Primary Muscles

1-12 Primary Muscles
Anatomical Drawing

1. Deltoid: 7 bundles.
Origin: lateral third of clavicle, acronium process and scapular spine.
Insertion: lateral aspect of humerus.
Function: contraction will raise arm to horizontal plane.

2. Brachioradialis: longest forearm extender.
Origin: lower third of humerus.
Insertion: lateral side, lower end of radius.
Function: flexes forearm and supinates forearm in extension.

3. Pectoralis major: triangular muscle composed of three parts.
Origin: medial half of clavicle, sternum and abdominal sheath.
Insertion: anterior side of humerus.
Function: adduction of arm and traction of the raised arm downward.

4. Trapezius: trapezoidal shape.
Origin: occipital bone of the skull, cervical and thoracic vertebrae.
Insertion: clavicle, acromiom process and spine of scapula.
Function: draws scapula toward spine. Cervical portion raises shoulder.

5. Quadriceps: 4 extensors of the thigh.
• Vastus lateralis: lateral side.
Origin: linea aspera of femur and below the great trochanter.
Insertion: lateral border of patella.
• Vastus medialis: medial side.
Origin: linea aspera of femur.
Insertion: medial border of patella.
• Rectus femoris: front of thigh.
Origin: anterior, inferior illiac spine.
Insertion: base of the patella.
Function: extention fo the leg.

6. Biceps (brachii): 2 heads (long and short) flexor muscle. Low riser.
Origin: long head (lateral) tuberosity above glenoid fossa of scapula through bicepital groove. Short head (medial) on the coracoid process.
Insertion: tuberosity of radius bone.
Function: flex arm and supinate pronated arm.

7. Triceps: 3 heads (long, medial and lateral) extensor muscle.
Origin: posterior surface of humerus bone. Long head originates on the scapula.
Insertion: oleocranon process of ulna bone.
Function: extends forearm.



8. Rectus abdominus: 8 pack.
Origin: costal cartilages 5, 6 and 7.
Insertion: pubic symphysis.
Function: forward flexion of the trunk.

9. Latissimus dorsi: broad flat muscle.
Origin: 6 lower thoracic, all lumbar and sacral vertebrae and posterior section of the illiac crest.
Insertion: anterior surface of the humerus.
Function: With pectoralis, traction of the raised arm downwards. Draws arm backward and medially.

10. Gluteus maximus: buttock muscle.
Origin: surface of illiac, sacrum and coccygeal.
Insertion: posterior surface of femur.
Function: extends thigh backwards.

11. Sternomastoid: 2 heads.
Origin: manubrium and sternal edge of clavicle.
Insertion: mastoid process and occipital bone.
Function: turns head to opposite side. Both together lift face and tip head backwards.

12. Triceps surae: calf muscle (3 heads).
Origin: lateral condyle of femur.
Insertion: heel bone ( calcaneus).
Function: flexes leg and points foot.