CHAPTER 6-BONES AND SKELETAL TISSUES

I. Bone tissue is an ever-changing, growing, developing tissue in the human body. It serves as the major support tissue for the human body. A. Osteology
II. FUNCTIONS OF BONE TISSUE A. Support-bone provides a framework for the human body. It supports soft tissues and serves as a region for muscle attachment. B. Protection C. Movement-skeletal muscle attaches to and moves bones. D. Mineral Storage-bone is a reservoir for calcium and phosphate. On demand, bone tissue can release both of these minerals into the bloodstream for use in the human body. E. Blood Cell Production 1. Hemopoiesis (hematopoiesis)-the formation/production of blood cells. This process takes place in red bone marrow. F. Energy Storage 1. Yellow Bone Marrow-associated with bone. This material is composed of adipose tissue and scattered leukocytes. The adipose tissue serves as a source of energy for the human body.
III. ORGANIZATION OF THE SKELETAL SYSTEM A. The human skeleton is composed of 206 bones dispersed throughout the body. These bones are classified into two major skeletal divisions: 1. The Axial Skeleton-bones located along the central axis of the body. 2. The Appendicular Skeleton-bones of the extremities. b. Types of Bones in the Human Skeleton-based on shape. 1. Long Bones-are longer than they are wide. a. Are typically curved. The curvature acts to increase their strength which allows them to withstand great stress; thus reducing the chance of fracture. b. The Major Parts of a Long Bone: 1) Diaphysis-the shaft of the bone. 2) Epiphyses-the ends of the bone. These are covered and protected by hyaline cartilage. 3) Metaphysis-the region in a mature bone where the diaphysis meets the epiphysis. This region of the bone contains the epiphyseal plate-a region where cartilage is replaced by bone. The epiphyseal plate is involved in bone growth. 4) Hyaline (Articular) Cartilage-a layer of cartilage that covers the ends of a long bone. The cartilage serves as a shock absorber between bones. 5) Periosteum-a membrane that surrounds the surface of a bone. It is composed of 2 Layers: a) An outer fibrous layer that is composed of dense irregular connective tissue. This layer contains blood vessels, nerves and lymphatic vessels that pass into the bone. b) An inner osteogenic layer that contains elastic fibers, blood vessels and bone cells. c) Overall, the periosteum is involved in bone growth, repair and development. It also serves as a site of attachment for ligaments and tendons. 6) Medullary (Marrow) Cavity-an open space within the diaphysis of a bone. It contains yellow bone marrow. 7) Endosteum-a membrane that covers and lines the medullary cavity of a bone. It contains 2 specialized types of bone cells: osteoprogenitor cells and osteoclasts. 2. Short Bones-are cube-shaped. These are composed of spongy bone tissue except for an outer layer of compact bone tissue. The carpals and tarsals are examples of short bones. 3. Flat Bones-are very thin bones. The cranial bones, sternum and ribs are flat bones. a. These are composed of 2 plates of compact bone tissue that encloses a layer of spongy bone. These bones provide considerable protection and they offer a great surface area for tendon and ligament attachment. 4. Irregular Bones-have complex shapes. The vertebrae of the spinal column and some facial bones are classified as irregular bones. 5. Sesamoid Bones-small bones embedded in tendons in the body. The patella is an example.
IV. HISTOLOGY OF BONE TISSUE A. Overall, bone tissue is composed of 4 types of cells that are embedded in a thick,