The Skeletal System – Part I Learning Outcome C1

Student Achievement Indicators At the end of this learning outcome students should be able to: Describe the general structure of bone and the functions of its parts Explain the process of bone growth and repair Explain the causes, effects, symptoms and treatments of osteoporosis

Skeletal System Consists of bones, joints, cartilage and ligaments Bone tissue is living, but contains non-living minerals such as calcium and phosphorus Appears dead and dried up Contains 206 bones

Function Support weight Protect and support soft body organs With assistance from the muscles, allows the body to move Stores minerals such as calcium and phosphorus Bone marrow produces red blood cells

Size and Shape Reflect function Bones are classified in the following ways: Long bones – longer than wide (arms and legs) Short bones – shaped like cubes (ankles and wrists) Flat bones – thin, flat and curved (breastbone and skull) Irregular bones – unique shape (hip bone, vertebrae)

Bone Formation Known as osseous tissue Bone cells are called octeocytes Osteocytes secrete a matrix that contains calcium and other minerals. Bones contain protein that made bones elastic Minerals make bones hard Bone is the hardest type of connective tissue

Compact & Spongy Bone There are two type of osseous tissue: Compact bone – hard, dense, found in the shafts of long bones and on the outer surface of other bones. Made up of microscopic units called haversian systems Spongy bone – less dense, and located at the ends of long bones and in the centers of other bones.

Compact & Spongy Bone Spaces in the spongy bone are important for two reason: Decrease the weight of the bone Contain red bone marrow, which supplies the bone with blood and produces red blood cells.

Parts of a Long Bone Diaphysis Shaft of bone Made up of compact bone Designed for strength

Parts of a Long Bone Epiphyisis Epiphyseal Disc Enlarged ends of long bones Articulates with another bone at a joint Epiphyseal Disc Band of hyaline cartilage located a the ends of long bones between the epiphysis and diaphyisis Location of longitudinal growth

Parts of a Long Bone Medullary Cavity Periosteum Hollow center of diaphysis In infancy filled with bone marrow to form red blood cells Adults filled with yellow marrow, which functions in fat storage Periosteum Fibrous connective tissue that covers the diaphysis Provides point of attachment for muscle, and contain blood vessels for underlying bone.

Parts of a Long Bone Articular cartilage Outer surface of epiphysis and forms a smooth shiny surface that reduces friction at joints

Ossification Formation of bone Fetus – converts cartilage and connective tissue to bone Ossification begins with osteoblasts Osteoblasts secrete calcium and other minerals into spaces between connective tissue. Occurs when cartilage is replaced with bone Occurs in long bones until all cartilage is replaced by but articular cartilage.

Growing Taller Occurs at epiphyseal plants Growth continues as long as cartilage is formed at the epiphyseal plate. Growth stops when epiphyseal play become ossified Epiphyseal plat is sensitive to growth and sex hormones Growth hormones stimulate growth Sex hormones cause plate to fuse and growth to stop. Epiphyseal plate is very sensitive to estrogen, reason why girls are generally shorter An injured epiphyseal plate can stop growth Example – one leg longer than the other.

Growing Thicker and Wider Bones continue to grow in with even after they stop growing in length. Bones are constantly reshaped by osteoblast (bone-forming cells) and osteoclasts (bone-destroying cells). Osteoclasts break down old bone Osteoblasts lay down new bone Exercise helps promote bone growth because it keeps calcium in the bones.

Break vs. Fracture A compound fracture is a broken bone that pierced the skin. The ends of the bone usually cause extensive tissue damage Greater chance of infection

Greenstick Fracture An incomplete break in the bone Usually occurs in children Named after the bending of a young tree