💀Anatomy and Physiology I Unit 8 – The Appendicular Skeleton

Overview and Structure

• Appendicular skeleton consists of the bones of the upper and lower limbs, including the shoulder and pelvic girdles
• Comprised of 126 bones in total, representing the majority of the bones in the human body
• Upper limb includes the arm, forearm, wrist, and hand, while the lower limb includes the thigh, leg, ankle, and foot
• Shoulder girdle (pectoral girdle) attaches the upper limbs to the axial skeleton and includes the clavicle and scapula
• Pelvic girdle attaches the lower limbs to the axial skeleton and includes the hip bones (ilium, ischium, and pubis)
• Bones of the appendicular skeleton are connected by various types of joints, allowing for a wide range of movements
• Muscles of the appendicular skeleton attach to the bones, enabling movement and stability of the limbs

Bones of the Upper Limb

• Humerus is the longest and largest bone of the upper limb, located in the arm between the shoulder and elbow
  • Proximal end includes the head, which articulates with the glenoid cavity of the scapula, and the greater and lesser tubercles for muscle attachment
  • Distal end includes the trochlea and capitulum, which articulate with the ulna and radius, respectively
• Radius is located on the lateral side of the forearm and is slightly shorter than the ulna
  • Proximal end includes the head, which articulates with the capitulum of the humerus, and the radial tuberosity for muscle attachment
  • Distal end articulates with the carpal bones of the wrist
• Ulna is located on the medial side of the forearm and is slightly longer than the radius
  • Proximal end includes the olecranon process, which forms the point of the elbow, and the trochlear notch, which articulates with the trochlea of the humerus
  • Distal end includes the head, which articulates with the distal end of the radius
• Carpal bones are eight small, irregular bones arranged in two rows in the wrist
  • Proximal row includes the scaphoid, lunate, triquetrum, and pisiform
  • Distal row includes the trapezium, trapezoid, capitate, and hamate
• Metacarpal bones are the five long bones of the palm, numbered 1-5 from the thumb to the little finger
• Phalanges are the bones of the fingers, with each finger having three phalanges (proximal, middle, and distal), except for the thumb, which has two (proximal and distal)

Bones of the Lower Limb

• Femur is the longest and strongest bone in the human body, located in the thigh between the hip and knee
  • Proximal end includes the head, which articulates with the acetabulum of the hip bone, and the greater and lesser trochanters for muscle attachment
  • Distal end includes the medial and lateral condyles, which articulate with the tibia
• Patella is a large sesamoid bone located within the tendon of the quadriceps femoris muscle, anterior to the knee joint
• Tibia is the larger and medial bone of the leg, located between the knee and ankle
  • Proximal end includes the medial and lateral condyles, which articulate with the femur, and the tibial tuberosity for muscle attachment
  • Distal end forms the medial malleolus of the ankle and articulates with the talus
• Fibula is the smaller and lateral bone of the leg, located parallel to the tibia
  • Proximal end articulates with the lateral condyle of the tibia
  • Distal end forms the lateral malleolus of the ankle and articulates with the talus
• Tarsal bones are the seven irregular bones of the ankle and hindfoot, including the talus, calcaneus, navicular, cuboid, and three cuneiforms (medial, intermediate, and lateral)
• Metatarsal bones are the five long bones of the foot, numbered 1-5 from the medial to the lateral side
• Phalanges are the bones of the toes, with each toe having three phalanges (proximal, middle, and distal), except for the great toe, which has two (proximal and distal)

Joints and Articulations

• Synovial joints are the most common and movable type of joint in the appendicular skeleton, characterized by a joint cavity containing synovial fluid
  • Examples include the shoulder (glenohumeral), elbow, wrist, hip, knee, and ankle joints
• Shoulder joint is a ball-and-socket joint formed by the head of the humerus and the glenoid cavity of the scapula, allowing for a wide range of motion
• Elbow joint is a hinge joint formed by the articulation of the trochlea of the humerus with the trochlear notch of the ulna and the capitulum of the humerus with the head of the radius
• Wrist joint is an ellipsoid joint formed by the articulation of the distal end of the radius with the proximal row of carpal bones
• Hip joint is a ball-and-socket joint formed by the head of the femur and the acetabulum of the hip bone, allowing for a wide range of motion
• Knee joint is a modified hinge joint formed by the articulation of the femoral condyles with the tibial condyles, with the patella gliding along the anterior surface of the femur
• Ankle joint is a hinge joint formed by the articulation of the distal ends of the tibia and fibula with the talus

