Lec 1 Hist2.ppt.pdf

+ Bone Repair Prof. Dr. Hala El-Haroun  Types of Bone Cells Osteocytes Osteoclasts Mature bone cells Bone-destroying cells Osteoblasts...

+ Bone Repair Prof. Dr. Hala El-Haroun  Types of Bone Cells Osteocytes Osteoclasts Mature bone cells Bone-destroying cells Osteoblasts Break down bone matrix for remodeling and release of Bone-forming cells calcium Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Bone Development In embryos, the skeleton is primarily hyaline cartilage Uses hyaline cartilage “bones” for bone construction During development, much of this cartilage is replaced by bone Begins in second month of development Bone Development Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Bone Growth Epiphyseal plates allow for growth of long bone during childhood New cartilage is continuously formed Older cartilage becomes ossified Cartilage is broken down Bone replaces cartilage Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide.+ Bone Maintenance & Repair A. Bone remodeling: 1. Life long process 2. Local areas of bone are destroyed and rebuilt 3. Repairs microdamage caused by normal wear and tear + Hormonal Regulation of Bone Growth During Youth ◼ During infancy and childhood, epiphyseal plate activity is stimulated by growth hormone ◼ During puberty, testosterone and estrogens: ◼ Cause masculinization and feminization of specific parts of the skeleton ◼ Laterinduce epiphyseal plate closure, ending longitudinal bone growth + Bone Remodeling ◼Bonesare remodeled continually in response to changes in two factors: ◼ Calcium Levels in the blood ◼ Thepull of gravity and muscles on the skeleton + Bone remodeling ◼ When blood calcium levels drop below homeostatic levels, the parathyroid glands release Parathyroid hormone ◼ PTH activates osteoclasts to break down bone matrix and release calcium ions into the blood ◼ Boneremodeling is crucial for maintaining appropriate proportions and strength during extended bone growth. ◼ Accounts for the fact that bones become thicker and form large projections to increase strength in areas where bulky muscles are attached Fractures and Bone Healing + Bone Fractures A break in a bone Types of bone fractures Closed (simple) fracture – break that does not penetrate the skin Open (compound) fracture – broken bone penetrates through the skin Displaced – the bone snaps into two or more parts and moves so that the two ends are NOT lined up straight Non-displaced – the bone cracks either part of all of the way through, but does move and maintains its proper alignment + Fractures 1. Simple bone breaks cleanly, does not break through skin + 2. Compound broken ends protrude through the skin, risk of bone infection + 3. Greenstick Does not break completely Greenstick: (children) + + Transverse fracture ◼ Broken straight across the bone + Spiral or Oblique ◼ (twisting movements) + Greenstick ◼ Occurs in children: bones soft and bend without fracturing completely + Crush fractures ◼ Fracture in cancellous bone: result of compression (osteoporosis) + Impacted fracture ◼ Bone fragments are impacted into each other. + Comminuted fracture ◼ Two or more bone pieces + Bone Repair! + Repair of Bone Fractures 1. Hematoma (blood-filled swelling) is formed 2. Break is healed (replaced) by fibrocartilage to form a callus 3. Fibrocartilage callus is replaced by a bony callus 4. Bony callus is remodeled to form a permanent patch Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 5.18 +Stages in the Healing of a Bone Fracture Figure 5.5 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 5.19 + Stages in the Healing of a Bone Fracture Hematoma ◼ Hematoma formation ◼ Torn blood vessels hemorrhage ◼ A mass of clotted blood (hematoma) forms at the fracture site ◼ Site becomes swollen, painful, and inflamed 1 Hematoma formation Figure 6.14.1 + Stages in the Healing of a Bone Fracture ◼ Fibrocartilaginous callus forms External callus ◼ Granulation tissue (soft callus) forms a few days after the New blood fracture Internal vessels callus ◼ Capillariesgrow into (fibrous tissue and Spongy the tissue and cartilage) bone phagocytic cells trabeculae begin cleaning debris 2 Fibrocartilaginous callus formation Figure 6.14.2 + Stages in the Healing of a Bone Fracture ◼ The fibrocartilaginous callus forms when: ◼ Osteoblasts and fibroblasts migrate to the fracture and begin reconstructing the bone ◼ Fibroblasts secrete collagen fibers that connect broken bone ends ◼ Osteoblasts begin forming spongy bone ◼ Osteoblasts furthest from capillaries secrete an externally bulging cartilaginous matrix that later calcifies + Stages in the Healing of a Bone Fracture ◼ Bony callus formation ◼ New bone trabeculae Bony callus of appear in the spongy fibrocartilaginous callus bone ◼ Fibrocartilaginouscallus converts into a bony (hard) callus ◼ Bone callus begins 3-4 weeks after injury, and 3 Bony callus continues until firm union formation is formed 2-3 months later Figure 6.14.3 + Stages in the Healing of a Bone Fracture ◼ Bone remodeling ◼ Excess material on the bone shaft exterior and in the medullary canal is removed Healing fracture ◼ Compact bone is laid down to reconstruct shaft walls 4 Bone remodeling Figure 6.14.4 + Repair of Bone Fractures Hematoma (blood-filled swelling) is formed Break is splinted by fibrocartilage to form a callus Fibrocartilage callus is replaced by a bony callus Bony callus is remodeled to form a permanent patch Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 5.18