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Questions and Answers
What is the primary structural characteristic of the myotendinous junction?
Which component makes up the interfibrillar part of the tendon’s extracellular matrix?
Which type of cartilage is primarily found in intervertebral disks and provides minimal motion at joints?
What structure encloses the secondary bundles of fibers within a tendon?
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What is a major function of bursae in the musculoskeletal system?
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What type of joint allows motion in only one plane and is described as having one degree of freedom?
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Which type of cartilage is primarily found in symphyses and is characterized by discs or pads?
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What is the main role of bursae in synovial joints?
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Which of the following correctly describes syndesmosis joints?
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What type of joint is characterized by a connection via a sutural ligament, exemplified by the joints in the skull?
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Study Notes
Tendons and Their Structure
- Tendons connect muscles to bones, playing a crucial role in movement and force transmission.
- Composed of fibroblasts (cellular component) and a significant extracellular matrix.
- Extracellular matrix includes:
- Interfibrillar component: water, proteoglycans (PGs), glycosaminoglycans (GAGs).
- Fibrillar component: collagen and elastin in varying ratios.
- Collagen fibrils form microfibrils, which group into fibers and primary bundles.
- Fiber bundles enveloped by loose connective tissue are termed endotendon.
- Endotendon contains types I and II collagen, enclosing nerves, lymphatics, and blood vessels to form fascicles.
- The outer sheath covering all secondary bundles is known as epitenon.
- Peritenon (or paratenon) is a double-layered, loosely attached sheath of areolar tissue around the epitenon.
- At the tendon’s bony ends, connective tissue transitions to unmineralized fibrocartilage, then to mineralized fibrocartilage, and finally to bone.
- Myotendinous junctions form where tendon collagen fibers merge with muscle actin filaments within sarcomeres.
Bursae
- Bursae are flat sacs lined with synovial membrane and filled with synovial fluid, reducing friction between moving structures.
- Located between tendon and bone, bone and skin, muscle and bone, or ligament and bone.
- Types of bursae include subcutaneous, subtendinous, and submuscular bursae.
Types of Cartilage
- White fibrocartilage: Forms bonding cement in joints allowing limited movement; found in intervertebral discs and labra; consists mainly of type I collagen.
- Yellow elastic fibrocartilage: Found in ears and epiglottis with a higher elastin-to-collagen ratio.
- Hyaline articular cartilage: Covers the ends of joints, providing a low-friction surface capable of weight-bearing throughout life.
Types of Joints
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Synarthroses: Immovable joints divided into fibrous and cartilaginous joints.
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Fibrous joints include:
- Sutures: Connected by sutural ligament; allows slight movement; found in the skull.
- Gomphosis: Peg-and-hole connection; example: tooth in mandible/maxilla.
- Syndesmosis: Joined by interosseus ligament; allows some motion; example: tibia and fibula.
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Cartilaginous joints include:
- Symphyses: Jointed by fibrocartilage disks; examples: pubis and intervertebral joints.
- Synchondroses: Joined by hyaline cartilage; example: first chondrosternal joint.
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Fibrous joints include:
Diarthroses
- Characters with a joint capsule enclosing the joint, including:
- Joint cavity
- Synovial membrane
- Synovial fluid
- Hyaline cartilage
- Classified into types based on movement axes:
- Biaxial: Condyloid and saddle joints.
- Triaxial: Plane and synovial joints.
- Uniaxial: Pivot and hinge joints.
Uniaxial Joints
- Allow motion only in one plane around one axis, characterized by one degree of freedom of movement.
- Pivot joints: One bone component shaped like a ring with another component fitting inside.
- Hinge joints: Similar to a door hinge, allowing movement primarily in one direction.
Joint Design Principles
- Joints serving a single function are less complex compared to multifaceted joints.
- Joint design is influenced by its function and component nature.
Structure of Joints
- Composed of various connective tissues: bursae, bones, ligaments, tendons, menisci, etc.
- Biomechanical properties and compositions of connective tissues vary widely.
Objectives of Joint Study
- Define joints and their functions (mobility, stability, dynamic).
- Classify connective tissues and their structures.
- Differentiate between open and closed kinematic chains.
- Explain joint positions and arthrokinematics vs osteokinematics.
- Analyze load deformation/stress-strain curves in specific connective tissues.
- Examine effects of aging, immobilization, and injury on connective tissues.
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Description
Test your knowledge on the structure and function of tendons, including their cellular components and extracellular matrix. This quiz covers key concepts such as collagen fibrils and the role of fibroblasts in tendon biology.