Muscle Attachments

• Muscles of the appendicular skeleton attach to the bones via tendons, allowing for movement and stability of the limbs
• Origin is the attachment site of a muscle that remains relatively fixed during contraction, while the insertion is the attachment site that moves
• Rotator cuff muscles (supraspinatus, infraspinatus, teres minor, and subscapularis) attach to the greater and lesser tubercles of the humerus, stabilizing the shoulder joint
• Biceps brachii muscle attaches to the radial tuberosity and supraglenoid tubercle of the scapula, flexing the elbow and supinating the forearm
• Triceps brachii muscle attaches to the olecranon process of the ulna, extending the elbow
• Quadriceps femoris muscle (rectus femoris, vastus lateralis, vastus medialis, and vastus intermedius) attaches to the tibial tuberosity via the patellar tendon, extending the knee
• Hamstring muscles (biceps femoris, semitendinosus, and semimembranosus) attach to the ischial tuberosity and the proximal tibia and fibula, flexing the knee and extending the hip
• Gastrocnemius and soleus muscles (calf muscles) attach to the calcaneus via the Achilles tendon, plantar flexing the ankle

Function and Movement

• Appendicular skeleton provides attachment points for muscles, facilitating movement and locomotion
• Upper limb movements include flexion, extension, abduction, adduction, rotation, circumduction, and various hand and finger movements
  • Shoulder joint allows for flexion, extension, abduction, adduction, and rotation
  • Elbow joint allows for flexion and extension
  • Radioulnar joints allow for pronation and supination of the forearm
  • Wrist and hand joints allow for flexion, extension, abduction, adduction, and circumduction
• Lower limb movements include flexion, extension, abduction, adduction, and rotation
  • Hip joint allows for flexion, extension, abduction, adduction, and rotation
  • Knee joint allows for flexion and extension
  • Ankle joint allows for dorsiflexion and plantar flexion
  • Foot and toe joints allow for inversion, eversion, and various toe movements
• Appendicular skeleton also plays a crucial role in weight-bearing and transfer of forces during walking, running, and other activities

Clinical Relevance

• Fractures of the appendicular skeleton are common, particularly in the upper limb (e.g., colles fracture of the distal radius) and lower limb (e.g., femoral neck fracture)
  • Treatment may involve immobilization, reduction, and fixation (e.g., casting, surgical intervention with plates and screws)
• Dislocations occur when the bones of a joint are forced out of their normal alignment, often due to trauma or excessive force
  • Common dislocations include the shoulder (glenohumeral), elbow, and hip joints
  • Treatment involves reduction (manual or surgical) and immobilization to allow for healing
• Osteoarthritis is a degenerative joint disease characterized by the breakdown of articular cartilage, often affecting the hip, knee, and hand joints
  • Symptoms include pain, stiffness, and reduced range of motion
  • Treatment may involve physical therapy, medications, and in severe cases, joint replacement surgery
• Rotator cuff tears are common injuries involving the muscles and tendons that stabilize the shoulder joint, often due to overuse or trauma
  • Symptoms include pain, weakness, and reduced range of motion
  • Treatment may involve rest, physical therapy, and in some cases, surgical repair
• Carpal tunnel syndrome is a condition caused by compression of the median nerve as it passes through the carpal tunnel in the wrist
  • Symptoms include pain, numbness, and tingling in the hand and fingers
  • Treatment may involve wrist splinting, medications, and in severe cases, surgical release of the transverse carpal ligament

Key Terms and Concepts

• Appendicular skeleton: The portion of the skeleton that includes the bones of the upper and lower limbs, as well as the shoulder and pelvic girdles
• Synovial joint: A highly movable joint characterized by a joint cavity containing synovial fluid, articular cartilage, and a fibrous capsule
• Origin: The attachment site of a muscle that remains relatively fixed during contraction
• Insertion: The attachment site of a muscle that moves during contraction
• Flexion: A movement that decreases the angle between two bones or body parts
• Extension: A movement that increases the angle between two bones or body parts
• Abduction: A movement that pulls a limb or body part away from the midline of the body
• Adduction: A movement that pulls a limb or body part toward the midline of the body
• Rotation: A movement that involves turning a bone or body part around its longitudinal axis
• Circumduction: A circular movement that combines flexion, extension, abduction, and adduction
• Pronation: A movement that rotates the forearm so that the palm faces posteriorly or downward
• Supination: A movement that rotates the forearm so that the palm faces anteriorly or upward
• Dorsiflexion: A movement that brings the foot or toes closer to the shin
• Plantar flexion: A movement that points the foot or toes away from the shin
• Inversion: A movement that turns the sole of the foot inward
• Eversion: A movement that turns the sole of the foot outward