some synovial joints are relatively immobile, but are more stable.
Others have multiple degrees of freedom of movement, but at the
expense of stability.[3] In ascending order of mobility, they are:
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Types of Synovial Joints /2
1.
Plane joints (Planar joints): Plane joints permit sliding or gliding
movements in the plane of articular surfaces. The opposed
surfaces of the bones are flat or almost flat, with movement
limited by their tight joint capsules.
Hinge joints: These joints act as a door hinge does, allowing .2
flexion and extension in just one plane.
Pivot joints: In these types of synovial joints, one bone rotates .3
about another.
Condyloid joints (Ellipsoidal joints): A condyloid joint is where .4
two bones fit together with an odd shape (e.g. an ellipse), and
while one bone is concave, the other is convex; these joints allow
flexion, extension, abduction, and adduction movements and also
(circumduction).
Saddle joints: Saddle joints, which resemble a saddle, permit .5
the same movements as the condyloid joints.
Ball and socket joints: These allow for all movements except .6