Appendicular Skeleton: Structure and Function in Human Anatomy

Appendicular Skeleton

Overview

The appendicular skeleton consists of the bones of the upper and lower limbs, as well as the girdles that attach them to the axial skeleton. It plays a crucial role in movement and manipulation of the environment.

• Upper limb: Includes the pectoral girdle (clavicle and scapula), arm, forearm, wrist, and hand.

• Lower limb: Includes the pelvic girdle (coxal bones), thigh, leg, ankle, and foot.

Upper Limb

Pectoral Girdle

The pectoral girdle attaches the upper limb to the trunk and provides attachment points for muscles that move the limb.

• Clavicle: S-shaped bone that articulates medially with the sternum (sternal end) and laterally with the scapula (acromial end).

• Scapula: Flat, triangular bone with several important features:

  • Spine – prominent ridge on the posterior surface

  • Acromion – lateral extension of the spine, articulates with clavicle

  • Coracoid process – anterior projection for muscle attachment

  • Glenoid cavity – shallow socket that articulates with the head of the humerus

  • Fossae: subscapular, supraspinous, infraspinous

Segments of the Upper Limb

Segment	Location	Description
Shoulder	Proximal region overlapping neck, back, thorax	Contains one clavicle and one scapula; includes shoulder joint
Arm	Between shoulder and elbow	Contains one humerus
Forearm	Between elbow and wrist	Contains one radius and one ulna
Wrist and hand	Distal to forearm	Contains 8 carpals, 5 metacarpals, and 14 phalanges

Key Terminology: Upper Limb

• Clavicle: Acromial end, sternal end

• Scapula: Spine, acromion, coracoid process, glenoid cavity, fossae

• Humerus: Head, greater and lesser tubercles, shaft, deltoid tuberosity, trochlea, capitulum, olecranon fossa, medial and lateral epicondyles

• Ulna: Olecranon, coronoid process, trochlear notch, radial notch, styloid process, ulnar head

• Radius: Head, neck, radial tuberosity, styloid process

• Hand: Carpals, metacarpals, proximal/middle/distal phalanges, pollex (thumb), metacarpophalangeal and interphalangeal joints

Lower Limb

Pelvic Girdle

The pelvic girdle supports the weight of the upper body and protects pelvic organs. It consists of two coxal (hip) bones, each formed by the fusion of three bones:

• Ilium

• Ischium

• Pubis

The pelvic girdle articulates with the sacrum (axial skeleton) and forms the bony pelvis.

Key Terminology: Pelvic Girdle

• Acetabulum: Deep socket for the head of the femur

• Obturator foramen: Large opening for nerves and blood vessels

• Iliac crest, iliac fossa, ischial spine, pubic symphysis, pubic arch

Segments of the Lower Limb

Segment	Location	Description
Thigh	Between hip and knee	Contains one femur
Leg	Between knee and ankle	Contains tibia (weight-bearing) and fibula (lateral, non-weight-bearing)
Ankle and foot	Distal to leg	Contains 7 tarsals, 5 metatarsals, and 14 phalanges

Key Terminology: Lower Limb

• Femur: Head, neck, greater and lesser trochanters, shaft, linea aspera, medial/lateral condyles, epicondyles, patellar surface

• Tibia: Medial/lateral condyles, tibial tuberosity, medial malleolus

• Fibula: Head, lateral malleolus

• Foot: Tarsals (talus, calcaneus, cuboid, navicular, cuneiforms), metatarsals, phalanges

• Arches of the foot: Medial longitudinal, lateral longitudinal, transverse

Articulations and Functional Anatomy

Upper Limb Articulations

• Shoulder joint: Glenohumeral joint (scapula and humerus)

• Elbow joint: Humerus, radius, and ulna

• Wrist joint: Radius and carpal bones

• Hand joints: Metacarpophalangeal and interphalangeal joints

Lower Limb Articulations

• Hip joint: Acetabulum of pelvis and head of femur

• Knee joint: Femur, tibia, and patella (fibula does not participate in knee joint)

• Ankle joint: Tibia, fibula, and talus

• Foot joints: Intertarsal, tarsometatarsal, metatarsophalangeal, and interphalangeal joints

Self-Test and Identification Practice

• Be able to identify bones and major landmarks from anterior, posterior, and lateral views.

• Practice distinguishing left/right bones and recognizing key features (e.g., glenoid cavity, acetabulum, malleoli).

Summary Table: Major Bones and Landmarks

Region	Bone	Key Landmarks
Pectoral Girdle	Clavicle	Acromial end, sternal end
Pectoral Girdle	Scapula	Spine, acromion, coracoid process, glenoid cavity
Arm	Humerus	Head, tubercles, epicondyles, olecranon fossa
Forearm	Radius	Head, styloid process
Forearm	Ulna	Olecranon, styloid process
Hand	Carpals, Metacarpals, Phalanges	Pollex (thumb)
Pelvic Girdle	Coxal bone	Ilium, ischium, pubis, acetabulum
Thigh	Femur	Head, neck, trochanters, condyles
Leg	Tibia	Condyles, tibial tuberosity, medial malleolus
Leg	Fibula	Head, lateral malleolus
Foot	Tarsals, Metatarsals, Phalanges	Talus, calcaneus, arches

Example: The glenoid cavity of the scapula articulates with the head of the humerus to form the shoulder joint, allowing for a wide range of motion.

Additional info: The appendicular skeleton is essential for locomotion and manipulation, and its joints are generally more mobile than those of the axial skeleton, but also more prone to injury.