BIOL1410 Lecture #10 Bone Structure and Composition PDF

Lecture #10 Bone Structure and Composition Textbook Chapter 8  Components of a Long Bone Long bones include the humerus, radius, ulna, fibula, tibia and the femur Each of these bones is composed of a: 1. Diaphysis: The shaft/body of the bone Composed of c...

Lecture #10 Bone Structure and Composition Textbook Chapter 8  Components of a Long Bone Long bones include the humerus, radius, ulna, fibula, tibia and the femur Each of these bones is composed of a: 1. Diaphysis: The shaft/body of the bone Composed of compact bone 2. The medullary cavity of the diaphysis: Contains red bone marrow in a child Contains yellow bone marrow in an adult Contains fat Lined by endosteum 3. Epiphysis: These are the proximal and distal entities  Components of a Long Bone 4. Epiphyseal plate: Composed of hyaline cartilage Bone growth in length occurs at this plate Bone growth is called endochondral ossification 5. Epiphyseal line: Replaces the epiphyseal plate when growth is finished Appears as a line because it is the junction of the diaphysis and the epiphysis 6. Endosteum: Connective tissue Very delicate Lines the internal surfaces of bone and canals that move through compact bone Contains osteoblasts and osteoclasts  Components of a Long Bone 7. Periosteum membrane: Composed of fibrous connective tissue Allows the bone to grow in diameter via intramembranous ossification Is a double membrane that covers the entire bone surface (except for the joint) The outer layer is dense irregular connective tissue The inner layer is osteogenic Bone forming and consists of osteoblasts and osteoclasts 8. Articular cartilage: Hyaline cartilage that functions to prevent friction Found on the epiphyseal surfaces of long bone  Tissues of the Skeletal System There are two primary tissues of the skeletal system 1. Bone 2. Cartilage 1. Bone: Bone is either compact or spongy Osteoprogenitor cells are cells that give rise to one of the following three cell types 1. Osteoblasts: build the matrix 2. Osteocytes: maintain the matrix 3. Osteoclasts: resorb (breakdown) the matrix The cells of the connective tissue are separated by a matrix that consists of: Collagen fibers for flexibility Ground substance: hydroxyapetite crystals for strengthà made from insoluble calcium phosphate salts Gives bone its characteristic strength Water  Types of Bone Compact bone is found on the exterior surface of all bones It is composed of individual structural units called osteons or Haversian Systems An osteon is composed of: Osteocytes found within special spaces called lacunae Lamellae which are concentric circles of bone matrix Osteocytes are present between the lamellae Canaliculi connect cells and blood vessels Haversian Canals contain the blood vessels and the nerves Lined with endosteum Volkmann’s Canals are found at a right angle to blood vessels found in Haversian Canals These connect the periosteum to the endosteum providing blood supply to the medullary cavity and the Haversian Canals  Types of Bone Spongy bone is not organized into osteons Plates of bone are called trabeculae Irregularly arranged lamellae containing osteocytes Osteocytes are located in lacunae and are connected by canaliculi Found in the epiphyses of long bone as well as in flat bones such as the skull and the ribs The spaces of the spongy bone contain red bone marrow These spaces produce blood cells and provide a blood supply to developing osteocytes  Hyaline Cartilage The cells of the cartilage are chondrocytes and are found within lacunae The matrix is composed of: Collagen fibers Ground substance consisting of chondroitin sulfate and hyaluronic acid Water Avascular tissue  Articulations and Joints Articulations and joints are points of contact between two or more bones: These can be classified on either structure or function 1. Functional classification: This is based on the degree of movement a. Synarthrotic: immovable joints Example: sutures b. Amphiarthrotic: slightly moveable joints Example: pubic symphysis c. Diarthrotic: freely moveable joints Example: hip, knee, elbow, shoulder  Articulations and Joints 2. Structural classification is based on: The presence or the absence of a joint cavity and the type of tissue connecting two bones There are three structural classifications of joints: 1. Fibrous joints: No joint cavity, composed of fibrous connective tissue Example: sutures on the skull 2. Cartilaginous joints: No joint cavity, composed of cartilage Example: pubic symphysis and intervertebral disks 3. Synovial joints: Contain a joint cavity filled with synovial fluid Bones are held together by a joint cavity and associated ligaments All diarthrotic joints are synovial joints Example: knee, shoulder, hip, elbow  Synovial Joints All synovial joints contain: 1. Articular cartilage: Hyaline cartilage located on the ends of the bones Reduces friction 2. Joint cavity: Contains synovial fluid 3. Joint capsule: Contains an outer layer of fibrous connective tissue that attaches to the periosteum An inner synovial membrane which secretes synovial fluid  Types of Synovial Joints There are four primary types of synovial joints: Grouped according to the shape of articulating bones 1. Gliding (plane): Flat surfaces Example: sacroiliac joint 2. Hinge: Concave and convex surfaces Example: elbow, knee 3. Pivot: Example: odontoid process of the axis 4. Ball and socket: Head of the femur and the acetabulum (hip) Head of the humerus and the glenoid fossa (shoulder) Allows for a large freedom of movement