Metabolic Bone Disorders Flashcards
Define Osteopenia- when does this occur?
Decreased bone density or increased radiolucency of bone (darker radiographically)
Occurs when bone reabsorption exceeds bone formation
Is osteopenia a precise diagnosis?
NO it is just a descriptive term
Osteopenia is the opposite of…
Osteosclerosis
What are the major causes of diffuse osteopenia
Osteoporosis
osteomalacia/rickets
hyperparathyroidism (HPT)
Neoplasm (ex lymphoma)
Where would we commonly find hyper para-thyroidism?
look to the hands
Considering neoplasm for the reason of bone destruction what would (1) a child with osteopenia most likely have and (2) what would an adult with osteopenia most likely have?
Child with osteopenia most likely has leukemia
Adult with osteopenia most like would have multiple myeloma
Do see bone density changes where is the best place to look?
Usually you want to look some where other than the spine to find bone density changes
What are the 5 bone cells?
Osteoprogenitor Osteoblast Osteocyte Bone Lining Cells Osteoclasts
Where are osteoprogenitor cells formed and what do they develop into?
From marrow stem cells
Develop into osteoblasts
What do osteoblasts produce?
When does it decrease in number?
Osteoid = SOFT material
90-95% collagen
Ground substance = mucopolysaccharides
*Osteblasts begin numerous and large in size - but they decrease in size and number at maturity which is about 21 years old
OsteoCYTE
- Who do they arise from?
- What is their function?
- What qualities do they have?
Arises from osteoblasts that become entrapped in their own osteoid
- They maintain the integrity of surrounding bone; connected through cannuliculij - they can reabsorb bone
- they are considered a mature bone cell
- both osteoclastic and plastic qualities
Which bone cell is considered the mature bone cell?
Osteocyte
Osteoclasts
- function?
- Derived from?
Bone resorptive cells
Derived from hematopoietic monocyte linage (macrophages from the same lineage - also have the ability to resorb bone)
Osteoprogenitor, osteoblast, osteocyte and bone lining cells all arise from the same linage T/F
True
Bone is in a constant state of turn over T/F
True
Water makes up ____% of bone weight
20%
Organic Matrix/osteoid is made up of ____% of _______ and ____% of ______.
Organic Matrix/osteoid is made up of 30% collagen and 10% mucopolysaccharide.
Organic matrix/osteoid make up ____ % of the dry weight of bone.
30%
Inorganic materials are minerals they make up ___% of dry weight of bone/
70%
Bone quality ratio is comparing
Matrix (30%) : Mineral (70%)
Inorganic minerals in bone are
Ca10 (Po4)6OH aka calcium hydroxyapatite
Skeletal bone contains ___% of calcium as serum calcium
99%
What two mechanisms does bone play in calcium homeostasis?
- percentage of calcium they work with
- which one is more predominate way of maintaining calcium hemostasis?
1) continuous exchange of calcium ions between the bone and ECF (70%)
2) Mediated PREDOMINANTLY by ParaThyroid Hormone and other hormones (30%)
If someone is hypocalcemia this stimulates the rebase of Ca++ from______.
Bone
If someone is hypercalcemic this produces an influx of Ca++ into _____ form the _____.
Into the bone
From the ECF
Where do osteoclasts exist in bone?
On the bone surface in pits known as, HOWSHIP LACUNA
Explain the mechanisms of Osteoclasts
Osteoclasts secrete acid to break down bone
This unit of acid is hydroxyapatite and collagenase - this will break down osteoid
Then they secrete substance to attract and promote osteoblast function
What stimulates activity of osteoclasts
Parathyroid hormone VitD metabolites Prostaglandin E2 Thyroid hormone Heparin
What inhibits activity of osteoclasts
calcitonin and estrogen
What mineralizes osteoblasts once they produce osteoid/matrix
calcium hydroxyapatite
Osteoblast activity is stimulated by
calcitonin
Scurvy is a result of what vitamin deficiency
Vitamin C
Vitamin C is required for ______ formation
collagen
What is the result of scurvy on bone density?
Scurvy will cause you to have osteopenia via osteoporosis
List the normal physiological needs for normal bone density requirements
Weight bearing exercise normal nervous system function normal GI function (ca++ absorption) Normal liver function (hydroxylations) Normal Renal functions Dietary Ca++ and Phosphate Normal endocrine function (need to have PTH****)
Why is osteoporosis NOT a bone softening disease
Because in osteoporosis the quality of the bone is normal - it is just the quantity that is not normal - there is not enough cortical or trabecular bone
T/F Osteoporosis is the most frequent metabolic bone disease in humans
true
______% bone loss before radiographic detectability
30 - 50%
Bone loss in the spine is only noticeable at ____% loss because
50% loss because its mostly trabecular
Bone loss in extremities is only noticeable at ____% loss
30%
What two places does osteoporosis predominate?
Axial Skeleton and proximal long bones
