Exercise 10 Review Sheet The Appendicular Skeleton

Exercise 10 Review Sheet: The Appendicular Skeleton

This comprehensive review sheet covers the appendicular skeleton, focusing on key bones, their articulations, and clinical correlations. Understanding this complex system is crucial for anyone studying anatomy and physiology, physical therapy, or related fields. We'll explore the upper and lower extremities, highlighting key features for effective memorization and application.

I. The Upper Appendicular Skeleton: Bones and Articulations

The upper appendicular skeleton comprises the bones of the pectoral girdle (shoulder girdle) and the free upper limb. Let's break it down:

A. Pectoral Girdle: The Foundation of Movement

The pectoral girdle, unlike the pelvic girdle, is relatively lightweight and highly mobile. This mobility allows for a wide range of arm movements. Its key components are:

• Clavicle (Collarbone): A long, S-shaped bone that articulates medially with the sternum (sternoclavicular joint) and laterally with the scapula (acromioclavicular joint). Its function is to transmit forces from the upper limb to the axial skeleton. Fractures of the clavicle are common, often resulting from direct trauma.

• Scapula (Shoulder Blade): A flat, triangular bone located on the posterior aspect of the thorax. It possesses several important features:

  • Acromion: The lateral, expanded end that articulates with the clavicle.
  • Coracoid Process: A curved process that projects anteriorly and provides attachment points for muscles.
  • Glenoid Cavity: A shallow, pear-shaped fossa that articulates with the head of the humerus, forming the glenohumeral joint (shoulder joint). The shallowness of this cavity contributes to the shoulder's high mobility but also its inherent instability. Dislocations are common here.
  • Spine: A prominent ridge that runs across the posterior surface of the scapula.

B. The Free Upper Limb: Precision and Power

The free upper limb consists of the following segments:

• Humerus (Arm Bone): The longest bone of the upper limb. Key features include:

  • Head: Articulates with the glenoid cavity of the scapula.
  • Greater and Lesser Tubercles: Sites for muscle attachments.
  • Deltoid Tuberosity: A roughened area for the insertion of the deltoid muscle.
  • Medial and Lateral Epicondyles: Prominent bony projections near the elbow joint, providing attachment sites for forearm muscles. Epicondylitis (tennis elbow or golfer's elbow) is inflammation of the tendons surrounding these epicondyles.
  • Capitulum and Trochlea: Articulating surfaces of the distal humerus with the radius and ulna, respectively, forming the elbow joint.

• Radius and Ulna (Forearm Bones): These two bones articulate with each other at the proximal and distal radioulnar joints, allowing for pronation and supination of the forearm (rotating the palm up and down).

  • Radius: The lateral bone of the forearm, thicker at its distal end. The radial head articulates with the capitulum of the humerus.
  • Ulna: The medial bone of the forearm, with the olecranon process forming the point of the elbow. The trochlear notch articulates with the trochlea of the humerus. The ulnar styloid process is easily palpable at the wrist.

• Carpals (Wrist Bones): Eight small bones arranged in two rows. These bones contribute to the complex mechanics of the wrist, allowing for a wide range of movements. Carpal tunnel syndrome is a common condition affecting the nerves and tendons passing through this area.

• Metacarpals (Palm Bones): Five long bones forming the palm. Fractures of the metacarpals are common, particularly in contact sports.

• Phalanges (Fingers): Fourteen bones comprising the fingers; each finger (except the thumb) has three phalanges (proximal, middle, and distal). The thumb has only two (proximal and distal).

II. The Lower Appendicular Skeleton: Support and Locomotion

The lower appendicular skeleton is responsible for supporting the body's weight and enabling locomotion. It is characterized by its robustness and stability.

A. Pelvic Girdle: Stability and Strength

The pelvic girdle is formed by the two hip bones (coxal bones), which articulate with each other anteriorly at the pubic symphysis and with the sacrum posteriorly at the sacroiliac joints. The pelvic girdle provides a strong foundation for the lower limbs and protects the pelvic organs. Each hip bone is composed of three fused bones:

• Ilium: The largest part of the hip bone, forming the superior portion of the pelvis. The iliac crest is a prominent landmark.
• Ischium: The inferior and posterior portion of the hip bone. The ischial tuberosity is the bony prominence you sit on.
• Pubis: The anterior portion of the hip bone. The pubic symphysis is the cartilaginous joint between the two pubic bones.

