Anatomy & Physiology: Joints.
Structure.
- Structural classification: based on whether or not there is space tween the articulating bones; type of connective tissue that holds the bones together.
- Fibrous joints: no synovial cavity; dense collagen-fiber-rich connective tissue.
- 3 types of fibrous joints: sutures, syndesmoses, & interosseous membranes.
- Sutures: fibrous joint made of thin layer of dense connective tissue. Only occurs in skull bones. Strength from irregular and interlocking edges. In infants and young children the sutures are amphiarthrotic; in adults the sutures are fused and immoveable (synarthrotic).
- Synostosis: suture present in infants/children but ossified in adults. Synarthrotic.
- Frontal/metopic suture: if the suture exists past 6 yrs old.
- Syndesmoses: fibrous joint with some distance between the two bones. Dense connective tissue arranged in bundles (ligamentous) limiting the joint movement. E.g. distal tibiofibular joint.
- Gomphosis: peg fitting into a socket. E.g. teeth and teeth sockets (alveoli).
- Interosseous membrane: sheet-like dense connective tissue between long bones; amphiarthrotic. E.g. between ulna and radius; between tibia and fibula.
- Cartilaginous joints: no synovial cavity; cartilaginous connective tissue (hyaline or fibrocartilage).
- Synchondroses: hyaline connective tissue. E.g. epiphyseal plate. Synarthrotic (immoveable).
- Symphasis: ends of bones covered by hyaline cartilage with a broad flattish fibrocartilage connecting the bones. All symphsis occur in the body’s midline. E.g. pubic symphasis; sternal angle between the manubrium and sternal body; intervertebral joints between vertebral bodies.
- Synovial joints: presence of synovial cavity; articular capsule with dense connective tissue and often accessory ligaments present. Diarthrotic (freely moving).
- Bones covered with articular cartilage (a layer of hyaline) to reduce friction.
- Articular (joint) capsule: sleevelike; encloses the joint cavity where the two bones articulate with each other. Has 2 layers: fibrous membrane (mostly collagen, dense) attaches to periosteum of bones; synovial membrane (inner membrane) of areolar connective tissue.
- Articular fat pads: fatty pads act as cushioning.
- Synovial fluid: lubrication and reduce friction. Clear and viscous. Fibroblast-like cells in synovial membrane secrete this hyaluronic acid. Also some fluid from blood plasma. Has phagocytic cells as “clean-up” crew.
- Accesory ligaments.
- Articular menisci: pads of fibrocartilage.
- Functional classification: based on how much movement is allowed in a joint.
- Synarthrosis: immoveable.
- Amphiarthrosis: somewhat moveable.
- Diarthrosis: freely moveable joint.
- Bursae: fluid-filled sacs between skin-bones, tendons-bones, muscles-bones, or ligaments-bones.
- Tendon sheaths: reduce friction at joints. Tubelike bursa wrap around tendons.
- Fibrous joints: no synovial cavity; dense collagen-fiber-rich connective tissue.
Function.
Clinical Significance.
References
Biel, A. (2015). Trail guide to the body: A hands-on guide to locating muscles, bones and more.
Cedars-Sinai. (2018). Vertebrae of the spine. Retrieved from https://www.cedars-sinai.org/health-library/diseases-and-conditions/v/vertebrae-of-the-spine.html
Jenkins, G., & Tortora, G. J. (2012). Anatomy and Physiology: From Science to Life, 3rd Edition International Stu. John Wiley & Sons.
Muscolino, J. E. (2017). The muscular system manual: The skeletal muscles of the human body.
