Muscle attachments

Trapezius –

Origin –

  1. Medial third of superior nuchal line
  2. External occipital protuberance
  3. Nuchal ligament
  4. Spinous process of C7 to T12

Insertion –

  1. Lateral third of clavicle
  2. Acromian process
  3. Spine of scapula

Innervation –

  1. Spinal accessory nerve (CN 9)
  2. Cervical nerves C3-C4

Movement –

  1. Descending part – elevates scapula
  2. Transverse part – retracts scapula
  3. Ascending part – depresses scapula
  4. Descending and ascending working together – superior rotation of scapula

 

Pectoralis major –

Origin –

  1. Clavicular head – anterior surface of medial half of clavicle
  2. Sternocostal head – anterior surface of sternum, superior six costal cartilages
  3. Abdominal part – aponeurosis of external oblique

Insertion –

Crest of greater tubercle of intertubercular sulcus (lateral lip of bicipital groove)

Innervation –

Lateral and medial pectoral nerves

Action –

  1. Adducts and medially rotates humerus
  2. Draws scapula anteriorly and inferiorly
  3. Clavicular head alone – flexes humerus
  4. Sternocostal head alone – extends humerus from flexed position.

 

Pectoralis minor –

Origin –

3rd to 5th ribs near their costal cartilages

Insertion –

Medial border and superior surface of coracoid process of scapula.

Innervation –

Medial pectoral nerve (C8-T1)

Function –

Stabilizes scapula by drawing it inferiorly and anteriorly against chest wall

 

Serratus anterior –

Origin –

External surface of lateral part of 1st to 8th-9th ribs

Insertion –

Anterior surface of medial border of scapula

Innervation –

Long thoracic nerve (C5, 6, 7)

Action –

  1. Protracts scapula and holds it against thoracic wall
  2. Rotates scapula

 

Latissimus dorsi –

Origin –

  1. Spinous process of inferior six thoracic vertebrae (T7-T12)
  2. Thracolumbar fascia
  3. Iliac creast
  4. Inferior 3 or 4 ribs

Insertion –

Intertubercular sulcus (bicipital groove) of humerus

Innervation –

Thoracodorsal nerve (C6-8)

Action –

Extends, adducts and medially rotates humerus

Rectus abdominis –

Origin –

Pubic symphysis and pubic crest

Insertion –

Xiphoid process and 5th -7th costal cartilages

Innervation –

Thoracoabdominal nerves and anterior rami of inferior thoracic nerves

Action –

Flexes trunk and compresses abdominal viscera.

Gracilis –

Origin –

Body of pubis and inferior pubic ramus

Insertion –

Superior part of medial surface of tibia

Innervation –

Obturator nerve

Action –

Adducts thigh, flexes leg and rotates leg medially.

Gastrocnemius –

Origin –

  1. Lateral head – lateral aspect of lateral condyle of femur
  2. Medial head – superior to medial condyle

Insertion –

Posterior surface of calcaneus with calcaneal tendon (tendoachillis)

Innervation –

Tibial nerve

Action –

  1. Plantarflex ankle when knee is extended
  2. Raises heel during walking
  3. Flexes leg at knee joint.

Soleus –

Origin –

  1. Posterior aspect of head of fibula
  2. Superior fourth of posterior surface of fibula
  3. Soleal line and medial border of tibia

Insertion –

Posterior surface of calcaneus with calcaneal tendon (tendoachillis)

Innervation –

Tibial nerve

Action –

  1. Plantar flexes ankle (independent of knee position)
  2. Steadies leg on foot

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