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Skeletal System & Joints (Components of Long Bones (Spongy Bone:…
Skeletal System & Joints
Types of Bone Cells
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Osteoclast
Derived from leukocytes (white blood cells) that are responsible for resorption of bone. They break down bone by secreting enzymes through microvilli. Enzymes break down the organic part of the bone, and liberates the mineral part to be reabsorbed into the blood.
Osteoblast
Produce and secrete organic components of extracellular matrix - ground substance and collagen fibers. Occurs in growing bone & remodeling bone (whole life).
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Fibrous Joints
Sutures
Fixed, No movement in adults
Fontanelles: Membranes between cranial bones in infants. Soft spots where sutures haven't formed yet.
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Syndesmosis
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Little movement, mostly just holds bones together
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Synovial Joints
Synovial Fluid: Slippery and lubricating to ease movement at the joint. Reduces shock, and nourishes articular (hyaline) cartilage.
Synovial Membrane: Lining of all internal joint surfaces that are not covered by cartilage, and produces synovial fluid to fill the joint cavity.
Bursa
Located between bone & skin, bone & tendons, bone & ligaments, and bone & muscle
Synovial membrane in a sac filled with synovial fluid. Reduces friction between body elements that move over one another
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Articular Disc
Medial and lateral miniscus in the knee, contains fibrocartilage
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Articular Cartilage: Hyaline cartilage on the ends of opposing bone. Acts as cushion to absorb compressing force
Tendon Sheath
Located in carpal (wrist), and where many tendons come together and form tunnels
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Cartilaginous Joints
Synchondrosis
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Located in epiphyseal plates, and between 1st rib and manubrium
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Synphysis
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Located in intervertebral joints, and pubic symphysis
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Components of Long Bones
Spongy Bone: Internal layer found at end of bones and middle of hollow bones. Contains osteocytes in lacunae. Trabeculae - Ppicules in the spongy bone with open spaces filled with bone marrow.
Epiphyseal Line: Between diaphysis and each epiphysis of adult long bone. Consists of hyaline cartilage disc that growns during childhood to lengthen bone
Compact Bone: External layer of bone surface. Contains osteons, structured in long columns close together. And contains osteocytes in lacunae.
Medullary Cavity: Center of diaphysis containing no bone tissue, filled with yellow bone marrow
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Endosteum: Membrane covering internal surface of bone surfaces. Lines medullary cavity and covers trabeculae of spongy bone. Osteogenic (osteoblasts and osteoclasts)
Nutrient Arteries: Running through walls of diaphysis to supply the bone marrow and spongy bone. Branches extend outward to supply compact bone.
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Perforating Fibers (Sharpey's Fibers): Thick bundles of collagen that run from periosteum into bone matrix. Secures periosteum to underlying bone
Periosteum: Membrane covering external surface of each bone except the ends of epiphysis where there is articular cartilage. Outter layer - dense irregular connective tissue, attachment place for tendons/ligaments. Inner layer - osteogenic cellular layer (osteoblasts and osteoclasts)
Diaphysis: Middle/shaft, forms the long axis of long bone.