Ch. 6 Bone Tissue

What are the functions of the skeletal system?

1. Support: for the body and soft organs

2. Protection: for brain, spinal cord, and vital organs

3. Movement: levers for muscle action

4. Storage: Minerals (calcium and phosphorus) and growth factors

5. Blood cell formation (hematopoiesis): in marrow cavities

6. Triglyceride (energy) storage: in bone cavities

What are the two main groups of the skeletal system?

Axial skeleton and Appendicular skeleton

What are the four classification of bones by shape?

1. Long bones: longer than they are wide (e.g., humerus)

2. Short bones: cube-shaped bones (in wrist and ankle); Sesamoid bones (within tendons, e.g., patella, talus)

3. Flat bones: Thin, Flat, slightly curved (e.g., sternum)

4. Irregular bones: complicated shapes (e.g., vertebrae)

What are the two bone textures?

1. Compact bone: Dense outer layer

2. Spongy (cancellous) bone: Honecomb of trabeculae

What is the structure of a long bone?

1. Diaphysis (shaft): Compact bone collar surrounds medullary (marrow) cavity; Medullary cavity in adults contains fat (yellow marrow)

2. Epiphyses: Proximal epiphysis & Distal epiphysis

   1. Expanded ends

   2. Spongy bone interior

   3. Epiphyseal line (remnant of growth plate)

   4. Articular hyaline) cartilage on joint surface

What are the two layers of the membranes of bone?

Periosteum & Endosteum

What is found in the Periosteum membrane of bones?

• Outer fibrous layer

• Inner osteogenic layer

  • Osteoblasts (bone-forming cells)

  • Osteoclasts (bone-destroying cells)

  • Osteogenic cells (stem cells)

• Nerve fibers, nutrient blood vessels, and lymphatic vessels enter the bone via nutrient foramina

• Secured to underlying bone by Sharpey’s fibers

What is found in the Endosteum of the membranes of bones?

• Delicate membrane on internal surfaces of bone

• Also contains osteoblasts and osteoclasts

What is the structure of short irregular, and flat bones?

• Periosteum-covered compact bone on the outside

• Endosteum-covered spongy bone within

• SPongy bone called diploe in flat bones

• Bone marrow between the trabeculae

What are/aren’t found in skeletal cartilage?

• Contain no blood vessels or nerves.

• Dense connective tissue girdle of perichondrium contains blood vessels for nutrient delivery to cartilage

What are the three types of skeletal cartilage and what are their functions?

1. Hyaline cartilages: Provide support, flexibility, and resilience (most abundant type) (e.g., costal cartilage, cartilages in the nose, articular cartilage of a joint)

2. Elastic cartilages: similar to hyaline cartilages, but contain elastic fibers (e.g., cartilage in external ear)

3. Fibrocartilages: Collagen fibers - have great tensile strength (e.g., meniscus)

What are the four cells of the bone? what are their functions?

1. Osteogenic (osteoprogenitor) cells: stem cells in periosteum and endosteum that give rise to osteoblasts

2. Osteoblasts: Bone-forming cells; Matrix-syntehsizing cell responsible for bone growth

3. Osteocytes: Mature bone cells that maintains the bone matrix

4. Osteoclasts: cells that break down (resorb) bone matrix

What are the microscopic anatomy of compact bone?

• Osteon: structural unit

  • Lamellae: weight-bearing, column-like matrix tubes

• Central canal: contains blood vessels and nerves

• Perforating canals

  • At right angles to the central canal

  • Connects blood vessels and nerves of the periosteum and central canal

• Lacunae: small cavities that contain osteocytes

• Canaliculi: hairlike canals that connect lacunae to each other and the central canal

What is the microscopic anatomy of the spongy bone?

• Trabeculae

  • Align along lines of stress

  • No osteons

  • Contains irregularly arranged lamellae, osteocytes, and canaliculi