Joints - BIOL 243 Week 7 Part A PDF

Joints Classification of Joints Understanding the nature of joints will help you treat patients with injuries such as ankle sprains Joints, also called articulations: sites where two or more bones meet Functions of joints: give skeleton mobility and hold skeleton together Structural and Functional...

Joints Classification of Joints Understanding the nature of joints will help you treat patients with injuries such as ankle sprains Joints, also called articulations: sites where two or more bones meet Functions of joints: give skeleton mobility and hold skeleton together Structural and Functional Classification of Joints Two classifications: I. Structural: three types based on what material binds the joints and whether a cavity is present 1. Fibrous 2. Cartilaginous 3. Synovial II. Functional classifications: three types based on movement joint allows 1. Synarthroses: immovable joints 2. Amphiarthroses: slightly movable joints 3. Diarthroses: freely movable joints Fibrous Joints Bones joined by dense fibrous connective tissue No joint cavity Most are immovable ◦ Depends on length of connective tissue fibers Three types of fibrous joints 1. Sutures 2. Gomphoses 3. Syndesmoses Adapted from Pearson Education Fibrous Joints - Sutures Structural Classification - Sutures Sutures are rigid, interlocking joints of skull Allow for growth during youth ◦ Contain short connective tissue fibers that allow for expansion In middle age, sutures ossify and fuse ◦ Immovable joints join skull into one unit that protects brain ◦ Closed, immovable sutures referred to as synostoses Adapted from Anatomy and Physiology 2e OpenStax.org Fibrous Joints - Gomphoses Structural Classification - Gomphoses Gomphoses are peg-in-socket joints Only examples are the teeth in alveolar sockets Fibrous connection is the periodontal ligament ◦ Holds tooth in socket Adapted from Anatomy and Physiology 2e OpenStax.org Fibrous Joints - Syndesmoses Structural Classification - Syndesmoses In syndesmoses, bones connected by ligaments, bands of fibrous tissue Fiber length varies, so movement varies ◦ Short fibers offer little to no movement ◦ Example: inferior tibiofibular joint ◦ Longer fibers offer a larger amount of movement ◦ Example: interosseous membrane connecting radius and ulna Adapted from Anatomy and Physiology 2e OpenStax.org Structural Classification - Cartilaginous Joints Bones united by cartilage Like fibrous joints, have no joint cavity Not highly movable Two types 1. Synchondroses 2. Symphyses Adapted from Anatomy and Physiology 2e OpenStax.org Cartilaginous Joints - Synchondroses Structural Classification – synchondroses In synchondroses, a bar or plate of hyaline cartilage unites bones Almost all are synarthrotic (immovable) Examples ◦ Temporary epiphyseal plate joints ◦ Become synostoses after plate closure ◦ Cartilage of 1st rib with manubrium of sternum Adapted from Anatomy and Physiology 2e OpenStax.org Cartilaginous Joints - Symphyses Structural Classification – symphyses Fibrocartilage unites bone in symphysis joint ◦ Hyaline cartilage also present as articular cartilage on bony surfaces Symphyses are strong, amphiarthrotic (slightly movable) joints Examples ◦ Intervertebral joints ◦ Pubic symphysis Adapted from Anatomy and Physiology 2e OpenStax.org Structural Classification - of Synovial Joints Bones separated by fluid-filled joint cavity All are diarthrotic (freely movable) Include almost all limb joints Characteristics of synovial joints ◦ Have six general features ◦ Have bursae and tendon sheaths associated with them ◦ Stability is influenced by three factors ◦ Allow several types of movements ◦ Classified into six different types Adapted from Anatomy and Physiology 2e OpenStax.org Types of Synovial Joints There are six different types of synovial joints ◦ Categories are based on shape of articular surface, as well as movement joint is capable of 1. Plane - nonaxial 2. Hinge - uniaxial 3. Pivot - uniaxial 4. Condylar - biaxial 5. Saddle - biaxial 6. Ball-and-socket – multiaxial (polyaxial) Adapted from Anatomy and Physiology 2e OpenStax.org Synovial Joint Shapes – Plane Joint Adapted from Pearson Education Synovial Joint Shapes – Hinge Joint Adapted from Pearson Education Synovial Joint Shapes – Pivot Joint Adapted from Pearson Education Synovial Joint Shapes – Condylar Joint Adapted from Pearson Education Synovial Joint Shapes – Saddle Joint Adapted from Pearson Education Synovial Joint Shapes – Ball and Socket Joint Adapted from Pearson Education  Synovial Structure (1/2) Synovial joints have six general features: 1. Articular cartilage: consists of hyaline cartilage covering ends of bones ◦ Prevents crushing of bone ends 2. Joint (synovial) cavity: small, fluid-filled space 3. Articular (joint) capsule: two layers thick ◦ External fibrous layer: dense irregular connective tissue ◦ Inner synovial membrane: loose connective tissue that makes synovial fluid Adapted from Anatomy and Physiology 2e OpenStax.org Synovial Structure (2/2) 4. Synovial fluid: viscous, slippery filtrate of plasma and hyaluronic acid ◦ Lubricates and nourishes articular cartilage ◦ Contains phagocytic cells to remove microbes and debris 5. Different types of reinforcing ligaments ◦ Capsular: thickened part of fibrous layer ◦ Extracapsular: outside the capsule ◦ Intracapsular: deep to capsule; covered by synovial membrane 6. Nerves and blood vessels ◦ Nerves detect pain; monitor joint position and stretch ◦ Capillary beds supply filtrate for synovial fluid Adapted from Pearson Education Synovial Structure: Other Features (1/2) Other features of some synovial joints: ◦ Fatty pads ◦ For cushioning between fibrous layer of capsule and synovial membrane or bone ◦ Articular discs (menisci) ◦ Fibrocartilage separates articular surfaces to improve “fit” of bone ends, stabilize joint, and reduce wear and tear Adapted from Pearson Education Synovial Structure: Other Features (2/2) ◦ Bursae: reduce friction where ligaments, muscles, skin, tendons, or bones rub together ◦ Bags of synovial fluid that act as lubricating “ball bearing” ◦ Not strictly part of synovial joints, but closely associated ◦ Tendon sheaths: elongated bursae wrapped completely around tendons subjected to friction Adapted from Pearson Education Factors Influencing Stability of Synovial Joints Three factors determine stability of joints to prevent dislocations: 1. Shape of articular surface (minor role) ◦ Shallow surfaces less stable than ball-and-socket 2. Ligament number and location (limited role) ◦ The more ligaments, the stronger the joint 3. Muscle tone keeps tendons taut as they cross joints (most important) ◦ Extremely important in reinforcing shoulder and knee joints and arches of the foot Adapted from Pearson Education Adapted from Pearson Education Adapted from Pearson Education Discussion Explain why joints differ in their degree of mobility. Safely demonstrate the types of joint movements available at a ball-and-socket joint. Which factor has the greatest influence on the stability of synovial joints? 5 minutes to write it down, 5-10 min to discuss, 5-10 min share with class