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JOINTS

Dr.LUBNA NAZLIASST. PROF. ANATOMY

RAK MHSU

Dt. 1/10/2007

Mon 8.30-9.20am

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Objectives:

1. Definition.2. Classification of joints.3. Types of joints.4. Movements of different joints.5. Structure of synovial joints.6. Nerve supply of joints.7. Blood supply of joints.8. Stability of joints.9. Applied anatomy.

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Definition:

The bones of the skeleton are joined to one another at different sites, such connections are

termed Joints or Articulations.

 

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Classification of Joints

The joints are divided into three types:

1. Fibrous or immovable joints.(Synarthroses)

2. Cartilaginous or slightly movable joints. (Amphiarthroses)

3. Synovial or freely movable joints. (Diarthroses)   

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Fibrous or immovable joints:

The joint surfaces of the bones are in direct contact, held together by connective tissue or hyaline cartilage.

There is no movement.

Eg: joints between the bones of the skull, excepting those of the mandible.

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TYPES OF FIBROUS JOINTS

There are four types: Sutures. Schindylesis. Gomphosis. Synchondrosis.

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SUTURES

Suture is a form of joint where the bones are united by a thin layer of fibrous tissue continuous externally with the pericranium and internally with the dura mater.

Eg: skull joints.

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JOINT BETWEEN SKULL BONES

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TYPES OF SUTURES

There are three varieties: 1. Dentate suture. 2. Serrate suture. 3. Limbous suture.

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The dentate suture has tooth-like form of the projecting processes,seen in the suture between the parietal bones.

In the serrate suture the edges of the bones are serrated like the teeth of a fine saw, as between the two portions of the frontal bone.

In the limbous suture, there is interlocking with a certain degree of bevelling of the articular surfaces, so that the bones overlap one another, as in the suture between the parietal and frontal bones.

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Schindylesis

Schindylesis is that form of articulation in which a thin plate of bone is received into a cleft or fissure formed by the separation of two laminae in another bone.

Eg: articulation of the rostrum of the sphenoid and perpendicular plate of the ethmoid with the vomer.

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Gomphosis

Gomphosis is articulation by the insertion of a conical process into a socket.

Eg: articulations of the roots of the teeth with the alveoli of the mandible and maxillae.

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Synchondrosis

Where the connecting medium is cartilage the joint is termed a synchondrosis. This is a temporary form of joint, for the cartilage is converted into bone before adult life.

Eg: Between the epiphysis and bodies of long bones.

Between the occipital and the sphenoid.

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Cartilaginous or slightly movable joints

In these articulations the bony surfaces are connected by broad flattened discs of fibrocartilage.

Eg: articulations between the bodies of the vertebrae.

Eg: inferior tibiofibular articulation. United by an

interosseous ligament. The first form is termed a symphysis. The second is syndesmosis.

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Symphysis

Fibrocartilage

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Syndesmosis

Interosseous membrane

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Cartilaginous joint

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SYNOVIAL JOINTS

Structure of synovial joint :

1. The ends of the opposing bones are covered with hyaline cartilage, the articular cartilage.

2. They are separated by a space called the joint cavity.

3. The joints are enclosed in a dense fibrous joint capsule.

4. The outer layer of the capsule consists of the ligaments that hold the bones together.

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5. The inner layer is the synovial membrane that secretes synovial fluid into the joint cavity for lubrication.

6. As these joints have a synovial membrane, they are called synovial joints.

7. The joint may be divided, completely or incompletely,

by an articular disc or meniscus.

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Synovial joint

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Synovial joint with intra-articular disc

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Types of synovial joints: They are determined by the kind of movement permitted

in each.

Uniaxial: All movements take place around one axis. 1. Ginglymus joint. 2. Pivot joint. 3. Bicondylar joint.

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Ginglymus or hinge joint The axis is transverse. It permits movement only in one plane,

forward and backward.

Examples of ginglymus: 1. interphalangeal joints. 2. Elbow joint.

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Ginglymus or Hinge joint

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Trochoid or pivot-joint. It is longitudinal. Movement is limited to rotation, the joint is

formed by a pivot-like process turning within a ring.

Eg: Proximal radioulnar Articulation of the odontoid process of

the axis with the atlas.

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Pivot joint

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Condylar (Bicondylar)This joint allows primary movement in one

plane flexion, extension with small amounts of movement in another plane (rotation).

Eg: knee joint

temporomandibular joint.

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Bicondylar joint

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Biaxial:

Movement is around two horizontal axes at right angles to each other.

1. Condyloid joint.

2. Saddle-joint.

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Condyloid / Ellipsoid joint — an ovoid articular surface or condyle, is received into an elliptical cavity to permit flexion, extension, adduction, abduction, and circumduction, but no axial rotation.

Eg: wrist-joint.

metacarpophalangeal joint.

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Ellipsoid joint

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Saddle-joint : The opposing surfaces are reciprocally concavo-convex. The movements are flexion, extension, Adduction, abduction, and circumduction are allowed; but no axial rotation.

Eg: carpometacarpal joint of the thumb.

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Polyaxial: movement is in 3 or more directions. Flexion/Extension, adduction/abduction, medial and lateral rotation.

Ball-and-socket joint is formed by the reception of a globular head into a cup-like cavity.

Eg: hip joint. shoulder joint.

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Ball and Socket joint

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Gliding or plane joint. It is formed by the apposition of plane surfaces,

one slightly concave, the other slightly convex, the movement between them is limited by the ligaments or bony processes surrounding the joint.

Eg: between the articular processes of the vertebræ.

The carpal joints. The tarsal joints.

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Plane or Gliding joint

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Nerve supply of joints

A sensory nerve supplying the joint also supplies the muscles moving the joint and the skin overlying the joint. This is called HILTON’S LAW.

Joints transmit a sensation called proprioception, which provides an awareness of movement and position of the parts of the body.

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BLOOD SUPPLY OF JOINTS

Joints receive blood supply from the periarticular arterial plexus whose branches pierce fibrous capsule and form subsynovial vascular plexus.

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STABILITY OF JOINTS

It depends on 3 factors.

1. Articular surfaces: shape, size and arrangement of bones.

2. Ligaments: fibrous and elastic ligaments prevent excessive movement.

3. Muscles: tone of muscles acting on the joint.

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APPLIED ANATOMY

JOINT DISLOCATIONS & SUBLUXATIONIt is caused by trauma and characterized by

pain, deformity and loss of function.

SPRAIN is caused by ligamentous tear.

ARTHRITIS is inflammation of joints. Osteoarthritis is due to degenerative changes in articular cartilage.

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STIFFNESS OF JOINTS: It is related to weather. The viscosity of synovial fluid increases with fall in temperature leading to stiffness of joints.

NEUROPATHIC JOINT: It is due to complete denervation of joint caused by leprosy and tabes dorsalis. The reflexes are eliminated and joint is unprotected.