-
FXNS of bone and skeletal system
- 1 - support
- 2 - protection
- 3 - mineral homeostasis
- 4 - blood cell production
- 5 - assistance in movement
- 6 - TRIglyceride Storage
-
role and facts of mineral homeostasis
- bone tissue acts as a reservoir of critical minerals
- - 99% of body's CALCIUM is stored here
- - PHOSPHORUS stored here
-
most abundant mineral salt in bone tissue
calcium phosphate
-
extracellular matrix components
- 25% H20
- 25% collagen fibers
- 50% crystallized MINERAL salts
-
periosteum
surrounds external bone surface
-
endosteum
surrounds interior lining of bone surface facing the medullary cavity
-
medullary cavity
marrow cavity - cylindrical space within the diaphysis - contains yellow bone marrow
-
diaphysis
bone's shaft or body
-
epiphysis
proximal or distal ends of bone
-
types of cells present in bone tissue
- 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
-
Osteons or Haversion Systems
arrangements of components of compact bone
-
central canals
run longitudinally through bones
-
concentric LAMELLAE
rings around central canals
-
LACUNAE
- small spaces between Lamellae
- contain OSTEOCYTES
-
CanaliCULI
filled with extracellular fluid, radiate in all directions from the LACUNAE
-
perforating canals
run perpendicular to central canals
-
Spongy bone
LACKS osteons - lamellae are arranged around thin columns called TRABECULAE
-
Trabeculae location
They are oriented around lines of STRESS
-
Blood and nerve supply
- Periosteum is rich in sensory nerves sensitive to TEARING or TENSION
- Endosteum very vascularized
-
OSSIFICATION
- 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
-
Formation of bone in an EMBRYO
- 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
-
Endochondral ossification process
- 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
-
Bone Growth in Length
- 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
-
epiphyseal line
when in adulthood bone replaces the cartilage of the epiphyseal line, leaving a bony structure, called the epiphyseal plate
-
REmodeling of bone
- 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
-
Osteoporosis and Osteomalacia
- in osteoporosis, there is a loss of calcium which weakens the bones
- in osteomalacia, bone becomes to flexible (also in rickets)
-
Minerals in bone
- mostly calcium and phosphorus
- small amounts of Magnesium (Mg), Fluoride (Fl) and Manganese
-
Vitamins that are helpful for bone growth
- 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
-
Hormones affecting bone growth
- 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 and PTH role in bone formation/resorption
- 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
-
hypocalcemia
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
-
Open (Compound) Fracture
- broken end of bone comes out through skin
- Muscle loss occurs
-
Closed (Simple) Fracture
Does not break thru skin
-
Comminuted Fracture
bone splintered, crushed or broken into pieces
-
Greenstick fracture
partial fracture with one side of bone broken and other side BENDS
-
Impacted Fracture
One end of the fractured bone is forcefully driven into another
-
Steps to repair a bone fracture
- 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
-
What cells need Ca to function properly
Nerve and Muscle cells
-
Bone Strength when under STRESS
Bone tissue becomes stronger through Mineral salts deposition and production of collagen fibers by osteoblasts
-
Aging and Bone Tissue
- 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.
-
2 Effects of Aging on Bone Tissue
- 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.
|
|