Category Archives: Anatomy

Know your body

Muscles

Hello, dears 🙂

I´ve been using the Photoshop Curves Tool. I hope these help to identify the targeted muscle in each exercise. Btw, +100 exercises are waiting for you, here 🙂

The forgotten forearms (Posterior compartment)

Last but not least, the muscles located at the posterior compartment of the forearms.

Superficial posterior compartment

The extensor digitorum muscle helps in the movements of the wrists and the elbows. It extends the phalanges, then the wrist, and finally the elbow. It acts principally on the proximal phalanges. It tends to separate the fingers as it extends them.

Extensor digitorum

Origin:

  1. lateral epicondyle via the CET (common extensor tendon).
  2. antebrachial fascia.

Insertion:

  1. the base of middle phalanx of each of the four fingers (central band).
  2. the base of distal phalanx of each of the four fingers (2 lateral bands).

The extensor digiti minimi is a two joint muscle. It acts as an extensor in both joints. It extends the wrist, which means it moves the back of the hand toward the back of the forearm. It also extends the little finger, which means it straightens the little finger from a fist. When the muscle moves, it forces the little finger to bend and stretch. Sudden or unexpected movement of the finger or trauma may damage the muscle. Traction to keep the little finger from moving is typically recommended to treat the injury. Sprain of this muscle is common in athletes but is not considered to be a serious injury.

Extensor digiti minimi

Origin:

  1. lateral epicondyle via the CET (common extensor tendon).
  2. antebrachial fascia.
  3. the ulnar aspect of extensor digitorum.

Insertion:

  1. the base of middle phalanx of the 5th digit (central band).
  2. the base of distal phalanx of the 5th digit (2 lateral bands).

The extensor carpi ulnaris muscle allows the wrist, or carpus, to extend and bend. It works in conjunction with the flexor carpi ulnaris muscle during the adduction of the wrist, meaning when the wrist bends toward the body’s midline. However, it is the only muscle responsible for ulnar deviation. This refers to the movement of the hand sideways in the direction of the pinky. The extensor carpi ulnaris muscle is the primary muscle used when you accelerate your motorcycle.

Extensor carpi ulnaris

Origin:

  1. 1st head – lateral epicondyle via the CET (common extensor tendon).
  2. 2nd head – the posterior body of the ulna.
  3. antebrachial fascia.

Insertion:

medial side of the base of the 5th metacarpal.

A common injury to the extensor carpi ulnaris is tennis elbow. This injury occurs in people that participate in activities requiring repetitive arm, elbow, and wrist, especially when they are tightly gripping an object. Some symptoms include pain when shaking hands or when squeezing/gripping an object. The pain worsens when a person moves their wrist with force. The pain intensifies because the extensor carpi ulnaris has an injury near the elbow area and as a person moves their arm, the muscle contracts, thus causing it to move over the lateral epicondyle of the humerus. This causes irritation to the already existing injury.

The brachioradialis flexes the forearm at the elbow. It enables flexion of the elbow joint. The muscle also assists with pronation and supination of the forearm. These two movements allow the forearm and hand to turn so that the palm faces up or down. The arms are the only part of the body with this ability. The muscle is used to stabilize the elbow during rapid flexion and extension while in a mid position, such as in hammering.

Brachioradialis

Origin:

  1. the upper lateral supracondylar ridge of the humerus (between the triceps and brachialis muscles).
  2. the lateral intermuscular septum of the humerus.

Insertion:

  1. the superior aspect of the styloid process of the radius.
  2. the lateral side of the distal 1/2 to 1/3 of the radius.
  3. antebrachial fascia.

The extensor carpi radialis longus is a long muscle that connects the outside of the elbow to the bone at the base of the first finger. It extends the wrist and abducts the hand.

Extensor carpi radialis longus

Origin:

  1. lower lateral supracondylar ridge (below the brachioradialis).
  2. the lateral intermuscular septum of the humerus.

