Which bone has lamellae

Can you identify the primary and secondary Haversian systems, central canals and bone lamellae? This is a high power photo of a single Haversian system. Can you identify the concentric lamellae, central canal and the lacunae.

Because of the way the bone is prepared for sectioning, you cannot see the osteocytes in the lacunae, only the spaces left behind. The surrounding mesenchymal cells are stellate in appearance. Endochondral bone formation is represented in this slide. Bone arises by replacement of a small hyaline cartilage model. Locate the epiphyseal plate ; it is the site for bone elongation.

First, find the hyaline cartilage and move toward the bone marrow. Identify the 5 overlapping zones:. Zone of Reserve or Resting Cartilage - young small cells evenly distributed, appears as typical hyaline cartilage. Zone of Cell Proliferation - chondrocytes divide, forming parallel columns. Zone of Cell Maturation and Hypertrophy - cells produce collagen and ground substance. Zone of Cartilage Calcification - septa of cartilage matrix become calcified, cells die.

Zone of Ossification - osteoblasts invade cavities, and deposit bone matrix. Bone is divided into two types that are different structurally and functionally.

Most bones of the body consist of both types of bone tissue:. Long bones are composed of both cortical and cancellous bone tissue. They consist of several areas:. Different areas of the bone are covered by different tissue:. Compact bone is organized as parallel columns, known as Haversian systems, which run lengthwise down the axis of long bones. These columns are composed of lamellae, concentric rings of bone, surrounding a central channel, or Haversian canal, that contains the nerves, blood vessels, and lymphatic system of the bone.

The parallel Haversian canals are connected to one another by the perpendicular Volkmann's canals. The lamellae of the Haversian systems are created by osteoblasts. As these cells secrete matrix, they become trapped in spaces called lacunae and become known as osteocytes. Osteocytes communicate with the Haversian canal through cytoplasmic extensions that run through canaliculi, small interconnecting canals. The layers of a long bone, beginning at the external surface, are therefore:.

Bone development begins with the replacement of collagenous mesenchymal tissue by bone. This results in the formation of woven bone, a primitive form of bone with randomly organized collagen fibers that is further remodeled into mature lamellar bone, which possesses regular parallel rings of collagen. Lamellar bone is then constantly remodeled by osteoclasts and osteoblasts. There are two different methods by which bone is produced from mesenchymal tissue:.

Pigmented Villonodular Synovitis P The ends of long bones or epiphyses consist mainly of spongy bone. Compact bone - does not have any spaces or hollows in the bone matrix that are visible to the eye. Woven bone - immature, disorganised bone. Compact Bone Cortical Compact bone consists almost entirely of extracellular substance - the matrix. Osteoblasts deposit the matrix in the form of thin sheets which are called lamellae. Lamellae are microscopic structures.

Collagen fibres within each lamella run parallel to each other. Collagen fibres which belong to adjacent lamellae run at oblique angles to each other.