ch 6.txt

• 1 - support
• 2 - protection
• 3 - mineral homeostasis
• 4 - blood cell production
• 5 - assistance in movement
• 6 - TRIglyceride Storage

• bone tissue acts as a reservoir of critical minerals
• - 99% of body's CALCIUM is stored here
• - PHOSPHORUS stored here

calcium phosphate

• 25% H20
• 25% collagen fibers
• 50% crystallized MINERAL salts

surrounds external bone surface

surrounds interior lining of bone surface facing the medullary cavity

marrow cavity - cylindrical space within the diaphysis - contains yellow bone marrow

bone's shaft or body

proximal or distal ends of bone

• Osteogenic Cells: undergo cell division, resulting cells develop into osteoblasts
• Osteoblasts: bone building cells, synthesize extracellular matrix of bone tissue
• Osteocytes: mature bone cells that exchange NUTRIENTS and WASTES with the blood
• Osteoclasts: release enzymes that digest mineral components of bone matrix - RESORPTION

arrangements of components of compact bone

run longitudinally through bones

rings around central canals

• small spaces between Lamellae
• contain OSTEOCYTES

filled with extracellular fluid, radiate in all directions from the LACUNAE

run perpendicular to central canals

LACKS osteons - lamellae are arranged around thin columns called TRABECULAE

They are oriented around lines of STRESS

• Periosteum is rich in sensory nerves sensitive to TEARING or TENSION
• Endosteum very vascularized

• process of bone formation, four types of occurances
• 1 - formation of bone in an embryo
• 2 - growth of bones until adulthood
• 3 - remodeling of bone
• 4 - repair of FRACTURES

• Follows one of 2 pathways,
• Intramembranous ossification: Flat bones of the skull and mandible are formed this way. Soft spots help fetus skull pass thru birth canallater become ossified
• Endochondral ossification: replacement of CARTILAGE by bone, most bones of the body are formed in this way, ie long bones

• bone forms within the hyaline cartilage
• 1 - hyaline cartilage develops
• 2 - know primary ossification center (in diaphysis)
• 3 - secondary ossification center (in epiphysis)
• 4 - articular cartilage forms around edges of bone

• involves 2 events
• 1. growth of cartilage on Epiphyseal plate
• 2. replacement of cartilage by bone tissue in epiphyseal plate
• - osteoclasts dissolve calcified cartilage and osteoblasts lay down the bone matrix
• - below epiphyseal plate is ossified bone, above is the cartilage prior to replacement by bone

when in adulthood bone replaces the cartilage of the epiphyseal line, leaving a bony structure, called the epiphyseal plate

• bone forms before birth and continually RENEWS itself
• ongoing replacement of old bone tissue by new bone tissue
• old bone is continuously destroyed and new bone is formed in its place throughout someone's life

• in osteoporosis, there is a loss of calcium which weakens the bones
• in osteomalacia, bone becomes to flexible (also in rickets)

• mostly calcium and phosphorus
• small amounts of Magnesium (Mg), Fluoride (Fl) and Manganese

• Vit A: stimulates osteoBLAST activity
• Vit C: needed for COLLAGEN synthesis
• Vit D: increasing absorption of Calcium from foods in GI tract into the blood
• Vit K and B12: helpful for synthesis of bone proteins

• IGFs (growth factors): produced by liver stimulate osteoblasts, promote cell division at epiphyseal plate and enhance protein synthesis
• Thyroid hormones: stimulate Osteoblasts
• Insulin: increases synthesis of bone proteins
• Estrogen & Testosterone: cause a SHUT down of growth at epiphyseal plate

• calcitonin is secreted by Thyroid gland. It works to decrease Ca in the blood by INHIBITING osteoclast activity. It also promotes bone Formation
• Parathyroid Hormone (PTH) works to INCREASE blood Ca by breaking down bone (osteoCLAST activity). PTH also acts on kidneys to decrease loss of Ca in urine

this is when there are LOW Ca levels in the blood…so to help this condition, Parathyroid hormone works to help INCREASE blood CA levels

• broken end of bone comes out through skin
• Muscle loss occurs

Does not break thru skin

bone splintered, crushed or broken into pieces

partial fracture with one side of bone broken and other side BENDS

One end of the fractured bone is forcefully driven into another

• 1. Formation of a Fracture HEMATOMA: blood leaks from torn ends of blood vessels, a clotted mass of blood forms around site of fracture
• 2. FibroCARTILAGINOUS Callus formation: fibroblasts invade fracture site and produce collagen fibers…bridging the broken ends of bone
• 3. BONY Callus formation: osteoblasts begin to produce SPONGY bone
• 4. Bone Remodeling: Compact bone replaces Spongy Bone

Nerve and Muscle cells

Bone tissue becomes stronger through Mineral salts deposition and production of collagen fibers by osteoblasts

• As you get older and level of sex hormones diminishes, there is a DECREASE in bone mass.
• Bone resorption by Osteoclasts outpaces bone deposition by osteoblasts
• Loss of bone mass in old age has a larger affect in FEMALES than males.

• 1. Loss of Bone Mass: results from loss of Ca from bone matrix (a symptom in osteoporosis)
• 2. Brittleness: results from a decreased rate of Protein Synthesis. Collagen fibers give bone its tensile strength so when this is lost, the bones become BRITTLE and susceptible to fracture.