Anatomía - Músculos del Hombro (Origen, Inserción, Acción, Inervación, Irrigación)

Muscles of the Shoulder: An Overview

Introduction to Shoulder Muscles

• The class focuses on the muscles of the shoulder, specifically the posterolateral region as indicated by Rubier. Key muscles include:

• Deltoid

• Supraspinatus

• Infraspinatus

• Teres Major and Minor

• Subscapularis

• Rotator Cuff and Triangle of Teres

• A quadrilateral structure will also be discussed later in the session. Diagrams will be available in the description.

Anatomy of the Deltoid Muscle

• The deltoid is a large, superficial muscle with a triangular shape; its base points upward while its apex points downward.

Origin and Insertion

• Origin:

• Anteriorly from the outer third of the superior surface and anterior border of the clavicle.

• Also originates from the acromion of the scapula and inferior lip of the spine of the scapula.

• Insertion:

• Inserts at the upper lip of a structure known as deltoid impression or V-shaped area on humerus. Preferred term is "V deltoidea."

Relationships and Surroundings

• Beneath the deltoid lies a synovial bursa called subdeltoid bursa.

• The anterior edge of deltoid forms a space with pectoralis major known as:

• Deltopectoral groove (or Morhe channel), which allows passage for:

• Cephalic vein (primary)

• Branch from acromiothoracic artery

Blood Supply and Innervation

• Blood Supply: Provided by posterior circumflex humeral artery.

• Innervation: Motor innervation via axillary nerve, originating from posterior cord of brachial plexus; sensory innervation comes from cervical plexus.

Actions Performed by Deltoid Muscle

• Assists in abduction, extension, and flexion movements at shoulder joint.

• Notably contributes to lifting arm away from body (abduction) and extending it backward.

Overview of Supraspinatus Muscle

Location and Structure

• Located in supraspinous fossa; has a flattened triangular shape.

• Originates from supraspinous fossa and fascia covering it. Inserts at greater tubercle (troquiter) on humerus.

Blood Supply and Innervation for Supraspinatus

• Blood Supply: Supplied by suprascapular artery.

Muscle Anatomy: Infraespinoso, Redondo Menor, and Redondo Mayor

Infraespinoso Muscle Overview

• The infraespinoso muscle is responsible for the abduction of the upper limb when it contracts. This action can be observed clearly in practice.

• It originates from the medial two-thirds of the fossa infraespinosa and also attaches to the infraespinous fascia. A fibrous septum separates it from the redondo menor and redondo mayor muscles.

• The muscle inserts at the greater tuberosity of the humerus, specifically at its termination point. This anatomical detail is crucial for understanding its function.

• Its blood supply comes from two arteries: the inferior scapular artery and the posterior scapular artery, while innervation is provided by the suprascapular nerve, similar to that of the supraspinatus muscle.

• The primary actions include lateral rotation and abduction of the arm, which are essential movements in various physical activities.

Redondo Menor Muscle Insights

• The redondo menor muscle is cylindrical and somewhat thicker than other muscles in this group; it assists in lateral rotation of the arm alongside infraespinosus.

• It originates from a specific area on the lateral side of the fossa infraespinosa and extends upward to insert at the greater tuberosity of the humerus, sharing this insertion with other rotator cuff muscles.

• Blood supply for this muscle includes branches from both suprascapular artery, as well as inferior scapular and posterior circumflex humeral arteries; however, innervation is primarily through the axillary nerve (circumflex). Emphasis on innervation is critical due to its importance over blood supply in functional anatomy discussions.

• Like infraespinosus, redondo menor aids in lateral rotation but also plays a role in stabilizing shoulder movements during various activities.

Redondo Mayor Muscle Characteristics

• The redondo mayor muscle appears wider and flatter compared to redondo menor; it originates from below on the lateral border of scapula or sometimes referred to as lower angle of scapula (omóplato).

• Its insertion occurs at a specific location known as labrum posterior or internal lip of bicipital groove on humerus, which allows for effective movement mechanics during adduction tasks.

• Blood supply comes mainly from subscapular artery while innervation is via subscapular nerve inferiorly; these details are vital for understanding potential injury impacts or surgical considerations related to these muscles.

• Actions include aiding adduction towards midline along with medial rotation—opposite functions compared to previously discussed muscles—highlighting their complementary roles within shoulder dynamics during motion execution.

Subescapular Muscle Overview

• The final focus shifts towards discussing subescapularis—a broad flat muscle occupying entire extent within its respective fossa—integral for comprehensive understanding regarding shoulder musculature interactions overall.

Muscle Anatomy and Triangles of the Shoulder

Subscapular Muscle Overview

• The subscapular muscle originates in the subscapular fossa, with its fascicles directed upwards and outwards, terminating at a broad tendon near the lesser tuberosity of the humerus.

• Innervation is provided by the upper and lower subscapular nerves, while blood supply comes from the subscapular artery.

• The primary action of the subscapular muscle is to facilitate medial rotation of the arm. This function is visually demonstrated as the image rotates to highlight its position.

Triangle of the Teres Muscles

• The triangle formed by the teres major, teres minor, and surgical neck of the humerus serves as an anatomical landmark connecting anterior axillary space with posterior arm compartment.

• Boundaries are defined: superiorly by teres minor, inferiorly by teres major, and laterally by surgical neck of humerus. This triangle also contains smaller geometric figures due to presence of long head of triceps.

Omotricipital Triangle

• Identified as "triangle omotricipital," it has boundaries set by teres minor (superior), teres major (inferior), and long head of triceps (lateral). Its content includes circumflex scapular artery.

• Also referred to as "escápulo-tricipital" or "triángulo de Velpo," highlighting its significance in anatomical nomenclature.

Humerotricipital Quadrilateral

• Known as "humerotricipital quadrilateral" or "quadrilátero de Velpo," this structure lies between humerus and long head of triceps with specific boundaries: superior (teres minor), inferior (teres major), medial (long head of triceps), lateral (surgical neck). Contains circumflex nerve and posterior humeral circumflex artery.

Humeral Tricipital Triangle

• A smaller triangle called "húmero tricipital" or after Argentino Avelino Gutiérrez features boundaries set by teres major (superior), long head of triceps (medial), and humerus (lateral). Its contents include radial nerve and deep brachial artery which do not penetrate but pass through this area visibly.

Rotator Cuff Muscles

• The rotator cuff comprises four muscles that stabilize glenohumeral joint: supraspinatus, infraspinatus, teres minor, and subscapularis; each inserts at either greater or lesser tubercle on humerus for effective stabilization during movement.