Skeletal System and Articulations: Study Guide for Anatomy & Physiology

Chapter 6: The Skeletal System

6.1 Main Components and Functions of the Skeletal System

The skeletal system is a complex framework of bones and connective tissues that provides structure, protection, and support for the body.

• Main Components: Bones, cartilage, ligaments, and joints.

• Main Functions:

  • Support: Provides a structural framework for the body.

  • Protection: Shields vital organs (e.g., skull protects the brain).

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

  • Mineral Storage: Stores calcium and phosphorus.

  • Blood Cell Production: Houses bone marrow for hematopoiesis.

  • Energy Storage: Stores lipids in yellow marrow.

6.2 Bone Shapes and Markings

Bones are classified by their shapes and surface features, which relate to their functions and locations.

• Bone Shape Examples:

  • Long bones (e.g., femur, humerus)

  • Short bones (e.g., carpals, tarsals)

  • Flat bones (e.g., sternum, skull)

  • Irregular bones (e.g., vertebrae)

  • Sesamoid bones (e.g., patella)

• Bone Markings: Surface features such as facets (smooth, flat surfaces for articulation), foramina (holes for nerves/vessels), and processes (projections for muscle attachment).

6.3 Long Bone Regions

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

• Regions:

  • Epiphysis: The ends of long bones, often involved in joint articulation.

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

  • Metaphysis: The region between diaphysis and epiphysis, containing the growth plate.

6.4 Bone Location and Functions

Bones are located throughout the body and have specialized functions based on their location and structure.

• Example: Osteoclasts are cells that break down bone tissue, important for bone remodeling and calcium homeostasis.

6.11 Calcium Homeostasis

Calcium homeostasis is the regulation of calcium ion concentration in the blood, essential for muscle contraction, nerve function, and bone health.

• Key Hormones: Parathyroid hormone (PTH), calcitonin, and vitamin D.

• Feedback Mechanism: When blood calcium is low, PTH is released to increase calcium by stimulating osteoclasts. When high, calcitonin inhibits osteoclasts.

6.12 Fracture Types and Repair

Bones can fracture in various ways, and the body has a specific process for repair.

• Fracture Types: Comminuted (bone breaks into several pieces), simple, compound, greenstick, etc.

• Steps in Fracture Repair:

  1. Hematoma formation

  2. Fibrocartilaginous callus formation

  3. Bony callus formation

  4. Bone remodeling

Chapter 7: The Axial and Appendicular Skeleton

7.1 Axial Skeleton

The axial skeleton forms the central axis of the body and includes the skull, vertebral column, and thoracic cage.

• Main Bones: Skull, vertebrae, ribs, sternum.

• Number of Bones: 80 bones in the axial skeleton.

7.2 Skull Anatomy

The skull protects the brain and forms the structure of the face.

• Cranium Bones: Examples include the parietal bone.

• Cranial Sutures: Immovable joints between skull bones, such as the coronal suture.

7.3 Face Bones

The facial skeleton supports the facial structures and forms the cavities for the sense organs.

• Example: The vomer bone forms part of the nasal septum.

7.6 Thoracic Cage and Pectoral Girdle

The thoracic cage protects vital organs and supports the upper limbs, while the pectoral girdle connects the arms to the trunk.

• Thoracic Cage: Sternum, ribs (key structures: costal groove), thoracic vertebrae.

• Pectoral Girdle: Clavicle (medial end), scapula (lateral border), sternoclavicular and acromioclavicular joints.

7.7 Upper Limb Bones

The upper limb consists of the humerus, radius, ulna, carpals, metacarpals, and phalanges.

• Humerus: Features include the lesser tubercle.

• Radius and Ulna: Attachment points for muscles and ligaments.

• Carpal Bones: "So Long To Pinky, Here Comes The Thumb" mnemonic for carpal order (scaphoid, lunate, triquetrum, pisiform, hamate, capitate, trapezoid, trapezium).

7.9 Pelvic Girdle and Lower Limb

The pelvic girdle supports the lower limbs and protects pelvic organs.

• Hip Bones: Key parts include the ilium, ischium, and pubis.

• Landmarks: Acetabulum (hip socket), fibrocartilage between paired hip bones.

• Pelvis: Includes the sacrum and coccyx.

• Male vs. Female Pelvis: Female pelvis is wider and shallower for childbirth.

7.22 Lower Limb Bones

• Femur: Key landmark is the greater trochanter.

• Radius and Ulna: Medial border is a key landmark.

• Patella: Also known as the kneecap.

• Tarsal Bones: Includes the calcaneus (heel bone).

• Metatarsals and Phalanges: Bones of the foot and toes.

Chapter 8: Articulations (Joints)

8.1 Define Articulation

An articulation, or joint, is a point where two or more bones meet, allowing for movement and flexibility.

8.2 Synovial Joints

Synovial joints are the most movable type of joint in the body, characterized by a fluid-filled joint cavity.

• Parts: Articular cartilage, synovial membrane, joint cavity, synovial fluid, ligaments.

• Functions: Allow a wide range of movements, reduce friction, absorb shock.

• Key Components: Knee joint includes menisci, cruciate ligaments, and collateral ligaments.

8.3 Types of Motion

Joints allow different types of motion, classified by the number of axes and the nature of movement.

• Types: Gliding, angular (flexion, extension), rotation, circumduction.

• Axes: Uniaxial (one axis), biaxial (two axes), multiaxial (three or more axes).

• Relation to Joints: Example: Shoulder joint allows multiaxial movement.

8.4 Movements at Synovial Joints

Specific terms describe the movements possible at synovial joints.

• Flexion vs. Extension vs. Hyperextension: Decreasing, increasing, or exceeding the normal angle between bones.

• Abduction vs. Adduction: Movement away from or toward the midline.

• Circumduction: Circular movement combining flexion, extension, abduction, and adduction.

8.5 Special Movements

• Rotation: Movement around a longitudinal axis.

• Pronation vs. Supination: Rotation of the forearm (palm down vs. palm up).

• Opposition: Thumb movement to touch other fingers.

• Inversion vs. Eversion: Turning the sole of the foot inward or outward.

• Protraction vs. Retraction: Moving a body part forward or backward.

• Elevation vs. Depression: Lifting or lowering a body part.

8.9 Glenohumeral Joint Injuries

The glenohumeral (shoulder) joint is prone to injuries due to its wide range of motion.

• Common Injuries: Dislocation, rotator cuff tears.

• Location: The glenohumeral joint is where the humerus meets the scapula.

8.10 Knee Ligaments

The knee joint is stabilized by several key ligaments.

• Key Ligaments: Anterior cruciate ligament (ACL), posterior cruciate ligament (PCL), medial collateral ligament (MCL), lateral collateral ligament (LCL).

Table: Comparison of Axial and Appendicular Skeleton

Feature	Axial Skeleton	Appendicular Skeleton
Main Components	Skull, vertebral column, thoracic cage	Pectoral girdle, pelvic girdle, limbs
Number of Bones	80	126
Main Function	Protection, support	Movement, manipulation