Type of Joints - Structural and functional

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B. Pharm. 1st semester
Human Anatomy & Physiology-I
BP-101T

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MODULE 2
Skeletal System
Joints : Structural and functional
classification, types of joints
movements and its articulation

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Joints
A joint is the site at which any two or more bones articulate or come
together. Joints allow flexibility and movement of the skeleton and
allow attachment between bones.

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Structural classification
of joints
• Structural classification names and divides joints
according to the type of binding tissue that connects the
bones to each other. There are three structural
classifications of joints:
• Fibrous Joints - joined by dense regular connective
tissue that is rich in collagen fibers
• Cartilaginous Joints - joined by cartilage
• Synovial Joint - not directly joined the bones have a
synovial cavity and are united by the dense irregular
connective tissue that forms the articular capsule that is
normally associated with accessory ligaments. 4

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Functional classification
of joints
Functional classification (movement)
Joints can also be classified functionally according to the type
and degree of movement they allow:
Synarthrosis - permits little or no mobility. Most synarthrosis
joints are fibrous joints(e.g., skull sutures).
Amphiarthrosis - permits slight mobility. Most
amphiarthrosis joints are cartilaginous joints (e.g.
intervertebral discs)
Diarthrosis - freely movable. All diarthrosis joints
are synovial joints (e.g., shoulder, hip, elbow, knee, etc.), and
the terms "diarthrosis" and "synovial joint" are considered
equivalent.

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The bones forming these joints are linked with tough, fibrous
material. Such an arrangement often permits no movement. For
example, the joints between the skull bones, the sutures, are
completely immovable, and the healthy tooth is cemented into the
mandible by the periodontal ligament. The tibia and fibula in the
leg are held together along their shafts by a sheet of fibrous tissue
called the interosseous membrane. This fibrous joint allows a
limited amount of movement and stabilises the alignment of the
bones.
Fibrous joints

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Cartilaginous joints
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These joints are formed by a pad of tough
fibrocartilage that acts as a shock absorber.
The joint may be immovable, as in the
cartilaginous epiphyseal plates, which in
the growing child links the diaphysis of a
long bone to the epiphysis.
Some cartilaginous joints permit limited movement, as between the
vertebrae, which are separated by the intervertebral discs, or at the
symphysis pubis, which is softened by circulating hormones during
pregnancy to allow for expansion during childbirth.

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Synovial joints
Synovial joints are characterized by the
presence of a space or capsule between
the articulating bones. The ends of the
bones are held close together by a sleeve
of fibrous tissue, and lubricated with a
small amount of fluid. Synovial joints are
the most moveable of the body.
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Movements at synovial joints
Movement at any given joint depends on various
factors, such as the tightness of the ligaments
holding the joint together, how well the bones fit
and the presence or absence of intracapsular
structures. Generally, the more stable the joint,
the less mobile it is. The main movements
possible are summarized in the given table.

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Types of synovial joint
Synovial joints are classified according to the range of movement
possible or to the shape of the articulating parts of the bones
involved.
Ball and socket joints
The head of one bone is ball-shaped and articulates with a cup-
shaped socket of another. The joint allows for a wide range of
movement, including flexion, extension, adduction, abduction,
rotation and circumduction. Examples include the shoulder and hip.
Hinge joints
The articulating ends of the bones fit together like a hinge on a
door, and movement is therefore restricted to flexion and extension.
The elbow joint is one example, permitting only flexion and
extension of the forearm. Other hinge joints include the knee, ankle
and the joints between the phalanges of the fingers and toes
(interphalangeal joints).
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Gliding joints
The articular surfaces are flat or very slightly curved and glide over
one another, but the amount of movement possible is very restricted;
this group of joints is the least movable of all the synovial joints.
Examples include the joints between the carpal bones in the wrist,
the tarsal bones in the foot, and between the processes of the spinal
vertebrae.
Pivot joints
These joints allow a bone or a limb to rotate. One bone fits into a
hoop-shaped ligament that holds it close to another bone and allows
it to rotate in the ring thus formed. For example, the head rotates on
the pivot joint formed by the dens of the axis held within the ring
formed by the transverse ligament and the odontoid process of the
atlas.
Types of synovial joint

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Condyloid joints
A condyle is a smooth, rounded projection on a bone and in a
condyloid joint it sits within a cup-shaped depression on the other
bone. Examples include the joint between the condylar process of
the mandible and the temporal bone, and the joints between the
metacarpal and phalangeal bones of the hand, and between the
metatarsal and phalangeal bones of the foot. These joints permit
flexion, extension, abduction, adduction and circumduction.
Saddle joints
The articulating bones fit together like a man sitting on a saddle.
The most important saddle joint is at the base of the thumb, between
the trapezium of the wrist and the first metacarpal bone. The range
of movement is similar to that at a condyloid joint but with
additional flexibility; opposition of the thumb, the ability to touch
each of the fingertips on the same hand, is due to the nature of the
thumb joint.
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Types of synovial joint

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Common characteristics of
synovial joints
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Hyaline (articular) cartilage
The articular surfaces of bones are covered with hyaline cartilage. This
protects the bones tissue by smoothing and facilitating gliding movements
between the bone ends. It also helps to reduce friction between the bones.
Joint/articular capsule
This is a fibrous tissue encasing the joint, forming a capsule. It adds
stability to the joint and prevents unwanted material from entering the
joint.
Synovial membrane
The synovial membrane acts as a lining to the inside of the joint capsule
and secretes synovial fluid.
Synovial fluid
Synovial fluid fills the joint capsule; it nourishes and lubricates the
articulating surfaces and protects the joint by reducing friction. Synovial
fluid becomes less viscous (thick and sticky) with exercise.

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Ligaments
Ligaments are tough non elastic, fibrous connective tissue joining
bone to bone. They restrict the amount of movement that can occur
at a joint and provide stability.
Pads of fat
Pads of fat fill the gaps in and around the joints helping to protect
the bones from wear and tear.
Articular discs (menisci)
Articular discs lie between the articular surfaces and are attached to
the capsule at the outer edge. Their function is to absorb shock,
protect the bones surfaces and maintain joint stability.
Common characteristics of
synovial joints

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