Chapter 6: Skeletal System and Bone Development

Support

Bone provides hard structure; cartilage offers flexibility.

Ligaments

Connect bone to bone, allowing limited movement.

Protection

Bones shield vital organs from injury.

Movement

Muscles pull on bones via tendons for movement.

Storage

Bones store calcium, phosphate, and adipose tissue.

Blood Cell Production

Bone marrow produces blood cells and platelets.

Cartilage Types

Includes hyaline, fibrocartilage, and elastic cartilage.

Chondroblasts

Cells that form and secrete cartilage matrix.

Chondrocytes

Mature cartilage cells found in lacunae.

Matrix

Collagen fibers provide strength; proteoglycans add flexibility.

Perichondrium

Dense connective tissue covering cartilage, except joints.

Articular Cartilage

Hyaline cartilage at joints, facilitating smooth movement.

Appositional Growth

Cartilage expands by adding new matrix at edges.

Interstitial Growth

Cartilage lengthens as chondrocytes divide and add matrix.

Bone Matrix Composition

Organic (35%) collagen; inorganic (65%) hydroxyapatite crystals.

Osteoblasts

Bone-forming cells responsible for ossification.

Osteocytes

Mature bone cells maintaining bone matrix.

Osteoclasts

Cells that break down bone tissue via resorption.

Woven Bone

First bone type formed, collagen fibers randomly oriented.

Lamellar Bone

Mature bone organized in sheets for strength.

Spongy Bone

Contains trabeculae, filled with marrow, covered by endosteum.

Trabeculae

Interconnecting rods of bone providing structural support.

Compact Bone

Dense outer layer with more matrix than spongy bone.

Osteon

Functional unit of compact bone, arranged in concentric rings.

Haversian Canal

Central canal containing blood vessels in osteons.

Perforating Canal

Connects Haversian canals, oriented perpendicular to bone axis.

Diaphysis

Shaft of long bone, primarily compact bone.

Epiphysis

Ends of long bone, primarily spongy bone.

Periosteum

Connective tissue membrane covering outer bone surface.

Endosteum

Lining of internal bone cavities, contains bone cells.

Long Bone

Bone with diaphysis and epiphyses, elongated shape.

Flat Bones

Sandwich structure of spongy bone between compact bone.

Short Bones

Compact bone surrounding spongy bone, not elongated.

Irregular Bones

Complex shapes, compact bone surrounding spongy bone.

Sinuses

Air-filled spaces in some skull bones.

Intramembranous Ossification

Bone formation in embryonic connective tissue membrane.

Endochondral Ossification

Bone formation that occurs in cartilage.

Fontanels

Membrane-covered spaces between developing skull bones.

Bone Collar

Compact bone layer forming around cartilage model.

Primary Ossification Center

Site where bone replaces calcified cartilage.

Secondary Ossification Center

Site of bone formation in epiphyses.

Medullary Cavity

Hollow space in diaphysis for bone marrow.

Epiphyseal Plate

Cartilage layer for bone length growth.

Hyaline Cartilage

Smooth cartilage model for future bone shape.

Epiphyseal Line

Remnant of ossified epiphyseal plate in adults.

Bone Remodeling

Process of replacing woven bone with lamellar bone.

Osteochondral Progenitor Cells

Stem cells that differentiate into osteoblasts or chondroblasts.

Collagen Fibers

Protein fibers providing structure to bone matrix.

Hydroxyapatite Crystals

Minerals that provide hardness to bone matrix.

Zone of Resting Cartilage

Region with slowly dividing chondrocytes.

Zone of Proliferation

New cartilage produced as chondrocytes divide.

Zone of Hypertrophy

Chondrocytes mature and enlarge in this zone.

Zone of Calcification

Matrix calcified, leading to chondrocyte death.

Bone Growth in Width

Width increases through periosteum activity.

Nutrition Factors

Calcium and protein deficiencies affect bone size.

Vitamin D

Essential for calcium absorption in intestines.

Rickets

Vitamin D deficiency in childhood causing bone deformities.

Osteomalacia

Vitamin D deficiency in adulthood leading to soft bones.

Growth Hormone

Stimulates cartilage and bone growth.

Gigantism

Excess growth hormone leading to excessive growth.

Dwarfism

Insufficient growth hormone leading to reduced growth.

Basic Multicellular Units (BMUs)

Groups of osteoclasts and osteoblasts that remodel bone.

Mechanical Stress

Increased stress enhances bone strength through remodeling.

Bone Fracture Classification

Based on mechanism, soft-tissue damage, and pattern.

Hematoma Formation

Localized blood mass at fracture site.

Callus Formation

Tissue mass connecting broken bone ends.

Callus Ossification

Replacement of callus with woven, spongy bone.

Calcium Homeostasis

Balance of calcium levels through bone activity.

Parathyroid Hormone (PTH)

Regulates calcium levels by activating osteoclasts.

Calcitriol

Active vitamin D that increases calcium absorption.

Calcitonin

Lowers blood calcium by inhibiting osteoclasts.

Osteoporosis

Loss of bone matrix, leading to fractures.

Effects of Aging

Decreased bone matrix and increased brittleness.