Chapter 7: The Skeletal System – Structure, Components, and Bone Markings

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 several types of tissues and organs that work together to provide support, protection, and movement.

• Bone: A mineralized connective tissue containing blood, bone marrow, cartilage, adipose, nervous, and fibrous connective tissues. Bones provide structural support, protect organs, and serve as levers for movement.

• Cartilage: A flexible connective tissue that acts as a precursor for 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 and guiding joint movement.

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 cartilage (ribs), respiratory tract, and nasal cartilage. It is the most common type and serves as a model for endochondral ossification (bone development).

• 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.

Example: The meniscus in the knee is made of fibrocartilage, allowing it to withstand compressive forces during movement.

Bones in the Typical Adult Skeleton

Axial and Appendicular Skeleton

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

• Axial Skeleton (central axis):

  • Skull: 22 bones

  • Auditory ossicles: 6 bones

  • Hyoid bone: 1 bone

  • Vertebral column: 33 bones

  • Thoracic cage: 25 bones

• Appendicular Skeleton (limbs and girdles):

  • Pectoral girdles: 4 bones

  • Upper limbs: 60 bones

  • Hip bones: 2 bones

  • Lower limbs: 60 bones

Example: The femur is part of the appendicular skeleton and is the longest bone in the body.

Additional info:

• The skeletal system also includes sesamoid bones (e.g., patella) and sutural bones (extra bones in the skull).

• Bone markings are important for muscle attachment, joint formation, and passage of nerves and blood vessels.