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AH Bone
| Question | Answer |
|---|---|
| What is bone? | A connective tissue characterized by a mineralized extracellular matrix. The mineral is hydroxyapatite crystals. |
| What are the functions of bone? | To support and protect our bodies, and due to its mineral content, it also is a storage site for calcium and phosphate. Both can be mobilized from the bone matrix and taken up by the blood as needed to maintain appropriate levels throughout the body. |
| What is the structure of bone matrix? | Spaces called lacunae contains a bone cell, osteocyte. The osteocyte extends processes into small tunnels called canaliculi. These connect adjacent lacunae and allowing contact between the cell processes of neighboring osteocytes. |
| What other cells are present in bone? | Osteoprogenitor Cells: Give rise to osteoblasts. Osteoblasts: Cells that secrete the extracellular matrix ; once surrounded with its secreted matrix, it is referred to as an osteocyte. Osteoclasts: Bone-resorbing cells present on bone surfaces. |
| What are the two classifications of bone tissue? | 1. Compact (dense) 2. Spongy (cancellous) |
| What are the different bone shapes? | Long Bones Short Bones Flat Bones Irregular Bone |
| What is the periosteum? | Bones are covered by periosteum, a sheath of dense fibrous connective tissue containing osteoprogenitor cells. |
| What is the endosteum? | Bone cavities are lined by endosteum, a layer of connective tissue cells that contains osteoprogenitor cells. These endosteal cells are flattened and resemble fibroblasts. They differentiate into osteoblasts in response to appropriate stimuli. |
| What is the interior of bone like? | The marrow cavity and the spaces in spongy bone contain bone marrow. Red marrow has developing blood cells, yellow marrow is no longer developing and is full of fat. |
| What is the structure of mature lamellar/compact bone? | Structural units called osteons (Haversian systems). They consist of concentric lamellae of bone matrix, surrounding a central canal which contains the vascular and nerve supply of the osteon. Canaliculi arranged in a radial pattern. |
| What is the interstitial bone? | Between the osteons are remnants of previous concentric lamellae. |
| What is the structure of mature spongy/cancellous bone? | Similar to compact bone. However, arranged as trabeculae or spicules, numerous interconnecting marrow spaces of various size are present between the bone tissue. Matrix is lamellated. If the trabeculae are sufficiently thick, they will contain osteons. |
| How does immature bone differ from mature bone? | 1. Nonlamellar/bundle/woven. 2. More cells per unit area than mature bone. 3. Randomly arranged cells 4. More ground substance in its matrix. |
| What are the two types of bone formation? | 1. Intramembranous Ossification 2. Endochondral Ossification |
| How does intramembranous ossification occur? | Bone is formed by differentiation of mesenchymal cells into osteoblasts. Newly formed bone matrix appears in histologic sections as small, irregularly shaped spicules and trabeculae. |
| How does endochondral ossification occur? | Hyalin Cartilage model Cuff of bone around it Periosteal bony collar Chondrocytes in midregion of cartilage model become hypertrophic. Calcified matrix causes death of chondrocytes. Periosteal cells migrate into the cavity. |
| What is seen during endochondral bone grow? | resorption: Nearest the diaphysis. The calcified cartilage here is in direct contact with the connective tissue of the marrow cavity. |
Created by:
mattdomin