Bones

  • support - form the framework that supports the body and cradles soft organs; it protects internal 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

  • calcium phosphate = salt

  • Blood Cell formation - hematopoiesis occurs within the marrow cavities of bones

  • long bones - longer than they are wide

  • short bones - cube shaped bones (ie wrist and ankle bones)

  • flat bones - thin, flattened, and a bit curved (ie - sternum, and most skull bones)

  • irregular bones - bones with complicated shapes (ie - vertebrae and hip bones)

  • compact bone - dense outer layer

  • spongy bone - honeycomb of trabeculae filled with red bone marrow

  • Osteon - structural unit of compact bone

  • osteons together form compact bone

  • spongy bone tissue: NO osteons; open framework of interconnecting calcified rods

  • Red bone marrow makes blood cells (hematopoeisis)

  • yellow bone marrow consists of adipose cells

  • red bone marrow found in spongy bone

  • spongy bone is mainly found in the ends of long bones and also flat bones (middle of)

  • Diaphysis - tubular shaft that forms the axis of long bones

  • diaphysis is composed of compact bone that surrounds the medullary cavity (contains yellow bone marrow)

  • Epiphyses - the end of long bones

  • Epiphyses - expanded ends of long bones, exterior is compact bone, and the interior is spongy bone, joint surface is covered with articular or hyaline cartilage

  • hyaline cartilage provides support, resilience, and is the most abundant cartilage type

  • hyaline cartilage is present in these areas: articular which covers the ends of long bones, costal which connects the ribs to the sternum, respiratory which makes up the larynx and reinforces air passages, and nasal which supports the nose

  • the structure of short, irregular and flat bones is thin plates compact bone on the outside covering spongy bone on the inside, they have no diaphysis or epiphyses, contain red bone marrow in the spongy bone

  • Bone markings: bulges, depressions, and holes that serve as: sites of attachment for muscles, ligaments, and tendons, joint surfaces, conduits for blood vessels and nerves

  • Inorganic - hydroxyapatite, or mineral salts; mainly calcium phosphates which makes bone hard, responsible for bone hardness and its resistance to compression

  • Organic: osteoblasts; bone-forming cells (they form new bone), osteocytes; mature bone cells, Osteoclasts; large cells that resorb or break down bone matrix (break down existing bone

  • formation of the bony skeleton begins at week 8 of embryo development

  • intramembraneous ossification - bone develops from a fibrous membrane. Formation of most of the flat bones of the skull and the clavicles

  • endochondrial ossification - bone forms by replacing hyaline cartilage. Begins in the second month of development. Growth by all bones except most bones of the skull and clavicles. Presence of growth plate.

  • most bones grow through the process of using a growth plate

  • growth plate is made of hyaline cartilage

  • if growth plate is closed no hyaline cartilage and it is all bone marrow, no further growth

  • during infancy and childhood, epiphyseal plate activity is stimulated by growth hormone. main cells target bone and skeletal muscle. produced by anterior pituitary

  • during puberty, by testosterone and estrogens. initially promote adolescent growth spurts. later induce epiphyseal plate closure, ending longitudinal bone growth. stimulate growth of a bone primarily in length

  • signal end of bone growth at the end of puberty

  • bone is constantly making and breaking bone

  • bones are constant throughout life

  • early years: D > R

  • adolescence: D ~ R

  • adulthood and old age: R > D

  • bone decomposition is accomplished by osteoblasts

  • bone reabsorption is accomplished by osteoclasts

  • two control loops regulate bone remodeling, hormonal mechanism that maintains calcium homeostasis in the blood. mechanical and gravitational forces acting to the skeleton

  • calcium is necessary for transmission of nerve impulses, muscle contraction, blood coagulation, secretion by glands and nerve cells, and cell division

  • rising CA2+ levels trigger the thyroid to release calcitonin

  • calcitonin stimulates calcium salt deposit in bone

  • falling blood CA2+ levels signal the parathyroid glands to release PTH

  • PTH signals osteoclasts to degrade bone matrix and release CA2+ into the blood

  • Wolff’s law - a bone grows or remodels in response to the forces or demands placed upon it

  • where ever bone feels the most force, your going to deposit more bone there

  • bone fractures are classified by: the position of the bone ends after fracture. Completeness of the break. the orientation of the bone to the long axis. whether or not the bones ends penetrate the skin.

  • nondisplaced: bone ends retain their normal position

  • displaced: bine ends are out of normal alignment

  • complete: bone is broken all the way through

  • incomplete: bone is not broken all the way through

  • linear: fracture is parallel to the bone long axis

  • transverse: fracture is perpendicular to the bone long axis

  • open: bone ends penetrate the skin, goes out, breaks into skin, can see with the naked eye

  • closed: bone ends do not penetrate the skin

  • ligaments: connect bones together at joints

  • ligaments connect bone to bone

  • ligament under microscope is dense regular connective tissue proper