Section 25: Joints – Structure and Function 25-1
Joint s Joints attach bones, provide support and protection, and allow for body movement for body movement. Joints are categorized by their categorized by their structural classification and their functional classification. 25-2 From: Ames Chapter 5 – The Skeletal System
Joints Joints • Provide necessary range of motion Provide necessary range of motion • Classification based on structure: fibrous, cartilagenous synovial cartilagenous, synovial • Classification based on function: synarthroses (immovable), amphiarthroses th (i bl ) hi th (slightly movable), diarthoses (freely movable) bl ) 25-3 From: Arora
JOINTS JOINTS • Joints are where two or more bones articulate ( (move). ) • Joints are classified according to how much movement they allow movement they allow. 1. Fibrous – these are fixed or immovable joints such as the cranium sacrum and the coccyx such as the cranium, sacrum and the coccyx. 2. Cartilaginous – these are slightly movable joints such as the vertebrae joints such as the vertebrae. 3. Synovial – these are freely movable joints such as the shoulder and hip as the shoulder and hip. 25-4 From: Essex
Cartilaginous joints Cartilaginous joints • Articulating bones are united by cartilage Articulating bones are united by cartilage • Lack a joint cavity • Two types – synchondroses and T t h d d symphyses 25-5 From: Mathis
Cartilaginous joints: synchondroses Cartilaginous joints: synchondroses • A bar or plate of hyaline cartilage unites A bar or plate of hyaline cartilage unites the bones • All synchondroses are synarthrotic • All synchondroses are synarthrotic • Examples include: – Epiphyseal plates of children – Joint between the costal cartilage of the first rib and the sternum 25-6 From: Mathis
From: Mathis 25-7
Cartilaginous joints: symphyses Cartilaginous joints: symphyses • Hyaline cartilage covers the articulating Hyaline cartilage covers the articulating surface of the bone and is fused to an intervening pad of fibrocartilage intervening pad of fibrocartilage • Amphiarthrotic joints designed for strength and flexibility and flexibility • Examples include intervertebral joints and the pubic symphysis of the pelvis th bi h i f th l i 25-8 From: Mathis
From: Mathis 25-9
Synovial Joints Synovial Joints • Bone ends separated by a joint cavity Bone ends separated by a joint cavity containing synovial fluid • Most joints of the limbs • Most joints of the limbs • Full range of motion available in most j i t joints 25-10 From: Arora
Synovial joints Synovial joints • Those joints in which the articulating Those joints in which the articulating bones are separated by a fluid-containing joint cavity joint cavity • All are freely movable diarthroses • Examples – all limb joints, and most joints E l ll li b j i t d t j i t of the body 25-11 From: Mathis
Components of synovial joints Components of synovial joints • A joint capsule consists of two layers j p y – Fibrous capsule holds the ends of the bones together and allows movement of the joint – Synovial membrane which consists of connective Synovial membrane which consists of connective tissue • Synovial fluid : combination of materials filtered y from blood and secreted by cells of the synovial membrane – Contains hyaluronic acid, which makes the fluid very C t i h l i id hi h k th fl id slippery – Lubricant to reduce friction within the joint 25-12 From: Hoxha
• Articular (hyaline) cartilage covers ends Articular (hyaline) cartilage covers ends of the bones. Smooth and resilient. • Joint cavity is a small space bounded by • Joint cavity is a small space bounded by the synovial membrane and the articular cartilages It is filled with synovial fluid cartilages. It is filled with synovial fluid 25-13 From: Hoxha
Structure of synovial joints Structure of synovial joints • Articular cartilage – hyaline Articular cartilage hyaline • Fibrous capsule • Joint cavity, contains synovial fluid J i t it t i i l fl id • Reinforcing ligaments 25-14 From: Arora
Synovial joints: general structure Synovial joints: general structure • Synovial joints all have the following Synovial joints all have the following – Articular cartilage – Joint (synovial) cavity Joint (synovial) cavity – Articular capsule – Synovial fluid Synovial fluid – Reinforcing ligaments 25-15 From: Mathis
From: Mathis 25-16
Synovial joints: friction-reducing and extra structures d • Bursae – flattened fibrous sacs lined with Bursae flattened, fibrous sacs lined with synovial membranes and containing synovial fluid synovial fluid – Common where ligaments, muscles, skin, tendons or bones rub together tendons, or bones rub together • Tendon sheath – elongated bursa that wraps completely around a tendon wraps completely around a tendon • Fat pads 25-17 From: Mathis
From: Mathis 25-18
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