Insertion:

the base of 2nd metacarpal.

The extensor carpi radialis brevis muscle aids in moving the hand. Specifically, it abducts and extends the hand at the wrist joint. It is an extensor, and an abductor of the hand at the wrist joint. That is, it serves to manipulate the wrist so that the hand moves away from the palm and towards the thumb.

Extensor carpi radialis brevis

Origin:

  1. lateral epicondyle via the CET (common extensor tendon).
  2. radial collateral ligament.
  3. antebrachial fascia.

Insertion:

base of 3rd metacarpal.

Deep posterior compartment

Supinator consists of two planes of fibers, between which the deep branch of the radial nerve lies. Its function is to supinate the forearm. Supinator always acts together with biceps, except when the elbow joint is extended.

Supinator

Origin:

  1. lateral epicondyle of humerus.
  2. supinator crest of ulna.
  3. radial collateral ligament.
  4. annular ligament.
  5. antebrachial fascia.

Insertion:

the proximal portion of the anteriorlateral surface of the radius

The extensor indicis extends the index finger, and by its continued action assists in extending the wrist and the mid carpal joints. Because the index finger and little finger have separate extensors, these fingers can be moved more independently than the other fingers.

Extensor indicis

Origin:

  1. the posterior surface of ulna (distal to extensor pollicis longus).
  2. interosseous membrane.
  3. antebrachial fascia.

Insertion:

the base of the middle and distal phalanx of the index finger

The abductor pollicis longus muscle is one of three muscles in the forearm that facilitate the movements of the thumb. The others are the extensor pollicis brevis and extensor pollicis longus. These three muscles, along with the extensor indicis, make up the group of muscles called the deep extensors.The abductor pollicis longus lies immediately below the supinator and is sometimes united with it. The chief action of abductor pollicis longus is to abduct the thumb. It also assists in extending and rotating the thumb.

Abductor pollicis longus muscle

Origin:

  1. posterior surfaces of ulna and radius.
  2. interosseous membrane.
  3. antebrachial fascia.

Insertion:

lateral aspect of base of 1st metacarpal

The extensor pollicis brevis muscle is located on the dorsal side of the forearm. In a close relationship to the abductor pollicis longus, the extensor pollicis brevis both extends and abducts the thumb.

Abductor pollicis brevis muscle

Origin:

  1. posterior surfaces of radius (below abductor pollicis longus).
  2. interosseous membrane.
  3. antebrachial fascia.

Insertion:

the base of proximal phalanx of thumb (often a slip inserts into extensor pollicis longus tendon)

The extensor pollicis longus extends the terminal phalanx of the thumb. When moving the thumb, the muscle uses the radial tubercle as a pulley.

Extensor pollicis longus

Origin:

  1. posterior surface of ulna.
  2. interosseous membrane.
  3. antebrachial fascia.

Insertion:

distal phalanx of the thumb.

The forgotten forearms (Anterior compartment)

The lower “arm” is called the forearm. The forearm contains many muscles, including the flexors and extensors of the digits, a flexor of the elbow (brachioradialis), and pronators and supinators that turn the hand to face down or upwards, respectively. In cross-section, the forearm can be divided into two fascial compartments. The posterior compartment contains the extensors of the hands, which are supplied by the radial nerve. The anterior compartment contains the flexors, and is mainly supplied by the median nerve. Let´s focus on this one.

Superficial anterior compartment

Pronator teres pronates the forearm, turning the hand posteriorly. If the elbow is flexed to a right angle, then pronator teres will turn the hand so that the palm faces inferiorly. It is assisted in this action by pronator quadratus.

It also weakly flexes the elbow, or assists in flexion at the elbow when there is strong resistance.

Pronator teres syndrome is one cause of wrist pain. It is a type of neurogenic pain.

