Introduction to the Skeletal System

Overview of the Skeletal System

The skeletal system forms the structural framework of the human body and is essential for movement, protection, and various metabolic functions.

• Bones of the skeleton: The rigid organs that make up the majority of the skeletal system.

• Cartilages, ligaments, and connective tissues: Support and connect bones, providing flexibility and stability.

Functions of the Skeletal System

Major Functions

The skeletal system performs several vital functions necessary for survival and homeostasis.

• Support: Provides structural support for the entire body.

• Storage of minerals (calcium): Bones act as reservoirs for minerals, especially calcium, which is critical for many physiological processes.

• Storage of lipids (yellow marrow): Yellow bone marrow stores fat, serving as an energy reserve.

• Blood cell production (red marrow): Red bone marrow is the site of hematopoiesis, the production of blood cells.

• Protection: Bones protect vital organs (e.g., skull protects the brain, rib cage protects the heart and lungs).

• Leverage (force of motion): Bones act as levers to facilitate movement when muscles contract.

Classification of Bones

Criteria for Classification

Bones are classified based on their shape, internal tissue organization, and surface features known as bone markings.

• Shape: The external form of the bone.

• Internal tissue organization: The arrangement of bone tissue within the bone.

• Bone markings (surface features; marks): Distinctive features on the bone surface that serve as attachment points or passageways.

Bone Shapes

Bones are categorized into several types based on their shapes, each with specific locations and functions.

• Long bones: Long and thin; found in arms, legs, hands, feet, fingers, and toes. Example: Humerus, femur.

• Flat bones: Thin with parallel surfaces; found in the skull, sternum, ribs, and scapulae. Example: Parietal bone, sternum.

• Sutural bones: Small, irregular bones located between the flat bones of the skull. Example: Sutures in the skull.

• Irregular bones: Have complex shapes; examples include spinal vertebrae and pelvic bones.

• Short bones: Small and thick; examples include ankle and wrist bones (carpals and tarsals).

• Sesamoid bones: Small and flat; develop inside tendons near joints of knees, hands, and feet. Example: Patella.

Bone Markings

Bone markings are surface features that serve as sites for muscle, tendon, and ligament attachment, as well as passageways for nerves and blood vessels.

• Depressions or grooves: Found along the bone surface; often serve as pathways for nerves and blood vessels.

• Projections: Raised areas where tendons and ligaments attach or where bones articulate with each other.

• Tunnels: Openings or channels through which blood vessels and nerves enter the bone.

Table: Classification of Bones by Shape

Table: Types of Bone Markings

Additional info: These notes are based on PowerPoint lecture slides for Chapter 6 of "Fundamentals of Anatomy & Physiology" by Martini & Nath, focusing on osseous tissue and bone structure. The tables and expanded explanations provide academic context for college-level Anatomy & Physiology students.