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BIOB32H3 Lecture Notes - Chondrocyte, Cell Division, Weight-Bearing

Biological Sciences
Course Code
Kenneth Welch

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Bones and Skeletal Tissue
Skeletal Cartilage
Contains no blood vessels or nerves
Surrounded by the perichondrium (dense irregular CT) that resists outward expansion
Three types hyaline, elastic, and fibrocartilage
Hyaline Cartilage
Provides support, flexibility, and resilience
Is the most abundant skeletal cartilage
Is present in these cartilages:
Articular covers the ends of long bones
Costal connects the ribs to the sternum
Respiratory makes up the larynx and reinforces air passages
Nasal supports the nose
Elastic Cartilage
Similar to hyaline cartilage but contains elastic fibers
Found in the external ear and the epiglottis
Highly compressed with great tensile strength
Contains collagen fibers
Found in menisci of the knee and in intervertebral discs
Growth of Cartilage
Appositional cells in the perichondrium secrete matrix against the external face of existing
Interstitial lacunae-bound chondrocytes inside the cartilage divide and secrete new matrix,
expanding the cartilage from within
Bones and Cartilages of the Human Body
Classification of Bones
Axial skeleton bones of the skull, vertebral column, and rib cage
Appendicular skeleton bones of the upper and lower limbs, shoulder, and hip
Classification of Bones: By Shape
Long bones longer than they are wide
(e.g., humerus)
Classification of Bones: By Shape
Short bones
Cube-shaped bones of the wrist and ankle
Bones that form within tendons (e.g., patella)
Classification of Bones: By Shape
Flat bones thin, flattened, and a bit curved (e.g., sternum, and most skull bones)
Irregular bones bones with complicated shapes (e.g., vertebrae and hip bones)
Function of Bones
Support form the framework that supports the body and cradles soft organs
Protection provide a protective case for the brain, spinal cord, and vital organs
Movement provide levers for muscles
Mineral storage reservoir for minerals, especially calcium and phosphorus
Blood cell formation hematopoiesis occurs within the marrow cavities of bones

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Gross Anatomy of Bones
Compact bone dense outer layer
Spongy bone honeycomb of trabeculae filled with yellow bone marrow
Structure of Long Bone
Tubular shaft that forms the axis of long bones
Composed of compact bone that surrounds the medullary cavity
Yellow bone marrow (fat) is contained in the medullary cavity
Expanded ends of long bones
Exterior is compact bone, and the interior is spongy bone
Joint surface is covered with articular (hyaline) cartilage
Epiphyseal line separates the diaphysis from the epiphyses
Bone Membranes
Periosteum double-layered protective membrane
Outer fibrous layer is dense regular CT
Inner osteogenic layer is composed of osteoblasts and osteoclasts
Richly supplied with nerve fibers, blood, and lymphatic vessels, which enter the bone via
nutrient foramina
Secured to underlying bone by Sharpey’s fibers
Endosteum delicate membrane covering internal surfaces of bone
Structure of Short, Irregular, and Flat Bones
Thin plates of periosteum-covered compact bone on the outside with endosteum-covered
spongy bone (diploë) on the inside
Have no diaphysis or epiphyses
Contain bone marrow between the trabeculae
Location of Hematopoietic Tissue (Red Marrow)
In infants
Found in the medullary cavity and all areas of spongy bone
In adults
Found in the diploë of flat bones, and the head of the femur and humerus
Microscopic Structure of Bone: Compact Bone
Haversian system, or osteon the structural unit of compact bone
Lamella weight-bearing, column-like matrix tubes composed mainly of collagen
Haversian, or central canal central channel containing blood vessels and nerves
Volkmann’s canals – channels lying at right angles to the central canal, connecting blood
and nerve supply of the periosteum to that of the Haversian canal
Osteocytes mature bone cells
Lacunae small cavities in bone that contain osteocytes
Canaliculi hairlike canals that connect lacunae to each other and the central canal
Chemical Composition of Bone: Organic
Osteoblasts bone-forming cells
Osteocytes mature bone cells
Osteoclasts large cells that resorb or break down bone matrix
Osteoid unmineralized bone matrix composed of proteoglycans, glycoproteins, and
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