  • Patients with the pronator teres syndrome have numbness in median nerve distribution with repetitive pronation/supination of the forearm, not flexion and extension of the elbow.
  • Early fatigue of the forearm muscles is seen with repetitive stressful motion, especially pronation.
  • EMG may show only mildly reduced conduction velocities.
  • despite their anatomic proximity, patients with pronator teres syndrome do not have a higher incidence of AIN syndrome.

Pronator teres

Origin:

  1. Humeral head:

A. upper portion of medial epicondyle via the CFT (common flexor tendon).

B. medial brachial intermuscular septum.

2. Ulnar head – coronoid process of ulna.

3. Antebrachial fascia.

Insertion:

Lateral aspect of radius at the middle of the shaft (pronator tuberosity).

Flexor carpi radialis is a muscle of the human forearm that acts to flex and (radial) abduct the hand. It is a superficial muscle that becomes very visible as the wrist comes into flexion. The flexor carpi radialis muscle is located close to the palm side of the arm, which allows it to bend the wrist on its side. This helps to reduce the angle between the forearm and the thumb. The wrist remains straight and does not extend or bend backwards.

Flexor carpi radialis

Origin:

  1. Medial epicondyle via the CFT (common flexor tendon).
  2. Antebrachial fascia.

Insertion:

Base of the 2nd and sometimes 3rd metacarpals

Palmaris longus serves no apparent function in humans.For this reason, it is actually very popular with reconstructive surgeons because they can “harvest” the tissue or the tendon and use it to rebuild other useful muscles. What is even more interesting is the fact that the muscle is completely or partially absent in about 14 percent of the population.

Palmaris longus

 Origin:

  1. Medial epicondyle via the CFT (common flexor tendon).
  2. Antebrachial fascia.

Insertion:

  1. Central portion of the flexor retinaculum.
  2. Superficial portion of the palmar aponeurosis.

The flexor carpi ulnaris muscle works in tandem with the extensor carpi ulnaris. These muscles flex the wrist and adduct it (move it laterally in the direction of ulnar).

Flexor carpi ulnaris

Origin:

  1. Humeral head – medial epicondyle via the CFT (common flexor tendon).
  2. Ulnar head:
  • Medial aspect of olecranon.
  • Proximal 3/5 of dorsal ulnar shaft.
  • Antebrachial fascia.

Insertion:

  1. Pisiform & hamate bones (via the pisohamate ligament).
  2. Base of the 5th metacarpal (via the pisometacarpal ligament).

The flexor digitorum superficialis is an extrinsic muscle that allows the four medial fingers of the hand to flex. It flexes the middle phalanges of the fingers at the proximal interphalangeal joints, however under continued action it also flexes the metacarpophalangeal joints and wrist joint. The secondary role of the muscle is to flex the metacarpophalangeal joints. These are located between the proximal phalanges and the metacarpal bones of the palm.

Flexor digitorum superficialis

Origin:

  1. Humeral-ulnar head:
  • Medial epicondyle via the CFT (common flexor tendon).
  • Medial boarder of base of coronoid process of ulna.
  • Medial (ulnar) collateral ligament.
  • Antebrachial fascia.

2. Radial head: oblique line of radius along its upper anterior boarder.

Insertion:

Both sides of the base of each middle phalanx of the 4 fingers

Deep anterior compartment

The pronator quadratus is a muscle that is near the lower part of the radius. It is the only muscle attached only to the radius at one end and the ulna at the other.

Its function is to rotate the forearm and keep the proper distance and rotation between the ulna and radius. It is also used to turn the wrist and palm of the hand. When pronator quadratus contracts, it pulls the lateral side of the radius towards the ulna, thus pronating the hand. Its deep fibers serve to keep the two bones in the forearm bound together.

Pronator quadratus

Origin:

Distal 1/4 anteriomedial surface of ulna.

Insertion:

Distal 1/4 anteriolateral surface of radius.

The flexor digitorum profundus belly is located in the forearm. However, it is considered a hand muscle because it is primarily used for hand functionality. The muscle’s long tendons extend over the wrist and the metacarpals of the hand.

