Osseous Tissue and Bone Structure: Study Notes for Anatomy & Physiology

Osseous Tissue and Bone Structure

Functions of the Skeletal System

The skeletal system is essential for maintaining the structure and function of the human body. It is composed of bones and associated tissues that perform several vital roles.

• Support: Bones provide a rigid framework that supports the body and cradles soft organs.

• Storage of Minerals and Lipids: Bones act as reservoirs for minerals, especially calcium and phosphorus, and store lipids in yellow bone marrow.

• Blood Cell Production: Red bone marrow produces red blood cells, white blood cells, and platelets through the process of hematopoiesis.

• Protection: Bones protect vital organs, such as the brain (skull), heart and lungs (rib cage), and spinal cord (vertebrae).

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

Example: The femur supports body weight and enables walking and running.

Classification of Bones

Bones are classified based on their shape and internal tissue organization. This classification helps in understanding their function and location in the body.

• Shape: Bones are categorized as long, short, flat, irregular, and sesamoid.

• Internal Tissue Organization: Bones consist of compact (dense) bone and cancellous (spongy) bone.

Example: The humerus is a long bone, while the vertebra is an irregular bone.

Types of Bones by Shape

Type	Example	Description
Long Bones	Femur, Humerus	Longer than they are wide; mostly compact bone
Short Bones	Carpals, Tarsals	Cube-shaped; mostly spongy bone
Flat Bones	Parietal bone, Sternum	Thin, flattened, and usually curved
Irregular Bones	Vertebrae	Complex shapes not fitting other categories
Sesamoid Bones	Patella	Small, round, and embedded in tendons

Bone Markings

Bones have characteristic surface features called markings, which serve as sites for muscle, tendon, and ligament attachment, or as passages for nerves and blood vessels.

• Openings: Allow passage of blood vessels and nerves.

• Processes: Projections for muscle and ligament attachment.

• Depressions: Indentations or grooves for articulation or passage.

Common Bone Markings

Marking	Description
Sinus	Chamber within a bone, normally filled with air
Foramen	Rounded passageway for blood vessels and/or nerves
Fissure	Deep furrow, cleft, or slit
Meatus	Passage or channel, especially the opening of a canal
Canal	Duct or channel

Example: The foramen magnum in the skull allows passage of the spinal cord.

Additional info:

• Cancellous bone is another term for spongy bone, which is found at the ends of long bones and inside flat bones.

• Compact bone forms the dense outer layer of bones, providing strength for weight bearing.

• Bone markings are essential for identifying anatomical features and understanding muscle attachments and joint articulations.