Anatomy of the Upper Limb: Bones and Joints

Upper Limb Overview

Major Regions of the Upper Limb

The upper limb consists of several anatomical regions, each with distinct bones and functions. Understanding these regions is essential for studying limb movement and musculoskeletal anatomy.

• Arm: The region between the shoulder and elbow, primarily containing the humerus.

• Forearm: The region between the elbow and wrist, containing the radius and ulna.

• Hand: Composed of the carpal bones (wrist), metacarpals (palm), and phalanges (fingers).

Skeleton of the Hand includes:

• Carpals: Eight small bones forming the wrist.

• Metacarpals: Five bones forming the palm.

• Phalanges: Fourteen bones forming the fingers.

Shoulder Girdle

Clavicle

The clavicle, or collarbone, is a long bone that serves as a strut between the shoulder blade and the sternum. It stabilizes the shoulder and allows for a wide range of arm movements.

• Sternal (medial) end: Articulates with the sternum.

• Acromial (lateral) end: Articulates with the acromion of the scapula.

Scapula (Shoulder Blade)

The scapula is a flat, triangular bone located on the posterior side of the ribcage. It provides attachment points for muscles and articulates with the humerus at the shoulder joint.

• Coracoid process: A hook-like projection for muscle attachment.

• Acromion: The lateral extension that forms the highest point of the shoulder.

• Glenoid cavity: A shallow socket that articulates with the head of the humerus.

• Spine: A prominent ridge on the posterior surface.

Humerus

Structure and Landmarks

The humerus is the single bone of the arm, extending from the shoulder to the elbow. It features several anatomical landmarks important for muscle attachment and joint articulation.

• Head: Articulates with the glenoid cavity of the scapula.

• Greater and Lesser Tubercles: Sites for muscle attachment.

• Anatomical Neck: Just below the head, marking the joint capsule attachment.

• Surgical Neck: Common site of fractures.

• Deltoid Tuberosity: Attachment for the deltoid muscle.

• Medial and Lateral Epicondyles: Attachment points for forearm muscles.

• Capitulum and Trochlea: Articulate with the radius and ulna, respectively.

• Radial and Coronoid Fossae: Depressions for accommodating forearm bones during flexion.

Radius and Ulna

Forearm Bones

The radius and ulna are the two long bones of the forearm. They run parallel to each other and are connected by an interosseous membrane.

• Radius: Located on the lateral (thumb) side of the forearm.

• Ulna: Located on the medial (little finger) side of the forearm.

Key Landmarks

• Head of radius: Articulates with the capitulum of the humerus and the radial notch of the ulna.

• Radial tuberosity: Attachment for the biceps brachii muscle.

• Styloid process of radius: Distal projection for ligament attachment.

• Olecranon process (ulna): Forms the bony prominence of the elbow.

• Coronoid process (ulna): Fits into the coronoid fossa of the humerus during flexion.

• Trochlear notch (ulna): Articulates with the trochlea of the humerus.

• Radial notch (ulna): Articulates with the head of the radius.

Joints of the Forearm

• Proximal radioulnar joint: Allows rotation of the radius over the ulna (pronation and supination).

• Distal radioulnar joint: Also involved in forearm rotation.

• Interosseous membrane: Fibrous sheet connecting the radius and ulna along their lengths.

Elbow Joint

Anatomy and Articulations

The elbow joint is a complex hinge joint formed by the articulation of the humerus, radius, and ulna. It allows for flexion, extension, and rotation of the forearm.

• Capitulum (humerus): Articulates with the head of the radius.

• Trochlea (humerus): Articulates with the trochlear notch of the ulna.

• Radial fossa: Receives the head of the radius during flexion.

• Coronoid fossa: Receives the coronoid process of the ulna during flexion.

• Olecranon fossa: Receives the olecranon process of the ulna during extension.

Functional Movements

• Flexion and Extension: Movement of the forearm toward and away from the upper arm.

• Pronation and Supination: Rotation of the forearm so the palm faces down (pronation) or up (supination).

Table: Key Bones and Landmarks of the Upper Limb

This table summarizes the major bones and their important anatomical landmarks in the upper limb.

Bone	Key Landmarks	Articulations
Clavicle	Sternal end, Acromial end	Sternum, Scapula
Scapula	Acromion, Coracoid process, Glenoid cavity, Spine	Clavicle, Humerus
Humerus	Head, Greater/Lesser tubercles, Epicondyles, Capitulum, Trochlea	Scapula, Radius, Ulna
Radius	Head, Radial tuberosity, Styloid process	Humerus, Ulna, Carpal bones
Ulna	Olecranon process, Coronoid process, Trochlear notch, Radial notch, Styloid process	Humerus, Radius, Carpal bones
Hand	Carpals, Metacarpals, Phalanges	Radius, Ulna

Additional info:

• The anatomical neck of the humerus is the site of attachment for the joint capsule, while the surgical neck is a common site for fractures.

• The interosseous membrane between the radius and ulna provides additional stability and serves as an attachment for muscles.

• Movements at the elbow joint are essential for daily activities such as lifting, throwing, and writing.