Anatomy and Physiology of Dogs and Cats Bones, Joints, Synovial Fluid (Part Two)

Periosteum Composed of an outer fibrous layer and an inner cell-rich layer containing osteoblasts or other cells that can become osteoblasts

Periosteum Functions –Increase diameter of bone –Heals fractures

Haversian System/Osteon Unit of structure for compact bone Central haversian canal surrounded by concentric layers of bone (lamellae) Lack spongy bone Contain blood vessels, connective tissues, nerve fibers and lymphatic vessels

Cells Osteoblasts –Produces collagen for the initial unmineralized bone and then helps calcify the bone matrix

Cells Osteocyte –Mature bone cell –Maintains the bone matrix –Can synthesize and resorb matrix to an extent

Cells Osteoclasts –Large, motile, multinucleated –Resorb bone for remodeling

Joints and Synovial Fluid Synovial joints are those that allow one surface to glide over the other Motion is facilitated by articular cartilage and synovial joint fluid contained in joint capsule The meniscus within joint capsule serves as a cushioning function

Synovial Fluid Contains hyaluronic acid and lubricin (glycoprotein) Secreted by synovial membrane Lubricates articular surfaces (light vs heavy loads)

Blood and Lymph Supply to Synovial Joints Arteries enter the bone near the line of the capsule attachment and form a network around the joint –Capillaries deliver nutrients Lymph vessels present in blood vessels –Lymph vessels that leave joint, drain into regional lymph nodes

Nerve Supply and Synovial Joints Functions: –Pain and reflex –Role in posture, locomotion, and sense of tension from motion (tendons, muscles)