Study Guide: The Skeletal System (A&P Chapter 5)

The Skeletal System

Functions of the Skeletal System

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

• Support: Maintains body shape and supports soft tissues.

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

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

• Mineral Storage: Stores minerals such as calcium and phosphorus.

• Blood Cell Production: Houses bone marrow, which produces blood cells (hematopoiesis).

Bone Structure and Types

• Long Bones: Characterized by a shaft and two ends (e.g., femur, humerus).

• Short Bones: Cube-shaped, found in wrists and ankles (e.g., carpals, tarsals).

• Flat Bones: Thin and often curved (e.g., skull, ribs, sternum).

• Irregular Bones: Complex shapes (e.g., vertebrae, pelvis).

Parts of a Long Bone

• Diaphysis: The shaft, composed mainly of compact bone.

• Epiphyses: The ends, composed mainly of spongy bone and covered by articular cartilage.

• Metaphysis: Region between diaphysis and epiphysis, includes the growth plate.

• Medullary Cavity: Central cavity containing bone marrow.

• Periosteum: Tough outer membrane covering the bone.

Bone Formation and Growth

Bones grow and develop through a process called ossification. There are two main types:

• Intramembranous Ossification: Direct formation of bone from connective tissue (mainly in flat bones).

• Endochondral Ossification: Bone develops by replacing hyaline cartilage (most bones).

Growth in length occurs at the epiphyseal plate (growth plate) until adulthood.

Bone Remodeling and Healing

• Osteoblasts: Cells that build new bone tissue.

• Osteoclasts: Cells that break down bone tissue.

• Osteocytes: Mature bone cells that maintain bone tissue.

• First Step in Bone Healing: Formation of a hematoma (blood clot) at the fracture site.

Classification of Joints

Joints, or articulations, connect bones and allow for movement. They are classified by structure and function:

• Fibrous Joints: Immovable (e.g., sutures in the skull).

• Cartilaginous Joints: Slightly movable (e.g., intervertebral discs).

• Synovial Joints: Freely movable (e.g., knee, shoulder, hip).

Synovial joints are further classified by shape and movement (e.g., hinge, ball-and-socket, pivot).

Major Bones and Bone Groups

• Skull: Composed of cranial and facial bones.

• Vertebral Column: Cervical, thoracic, lumbar, sacral, and coccygeal regions.

• Thoracic Cage: Ribs and sternum.

• Upper Limb: Humerus, radius, ulna, carpals, metacarpals, phalanges.

• Lower Limb: Femur, tibia, fibula, tarsals, metatarsals, phalanges.

• Hand Bones: Carpals (wrist), metacarpals (palm), phalanges (fingers).

• Foot Bones: Tarsals (ankle), metatarsals (foot), phalanges (toes).

• Pelvis: Ilium, ischium, pubis.

• Tailbone: Coccyx.

Bone Markings and Features

• Foramen: Opening for nerves and blood vessels.

• Process: Projection for muscle attachment.

• Fossa: Depression in bone.

Bone Fractures

• Simple (Closed) Fracture: Bone breaks cleanly but does not penetrate skin.

• Compound (Open) Fracture: Bone breaks and penetrates skin.

• Comminuted Fracture: Bone shatters into several pieces.

• Greenstick Fracture: Incomplete break, common in children.

Table: Major Bones of the Human Body

Region	Main Bones
Skull	Frontal, parietal, temporal, occipital, mandible, maxilla
Vertebral Column	Cervical (7), thoracic (12), lumbar (5), sacrum, coccyx
Thoracic Cage	Sternum, ribs
Upper Limb	Humerus, radius, ulna, carpals, metacarpals, phalanges
Lower Limb	Femur, tibia, fibula, tarsals, metatarsals, phalanges
Pelvis	Ilium, ischium, pubis

Example: Bone Healing Process

• Step 1: Hematoma formation

• Step 2: Fibrocartilaginous callus formation

• Step 3: Bony callus formation

• Step 4: Bone remodeling

Additional info:

• The study guide covers all major concepts for the skeletal system, including bone structure, function, types, growth, healing, and classification of joints.

• For more detailed study, refer to diagrams of the skeleton and joint types, and practice labeling bones on a skeleton model.