The Skeletal System: Structure, Function, and Physiology

The Skeletal System

Overview

The skeletal system is a complex organ system that provides structural support, protection, and movement for the human body. It is composed of bones, cartilages, ligaments, and various connective tissues.

• Bones of the skeleton

• Cartilages, ligaments, and connective tissues

Primary Functions of the Skeletal System

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

• Storage of Minerals and Lipids: Stores calcium and phosphate ions (in bone matrix) and lipids (in yellow bone marrow).

• Blood Cell Production: Hematopoiesis occurs in red bone marrow, producing red and white blood cells and platelets.

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

• Leverage: Acts as levers for muscles to produce movement.

Classification of Bones

By Shape

Bones are classified by their shape, which relates to their function and location.

Type	Description	Example(s)
Sutural Bones	Small, flat, irregular bones between skull bones	Sutures of the skull
Irregular Bones	Complex shapes with short, flat, notched, or ridged surfaces	Vertebrae, pelvis
Short Bones	Boxlike in appearance	Carpal and tarsal bones
Flat Bones	Thin, parallel surfaces	Parietal bone, sternum, ribs, scapula
Long Bones	Long and slender	Humerus, femur, radius, ulna
Sesamoid Bones	Small, round, and flat; develop inside tendons	Patella

By Internal Organization

• Compact (Cortical) Bone: Dense and solid; forms the outer layer of bones.

• Spongy (Trabecular or Cancellous) Bone: Network of trabeculae; found at the ends of long bones and inside flat bones.

Bone Markings

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

Type	Description	Example
Process	Projection or bump	Mastoid process
Ramus	Extension of a bone forming an angle	Mandibular ramus
Sinus	Chamber within a bone, filled with air	Frontal sinus
Foramen	Rounded passageway for blood vessels/nerves	Foramen magnum
Fissure	Deep furrow, cleft, or slit	Superior orbital fissure
Meatus	Passage or canal	External acoustic meatus
Canal	Duct or channel	Carotid canal

Additional info: Memorizing the meanings of these terms aids in anatomical identification and lab work.