Arm Musculature of The Human Body

Origin – The fixed attachment point of a muscle. This is typically the end of the muscle that attaches to the more stationary bone in a pair of bones being moved by that muscle. The origin is generally proximal, meaning closer to the center of the body, or on the more stable part of the skeletal structure.

 

Insertion – The insertion point of a muscle is where it attaches to the bone and is the part that moves during muscle contraction. This part of the muscle is usually located far from the center of the body, and moves towards the muscle’s origin when it contracts. Understanding the insertion point is important in determining a muscle’s function in movement and leverage, as it influences the direction and force of the movement produced by the muscle contraction.

 

Isolated Function – The term “isolated function” refers to the specific action a muscle performs when it contracts independently, without the influence of other muscles. Understanding this concept is crucial for comprehending the primary role of each muscle in movement, as it highlights the muscle’s unique ability to produce a particular movement at a joint. The study of isolated functions is often used to understand muscle imbalances, rehabilitation needs, and design targeted exercises for strengthening or stretching a specific muscle.

 

Integrated Function – The coordinated action of muscles is crucial during complex movements and requires them to work in concert with other muscles and body systems. Isolated function, which focuses on a muscle acting alone, is not enough to fully understand bodily movements. Integrated function, on the other hand, emphasizes how muscles function together in groups, providing a more holistic view of bodily movements. This concept is essential to comprehend how muscles contribute to overall body mechanics, stability, and efficiency during everyday activities and sports.

 

Innervation – the supply of nerves to a muscle, which enables the muscle to receive and respond to neural signals. This connection is crucial for muscle activation and control, as it allows the nervous system to regulate muscle contractions, both voluntary and involuntary. Innervation is a key aspect in understanding how muscles function, their responsiveness to stimuli, and their role in movement and sensation.

 

Concentric – refers to a type of muscle contraction in which the muscle fibers shorten as they contract. This occurs when a muscle generates enough force to overcome resistance, resulting in the movement of body parts towards each other. A common example of a concentric contraction is the upward movement during a bicep curl, where the bicep muscle shortens to lift the weight. Concentric contractions are integral to many types of physical activities and exercises, playing a key role in building muscle strength and movement.

 

Eccentric – refers to a type of muscle contraction where the muscle lengthens while under tension. This occurs when a muscle gradually controls or resists the movement caused by an external force, like gravity. Eccentric contractions are often associated with controlled lowering or decelerating actions, such as lowering a weight during a bicep curl or descending stairs. They play a crucial role in activities requiring controlled movements and are significant in muscle strengthening and injury prevention.

 

Isometric – refers to a type of muscle contraction where the muscle generates force without changing its length. During isometric exercises, the muscle neither shortens (as in concentric contractions) nor lengthens (as in eccentric contractions), but tension is still produced. Common examples include holding a plank position or maintaining a squat. Isometric contractions are essential for stabilizing joints and maintaining posture, and they are often used in rehabilitation and strength training programs.

 

Biceps Brachii

 

Origin

Short head – Coracoid process

Long head – Tubercke above glenoid cavity on the humerus

 

Insertion

Radial tuberosity of the radius

 

Isolated Function

Concentric action – Elbow flexion, supination of the radioulnar joint and shoulder flexion 

 

Integrated Function

Eccentric action – Elbow extension, pronation of the radioulnar joint and shoulder extension

Isometric action – Stabilizes the elbow and shoulder girdle

 

Innervation

Musculocutaneous nerve

Triceps Brachii

Origin

 Long head – Infraglenoid tubercle of the scapula

Short head – Posterior humerus

Medial head – Posterior humerus

 

Insertion

Olecranon process of the ulna

 

Isolated Function

Concentric action – Elbow extension and shoulder extension

 

Integrated Function

Eccentric action – Elbow flexion and shoulder flexion

Isometric action – Stabilizes the elbow and shoulder girdle

 

Innervation

Radial nerve

 

Brachialis

Origin

 Humerus

 

Insertion

Coronoid process of the ulna

 

Isolated Function

Concentric action – Flexes elbow

 

Integrated Function

Eccentric action – Elbow extension 

Isometric action – Stabilizes the elbow

 

Innervation

Musculocutaneous and radial nerve

 

Anconeus

Origin

 Lateral epicondyle of humerus

 

Insertion

Olecranon process and posterior ulna

 

Isolated Function

Concentric action – Extends elbow

 

Integrated Function

Eccentric action – Elbow flexion

Isometric action – Stabilizes the elbow

 

Innervation

Radial nerve

 

Brachioradialis

Origin

 Lateral supracondylar ridge of humerus

 

Insertion

Syloid process of radius

 

Isolated Function

Concentric action – Flexes elbow

 

Integrated Function

 Eccentric action – elbow extension 

Isometric action – Stabilizes the elbow

 

Innervation

Radial nerve

 

Pronator Quadratus

Origin

 Distal ulna

 

Insertion

Distal radius

 

Isolated Function

Concentric action – Pronates forearm

 

Integrated Function

Eccentric action – Forearm supination

Isometric action – Stabilizes distal radioulnar joint

 

Innervation

Anterior interosseosus nerve

 

 

Pronator Teres

Origin

 Medial epicondyle of humerus and coronoid process of ulna

 

Insertion

Radius

 

Isolated Function

Concentric action: Pronates forearm

 

Integrated Function

Eccentric action – Forearm supination

Isometric action – Stabilizes proximal radioulnar joint and elbow

 

Innervation

Median nerve

 

Supinator

Origin

 Lateral epicondyle of humerus

 

Insertion

Radius

 

Isolated Function

Concentric action – Supinates forearm

 

Integrated Function

Eccentric action – forearm pronation

Isometric action – Stabilizes proximal radioulnar joint and elbow

 

Innervation

Radial nerve

 

Conclusion