Bones and Skeletal Tissues

Introduction

The skeletal system is composed of bones and skeletal tissues, including cartilage, which provide structural support, protection, and facilitate movement. This chapter explores the types of skeletal cartilage, bone classification, functions, and anatomical features.

Skeletal Cartilage

General Properties of Cartilage

• Cartilage is a type of connective tissue that contains no blood vessels or nerves, making it avascular and aneural.

• It is composed primarily of water, which allows it to be resilient and flexible.

• Cartilage is surrounded by the perichondrium, a dense layer of connective tissue that resists outward expansion and contains blood vessels for nutrient delivery.

Types of Cartilage

• Hyaline Cartilage: Provides support, flexibility, and resilience. It is the most abundant type of skeletal cartilage.

• Elastic Cartilage: Similar to hyaline cartilage but contains more elastic fibers, allowing greater flexibility.

• Fibrocartilage: Highly compressed with great tensile strength due to the presence of collagen fibers.

Locations and Functions of Cartilage Types

• Hyaline Cartilage is found in:

  • Articular cartilage: Covers the ends of long bones at joints.

  • Costal cartilage: Connects ribs to the sternum.

  • Respiratory cartilage: Forms the larynx and reinforces air passages.

  • Nasal cartilage: Supports the nose.

• Elastic Cartilage is found in:

  • External ear (auricle)

  • Epiglottis (flap covering the larynx during swallowing)

• Fibrocartilage is found in:

  • Menisci of the knee

  • Pubic symphysis

  • Intervertebral discs

Classification of Bones

Overview of the Human Skeleton

• The human skeleton contains 206 named bones.

• It is divided into two main regions:

  • Axial skeleton: Includes the bones of the skull, vertebral column, and rib cage.

  • Appendicular skeleton: Includes the bones of the upper and lower limbs, shoulder, and hip.

Types of Bones by Shape

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

• Short bones: Cube-shaped bones, found in the wrist (carpals) and ankle (tarsals).

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

• Irregular bones: Complex shapes (e.g., vertebrae, facial bones, pelvic bones).

• Sesamoid bones: Small, round bones formed in tendons (e.g., patella).

Functions of Bones

Major Functions

• Support: Bones provide a framework for the body and support soft organs.

• Protection: Bones protect vital organs such as the brain, spinal cord, and thoracic organs.

• Movement: Bones act as levers for muscle action, enabling movement.

• Mineral Storage: Bones store minerals, primarily calcium and phosphate, and growth factors.

• Blood Cell Formation (Hematopoiesis): Occurs in red bone marrow cavities.

• Triglyceride (Fat) Storage: Yellow bone marrow stores fat as an energy reserve.

Bone Markings

Types and Functions of Bone Markings

• Bulges, depressions, and holes on bones serve as:

  • Sites of attachment for muscles, ligaments, and tendons.

  • Joint surfaces for articulation.

  • Foramina (holes) that act as conduits for blood vessels and nerves.

Types of Cartilage in the Human Body

Summary Table: Cartilage Types and Locations

Additional info: The table above summarizes the main types of cartilage, their locations, and distinguishing features for quick reference.