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Skeletal System Functions of Bone • Major Functions: – Protection – Support – Movement • Minor Functions (though no less important!): – Mineral storage – Mineral homeostasis – Hematopoesis Skeletal Anatomy • Gross Skeletal Anatomy: • Anatomy of Bone: Gross Skeletal Anatomy Anatomy of Bone Types of Bone • Bone Tissue: – Compact – Spongy • Bone Shape: – – – – Long Flat Short Irregular Types of Bone • Compact Bone: • Spongy Bone –Dense –Homogenous –Composed of small pieces of bone and lots of space Types of Bone (Labeling) • Long Bone • Flat Bone Types of Bone • Irregular Bone • Short Bone Types of Bone Practice! Types of Bone (Characteristics) • Long Bone: – Typically longer than they are wide. – Typically have a shaft with heads at both ends – Mostly compact bone – Examples: bones of the limbs (except bones and ankles!) • Short Bones – Typically cube shaped – Mostly spongy bone – Examples: bones of wrist and ankles Types of Bone (Characteristics) • Flat Bones – Thin, flattened, usually curved – Two layers of compact bone sandwiching spongy bone in between – Examples: skull, ribs, sternum, scapula • Irregular Bones – Bones that do not fall into previous three categories – Examples: pelvis, vertebrae Bone Growth and Formation • Babies: • Adults: Bone Growth and Formation • Babies • Adults – Embryo: hyaline cartilage – Infant: mostly bone – Almost entirely bone – Isolated cartilage remains (nose, ear, etc) – Fibrous membranes connecting flat bones – Flat bones replace connective membranes Bone Growth and Formation • Bones use cartilage as “models” during bone formation (ossification) • Ossification happens in two steps: – Hyaline cartilage model is superficially covered with bone matrix by osteoblasts – Hyaline cartilage is broken down, leaving behind an empty, medullary cavity. Ossification Ossification Cont’d • After birth, only two regions of cartilage remain: articular cartilages and epiphyseal plates Bone Remodeling • Bones change as the body grows. Why is this necessary? • As the body changes in size and weight, our bones must compensate for the additional mass. Additionally, bones become thicker and form projections where bulky muscles attach. Bone Remodeling occurs in response to two factors: • Blood Calcium Levels • Pull of gravity and Calcium, PTH – PTH activates osteoclasts, which break down bone to release Calcium – – Calcium, Calcium is deposited in bones for storage – Determines when skeleton is remodeled muscles on the skeleton – Determines where skeleton is remodeled Healing a Bone • Occurs in 4 Steps: – Hematoma is formed – Break is splinted by fibrocartilage – Bony callus is formed – Bone remodeling occurs Healing a Bone Axial Skeleton • Skull, vertebral column, bony thorax Appendicular Skeleton • Bones of the limbs and girdles