The shape and size of the pelvis differ between males and females, reflecting reproductive differences. The female pelvis is wider and shallower than the male pelvis.

B. The Free Lower Limb: Weight-Bearing and Movement

The free lower limb consists of the following segments:

• Femur (Thigh Bone): The longest and strongest bone in the body. Key features include:

  • Head: Articulates with the acetabulum of the hip bone, forming the hip joint. Hip dislocations are less common than shoulder dislocations due to the deeper acetabulum.
  • Neck: A constricted region connecting the head to the shaft. Fractures of the femoral neck are common in elderly individuals.
  • Greater and Lesser Trochanters: Sites for muscle attachments.
  • Medial and Lateral Condyles: Articulating surfaces with the tibia, forming the knee joint.
  • Patellar Surface: A smooth area on the anterior surface that articulates with the patella (kneecap).

• Patella (Kneecap): A sesamoid bone embedded in the quadriceps tendon. It protects the anterior aspect of the knee joint and improves the leverage of the quadriceps muscle.

• Tibia and Fibula (Leg Bones): The tibia (shinbone) is the weight-bearing bone of the leg, while the fibula is slender and primarily involved in stabilizing the ankle.

  • Tibia: Articulates with the femur and fibula, forming the knee and ankle joints. Tibial plateau fractures are common injuries.
  • Fibula: Articulates with the tibia at the proximal and distal tibiofibular joints and with the talus at the ankle joint. Fibular fractures are also common.

• Tarsals (Ankle Bones): Seven bones forming the ankle. The talus is the most superior tarsal bone, articulating with the tibia and fibula. The calcaneus (heel bone) is the largest tarsal bone.

• Metatarsals (Foot Bones): Five long bones forming the midfoot. Metatarsal fractures are common in running and jumping activities.

• Phalanges (Toes): Fourteen bones comprising the toes; each toe (except the big toe) has three phalanges (proximal, middle, and distal). The big toe has only two (proximal and distal).

III. Clinical Correlations and Common Injuries

Understanding the anatomy of the appendicular skeleton is crucial for diagnosing and treating various injuries and conditions. Here are some key examples:

• Fractures: Fractures of the clavicle, humerus, femur, tibia, fibula, and metacarpals are common. The type and severity of the fracture determine the treatment approach.

• Dislocations: Shoulder and hip dislocations are relatively common, particularly in contact sports and falls. Reduction (repositioning) of the dislocated joint is often necessary.

• Sprains: Sprains involve injuries to the ligaments surrounding a joint. Ankle sprains are extremely common.

• Rotator Cuff Injuries: The rotator cuff is a group of muscles and tendons that stabilize the shoulder joint. Tears in the rotator cuff are common, particularly in older individuals.

• Carpal Tunnel Syndrome: Compression of the median nerve in the carpal tunnel can cause numbness, tingling, and weakness in the hand.

• Osteoarthritis: A degenerative joint disease that affects the articular cartilage. It is common in the knees and hips.

• Rheumatoid Arthritis: An autoimmune disease that affects the synovial joints, causing inflammation and pain.

IV. Study Tips and Memorization Techniques

Mastering the appendicular skeleton requires diligent study and effective memorization strategies. Here are some suggestions:

• Use Anatomical Models: Three-dimensional models provide a much better understanding than simply looking at diagrams.

• Active Recall: Test yourself frequently using flashcards or practice questions. Don't just passively reread the material.

• Clinical Correlation: Relating anatomical structures to clinical conditions helps solidify your understanding.

• Group Study: Explaining concepts to others can reinforce your knowledge.

• Labeling Diagrams: Repeatedly labeling diagrams of bones and joints is an effective way to improve your anatomical knowledge.

• Focus on Functional Anatomy: Understanding how bones and joints work together during movement can enhance your comprehension.

By combining these strategies with consistent effort, you can effectively master the complexities of the appendicular skeleton and its clinical significance. Remember that understanding the relationships between bones, joints, muscles, and nerves is key to a thorough understanding of the human body. Continue to build upon this foundation and explore further anatomical details to enhance your knowledge. Good luck!