The interplay between muscles and their attachments is what makes the artistry of biomechanics. There are 3 muscle types, which all having exquisite coordination.
From the vigorous contractions of major muscle groups for movement to the subtle stabilizing actions of smaller muscles, all fibers form a unity of symphony behind human motion.
Get ready to discover where these muscles originate, insert, innervation, action, and blood supply of each of these muscles.
20 Muscle Attachments and Actions
1. The Trapezius Muscle
The Trapezius is a flat, triangular muscle of the posterior thorax covering the neck and shoulders superior and posterior parts. Its superior, middle, and inferior fibers assist in the shoulder girdle (pectoral girdle) and neck movements.
- Origin: Occipital bone, ligamentum nuchae, and spinous processes of vertebrae C07-T12
- Insertion: Lateral third of the clavicle and acromion and spine of the scapula
- Innervation: Accessory nerve (CN11) and cervical plexus (C03 and C04)
- Action: Superior fibers assist in elevation and upward rotation of the scapula and extension and lateral flexion of the neck; middle fibers assist in adduction of the scapula; inferior fibers assist in depression and upward rotation of the scapula
- Blood supply: Transverse cervical
2. Latissimus Dorsi Muscle
The Latissimus Dorsi is a triangular and flat muscle situated in the posterior shoulder girdle. It joins the upper limb with the axial skeleton and helps in maintaining the proper movements of the upper limb. It covers the lumbar and lower half of the thoracic region and it is contracted into a narrow fasciculus at insertion into the humerus.
- Origin: Spinous processes of vertebrae T07-T12 and L01-LO5 and the sacrum, thoracolumbar fascia, inferior portion of the scapula, posterior third of the iliac crest, and ribs 9-12
- Insertion: Intertubercular groove of the humerus
- Innervation: Thoracodorsal (middle or long subscapular nerve) nerve, a branch of the posterior cord (C06-C08)
- Action: Extension, adduction, and medial (internal) rotation of the arm at the shoulder joint; downward rotation, depression, and adduction of the scapula; lateral flexion of the spine
- Blood supply: Thoracodorsal artery
3. Levator Scapulae Muscle
The 
Scapulae is a muscle of the posterior thorax, situated at the back and side of the neck, that assists in the shoulder girdle (pectoral girdle) movements.
- Origin: Transverse processes of vertebrae C01-C04
- Insertion: Superior part of the medial (spinal) border of the scapula Innervation: Dorsal scapular nerve (C05) and direct branches from nerves C03 and C04
- Action: Elevation and downward rotation of the scapula
- Blood supply: Dorsal scapular artery
Rhomboid Muscles
The Rhomboid muscles are a pair of skeletal muscles situated in the upper back between the shoulder blades. These muscles are important in controlling the shoulder blades’ movement and orientation. There are two rhomboid muscles on each side of the spine as follows:
- Rhomboid major
- Rhomboid minor
4. Rhomboid Major Muscle
The Rhomboid Major is a muscle of the posterior thorax that assists in movements of the shoulder girdle (pectoral girdle).
- Origin: Spinous processes of vertebrae Т02-T05
- Insertion: Medial (vertebral) border of the scapula below the scapular spine
- Innervation: Dorsal scapular nerve (C05)
- Action: Adduction (retraction), downward rotation, elevation, and stabilization of the scapula
- Blood supply: Dorsal scapular artery
5. Rhomboid Minor Muscle
The Rhomboid Minor is a muscle of the posterior thorax that assists in movements of the shoulder girdle (pectoral girdle).
- Origin: Spinous processes of vertebrae C07 and T01
- Insertion: Medial (vertebral) border of the scapula above the scapular spine
- Innervation: Dorsal scapular nerve (C05)
- Action: Adduction (retraction), downward rotation, elevation, and stabilization of the scapula
- Blood supply: Dorsal scapular artery
Serratus Posterior Muscle
The Serratus Posterior muscles are a pair of back muscles lying deep into the rhomboids. Two sets of Serratus Posterior muscles participate in respiratory movements and help maintain the stability of the thoracic (upper back) region. The two sets of Serratus Posterior muscles are as follows:
- Serratus Posterior Superior
- Serratus Posterior Inferior
6. Serratus Posterior Superior Muscle
The Serratus Posterior Superior is a thin muscle of the upper posterior thorax that elevates the ribs during forced inspiration.
- Origin: Supraspinal ligament, ligamentum nuchae, spinous processes of vertebrae T01-TO3, and vertebra C07
- Insertion: Upper borders of ribs 2-5
- Innervation: Intercostal nerves 2-5 (T01-Т05)
- Action: Elevation of the upper ribs
- Blood supply: Intercostal arteries
7. Serratus Posterior Inferior Muscle
The Serratus Posterior Inferior is located at the junction of the thoracic and lumbar regions, and it aids in depressing the ribs during forced expiration.
