lecture 1 test 2

What are the 6 main functions of the skeletal system

Support.

Protection of internal organs.

Assists body movements.

Mineral homeostasis (stores/releases calcium and phosphorus).

Blood cell production (hemopoiesis in red bone marrow).

Triglyceride storage (in yellow bone marrow).

What are the diaphysis and epiphyses of a long bone?

Diaphysis: The bone shaft (main long body).

Epiphyses: The two ends of the bone at the joints (proximal and distal).

What are the metaphyses, periosteum, endosteum, articular cartilage, and medullary cavity?

Metaphyses: Regions between the diaphysis and epiphyses (contains epiphyseal plate/line).

Articular Cartilage: Covers epiphyses to reduce friction.

Periosteum: Connective tissue sheath surrounding the diaphysis.

Medullary Cavity: Hollow space inside the diaphysis storing yellow marrow.

Endosteum: Thin membrane lining the medullary cavity.

What three components make up the bone extracellular matrix?

• 15% Water.

  
  

  
  

• 30% Collagen fibers (provides flexibility/tensile strength).

  
  

  
  

• 55% Crystallized mineral salts (hydroxyapatite: calcium phosphate + calcium hydroxide).

What are osteoprogenitor cells

Unspecialized bone stem cells (from mesenchyme); divide to form osteoblasts.

What are osteocytes

Mature bone cells trapped in matrix; maintain daily bone tissue metabolism.

Compare compact bone and spongy bone.

• Compact Bone: Composed of repeating structural units called osteons; strongest type; provides protection and support.

  
  

  
  

• Spongy Bone: Composed of an irregular lattice called trabeculae (no osteons); lightweight; supports red bone marrow.

How do periosteal and nutrient arteries enter a long bone?

• Periosteal Arteries & Nerves: Enter the diaphysis through Volkmann's (perforating) canals.

  
  

  
  

• Nutrient Artery: Enters the center of the diaphysis through the nutrient foramen.

  
  

  
  

• Epiphyses and metaphyses have their own dedicated arteries/veins.

In what 4 situations does bone formation (ossification) occur?

• Initial formation in embryo/fetus.

  
  

  
  

• Growth before adulthood.

  
  

  
  

• Bone remodeling throughout life.

  
  

  
  

• Repair of fractures.

What is the difference between intramembranous and endochondral ossification?

• Intramembranous: Bone replaces connective tissue membranes directly (forms flat bones of skull, cranial bones, and mandible).

  
  

  
  

• Endochondral: Bone replaces a hyaline cartilage model (forms most body bones/long bones).

What are the 4 zones of the epiphyseal plate from epiphysis to diaphysis?

• Zone of Resting Cartilage: Anchors plate to epiphysis.

  
  

  
  

• Zone of Proliferating Cartilage: Chondrocytes divide rapidly.

  
  

  
  

• Zone of Hypertrophic Cartilage: Chondrocytes mature and swell.

  
  

  
  

• Zone of Calcified Cartilage: Dead chondrocytes in calcified matrix replaced by bone.

How do bones grow in thickness/diameter?

• Osteoblasts in the periosteum deposit new circumferential lamellae on the outer surface.

  
  

  
  

• Osteoclasts in the endosteum break down bone, widening the medullary cavity from within.

What are the specific roles of Minerals, Vitamin A, Vitamin C, and Vitamin D?

• Calcium & Phosphorus: Harden matrix.

  
  

  
  

• Mg, F, Mn: Matrix formation and enzyme activation.

  
  

  
  

• Vitamin A: Supports osteoblast activity.

  
  

  
  

• Vitamin C: Essential for collagen synthesis.

  
  

  
  

• Vitamin D (Calcitriol): Increases calcium absorption from digestive tract.

  
  

• Vitamins K & B12: Needed for bone protein synthesis

How do GH, IGFs, sex hormones, and weight-bearing exercise affect bones?

• GH & IGFs: Stimulate osteoblasts and protein synthesis.

  
  

  
  

• Sex Hormones (Estrogen/Testosterone): Cause growth spurts; close epiphyseal plates around age 18–21.

  
  

  
  

• Exercise: Weight-bearing activities stimulate osteoblasts to build stronger, thicker bones.

What are the 3 phases of fracture repair?

• Reactive Phase: Early inflammation; formation of fracture hematoma.

  
  

  
  

• Reparative Phase: Fibrocartilaginous (soft) callus forms first, followed by a bony (hard) callus.

  
  

  
  

• Bone Remodeling Phase: Bony callus reshaped by osteoclasts/osteoblasts.

  
  

Define Open fracture

Ends break through skin.

How does the body respond when blood calcium drops?

• Parathyroid gland secretes Parathyroid Hormone (PTH).

  
  

  
  

• PTH stimulates osteoclasts to increase bone resorption.

  
  

  
  

• PTH causes kidneys to retain calcium in blood and produce calcitriol (active Vit D) to increase intestinal absorption.

What are Osteoporosis

Bone resorption outpaces deposition, decreasing bone mass (80% of cases affect women).

osteoblasts

Bone-building cells; secrete organic matrix and initiate calcification.

Osteomalacia

Inadequate matrix calcification in adults (causes bone tenderness/minor trauma fractures)

Rickets

Inadequate matrix calcification in children (causes bowed legs).

Comminuted fracture

Bone crushed/splintered into pieces.

greenstick fracture

Partial break (one side snaps, other bends); mostly in children.

Impacted fracture

One broken end driven forcefully into interior of other.

pott

Fracture of distal end of fibula.

colles

Fracture of distal end of radius (wrist displaced posteriorly).

Vertebral Compression

Vertebral body collapses into a wedge shape

Osteoclasts

Derived from white blood cell lineage (monocytes); have a ruffled border; perform bone resorption(breakdown of matrix)