Bones and Bone Structure: Anatomy & Physiology Study Notes

Functions of the Skeletal System

Overview of the Skeletal System

The skeletal system is a vital organ system that provides the framework for the human body. It consists of bones, cartilages, ligaments, and other connective tissues that stabilize and interconnect the bones.

• Structural support: Bones provide the rigid structure that supports the body and maintains its shape.

• Storage of minerals and lipids: Bones store essential minerals such as calcium and phosphorus, as well as lipids in yellow bone marrow.

• Blood cell production: Red bone marrow produces red blood cells, white blood cells, and platelets (a process called hematopoiesis).

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

• Leverage for movement: Bones act as levers that muscles pull on to produce movement.

Classification of Bones

Bone Classification by Shape

Bones are classified according to their shapes, which relate to their functions and locations in the body.

• Sutural bones (Wormian bones): Small, flat, irregularly shaped bones found between the flat bones of the skull. The number of sutural bones varies among individuals.

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

• Short bones: Boxy in appearance. Examples include carpal bones (wrist) and tarsal bones (ankle).

• Flat bones: Thin bones with parallel surfaces. Examples include bones of the skull roof, sternum, ribs, and scapulae.

• Long bones: Long and slender bones found in the arms, legs, palms, soles, fingers, and toes. Examples include the humerus and femur.

• Sesamoid bones: Small, round, and flat bones found within tendons near joints of the knees, hands, and feet. The location and number of sesamoid bones vary between individuals. Example: patellae (kneecaps).

Table: Classification of Bones by Shape

Bone Type	Description	Examples
Sutural	Small, flat, irregularly shaped; found in skull sutures	Between parietal bones
Irregular	Complex shapes	Vertebrae, pelvic bones
Short	Boxy, equal dimensions	Carpals, tarsals
Flat	Thin, parallel surfaces	Skull roof, sternum, ribs, scapulae
Long	Long and slender	Humerus, femur
Sesamoid	Small, round, flat; within tendons	Patellae

Bone Markings (Surface Features)

Types of Bone Markings

Bones have characteristic surface features called bone markings that serve as sites for muscle, tendon, and ligament attachment, articulation with other bones, and passageways for blood vessels and nerves.

• Projections: Raised areas for attachment of muscles, tendons, and ligaments, or for articulation with other bones.

• Openings and depressions: Indentations or holes that allow the passage of blood vessels and nerves.

Examples of Bone Markings

• Process: Any projection or bump (e.g., mastoid process of the skull).

• Foramen: A rounded passageway for blood vessels or nerves (e.g., foramen magnum).

• Fossa: A shallow depression (e.g., olecranon fossa of the humerus).

• Condyle: A smooth, rounded articular process (e.g., femoral condyles).

• Crest: A prominent ridge (e.g., iliac crest).

Summary Table: Bone Markings

Marking	Description	Function
Process	Projection or bump	Attachment/articulation
Foramen	Hole or opening	Passage for vessels/nerves
Fossa	Shallow depression	Articulation/support
Condyle	Rounded articular area	Joint formation
Crest	Prominent ridge	Attachment

Additional info:

• Bone markings are essential for identifying bones and understanding their functions in the body.

• Knowledge of bone shapes and markings is fundamental for clinical applications such as radiology, orthopedics, and forensic science.