Appendicular Skeleton, Joints, and Body Movements: Study Guide

Appendicular Skeleton

Comparison of Male and Female Pelvises

The pelvis is a key anatomical structure that differs between males and females, reflecting adaptations for childbirth and locomotion.

• Female Pelvis:

  • Wider and shallower

  • Larger, oval pelvic inlet

  • Broad subpubic angle (>80–90°)

  • Larger sciatic notch

  • Iliac crests flare outward

  • Adapted for childbirth

• Male Pelvis:

  • Narrower and deeper

  • Heart-shaped pelvic inlet

  • Narrow subpubic angle (<70°)

  • Smaller sciatic notch

  • Iliac crests more vertical

  • Adapted for strength and support

Feature	Female Pelvis	Male Pelvis
Pelvic Inlet	Oval, larger	Heart-shaped, smaller
Subpubic Angle	>80–90°	<70°
Sciatic Notch	Larger	Smaller
Iliac Crest	Flared outward	Vertical
Function	Childbirth	Strength/support

Upper Limb Bones and Markings

The upper limb consists of several bones, each with distinct anatomical landmarks important for movement and muscle attachment.

• Scapula:

  • Spine: Prominent ridge for muscle attachment

  • Acromion: Articulates with clavicle

  • Glenoid cavity: Socket for humerus

  • Coracoid process: Attachment for muscles and ligaments

• Clavicle: Connects sternum to scapula; stabilizes shoulder

• Humerus:

  • Head: Proximal, fits into glenoid cavity

  • Capitulum: Articulates with radius

  • Trochlea: Articulates with ulna

  • Medial/Lateral epicondyles: Muscle attachment

  • Olecranon fossa: Accommodates olecranon process of ulna

• Radius: Thumb side; head, radial tuberosity, styloid process

• Ulna: Pinky side; trochlear notch, olecranon process (forms elbow point)

• Hand Bones: Carpals (wrist) → Metacarpals (palm) → Phalanges (fingers)

  • Phalanges: Proximal, middle, distal (thumb has only proximal and distal)

Coxal Bones

The coxal (hip) bones are composed of three fused bones: ilium, ischium, and pubis. They form the acetabulum, the socket for the femur.

• Ilium: Iliac crest, acetabulum

• Ischium: Obturator foramen, acetabulum

• Pubis: Pubic symphysis, obturator foramen, acetabulum

• Acetabulum: Formed by all three coxal bones; articulates with femur

Lower Limb Bones

The lower limb supports body weight and enables locomotion.

• Femur: Head, greater trochanter, medial/lateral condyles

• Patella: Kneecap; protects knee joint

• Tibia: Main weight-bearing bone; medial/lateral condyles, tibial tuberosity, medial malleolus

• Fibula: Non-weight-bearing; lateral malleolus

• Foot Bones: Tarsals (ankle) → Metatarsals (foot) → Phalanges (toes)

  • Tarsals: Talus (ankle articulation), calcaneus (heel)

  • Phalanges: Proximal, middle, distal (big toe has only proximal and distal)

Articulations (Joints)

Structural Classification of Joints

Joints are classified based on the material binding the bones and the presence or absence of a joint cavity.

• Fibrous Joints:

  • Dense connective tissue

  • No joint cavity

  • Usually immovable

  • Examples: Skull sutures, teeth in sockets

• Cartilaginous Joints:

  • Bones connected by cartilage

  • Slight movement

  • Examples: Pubic symphysis, intervertebral discs

• Synovial Joints:

  • Joint cavity present

  • Freely movable

  • Examples: Shoulder, hip, knee, elbow

Functional Classification of Joints

Joints are also classified by their degree of movement.

• Synarthroses: Immovable (e.g., skull sutures)

• Amphiarthroses: Slightly movable (e.g., pubic symphysis)

• Diarthroses: Freely movable (e.g., synovial joints)

Synovial Joint Structures and Functions

Synovial joints are complex and allow for a wide range of movements.

Structure	Function
Ligament	Connects bone to bone
Joint cavity	Space containing synovial fluid
Synovial fluid	Lubricates and nourishes cartilage
Articular cartilage	Reduces friction and absorbs shock
Articular capsule	Encloses the joint
Synovial membrane	Produces synovial fluid
Fibrous capsule	Outer supportive layer

Types of Synovial Joints

Synovial joints are classified by the shapes of their articulating surfaces and the movements they allow.

• Plane (Gliding): Flat surfaces slide past one another (e.g., intercarpal joints)

• Hinge: Movement in one plane (e.g., elbow joint)

• Pivot: Rotation around a central axis (e.g., proximal radioulnar joint)

• Condylar (Ellipsoid): Movement in two planes (e.g., metacarpophalangeal joints)

• Saddle: Biaxial movement with opposing saddle-shaped surfaces (e.g., thumb carpometacarpal joint)

• Ball-and-Socket: Multiaxial movement (e.g., shoulder, hip)

Joint Stability vs. Range of Motion

Joint stability and mobility are influenced by several factors.

• Shape of Articular Surfaces: Deeper sockets provide more stability; shallower sockets allow greater mobility

• Ligaments: More ligaments increase stability; tight ligaments reduce range of motion

• Muscle Tone: Strong muscles and tendons stabilize joints; weak muscles decrease stability

Joint	Stability	Mobility
Shoulder	Less stable (shallow glenoid cavity)	Very mobile
Hip	More stable (deep acetabulum, strong ligaments)	Less range of motion

Synovial Joint Movements

Types of Movements

Synovial joints allow a variety of movements, each with specific anatomical definitions.

• Flexion: Decreases joint angle (e.g., bending the elbow)

• Extension: Increases joint angle (e.g., straightening the elbow)

• Hyperextension: Extension beyond anatomical position (e.g., looking upward)

• Abduction: Movement away from the midline (e.g., raising arm sideways)

• Adduction: Movement toward the midline (e.g., lowering arm to side)

• Rotation: Bone turns around its long axis (e.g., turning head side to side)

• Circumduction: Circular movement (e.g., making arm circles)

• Pronation: Palm turns downward/posteriorly (e.g., typing with palms down)

• Supination: Palm turns upward/anteriorly (e.g., holding a bowl of soup)

• Inversion: Sole of foot turns inward

• Eversion: Sole of foot turns outward

• Dorsiflexion: Toes move upward (e.g., standing on heels)

• Plantarflexion: Toes point downward (e.g., standing on tiptoes)

• Protraction: Anterior movement (e.g., rounding shoulders forward)

• Retraction: Posterior movement (e.g., pulling shoulders back)

High-Yield Memory Tricks

• RUM: Radius = Thumb side

• Tibia is Thick: Main weight-bearing lower leg bone

• Calcaneus: Heel bone

• Talus: Ankle articulation

• Carpals: Hand; Tarsals: Foot

• Capitulum → Radius; Trochlea → Ulna

• Shoulder = Mobility; Hip = Stability

• Supination = Holding Soup

• Inversion = INward; Eversion = Exit (outward)

• Epicondyles are above condyles

Summary Table: Synovial Joint Structures & Functions

Structure	Function
Ligament	Connects bone to bone
Joint cavity	Contains synovial fluid
Synovial fluid	Lubricates and nourishes cartilage
Articular cartilage	Reduces friction, absorbs shock
Articular capsule	Encloses joint
Synovial membrane	Produces synovial fluid
Fibrous capsule/layer	Provides strength

Additional info: The appendicular skeleton includes the limbs and girdles, which are essential for movement and manipulation of the environment. Joints, especially synovial joints, are critical for providing both stability and mobility, and their structure determines their function and range of motion.