Anatomy and Physiology HAP101 Chapter Notes - Chapter 9: Dense Irregular Connective Tissue, Hyaline Cartilage, Loose Connective Tissue

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HAP101 Chapter 9: Joints
Joint: also called an articulation, this is a point of contact between two bones, between bones and cartilage, or between bone
and teeth.
9.1 Joint Classification
They are classified based on their structure (based on anatomic positions) and functions (based on movement they permit)
The structural classifications of joints are based on two criteria: (1) the presence or absence of a space between the
articulating bone, called a synovial cavity and (2) the type of connective tissue that binds the bones together. They are
classified as one of the following:
o Fibrous Joints: no synovial cavity, bones are held together by dense, irregular connective tissue rich in collagen
fibres
o Cartilaginous Joints: no synovial cavity and bones are held by cartilage
o Synovial Joints: bones have a synovial cavity and are joined by dense, irregular connective tissue of an articular
capsule and are often accessory ligaments
The functional classification of joints relates to the degree of movement they permit. They are classified as one of the
following
o Synarthrosis: an immovable joint
o Amphiarthrosis: a slightly moveable joint
o Diarthrosis: a freely moveable joint; all are synovial joints and vary in shape/size to permit several different types of
movement.
9.2: Fibrous Joints
The three types of fibrous joints are sutures, syndesmoses, and interosseous membrane
o Suture: composed of a thin layer of dense connective tissue; only occur between bones of skulls and are excellent
shock absorbers. In infants, they are slightly movable (amphiarthroses), but in older adults, they are completely
immovable (synarthroses). Synostosis a joint in which there is a complete fusion of two separate bones into one
o Syndesmoses: has a greater distance between the articulating surfaces and denser irregular connective tissue that a
suture. The tissue is arranged in bundles (ligaments) to allow some movement.
o Interosseous Membrane: a substantial sheet of dense irregular connective tissue that binds neighbouring long bones
and permits slightest movement. There are two specific areas with this joint: between the radius and ulna of the
forearm, and between the tibia and fibula of the leg.
9.3: Cartilaginous Joints
Articulating bones are tightly connected by either hyaline cartilage or fibrocartilage. There are two types: synchondroses
and symphyses
o Synchondroses: the connecting material is hyaline cartilage. It is immovable (synarthrosis)
o Symphyses: the ends of the articulating bones are covered with hyaline cartilage, but a broad, flat disc of
fibrocartilage connects the bones. All occur in the midline of the body. It is slightly movable (amphiarthroses)
9.4: Synovial Joints
These joints are unique because they have the presence of a space called a synovial cavity between the articulating bones.
They are classified functionally as freely moveable joints (diarthrosis)
The bones at these joints are covered by a layer of hyaline cartilage called articular cartilage and it covers the surfaces of
bones with a smooth, slippery surface. However, it does not bind bones together. It helps reduce friction and absorbs shock
Articular Capsule: also known as joint capsule, this surrounds the synovial joint, encloses the synovial cavity, and unties
the articulating bones. It is composed of two layers, an outer fibrous membrane (connective tissue that attaches to
articulating periosteum) and an inner synovial membrane (composed of areolar connective tissue with elastic fibres). The
fibrous membrane provides tensile strength and movement at joints
Synovial Fluid: this is a viscous, clear or pale yellow fluid containing hyaluronic acid secreted by synovial cells in the
synovial membrane and interstitial fluid filtered from blood plasma. It forms a thin layer over surfaces within the articular
capsule. It reduces friction by lubricating joints, absorbs shock and supplies oxygen and nutrients to and removes carbon
dioxide/metabolic wastes from the chondrocytes within the articular cartilage. This fluid protects the joints form wear and
tear, however, a lack of exercise can cause the fluid to become viscous (gel-like).
Bursae and Tendon Sheaths: various movements cause friction. Bursae are sack-like structures filled with synovial fluid
that cushion movement from one body part to another. Tendon sheaths are tube-like bursae that wrap around tendons that
are subjected to great deal of friction
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