Bone Tissue and the Skeletal System

Functions of the Skeletal System

The skeletal system is essential for providing structure, protection, and support to the human body. It also plays a vital role in movement, mineral storage, and blood cell production.

• Supports the Body: The skeleton forms the framework that supports the body and maintains its shape.

• Facilitates Movement: Bones act as levers and points of attachment for muscles, enabling movement.

• Protects Internal Organs: Bones such as the skull and rib cage shield vital organs from injury.

• Produces Blood Cells (Hematopoiesis): Blood cell formation occurs in the red bone marrow.

• Stores and Releases Minerals and Fat: Bones store minerals like calcium and phosphorus, and release them into the bloodstream as needed. Fat is stored in yellow marrow.

Classification of Bones

Main Types of Bones

Bones are classified according to their shapes and functions. This classification helps in understanding their roles in the body.

• Long Bones: Cylindrical in shape and longer than they are wide. Examples: Humerus, femur, metacarpals, metatarsals.

• Short Bones: Cube-like in shape, equal in length, width, and thickness. Examples: Carpals (wrist bones), tarsals (ankle bones).

• Flat Bones: Thin and often curved. Examples: Scapulae, cranial (skull) bones, sternum.

Additional Bone Classifications

• Irregular Bones: Complex shapes that do not fit into other categories. Examples: Vertebrae, many facial bones.

• Sesamoid Bones: Small, round bones shaped like a sesame seed, often found embedded in tendons. Examples: Patella (kneecap), variable number in tendons.

Bone Anatomy Terms

Key Structural Features of Long Bones

Understanding the anatomy of bones is crucial for recognizing how they grow, repair, and function.

• Diaphysis: The tubular shaft of a long bone, providing leverage and major weight support.

• Epiphysis: The proximal and distal ends of the bone, often involved in joint formation.

• Metaphysis: The narrow area between the diaphysis and epiphysis, containing the growth plate in children.

• Medullary Cavity: The hollow region within the diaphysis, filled with yellow marrow (fat storage).

Additional Bony Anatomy Terms

• Epiphyseal Plate: Area of bone growth in length (also called the growth plate), located in the metaphysis of growing bones.

• Epiphyseal Line: The visible line that remains after the epiphyseal plate has closed, indicating the end of growth in length after childhood.

• Endosteum: Lining of the medullary cavity, site of bone growth, repair, and remodeling.

• Periosteum: A fibrous membrane covering the outer surface of bone, serving as a site for ligament and tendon attachment and containing cells important for bone growth and repair.

Summary Table: Bone Classification

Additional info: These notes are expanded from lecture slides and class notes, with academic context added for clarity and completeness. Further details on bone structure, growth, and repair are covered in subsequent sections of the chapter.