It is a flexor of the wrist and helps flex the fingers.

Flexor digitorum profundus 2

Origin:

  1. Anterior & medial surface of upper 3/4 ulna.
  2. Adjacent interosseous membrane.

Insertion:

Distal phalanx of medial 4 digits (through FDS tunnel).

The flexor pollicis longus muscle is located in the lower half of the arm, from the elbow down. It is an anatomical part that is unique to humans.

The flexor pollicis longus is a flexor of the phalanges of the thumb; when the thumb is fixed, it assists by flexing the wrist.

Flexor pollicis longus

Origin:

  1. Middle anterior surface of the radius.
  2. Interosseous membrane.
  3. (may also originate from lateral boarder of coronoid process.
  4. or medial epicondyle).

Insertion:

Palmar aspect of base of the distal phalanx of thumb (deep to flexor retinaculum).

Bigger arms!

Everyone wants bigger arms, but there’s no such thing as a magical workout you can do to get them.

Arms

Let´s see the most important ones:

The Coracobrachialis is a long, slender muscle of the shoulder joint.

The contraction of the coracobrachialis leads to two movements at the shoulder joint. On one hand, it bends the arm (flexion), and on the other hand, it pulls the arm towards the trunk (adduction). To a smaller extent, it also turns the humerus inwards (inward rotation). Another important function is the stabilization of the humeral head within the shoulder joint, especially when the arm is hanging freely straight down.

The overuse of the coracobrachialis can lead to stiffening of the muscle. Common causes of injury include chest workouts or activities that require pressing the arm very tight towards the body, e.g. work on the rings in gymnastics. Symptoms of overuse or injury: pain in the arm and shoulder, radiating down to the back of the hand.

Coracobrachialis

Origin:

Coracoid process of the scapula.

Insertion:

The medial shaft of the humerus at about its middle.

The Biceps brachii, commonly known as the biceps, is a two-headed muscle that lies on the upper arm between the shoulder and the elbow. The Biceps muscle is actually two separate bundles of muscles (heads). The two heads of the Biceps vary in length and as a result, are called the Short and the Long Biceps heads.

The biceps works across three joints.

Proximal radioulnar joint (upper forearm): It functions primarily as a powerful supinator of the forearm (turns the palm upwards). This action, which is aided by the supinator muscle, requires the elbow to be at least partially flexed.

Humeroulnar joint (elbow): It also functions as an important flexor of the forearm, particularly when the forearm is supinated. This action is performed when lifting an object, such as a bag of groceries. When the forearm is in pronation (the palm faces the ground), the brachialis, brachioradialis, and supinator function to flex the forearm, with minimal contribution from the biceps brachii.

Glenohumeral joint (shoulder): TIt weakly assists in forward flexion of the shoulder joint (bringing the arm forward and upwards). It also contributes to abduction (bringing the arm out to the side) when the arm is externally (or laterally) rotated. The short head also assists with horizontal adduction (bringing the arm across the body) when the arm is internally (or medially) rotated. Finally, the short head, due to its attachment to the scapula (or shoulder blade), assists with stabilization of the shoulder joint when a heavy weight is carried in the arm.

Biceps brachii

Origin:

  1. Long head- supraglenoid tubercle and glenohumeral labrum.
  2. Short head- tip of the coracoid process of the scapula.

Insertion:

  1. Radial tuberosity.
  2. Bicipital aponeurosis.

The brachialis is a muscle in the upper arm that flexes the elbow joint. It lies deeper than the biceps brachii, and is a synergist that assists the biceps brachii in flexing at the elbow.

Its primary action is to flex the forearm muscles at the elbow. Due to its high contractile strength, the branchialis makes many arm and elbow movements possible. Such movements are important for the activities of daily life. Because movements involving the arms and elbows are almost always continuous, injuries to the brachialis muscle are quite common.

