Ch 6 Bones and Skeletal Tissues

Vocabulary Overview

This chapter covers essential terminology related to the skeletal system, including bone structure, development, and remodeling. Key terms include hematopoiesis, axial skeleton, appendicular skeleton, compact bone, spongy bone, osteoblasts, osteoclasts, osteocytes, ossification, bone remodeling, and various bone disorders.

Types of Cartilage

Functional Properties and Locations

• Hyaline cartilage: Provides support, flexibility, and resilience; found in articular surfaces, costal cartilages, respiratory structures, and nasal cartilage.

• Elastic cartilage: Maintains shape while allowing flexibility; found in the external ear and epiglottis.

• Fibrocartilage: Highly compressible with great tensile strength; found in intervertebral discs and menisci of the knee.

• Example: The meniscus in the knee is an example of fibrocartilage.

Functions of the Skeleton

Main Functions

• Support: Provides a framework for the body.

• Protection: Shields vital organs (e.g., skull protects the brain).

• Movement: Acts as levers for muscles.

• Mineral Storage: Reservoir for calcium and phosphate.

• Blood Cell Formation: Occurs in red marrow (hematopoiesis).

• Fat Storage: Yellow marrow stores triglycerides.

Classification of Bones

Bone Classes and Examples

• Long bones: Longer than wide (e.g., femur, humerus).

• Short bones: Cube-shaped (e.g., carpals, tarsals).

• Flat bones: Thin, flattened, and usually curved (e.g., sternum, skull).

• Irregular bones: Complicated shapes (e.g., vertebrae, hip bones).

Gross Anatomy of Bones

Structure and Regions

• Diaphysis: Shaft of a long bone.

• Epiphyses: Ends of long bones.

• Membranes: Periosteum (outer) and endosteum (inner).

• Articular cartilage: Covers joint surfaces.

• Example: The femur has a diaphysis and two epiphyses.

Microscopic Anatomy of Bone

Bone Tissue Components

• Osteon (Haversian system): Structural unit of compact bone.

• Lamellae: Concentric rings of bone matrix.

• Central canal: Contains blood vessels and nerves.

• Lacunae: Small cavities housing osteocytes.

• Canaliculi: Tiny canals connecting lacunae.

Bone Marrow

Types and Locations

• Red marrow: Site of hematopoiesis; found in trabecular cavities of spongy bone in flat bones and epiphyses of long bones.

• Yellow marrow: Fat storage; found in medullary cavities of long bones.

Bone Markings

Importance and Types

• Projections: Sites of muscle and ligament attachment (e.g., tuberosity, crest).

• Surfaces: Form joints (e.g., head, facet).

• Depressions/Openings: Allow passage of vessels and nerves (e.g., foramen, fossa).

Bone Cells and Their Functions

Major Cell Types

• Osteogenic cells: Stem cells that differentiate into osteoblasts.

• Osteoblasts: Bone-forming cells.

• Osteocytes: Mature bone cells maintaining bone matrix.

• Osteoclasts: Bone-resorbing cells.

Bone Development and Growth

Ossification Processes

• Intramembranous ossification: Forms flat bones (e.g., skull, clavicle).

• Endochondral ossification: Forms most bones of the body from hyaline cartilage models.

• Growth in length: Occurs at epiphyseal plate via cartilage proliferation and ossification.

• Growth in width: Appositional growth by osteoblasts in periosteum.

Bone Remodeling and Repair

Processes and Disorders

• Remodeling: Continuous bone resorption and deposition by osteoclasts and osteoblasts.

• Hormonal regulation: Parathyroid hormone (PTH) and calcitonin regulate calcium levels.

• Fracture repair: Involves hematoma formation, fibrocartilaginous callus, bony callus, and bone remodeling.

• Disorders: Osteoporosis (decreased bone mass), osteomalacia (soft bones), Paget's disease (abnormal bone remodeling).

Key Equations and Concepts

• Calcium Homeostasis: Maintained by hormonal feedback mechanisms.

• Example Equation:

Summary Table: Bone Tissue Components

Additional info: Some details, such as the specific steps of fracture repair and the hormonal regulation of bone remodeling, were expanded for academic completeness.