Osteology notes.docx

7 Pages

Cellular, Anatomical and Physiological Sciences
Course Code
CAPS 391
Bruce Matheson

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1 Osteology Cartilage Part of development and growth of bones. Surfaces for articulating bones. Strong, flexible, cushioning joint structure There are three types- hyaline cartilage, fibrocartilage, and elastic cartilage  Consists of chondroblasts which produce a matrix surrounding them. When matrix surrounds a chondroblast it becomes a chondrocyte (mature cell) which occupy a space called a lacuna within the matrix.  Cartilage contains collagen, which provides strength, and proteoglycans, which make cartilage resilient by trapping water.  Surrounding most cartilage is a double layer of connective tissue called the perichondrium. The outer layer is dense irregular connective tissue containing fibroblasts. The inner layer has fewer fibers and contains chondroblasts.  Blood vessels and nerves penetrate the outer layer of the perichondrium but do not enter the matrix, so nutrients must diffuse through matrix to reach the chondroctyes.  Chondroblasts are at the boundary of the perichondrium and the cartilage, along with stem cells which give rise to chondroblasts  Articular cartilage covers the ends of bones where they come together to form joints to give a smooth friction free surface so they won’t grind each other down. These get their nourishment from synovial fluid as opposed to having a pericardium. Hyaline cartilage • Covers ends of articulating bones in moveable joints • Strong & flexible • Costal cartilage – where rib bones join sternum • Respiratory cartilage – larynx, trachea Elastic cartilage • Flexible – external ear, auditory tube Fibrocartilage • Great strength, supports a lot of weight • Intervertebral discs, prevent from cracking and • Menisci of knee joint, allow menisci of knee joint to provide support and not slip out • TMJ- Tempomandibular joint, in your mouth when you open and close your jaw 2 Bone Cells  Osteoblasts- bone forming cells for repair of fractures, they secrete the matrix(osteoid) which contains mineral salts that are precipitated  Osteoclasts- responsible for reabsorption, or breakdown, of bone damaged bone during repair or remodelling of old bone to new. They also release enzymes that digest protein components of the matrix Spongy bone More porous and has less bone matrix than compact bone. Consists of interconnecting rods or plates of bone called trabeculae. Between the trabeculae are spaces that are filled with bone marrow and blood vessels Trabeculae-  thin, consist of several lamellae with osteocytes located in a lacunae (spaces occupied by osteocyte cell bodies) between lamellae which release and maintain the minerals in each of the lamella.  Each osteocyte is associated with others through canaliculi. Usually no blood vessels penetrate the trabiculae, so osteocytes must obtain nutrients through their canaliculi.  Trebeculi develop beginning with woven bone (fetal production and repair of a fracture), the trabeculae are remodelled as we start walking and then they resist the 3 forces of gravity and become structured differently to compensate for this. They develop along stress lines. May contain red or yellow bone marrow within cavities Lamellea- mature bone that’s organized into sheets or layers called lamellae. Canaliculi- spaces occupied by the osteocyte cell processes. There is no central canal in the spongy bone because they can receive nutrients by diffusion as apposed to having blood vessels in the middle. Compact bone Denser and has fewer spaces than spongy bone. Blood vessels enter the substance of the bone itself, and the lamellae of compact bone are primarily oriented around those blood vessels. Central canal-  Central canals are lined with endosteum and contain blood vessels, nerves, and loose connective tissue.  Concentric lamellae are the circular layers of bone matrix that surround the canal.  Osteocytes receive nutrients and eliminate waste products through the canal system within compact bone. Blood vessels from the periosteum enter the bone through perforated canals. Perforated Canal-  Pass through the concentric lamellae of the osteons.  Central canals receive blood vessels from perforating canals. Nutrients in the blood vessels enter the central canals, pass into the canaliculi, and move through the cytoplasm of the osteocytes that occupy the canaliculi and lacunae to the most peripheral cells within each osteon. Waste products are removed in the reverse direction. 4 Osteon (heversian system)-  Consists of a single central canal and its contents are lamellae and osteocytes. these osteocytes are located within the lacunae between the lamellar rings and canaliculi radiate between lacunae across the lamellae looking like minute cracks across the rings.  All the osteocytes are interconnected by their cytoplasm canaliculi connected by gap junctions. Bone shapes and Structure Long bones are longer than they are wide, most of the bones of the upper and lower limbs are long bones. Structure of long bones: Diaphysis-  Shaft, composed primarily of compact bone, but it can also contain spongy bone. Primary ossification center for bone formation and growth is located here.
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