Skeletal System Overview

Functions of the Skeletal System

The skeletal system provides the framework for the body and serves several essential functions.

• Support: Provides structural support for the body.

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

• Leverage: Facilitates movement by serving as points of attachment for muscles.

• Production of Blood Cells: Hematopoiesis occurs in the red bone marrow.

• Storage of Minerals: Stores minerals such as calcium and phosphorus.

• Energy Storage: Stores lipids in yellow bone marrow.

Note: The skeletal system does not act as the main source of body heat or temperature maintenance.

Classification of Bones

Bone Shapes

Bones are classified according to their shapes, which relate to their functions.

• Long Bones: Longer than they are wide; found in limbs (e.g., femur, humerus).

• Short Bones: Approximately equal in length and width; found in wrists and ankles (e.g., carpals, tarsals).

• Flat Bones: Thin and broad; provide protection (e.g., skull, ribs, scapula).

• Irregular Bones: Complex shapes; do not fit other categories (e.g., vertebrae, pelvis).

Structure of a Long Bone

Parts of a Long Bone

Long bones have distinct regions that contribute to their function and growth.

• Diaphysis: The shaft or central part of a long bone.

• Epiphysis: The ends of the bone, which articulate with other bones.

• Marrow Cavity: The central cavity within the diaphysis, containing bone marrow.

• Periosteum: The outer fibrous covering of the bone.

Microscopic Structure of Bone

Osteon (Haversian System)

The osteon is the fundamental functional unit of compact bone.

• Central Canal (Haversian Canal): Located at the center of the osteon; contains blood vessels and nerves.

• Lacunae: Small spaces containing osteocytes (bone cells).

• Lamellae: Concentric rings of bone matrix around the central canal.

• Perforating (Volkmann's) Canals: Canals that run perpendicular to the central canal, connecting blood vessels between osteons.

• Trabeculae of Spongy Bone: Network of bony struts in spongy bone, providing structural support.

Articulations and Bone Landmarks

Wrist and Hand Bones

The wrist and hand are composed of several small bones that allow for a wide range of movement.

• Carpals: Eight small bones forming the wrist; allow gliding movements.

• Metacarpals: Five long bones forming the palm of the hand; located between the carpals and phalanges.

• Phalanges: Fourteen bones forming the fingers; each finger has three phalanges (proximal, middle, distal), except the thumb, which has two.

Types of Bones in the Hand

• Metacarpals: Classified as long bones due to their elongated shape.

• Phalanges: Also classified as long bones, despite their small size.

Vertebral Column Regions

Lumbar Vertebrae

The lumbar region consists of five vertebrae located in the lower back.

• Number: 5 lumbar vertebrae.

• Location: Between the thoracic vertebrae and the sacrum.

• Characteristics: Large size, bulky centrum, blunt spinous process.

• Function: Supports much of the body's weight and allows for flexibility and movement.

Note: The lumbar vertebrae are part of the axial skeleton, not the appendicular skeleton.

Scapula (Shoulder Blade) Landmarks

Major Landmarks of the Scapula

The scapula is a flat bone with several important anatomical features.

• Spine: Found on the posterior surface; easily palpated.

• Acromion Process: Lateral end of the spine; articulates with the clavicle to form the acromioclavicular joint.

• Coracoid Process: Projects anteriorly and laterally; serves as a site for muscle attachment and does not articulate with another bone.

• Glenoid Fossa: Shallow cavity that forms the socket of the shoulder joint.

• Subscapular Fossa: Found on the anterior surface; a shallow depression.

• Suprascapular Notch: Located on the superior border; serves as a passage for nerves.

Art-Based and Labeling Activities

Bone Shapes and Identification

Students should be able to identify bone shapes and label parts of bones and osteons.

• Diaphysis: Shaft of a long bone.

• Epiphysis: End of a long bone.

• Central Canal: Center of the osteon, contains blood vessels.

• Lacuna: Small cavity containing an osteocyte.

Microscopic Structure Table

Key Terms and Definitions

• Carpals: Eight small bones forming the wrist.

• Metacarpals: Five long bones forming the palm.

• Phalanges: Fourteen bones forming the fingers.

• Osteon: Structural unit of compact bone.

• Diaphysis: Shaft of a long bone.

• Epiphysis: End of a long bone.

• Central Canal: Center of the osteon.

• Scapula: Shoulder blade bone.

• Acromion Process: Lateral extension of the scapular spine.

• Coracoid Process: Anterior projection of the scapula.

Formulas and Equations

• Number of Phalanges in the Hand:

• Number of Carpals in the Wrist:

• Number of Lumbar Vertebrae:

Additional info: Academic context and definitions have been expanded for clarity and completeness.