Muscles of the upper body

Muscles of the Thorax

Pectoral Muscles

The pectoral muscles are located in the anterior thoracic region and play key roles in movements of the shoulder and respiration.

• MUSCHIUL PECTORAL MARE (m. pectoralis major): A large, fan-shaped muscle with three parts (clavicular, sternocostal, abdominal) originating from the medial clavicle, anterior sternum, and costal cartilages of ribs II-VII. Inserts on the crest of the greater tubercle of the humerus.

  Function: Adducts and medially rotates the arm; assists in inspiration when the arm is fixed.

• MUSCHIUL STERNAL (m. sternalis): Sometimes present, runs parallel to the sternum.

  Function: Unclear, possibly assists in movements of the anterior thoracic wall.

• MUSCHIUL PECTORAL MIC (m. pectoralis minor): Small, triangular muscle deep to pectoralis major, originates from ribs III-V and inserts on the coracoid process of the scapula.

  Function: Stabilizes and depresses the scapula.

• MUSCHIUL SUBCLAVICULAR (m. subclavius): Small muscle beneath the clavicle, originates from the first rib and inserts on the inferior surface of the clavicle.

  Function: Stabilizes the clavicle, assists in inspiration by elevating the first rib.

Intercostal Muscles

Intercostal muscles are located between the ribs and are essential for respiration.

• MUSCHIUL INTERCOSTAL EXTERN (mm. intercostales externi): Occupy the outermost intercostal spaces, run obliquely downward and forward.

  Function: Elevate the ribs during inspiration.

• MUSCHIUL INTERCOSTAL INTERN (mm. intercostales interni): Located deep to the external intercostals, run obliquely downward and backward.

  Function: Depress the ribs during expiration.

• MUSCHIUL INTERCOSTAL INTIMI (mm. intercostales intimi): The deepest layer, separated from the internal intercostals by neurovascular bundles.

  Function: Assist in forced expiration.

• MUSCHIUL SUBCOSTAL (mm. subcostales): Located on the inner surface of the posterior thoracic wall.

  Function: Depress the ribs, assist in expiration.

• MUSCHIUL TRANSVERSAL TORACELUI (m. transversus thoracis): Located on the inner surface of the anterior thoracic wall.

  Function: Depress the ribs, assist in expiration.

• MUSCHIUL RIDICATORI AL COASTELOR (mm. levatores costarum): Small muscles that elevate the ribs.

  Function: Assist in inspiration.

Diaphragm

The diaphragm is the principal muscle of inspiration, separating the thoracic and abdominal cavities.

• Origin: Lumbar vertebrae (crura), costal cartilages of lower ribs, and xiphoid process of the sternum.

• Insertion: Central tendon of the diaphragm.

• Function: Contracts to increase thoracic volume, drawing air into the lungs.

• Additional info: The diaphragm has three parts: lumbar, costal, and sternal. Openings in the diaphragm allow passage of the aorta, esophagus, and inferior vena cava.

Muscles of the Shoulder (Scapular Region)

Deltoid Muscle

The deltoid is the main abductor of the shoulder, covering the shoulder joint.

• Origin: Lateral clavicle, acromion, and spine of the scapula.

• Insertion: Deltoid tuberosity of the humerus.

• Function: Abducts, flexes, extends, and rotates the arm.

Rotator Cuff Muscles

The rotator cuff stabilizes the shoulder joint and allows rotation and abduction of the arm.

• MUSCHIUL SUPRASPINOS (m. supraspinatus): Originates from the supraspinous fossa of the scapula, inserts on the greater tubercle of the humerus.

  Function: Abducts the arm; stabilizes the shoulder joint.

• MUSCHIUL INFRASPINOS (m. infraspinatus): Originates from the infraspinous fossa, inserts on the greater tubercle of the humerus.

  Function: Laterally rotates the arm; stabilizes the shoulder joint.

• MUSCHIUL ROTUND MIC (m. teres minor): Originates from the lateral border of the scapula, inserts on the greater tubercle of the humerus.

  Function: Laterally rotates the arm.

• MUSCHIUL SUBSCAPULAR (m. subscapularis): Originates from the subscapular fossa, inserts on the lesser tubercle of the humerus.

  Function: Medially rotates and adducts the arm.

Other Scapular Muscles

• MUSCHIUL ROTUND MARE (m. teres major): Originates from the inferior angle and lateral border of the scapula, inserts on the crest of the lesser tubercle of the humerus.

  Function: Adducts and medially rotates the arm.

Muscles of the Upper Limb

Anterior Compartment of the Arm

These muscles are primarily responsible for flexion of the forearm at the elbow.

• MUSCHIUL BICEPS BRAHIAL (m. biceps brachii): Has two heads (long and short) originating from the supraglenoid tubercle and coracoid process of the scapula, respectively. Inserts on the radial tuberosity and bicipital aponeurosis.

  Function: Flexes the forearm; supinates the forearm.

