Bones and Bone Structure: Study Notes for Anatomy & Physiology

Bones and Bone Structure

Organs of the Skeletal System

The skeletal system is composed of bones and associated connective tissues that provide structure and support to the body.

• Bones of the skeleton: The rigid organs that form the framework of the body.

• Cartilages, ligaments, and other connective tissues: These structures stabilize or connect bones, contributing to joint function and skeletal integrity.

Functions of the Skeletal System

The skeletal system performs several essential functions necessary for survival and movement.

• Support: Provides a structural framework for the body and supports soft tissues.

• Storage of minerals and lipids: Bones store minerals such as calcium and phosphorus, and 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 (e.g., the skull protects the brain, the rib cage protects the heart and lungs).

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

Classification of Bones

Basis of Classification

Bones are classified according to their shape and internal structure, which relate to their function and location in the body.

• Shape: Bones are grouped into categories based on their external form.

• Structure: The internal organization of bone tissue also contributes to classification.

Bone Shapes

Sutural Bones (Wormian Bones)

Sutural bones are small, flat, and irregularly shaped bones found between the flat bones of the skull. Their borders are jagged, resembling pieces of a jigsaw puzzle.

• Location: Between the sutures of the skull.

• Size: Range from a grain of sand to a quarter.

• Function: Contribute to the structure of the skull; their number and location can vary between individuals.

• Example: Sutural bones are commonly found in the lambdoid suture at the back of the skull.

Irregular Bones

Irregular bones have complex shapes with short, flat, notched, or ridged surfaces. They do not fit into the other bone shape categories.

• Location: Vertebrae (spinal column), bones of the pelvis, and several skull bones.

• Function: Provide protection for nervous tissue (e.g., vertebrae protect the spinal cord), offer multiple anchor points for skeletal muscle attachment.

• Example: The vertebrae are classic examples of irregular bones.

Additional Bone Shapes (Inferred from Standard A&P Content)

• Short Bones: Boxlike in appearance; found in the wrists (carpals) and ankles (tarsals). Function in providing support and stability with little movement.

• Flat Bones: Thin, parallel surfaces; form the roof of the skull, sternum, ribs, and scapulae. Function in protection and providing surfaces for muscle attachment.

• Long Bones: Relatively long and slender; found in the arms, legs, palms, soles, fingers, and toes. Function as levers for movement.

• Sesamoid Bones: Usually small, round, and flat; develop inside tendons near joints (e.g., patella/kneecap). Function to protect tendons and increase their mechanical effect.

Additional info: The above bone shapes (short, flat, long, sesamoid) are standard categories in A&P and are logically included for completeness, though not all were shown in the provided images.

Summary Table: Bone Shape Classification

Bone Shape	Description	Examples
Sutural (Wormian)	Small, flat, irregularly shaped; found between skull bones	Sutures of the skull
Irregular	Complex shapes; notched or ridged surfaces	Vertebrae, pelvic bones, some skull bones
Short	Boxlike, nearly equal in length and width	Carpals (wrist), tarsals (ankle)
Flat	Thin, parallel surfaces	Sternum, ribs, scapulae, roof of skull
Long	Long and slender	Femur, humerus, phalanges
Sesamoid	Small, round, and flat; develop in tendons	Patella (kneecap)