Chapter 7: The Skeletal System – Structure, Components, and Functions

Chapter 7: The Skeletal System

Learning Outcomes

• Describe the tissues and organs that make up the skeletal system and their anatomical relationships.

• Identify and classify bone markings and describe their functions.

• Name and describe the adult skull bones, their articulations, and differences between adult and fetal skulls.

Skeletal System Components

Bones, Cartilages, and Ligaments

The skeletal system is composed of bones, cartilages, and ligaments, each serving distinct structural and functional roles.

• Bone: Mineralized connective tissue containing blood, bone marrow, cartilage, adipose, nervous, and fibrous connective tissues. Bones provide support, protection, and enable movement.

• Cartilage: A flexible connective tissue that acts as a precursor to bone tissue during development and covers most joints in adults, reducing friction and absorbing shock.

• Ligaments: Dense connective tissue bands that hold bones together at joints (articulations), providing stability.

Types of Cartilage in the Skeletal System

Classification and Locations

Cartilage is classified based on its structure and function within the skeletal system.

• Hyaline Cartilage: Found in articular surfaces of joints, costal cartilages (ribs), respiratory tract, and nasal cartilages. It is the most common type and serves as a model for endochondral ossification (bone formation).

• Elastic Cartilage: Located in the ear and epiglottis, providing high elasticity and flexibility.

• Fibrocartilage: Present in intervertebral discs and knee menisci, characterized by high compressibility and tensile strength.

Bones in the Typical Adult Skeleton

Axial and Appendicular Skeleton

The adult human skeleton consists of approximately 206 bones, organized into two major divisions:

• Axial Skeleton: Forms the central axis of the body and includes:

  • Skull (22 bones)

  • Auditory ossicles (6 bones)

  • Hyoid bone (1 bone)

  • Vertebral column (33 bones)

  • Thoracic cage (25 bones)

• Appendicular Skeleton: Comprises the limbs and girdles:

  • Pectoral girdles (4 bones)

  • Upper limbs (60 bones)

  • Hip bones (2 bones)

  • Lower limbs (60 bones)

Example: The femur is a bone of the lower limb (appendicular skeleton), while the vertebrae are part of the axial skeleton.

Additional info:

• The skeletal system also includes specialized bones such as sesamoid bones (e.g., patella) and sutural bones (extra bones within the skull sutures).

• Bone markings (not detailed in these slides) are anatomical features on bones that serve as attachment points for muscles and ligaments, or as passages for nerves and blood vessels.