Bone 2.pdf

Types of bone L.M. of Bone Compact Bone Compact bone is arranged in units called osteons or Haversian systems. Osteons. Consists of concentric lamellae, surrounding a central canal called Haversian canal that contains small blood vessels, nerves, and endosteum. Between successive lamellae are osteoc...

Types of bone L.M. of Bone Compact Bone Compact bone is arranged in units called osteons or Haversian systems. Osteons. Consists of concentric lamellae, surrounding a central canal called Haversian canal that contains small blood vessels, nerves, and endosteum. Between successive lamellae are osteocytes inside lacunae Canals also communicate with one another through transverse perforating canals (Volkmann canals). ❑ Scattered among the intact osteons are numerous irregularly shaped groups of parallel lamellae called interstitial lamellae. ❑ Compact bone also includes parallel lamellae organized as external circumferential lamellae immediately beneath the periosteum and fewer inner circumferential lamellae around the marrow cavity.. Spongy Bone thin plates of bone called trabeculae Spaces in between are filled with red marrow where blood cells develop. Found in (ends of long bones and inside flat bones such as the hip bones, sternum, sides of skull, and ribs). BONE FORMATION Intramembranous ossification is the formation of bone directly from or within fibrous connective tissue membranes. A primary center of ossification arises in the C.T. membrane. The cells of the primary center (Mesenchymal cells) differentiate into osteoblasts which deposit bone matrix, then calcification occurs and the cells become imprisoned in lacunae. At this time they are called osteocytes Endochondral ossification is the formation of bone from hyaline cartilage models. Bone Growth occurs only by appositional growth at the bone’s surface. New bone tissue is added beneath the periosteum in a process of appositional growth leading to increasing bone circumference Osteogenic cells differentiate into osteoblasts and form new concentric lamellae around periosteal blood vessel. A new osteon is formed. Bone Growth at epiphyseal plate Bone resembles cartilage in that Some differences between bone and cartilage 1 It consists of cells and extracellular matrix. 2. Its mature cells are present in lacunae. 3. It is covered with C.T. sheath called periosteum. 4. Grows by appositional growth. 1. It grows only by appositional growth. 2. Its intercellular substance is calcified 3. Bone matrix is vascular and osteocytes still survive in the calcified matrix. 4. Bone cells cannot divide, not even the osteoblasts, thus there is no interstitial growth