Bone Physiology

Front 1

describe how calcitonin reduces serum calcium concentrations

Back 1

Descreases serum Ca levels. Most important in growing children. Comes from Parafollicular C cells.

Front 2

Describe Bone modeling and how it affects bone shape

Back 2

as the skeleton grows and enlarges (modeling) bone formation predominates. Bone shape is directly affected by the process occurring at the time. More bone is synthesized in areas of increased stress

Front 3

Describe the process of haversian system remodeling

Back 3

sequence takes 8 months to occur. Osteoblasts secrete an enzyme which breaks down the osteoid. osteoblasts attract the clasts, which resorb new bone. osteoblasts form new osteoid and become trapped in the matrix and become osteocytes. Osteoblasts transformation to osteocytes takes 3 days.

Front 4

Describe how Vit D influences bone metabolism

Back 4

Increases the flux of calcium into the bones. Direct effect is to mobilize calcium out of bones. Osteoblasts produce alkaline phosphatase, collegenase, and plasminogen activator.

Front 5

Discuss the principle actions of PTH, Calcitonin, Vit D in intestine, Kidney, and bone

Back 5

PTH: the target cell in bones is osteoblast, acting on PTH 1R, a G protein linked receptor to adenylate cyclase. The receptor in the kidney and bone is identical. In the kidney, PTH increases phosphate secretion
Calcitonin: inhibits osteoclast fxn
VitD: Increases ca flux to bones. acts on small intestine and kidney to increase Ca reabsorption. induces the synthesis of Ca channels in the intestine

Front 6

Discuss the Dx tools to find short stature

Back 6

Consider Serum IGF1 levels, provocative tests of pituitary FXN. CBC, Sed Rate, antiGliaden IGG titers, Ft4 and TSH. Serum Transferrin and prealbumin for malnutrition.

Front 7

Discuss the MOA and clinical use of estrogens and raloxifene in the prevention and tx of osteoporosis

Back 7

Steroid hormones diffuse across the cell and bind to specific nuclear proteins. activated estrogen receptor complex interacts with nuclear chromatin to initiate RNA synthesis. The bone sparing effects of estrogen are thought to be mediated through an immune signaling molecule released by T cells, TGFB.
Reloxifene is a SERN mediated through estrogen receptors. Reduce the rate of bone loss at menopause and increase BMD.

Front 8

Explain how estradiol affects bone metabolism during different stages of reproductive life

Back 8

Estrogen is believed to have anti-reabsorption effects mediated through immune signaling molecules released by T cells. Estrodiol is important in M and F to develop and maintain bone density. mediates epiphyseal closure. Decrease in estrogen levels during menopause allow for large increases in bone reabsorption.

Front 9

Understand the normal growth of the newborn, infant, and child. Be able to identify changes in growth velocity

Back 9

The idea here is to be able to follow a growth chart

Front 10

Describe mechanisms for hypercalcemia associated with malignancy

Back 10

Caused by PTHrP solid tumors adult T cell leukemia syndrome. vit D secreting lymphomas, osteolytic hypercalcemia, multiple myeloma, leukemia, lymphoma. Enhanced bone resorption is primary mechanism.

Front 11

Describe the use of serum calcium and PTH for the DX of patients with hyper and hypocalcemia

Back 11

if the PTH is high - then its primary hyperparathyroidism causing the hypercalcemia. If the PTH is low and the calcium is low, then its primary hypoPTH. If the PTH is high and the calcium is low, then its secondary hyperPTH. if PTH is low and Calcium is High, then its Secondary HypoPTH

Front 12

Describe the bound and unbound forms of calcium and know the relative amnts normally found, and describe the relationship of serum calcium and albumin

Back 12

45% free ionized CA
45% bound to protein
10% bound to small organic anions
Increases in protein are associated with increases in total calcium

Front 13

Describe in detail the distribution of calcium in the human body and the levels of calcium in the individual compartments.

Back 13

99% of Ca is in bones and teeth
1% is available to buffer plasma changes.
total blood calcium is 10mg/dl

Front 14

Describe how calcium balance is maintained by the interaction of dietary calcium, ECF, bone, and excretion in both urine and feces

Back 14

350mg of Ca is absorbed from the GI tract by Vit D(by changind the binding of calmodulin to the brush border myosin which increases Ca uptake from the lumen.
ECF: ca gradient across the cell membrane is maintained by a Ca atpase, induced by VitD
Bone: Ca provides a rapid buffering to keep ca ion concentration in the ECF from rising to excessive lebels or falling to very low levels.
Urine: PTH increases Ca reabsorption. 800mg/day excreted ca in feces

Front 15

List the major fxns of phosphate and the major chemical forms in the body

Back 15

involved in glycolysis and respiration that synthesize ATP. Enzyme cofactors such as NAD, and energy regulators such as cyclic nucleotides, kinases, transcription factors. also in bone. Major forms: Nucleic acids, membrane phospholipids, phosphoproteins, intermediates of CHO metabolism, in serum, almost exclusively as free ion or associated with cation.