Brachialis

Origin:

  1. Lower 1/2 of anterior humerus.
  2. Both intermuscular septa.

Insertion:

  1. Ulnar tuberosity.
  2. Coronoid process of ulna slightly.

The Triceps Brachii muscles are located on the back of the humerus and more commonly referred to as the triceps. The triceps muscles have three muscle heads: Lateral, Medial and Long head.

Primarily responsible for the extension of the elbow joint (straightening of the arm). It can also fixate the elbow joint when the forearm and hand are used for fine movements, e.g., when writing. The lateral head is used for movements requiring occasional high-intensity force, while the medial fascicle enables more precise, low-force movements.

With its origin on the scapula, the long head also acts on the shoulder joint and is also involved in retroversion and adduction of the arm.

Triceps

Origin:

  1. Long head: infraglenoid tubercle of the scapula.
  2. Lateral head: upper half of the posterior surface of the shaft of the humerus, and the upper part of the lateral intermuscular septum.
  3. Medial head: posterior shaft of humerus, distal to radial groove and both the medial and lateral intermuscular septum (deep to the long & lateral heads).

Insertion:

  1. Posterior surface of the olecranon process of the ulna.
  2. Deep fascia of the antebrachium.

The anconeus muscle (or anconaeus/anconæus) is a small muscle on the posterior aspect of the elbow joint.

It assists in extension of the elbow, where the triceps brachii is the principal agonist, and supports the elbow in full extension. It also prevents the elbow joint capsule being pinched in the olecranon fossa during extension of the elbow. Anconeus also abducts the ulna and stabilizes the elbow joint. Anconeus serves to make minute movements with the radius on the ulna. In making slight abduction of the ulna, it allows any finger to be used as a axis of rotation of the forearm.

Anconeus

Origin:

Posterior surface of the lateral epicondyle of the humerus.

Insertion:

Lateral aspect of olecranon extending to the lateral part of ulnar body.

Shoulder

Shoulders

When we talk about the shoulder we usually mean the deltoid. This reduction or simplification works well until somebody has an injury in the shoulder but not specifically in the deltoid. I take this opportunity to greet all Anonimous Injuried Rotator Cuffs! Be patient, stay focus, you´ll get over it. And focusing the topic:

The Deltoid muscle is the muscle forming the rounded contour of the shoulder. It is divided into three portions, anterior, lateral and posterior, with the fibers having different roles due to their orientation.

  1. The anterior fibers are involved in shoulder abduction when the shoulder is externally rotated. It also works with the subscapularis, pecs and lats to internally (medially) rotate the humerus.
  2. The posterior fibers are strongly involved in transverse extension particularly as the latissimus dorsi is very weak in strict transverse extension. The infraspinatus and teres minor, also work with the posterior deltoid as external rotators, antagonists to strong internal rotators like the pecs and lats. The posterior deltoid is also the primary shoulder hyperextensor, more so than the long head of the triceps which also assists in this function.
  3. The lateral fibers perform the shoulder abduction when it is internally rotated, and perform shoulder transverse abduction when the shoulder is externally rotated.

Deltoid

Origin:

  1. Lateral, anterior 1/3 of the distal clavicle.
  2. Lateral boarder of the acromion.
  3. Scapular spine.

Insertion:

Deltoid tuberosity of the humerus.

The Teres major is a medial rotator and adductor of the humerus and assists the latissimus dorsi in drawing the previously raised humerus downward and backward (extension, but not hyperextension). It also helps stabilize the humeral head in the glenoid cavity. It is only functional when the Rhomboids fix the scapula. This muscle mainly helps latissimus dorsi.

Teres

Origin:

Inferior, lateral margin of the scapula.

Insertion:

Crest of lesser tubercle (just medial to the insertion of latissimus dorsi)

The Supraspinatus muscle is one of the four muscles which make up the rotator cuff. Its main function is to stabilize the upper arm by holding the head of the humerus in position. It is important in throwing motions to control any forward motion of the head of the humerus. Contraction of the supraspinatus muscle leads to the abduction of the arm at the shoulder joint. It is the main agonist muscle for this movement during the first 10-15 degrees of its arc. Beyond 30 degrees, the deltoid muscle becomes increasingly more effective at abducting the arm and becomes the main propagator of this action.

