Biology 2121 Chapter 6

 1. Bone Fractures and Breaks  2. Bone Healing

 Support  Protection  Movement  Mineral Storage  Blood Cell Formation (a). Hematopoiesis occurs in marrow cavities

A B A. Osteon B. Interstitial lamella

 (1). No osteons  (2). Trabeculae are disorganized, no pattern  (3). Irregular lamella and osteocytes connected by canaliculi  (4). Nutrients reach cells via diffusion from capillaries

 1. Fibrous CT  (a). Mesenchymal cells begin to differentiate into osteoblasts and form an “ossification center”  2. Osteoblasts secrete “osteoid” and mineralizes  (b). Osteoblasts which are trapped become “osteocytes”  3. Osteoid  (a). Continues to be produced and forms around embryonic blood vessels  (b). This is called a network of “trabeculae” (not lamellae)  (c). Mesenchyme condenses on the outside of the bone and forms the “periosteum”.  4. Trabeculae  (a). Thicken and form a woven bone which is replaced by mature lamellar bone  (b). Spongy bone consists of trabeculae and the vascular tissue becomes red marrow

 1. Begins at the center of the hyaline cartilage shaft (primary ossification center)  2. Perichondrium that covers the hyaline cartilage is infiltrated with blood vessels and is converted to periosteum  3. Osteoblasts  (a). in periosteum secrete osteoid against the hyaline cartilage forming a bone collar  4. Chondrocytes inside the shaft  (a). hypertrophy and signals the matrix of cartilage of calcify  (b). This substance is impermeable (chondrocytes die) and the matrix breaks down  (c). Stabilized by the ‘bone collar’

 5. Other than the central part of the cartilage that is breaking down  (a). other cartilage areas are growing (elongating)!  6. Month (3)  (a). Periosteal bud invades the internal cavity and spongy bone forms  (b). Nutrient artery, vein, lymphatics, nerves, red marrow elements, osteoblasts and osteoclasts  (c). Osteoclasts erode the cartilage matrix and osteoblasts secrete osteoid around the remaing hyaline cartilage (forms trabeculae)  7. As the center enlarges  (a). osteoclast break down the new spongy bone and opens up a medullary cavity

 8. The epiphyses continues growing (cartilage) and elongating  (a). Ossification chases cartilage formation (cartilage that is growing is eroded, ossified, etc)  9. At birth long bones  (a). contain a diaphyses which is bone, surrounded by spongy bone and a medullary cavity which enlarges  (b). The epiphyses remains cartilage tissue  10. The epiphyses will develop secondary ossification centers and bony tissue is formed  (a). Long bones both epiphyses form secondary ossification centers  (b). Posterior bud invades after the cartilage is degraded and spongy bone forms  (c). Spongy bone stays and is not eroded (primary it is eroded)  (d). Hyaline cartilage only remains in articulating cartilages and at the epiphyseal plate

Formation of bone collar around hyaline cartilage model Cavitation of the hyaline cartilage within the cartilage model. Invasion of internal cavities by the periosteal bud and spongy boneformation. Formation of the medullary cavity as ossification continues; appearance of secondary ossification centers in the epiphyses in preparation for stage 5. Ossification of the epiphyses; when completed, hyaline cartilage remains only in the epiphyseal plates and articular cartilages Hyaline cartilage Primary ossification center Secondary ossification center

 Endochondrial Bone Growth Endochondrial Bone Growth  Shows how growth of cartilage occurs at the growth plate and is replaced by bone matrix.  Please Note: this animation opens in a new window.

 (1). Injury or additional strength needed  (2). Nutrients required are minerals (Ca, P, Mg, Mn, etc) and vitamins (C, D, A)  (3). Include osteoclasts and osteoblasts

 (1). Osteoporosis – Animation IAnimation I  Animation II Animation II  (2). Osteomyelitis  (3). Paget’s and Rickets  Other Problems  (a). Scoliosis  (b). Lordosis  (c). Spina Bifida

 (1). Position of bones Nondisplaced fractures Bones retain normal position Displaced Out of normal alignment  (2). Completeness of break Complete or incomplete  (3). Orientation Linear – break parallel to long axis Transverse – perpendicular  (4). Penetration Compound vs. simple

 Fracture I and II  Go to Discovery Health. Then go to Site index. Go to Watch video. Go to Animated Body Atlas. Orthopedic Health. Then to Bone Fractures.  Blood Cell Production in Red Bone Marrow Blood Cell Production in Red Bone Marrow

External callus Spongy bone trabeculae Internal callus (fibrous tissue and cartilage) Fibrocartilaginous callus formation

Bony callus of spongy bone Bony callus formation

Healing fracture Bone remodeling