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Functions of bones: Support
- Form internal framework that supports and anchors all soft organs.
- The bones of the legs act as pillars to support the body trunk when we stand.
- The rib cage supports the thoracic wall.
Functions of bones: Protection
- Protect soft body organs
- Such as the fused bones of the skull provide a snug enclosure for the brain.
- The vertebrae surround the spinal cord and The rib cage helps protect the vital organs of the thorax.
Functions of bones: Movement
Skeletal Muscles, attached to bones by tendons, use the bones as levers to move the body and its parts.
Functions of bones: Storage
- Fat is stored in the internal cavities of bones.
- Bone itself serves as a storehouse for minerals, the most important being calcium and phosphorus, although others are also stored.
- A small amount of of calcium in its ion form must be present in blood at all times for the nervous system to transmit messages, for muscles to contract, and for blood to clot.
- Because body's calcium is deposited in the bones they are a good place to get more as it is used up.
- Hormones control the movement of calcium to and from the bones and blood according to the needs of the body.
Functions of bones: Blood cell formation
- or Hematopoiesis
- Occurs within the marrow cavities of certain bones
Classification of bones: Compact bone
- Type of bone tissue
- Looks smooth and homogeneous
Classification of bones: Spongy bone
- Type of bone tissue
- Composed of small needle like like pieces of bone and lots of open space.
Classification of bones: Long bones
- Longer than they are wide
- Have a shaft with heads at both ends
- Mostly compact bone
- All the bones of the limbs are long bones except wrist and ankle bones
Classification of bones: Short bones
- Cube shaped
- Mostly spongy bone
- Bone of the wrist and ankles
- Sesamoid bone which form within tendons are a special kind of short bone
Classification of bones: Flat Bones
- usually curved
- Two thin layers of compact bone sandwiching a layer of spongy bone
- Most bones of the skull, the ribs, and the sternum
Classification of bones: Irregular bones
- Dont fit into the following categories
Structure of long one: Gross anatomy
- Diaphysis or shaft
- makes up most of the bone length
- composed of compact bone
- Covered and protected by a fibrous connective tissue membrane the periosteum.
- Epiphyses are the ends of the long bone
- Each epiphyses consist of a thin layer of compact bone enclosing an area filled with spongy bone.
- Articular Cartilage covers the external surface, and because it is glassy hyaline cartilage it provides a smooth, slippery surface that decreases friction at joint surfaces.
- Epiphyseal line is where there is bony tissue spanning the epiphysis
- the epiphyseal line is a remnant of the Epipphyseal plate ( a flat plate of hyaline cartilage) seen in young growing bone.
- Epiphyseal plate are the cause of the length wise growth of the long bone.
- Yellow marrow or Medullary Cavity is a storage area for adipose fat tissue but in infants this area forms blood cells and red marrow is found there.
- In adults red marrow is confined to the cavities of spongy bone of flat bones and the epiphyses of some long bones.
Structure of long bone: Microscopic anatomy
- Osteocytes are mature bone cells found in tiny cavities within the matrix called lacunae.
- Lacunae are arraged concentric circles called lamellae around central canals.
- Each complex consisting of centrl canal and matrix rings is called an Osteon.
- Central canals run lengthways through the bony matrix carrying blood vessels and nerves to all areas of the bone.
- Tiny canals, or canaliculi radiate outward from the central canals to all lacunae
- The canaliculi form a transportation system that connects all the bone cells to the utrient supply through the hard bone matrix.
- The comunication pathway from the outside of the bone to its interior is completed by
- Preforating canals which run into the compact bone at right angles to the shaft.
- Calcium salts deposited in the matrix give bone its hardness, where as the organic parts (esspecially collogen fibers) provide for bones flexibility and great tensile strength.
Role of bone salts and organic matrix
- Bone salts: Give bone its hardness
- Organic matrix: Provide for bones flexibility and tensile strength
- Tuberosity: large rounded projection, roughened
- Crest: narrow ridge of bone
- Trochanter: very large, blunt, irregular shaped process
- Line: narrow ride of bone, less prominent then crest
- Tubercle: small, rounded projection
- Epicondyle: raised area on or above condyle
- Spine: sharp, slender often pointed projection
- Process: any bony prominence
- Head: bony expansion
- Facet: smooth nearly flat articular surface
- Condyle: Rounded articular projection
- Ramus: Armlike bar of bone
- Meatus: Canal-like passageway
- Sinus: Cavity within a bone
- Fossa: Shallow, basin like depression
- Groove: Furrow
- Fissure: Narrow slitlike opening
- Foramen: Round or oval opening through bone
Bone formation, Growth, and Remodeling
- The skeleton is formed by two of the strongest and most supportive tissues in the body (cartilage and bone).
- In embryos the skeleton is mostly hyaline cartilage, but in a young child it has all been replaced by bone.
- Except for flat bones which form on fibrous membranes, most bones develop using hyaline cartilage structures as there "models"
- Ossification: bone formation
- Two major phases...first the hyaline cartilage model is covered with bone matrix by bone forming cells called osteoblasts....then the enclosed hyaline cartilage model digests away, opening up a medullary cavity within the newly formed bone.
- By birth all, most hyaline cartilage is replaced by bone except for two regions: articular cartilages, and epiphyseal plates.
- Articular Cartilages exist for life reducing friction at joints
- Epiphyseal plates provide for a longitudinal growth of the long bones during childhood
- Bones must widen has they lengthen they do this by osteoblasts in the periosteum, add bone tissue to the external face of the diaphysis as osteoclasts in the endosteum remove bone from the inner face of the diaphysis wall. This is called appositional growth.
- Bone are remodeled continuously because of to factors: Calcium levels in blood and the pull of gravity and muscles on the skeleton.
- Osteoclasts: giant bone-destroying cells i bones to break down bone matrix and release calcium ions into the blood.
- Fractures: breaks
- Closed or simple fracture: breaks cleanly and doesnt penetrate the skin
- Open or compound fracture: when broken bone end penetrate through the skin
- Comminuted: Bone breaks into many fragments
- Compression: Bone is crushed
- Depressed: Broken bone portion is pressed inward
- Impacted: Broken bone ends are forced into each other
- Spiral: Ragged break occurs because of excessive twisting
- Greenstick: bone breaks incompletly
- A fracture is treated by a reduction which is the relignment of the broken bone ends.
- Closed reduction: bone ends are coaxed back into position there position by the physitians hands.
- Open reduction: Surgery is performed and the bone ends are secured together with pins or wires.
- Then bone is out into a cast to imbolized to allow for the healing process.
Importance of intervertebral discs and spinal curvatures
- Intervertebral discs: help cushion vertebrae and absorb shock
- Spinal Curvatures: help prevent shock to head when walking/running, makes the body trunk flexible
Four major events involving the repair of bones
- A hemotoma is formed. Blood vessels are ruptured when a bone bone breaks. A blood filled swelling called a hemotoma forms. Bone cells deprived of nutrition die.
- The break is splinted by a fibrocartilage callus. Growth of new capillaries (granulation tissue), into the clotted blood at the site of the damage and the disposal of dead tissue by phagocytes. As this goes on, connective tissue cells of various types form a mass of repair tissue.
- The bony callus is formed. As osteoblasts and clasts migrate into the re and multiply, fibro cartilage is gradually replaced by a callus made of spongy bone (bony callus).
- Over the next few months, the bony callus is remodeled in response to the mechanical stresses placed on it, so that it forms a strong permanent "patch" at the fracture site.