Supraspinatus

Origin:

  1. Supraspinous fossa.
  2. Muscle fascia.

Insertion:

Uppermost of three facets of the greater tubercle of the humerus.

The Infraspinatus muscle is another of the four rotator cuff muscles crossing the shoulder joint and is commonly injured. It is the main external rotator of the shoulder joint. When the arm is fixed, it abducts the inferior angle of the scapula. Its synergists are teres minor and the deltoid. The infraspinatus and teres minor rotate the head of the humerus outward (external, or lateral, rotation); they also assist in carrying the arm backward. Also reinforces the capsule of the shoulder joint.

Infraspinatus

Origin:

  1. Infraspinous fossa.
  2. Muscle fascia.

Insertion:

The middle facet of greater tubercle of the humerus.

The subscapularis rotates the head of the humerus medially (internal rotation); when the arm is raised, it draws the humerus forward and downward. It is a powerful defense to the front of the shoulder-joint, preventing displacement of the head of the humerus.

Subscapularis

Origin:

Subscapular fossa.

Insertion:

Lesser tubercle of the humerus.

The Teres minor is a narrow, elongated muscle of the rotator cuff.

The Teres minor and the infraspinatus attach to the head of the humerus; they help hold the humeral head in the glenoid cavity of the scapula. They work in tandem with the posterior deltoid to externally (laterally) rotate the humerus, as well as perform transverse abduction, extension, and transverse extension.

Rotator cuff

Origin:

The middle half of the scapula’s lateral margin.

Insertion:

Lowest of three facets of the greater tubercle of the humerus.

There are two types of rotator cuff injuries:

  1. Acute tears occur as a result of a sudden movement. This might include throwing a powerful pitch, holding a fast moving rope during water sports, falling over onto an outstretched hand at speed, or making a sudden thrust with the paddle in kayaking.
  2. A chronic tear develops over a period of time. They usually occur at or near the tendon, as a result of the tendon rubbing against the underlying bone.

Rotator cuff tear

Please, be careful 🙂

“Lats” & friends

The latissimus dorsi is the larger, flat, dorsolateral muscle on the trunk, posterior to the arm, and partly covered by the trapezius on its median dorsal region.

Lats and friends

It is responsible for extension, adduction, horizontal abduction, flexion from an extended position, and (medial) internal rotation of the shoulder joint. It also has a synergistic role in extension and lateral flexion of the lumbar spine.

Latissimus dorsi

Origin:

  1. Spinous process of T7-L5.
  2. Upper 2-3 sacral segments.
  3. Iliac crest.
  4. Lower 3 or 4 ribs.

Insertion:

Lateral lip of the intertubercular groove.

We usually forget that lats belong to another muscle group, the superficial back muscles. They originate from the vertebral column and attach to the bones of the shoulder – the clavicle, scapula, and humerus. All these muscles are therefore associated with movements of the upper limb.

The muscles in this group are the latissimus dorsi, trapezius, levator scapulae and the rhomboids.

The trapezius is a broad, flat and triangular muscle. The muscles on each side form a trapezoid shape. It is the most superficial of all the back muscles. It has three functional regions:

  1. Superior (descending part), which supports the weight of the arm.
  2. Intermediate (transverse part), which retracts the scapulae.
  3. Inferior (ascending part), which medially rotates and depresses the scapulae.

Contraction of the trapezius muscle can have two effects:

  1. Movement of the scapulae when the spinal origins are stable.
  2. Movement of the spine when the scapulae are stable. Its main function is to stabilize and move the scapula.

Trapezius

Origin:

  1. External occipital protuberance.
  2. Along the medial sides of the superior nuchal line.
  3. Ligamentum nuchae (surrounding the cervical spinous processes).
  4. Spinous processes of C1-T12.