• MUSCHIUL CORACOBRAHIAL (m. coracobrachialis): Originates from the coracoid process, inserts on the medial humerus.

  Function: Adducts and flexes the arm.

• MUSCHIUL BRAHIAL (m. brachialis): Located deep to the biceps, originates from the anterior humerus, inserts on the coronoid process and tuberosity of the ulna.

  Function: Flexes the forearm.

Posterior Compartment of the Arm

These muscles are responsible for extension of the forearm.

• MUSCHIUL ANCONEU (m. anconeus): Small muscle at the posterior elbow, originates from the lateral epicondyle of the humerus, inserts on the olecranon and proximal ulna.

  Function: Extends the forearm; stabilizes the elbow joint.

Muscles of the Back (Spatelui)

Superficial Back Muscles

These muscles connect the upper limb to the vertebral column and move the scapula.

• MUSCHIUL TRAPEZ (m. trapezius): Large, triangular muscle with three parts (descending, transverse, ascending) originating from the occipital bone, nuchal ligament, and spinous processes of cervical and thoracic vertebrae. Inserts on the clavicle, acromion, and spine of the scapula.

  Function: Elevates, retracts, and rotates the scapula.

• MUSCHIUL ROMBOIZI MARE ȘI MIC (mm. rhomboideus major et minor): Originate from the spinous processes of cervical and upper thoracic vertebrae, insert on the medial border of the scapula.

  Function: Retract and rotate the scapula.

• MUSCHIUL RIDICATOR AL SCAPULEI (m. levator scapulae): Originates from the transverse processes of the upper cervical vertebrae, inserts on the superior angle of the scapula. Function: Elevates the scapula.

• MUSCHIUL DINTAT POSTERIOR SUPERIOR (m. serratus posterior superior): Originates from the spinous processes of lower cervical and upper thoracic vertebrae, inserts on the upper ribs.

  Function: Elevates the ribs; assists in inspiration.

• MUSCHIUL DINTAT POSTERIOR INFERIOR (m. serratus posterior inferior): Originates from the spinous processes of lower thoracic and upper lumbar vertebrae, inserts on the lower ribs. Function: Depresses the ribs; assists in expiration.

Deep Back Muscles

These muscles stabilize and move the vertebral column.

• MUSCHIUL ERECTOR AL COLOANEI VERTEBRALE (m. erector spinae): Group of muscles running longitudinally along the spine, including iliocostalis, longissimus, and spinalis. Function: Extend and laterally flex the vertebral column.

• MUSCHI TRANSVERSOSPINALI (mm. transversospinales): Deep muscles connecting transverse and spinous processes, including semispinalis, multifidus, and rotatores.

  Function: Rotate and stabilize the vertebral column.

• MUSCHI INTERSPINOSI (mm. interspinales): Small muscles between adjacent spinous processes.

  Function: Extend the vertebral column.

Table: Comparison of Intercostal Muscles

Muscle	Location	Fiber Direction	Function
Intercostal Extern	Outer intercostal spaces	Oblique, downward & forward	Inspiration (elevate ribs)
Intercostal Intern	Deep to externals	Oblique, downward & backward	Expiration (depress ribs)
Intercostal Intimi	Deepest layer	Parallel to internals	Forced expiration
Subcostal	Inner posterior thoracic wall	Variable	Expiration (depress ribs)
Transversus Thoracis	Inner anterior thoracic wall	Transverse	Expiration (depress ribs)

Key Formulas and Concepts

• Muscle Contraction and Respiration: Inspiration: Diaphragm contracts, thoracic volume increases, air flows in. Expiration: Diaphragm relaxes, thoracic volume decreases, air flows out.

• Force of Muscle Contraction: $F = m imes a$ where $F$ is force, $m$ is mass, and $a$ is acceleration.

• Lever Systems in Musculoskeletal Movements: $M = F imes d$ where $M$ is moment (torque), $F$ is force, and $d$ is distance from the fulcrum.

Summary Table: Muscles of the Shoulder and Arm

Muscle	Origin	Insertion	Function
Deltoid	Clavicle, acromion, scapular spine	Deltoid tuberosity (humerus)	Abduction, flexion, extension, rotation of arm
Supraspinatus	Supraspinous fossa (scapula)	Greater tubercle (humerus)	Abduction of arm
Infraspinatus	Infraspinous fossa (scapula)	Greater tubercle (humerus)	Lateral rotation of arm
Teres Minor	Lateral border (scapula)	Greater tubercle (humerus)	Lateral rotation of arm
Teres Major	Inferior angle (scapula)	Crest of lesser tubercle (humerus)	Adduction, medial rotation of arm
Biceps Brachii	Scapula (supraglenoid tubercle, coracoid process)	Radial tuberosity, bicipital aponeurosis	Flexion, supination of forearm
Brachialis	Anterior humerus	Coronoid process, tuberosity (ulna)	Flexion of forearm
Anconeus	Lateral epicondyle (humerus)	Olecranon, proximal ulna	Extension of forearm