MPP: BLOCK 2: LOWERY: SKELETAL/BONE PHYS. & PHARM (PART 2 OF 4)

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Questions and Answers

What is a primary cause of bone mass accrual?

Increased bone resorption

Increased osteoblast activity (correct)

Increased osteoclast activity

Decreased osteoblast activity

What is a potential consequence of increased osteoclast activity?

Bone mass loss (correct)

Bone mass gain

Enhanced bone healing

Increased bone density

What regulates osteoclastogenesis?

Collagen and elastin

Calcium and vitamin D

RANKL and OPG (correct)

Estrogen and testosterone

What underlies osteopetrosis?

Defects in osteoclastogenesis or function Signup and view all the answers

What enzyme is secreted by activated osteoclasts that aids in bone matrix degradation?

Carbonic anhydrase Signup and view all the answers

High bone mass does not necessarily correlate with what?

Low fracture risk Signup and view all the answers

What do osteoclasts produce that plays a role in bone resorption?

Proteases and acid Signup and view all the answers

Which of the following represents the outcome of decreased osteoblast activity?

Bone mass loss Signup and view all the answers

Which cell type is primarily responsible for bone resorption?

Osteoclasts Signup and view all the answers

What is the formula that represents the relationship between bone mass and its formation and resorption rates?

Bone mass = formation rate - resorption rate Signup and view all the answers

Which of the following best describes the role of Sclerostin in bone physiology?

Inhibits osteoblast activity Signup and view all the answers

What effect does Growth Hormone have on bone formation?

Increases osteoblast proliferation Signup and view all the answers

What underlying condition is characterized by low bone mass and deterioration of bone tissue?

Osteoporosis Signup and view all the answers

Which statement best describes the impact of osteoblasts on osteoclastogenesis?

Osteoblasts regulate osteoclast formation via signaling molecules Signup and view all the answers

Which guidelines should be followed for initiating pharmacotherapy for osteoporosis?

NOF guidelines Signup and view all the answers

How is osteoporosis typically diagnosed?

Bone density scans and clinical assessment Signup and view all the answers

What is the equation used to represent bone mass?

Bone mass = formation rate - resorption rate Signup and view all the answers

Which statement accurately describes the coupling of bone matrix remodeling?

Bone matrix remodeling is coupled with specific cell functions. Signup and view all the answers

Which of the following cell types is primarily responsible for bone formation?

Osteoblasts Signup and view all the answers

What primarily happens to bone volume during remodeling?

Bone volume increases on surfaces. Signup and view all the answers

Which characteristic is associated with spongy bone?

Trabecular configuration Signup and view all the answers

Where do the majority of microcracks in bone typically occur?

In interstitial lamellae Signup and view all the answers

Which statement about bone matrix remodeling is incorrect?

It results in the complete loss of bone matrix. Signup and view all the answers

What role do serum markers like CTx and P1NP play in bone health?

They serve as indicators of bone turnover. Signup and view all the answers

What is the effect of low gonadal estrogen levels in post-menopausal women on bone resorption?

Increases bone resorption Signup and view all the answers

What is the impact of parathyroid hormone (PTH) on RANKL and OPG expressions?

Increases RANKL and decreases OPG Signup and view all the answers

What role do osteoclasts play in bone metabolism?

Degrade bone matrix Signup and view all the answers

How does primary hyperparathyroidism affect bone mass?

Promotes osteoclastogenesis Signup and view all the answers

Which drug targets osteocyte-derived protein?

Denosumab Signup and view all the answers

Which cell lineage do osteoblasts originate from?

Osteoprogenitor Signup and view all the answers

What is the primary function of osteocytes in bone health?

Maintain mineral homeostasis Signup and view all the answers

Which type of osteoporosis is primarily associated with reduced estrogen levels?

Post-menopausal osteoporosis Signup and view all the answers

Study Notes

Bone Remodeling

There are four major bone cell types: osteoblasts, osteocytes, osteoclasts, and bone lining cells.
Bone matrix remodeling occurs continually.
Bone mass is affected by the formation rate and resorption rate: Bone mass = formation rate – resorption rate
Bone matrix remodeling is coupled: Osteoblast and osteoclast activity are synchronized.
Specific cell types perform specific roles in the process of bone matrix remodeling, including:
- Osteoblasts synthesize new bone matrix.
- Osteocytes are embedded in the bone matrix and act as mechanosensors, regulating bone remodeling.
- Osteoclasts degrade bone matrix.
- Bone lining cells cover the bone surface.

Bone Structure

Compact bone (cortical bone) is the denser, outer layer of bone.
Spongy bone (trabecular bone or cancellous bone) is a porous, less dense bone found inside the compact bone.

Bone Remodeling Markers

Serum markers of bone turnover include Collagen I fragments (CTx) for resorption and Collagen I propeptide (P1NP) for formation.

Bone Math

Increased bone mass can be caused by increased osteoblast activity, decreased osteoclast activity, or both.
Decreased bone mass can be caused by decreased osteoblast activity, increased osteoclast activity, or both.

Osteoclasts

Osteoclasts are multinucleated cells derived from the monocyte/macrophage lineage.
Osteoclasts degrade the bone matrix by releasing proteases and acid.
Diseases that affect osteoclastogenesis and/or function can lead to osteopetrosis, characterized by dense bones that are prone to fracture.
Osteoclastogenesis is regulated by the actions of RANKL and OPG, both of which are produced by osteoblasts.

Osteoporosis

Estrogen is a potent inducer of osteoclast apoptosis, and it also reduces RANKL-dependent differentiation.
Low levels of estrogen in post-menopausal women may lead to increased bone resorption.
Hyperparathyroidism, in which parathyroid hormone (PTH) levels are abnormally high, leads to increased RANKL expression and decreased OPG expression, resulting in hypercalcemia and bone loss.

Bone Cell Types

Osteoblasts are responsible for bone matrix secretion.
Osteocytes act as mechanosensors and regulate mineral homeostasis.
Osteoclasts degrade bone matrix.

Bone Cell Targeting Drugs

Bisphosphonates, denosumab, and romosozumab target osteoclasts.
Teriparatide and abaloparatide target osteoblasts.

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Description

Explore the intricate processes of bone remodeling, including the roles of various bone cell types such as osteoblasts and osteoclasts. Understand the differences between compact and spongy bone and learn about the markers used to evaluate bone turnover. This quiz covers essential concepts in skeletal biology.