Insertion:

  1. Posterior, lateral 1/3 of clavicle.
  2. Acromion.
  3. The superior spine of the scapula.

The levator scapulae is a small strap-like muscle. It elevates the scapula.

Levator scapulae

Origin:

Transverse processes of C1-C3 or C4.

Insertion:

The superior angle of scapula toward the scapular spine.

There are two rhomboid muscles, major and minor. The rhomboid major helps to hold the scapula (and thus the upper limb) onto the ribcage. Together with the rhomboid major, the rhomboid minor retracts the scapula when trapezius is contracted. Acting as an antagonist to the trapezius, the rhomboid major and minor elevate the scapula medially and upward, working in tandem with the levator scapulae muscle to rotate the scapulae downward. While other shoulder muscles are active, the rhomboid major and minor stabilize the scapula.

Rhomboids

Rhomboid major:

Origin:

  1. Spinous processes of T2-T5.
  2. Supraspinous ligament.

Insertion:

Medial scapula from the scapular spine to the inferior angle

Rhomboid minor:

Origin:

  1. Spinous process of C7 & T1.
  2. Ligamentum nuchae.
  3. Supraspinous ligament.

Insertion:

Medial margin of the scapula at the medial angle

Pecs

We usually call our pectoral muscles “pecs”. “Chest day” is the most famous day for men all around the world 🙂 We celebrate it once a week. Some twice.

The first thing we need to know is that pectoral muscles are a group of muscles. So, let´s take a look at them.

The pectoralis major makes up the bulk of the chest muscles in the male and lies under the breast in the female. It has four actions:

  1. Flexion of the humerus, as in throwing a ball side-arm, and in lifting a child.
  2. Adducts the humerus, as when flapping the arms.
  3. Rotates the humerus medially, as occurs when arm-wrestling.
  4. Keeps the arm attached to the trunk of the body.

Origin:

  1. Medial 1/3 of the clavicle.
  2. Anterior aspect of manubrium & length of the body of the sternum.
  3. Cartilaginous attachments of upper 6 ribs.
  4. External oblique’s aponeurosis.

Insertion:

  1. Lateral lip of bicipital groove to the crest of the greater tubercle.
  2. Clavicular fibers insert more distally; sternal fibers more proximally.

Pectoral mayor

Most lesions are located at the musculotendinous junction and result from violent, eccentric contraction of the muscle, such as during bench press.

The pectoralis minor is a thin, triangular muscle, situated at the upper part of the chest, beneath the pectoralis major. The pectoralis minor depresses the point of the shoulder, drawing the scapula inferior, towards the thorax, and throwing its inferior angle posteriorly.

Origin:

The outer surface of ribs 2-5 or 3-5 or 6.

Insertion:

Medial aspect of the coracoid process of the scapula.

Pectoral menor

The subclavius is a small triangular muscle, placed between the clavicle and the first rib. Along with the pectoralis major and pectoralis minor muscles, the subclavius muscle makes up the anterior wall of the axilla.

The subclavius depresses the shoulder, carrying it downward and forward. It draws the clavicle inferiorly as well as anteriorly. Also protects the underlying brachial plexus and subclavian vessels from a broken clavicle (the most frequently broken long bone).

Origin:

First rib about the junction of bone and cartilage.

Insertion:

The lower surface of the clavicle.

Subclavius

The serratus anterior is found more laterally in the chest and, forms the medial wall of the axilla.

The pectoralis major has been resected to expose the deeper muscles of the chest.
The muscle consists of several strips.

The main action of the serratus anterior is to rotate the scapula, allowing the arm to be raised over 90 degrees. It also holds the scapula against the rib cage – this is particularly useful when upper limb reaches anteriorly (e.g punching).

Origin:

Fleshy slips from the outer surface of upper 8 or 9 ribs.

Insertion:

The costal aspect of medial margin of the scapula.

Serratus anterior