- Origin: Supraspinal ligament and spinous processes of vertebrae T11-LO3
- Insertion: Lower borders of ribs 9-12
- Innervation: Intercostal nerves 9-12 (T09-T12)
- Action: Depression of the ribs
- Blood supply: Intercostal arteries
Splenius Muscle
The Splenius is a deep back muscle that helps in the spinal column and head movements. This Muscle is usually included with the muscles of the posterior triangle of the neck. It is composed of two divisions (moving upward) as follows:
- Splenius Cervicis
- Splenius Capitis
8. Splenius Cervicis Muscle
- Origin: Spinous processes of vertebrae ТО3-Т06
- Insertion: Mastoid process
- Innervation: Dorsal rami of nerves C01-C06
- Action: Extension and lateral flexion of the neck and spine; ipsilateral rotation of the head (turning the head toward the side of the body that contains the muscles performing the action)
- Blood supply: Occipital artery and transverse cervical artery
9. Splenius Capitis Muscle
- Origin: Lower half of the ligamentum nuchae and spinous processes of vertebrae C07-T03
- Insertion: Mastoid process of the temporal bone including the rough surface of the occipital bone
- Innervation: Dorsal rami of the middle cervical nerves
- Action: Extension and lateral flexion of the neck and spine; ipsilateral rotation of the head (turning the head toward the side of the body that contains the muscles performing the action)
- Blood supply: Muscular branches
Rotator Cuff Muscles
The Rotator Cuff is a pack of four muscles and their tendons are around the shoulder joint. It is important for stability and movement of the shoulder. It surrounds the head of the humerus and is a group of muscles such as those that lift, rotate, and stabilize the shoulder. They make up what’s called ‘The Rotator Cuff’.
Rotator Cuff muscles include:
-
- Supraspinatus
- Infraspinatus
- Teres minor
- Subscapularis
10. Supraspinatus Muscle
The Supraspinatus is a muscle of the muscle type of rotator cuff, a categorization of shoulder muscles.
- Origin: All of the supraspinatus fossa
- Insertion: The greater tubercle of the humerus
- Innervation: Suprascapular nerve (C05, C06)
- Action: Assists deltoid in abducting the arm. Stabilizes the glenohumeral joint.
- Blood supply: Suprascapular artery
11. Infraspinatus Muscle
The Infraspinatus is a thick, and triangular type of muscle in the shoulder girdle’s rotator cuff. Along with the other muscles of the rotator cuff, the Infraspinatus assists in stabilizing the shoulder joint and maintaining the proper movements of the upper limbs.
- Origin: Infraspinatus fossa on the posterior surface of the scapula
- Insertion: Greater tubercle of the humerus
- Innervation: Suprascapular nerve (C05 and С06)
- Action: Lateral (external) rotation, abduction, and horizontal abduction of the arm at the shoulder joint; stabilization of the shoulder joint
- Blood supply: Suprascapular artery and circumflex scapular artery
12. Teres Minor Muscle
The Teres Minor is a narrow, and elongated muscle in the shoulder girdle’s rotator cuff. Along with the other muscles of the rotator cuff, the teres minor assists in stabilizing the shoulder joint and maintaining the proper movements of the upper limbs.
- Origin: Lateral border of the scapula
- Insertion: Greater tubercle of the humerus
- Innervation: Axillary nerve (C05 and C06)
- Action: Lateral (external) rotation and horizontal abduction of the arm at the shoulder joint; stabilization of the shoulder joint
- Blood supply: Circumflex scapular artery
13. Subscapularis Muscle
The Subscapularis is a large triangular type of muscle that helps to filler the subscapular fossa of the scapula and a muscle of the rotator cuff, a categorization of shoulder muscles.
- Origin: Subscapular fossa
- Insertion: Lesser tubercle of the humerus
- Innervation: Upper and Lower subscapular nerves (CO5, C06)
- Action: Medial (internal) rotation of the head of the humerus. Prevents anterior displacement of the humerus.
- Blood supply: Subscapular artery
14. Teres Major Muscle
The Teres Major is a thick but somewhat flattened scapulohumeral muscle located in the posterior shoulder girdle that assists in stabilizing the shoulder joint and maintaining the proper movements of the upper limbs.
- Origin: Inferior angle of the scapula
- Insertion: Intertubercular groove of the humerus
- Innervation: Lower subscapular nerve (C05 and C06)
- Action: Extension, adduction, medial (internal) rotation, and horizontal abduction of the arm located at the shoulder joint; stabilization of the shoulder joint
- Blood supply: Circumflex scapular artery
15. Quadratus Lumborum Muscle
The Quadratus Lumborum is a muscle which is located in the posterior abdomen, irregularly quadrilateral in shape and broader below than above.
- Origin: Aponeurotic fibers from the iliolumbar ligament and the adjacent portion of the iliac crest
- Insertion: Lower border of the last rib for about half its length and the transverse processes of L01-LO4
- Innervation: Spinal nerves T12 and L01-LO2
- Action: Depresses the 12th rib, unilaterally raises pelvis, helps with lumbar spine lateral flexion, and acts as a major stabilizer of the lumbar spine
- Blood supply: Subcostal artery, lumbar arteries, iliolumbar artery (lumbar branch)
16. Sternocleidomastoid Muscle
The Sternocleidomastoid is a muscle in the neck that is often classified with the lateral cervical muscles. It arises from two heads and assists in the vertebral column and head movements.
- Origin: Upper part of the anterior surface of the manubrium including the superior border and anterior surface of the medial third of clavicle.
- Insertion: At the Lateral surface of the mastoid process and nuchal line of the occipital bone.
- Innervation: Accessory nerve (CN11); branches from the anterior divisions of nerves C02 and CO3
- Action: Flexion, lateral flexion, and extension of the neck; contralateral rotation of the head (turning the head away from the side of the body that contains the muscles performing the action); lateral flexion of the spine
- Blood supply: Occipital artery and superior thyroid artery
Pectoralis Muscles
Pectoralis muscles, commonly called pecs, are a pair of large chest-region muscles. These muscles play major roles in many upper body movements, especially those involving the shoulder and arm. There are two main parts of the pectoralis muscles as follows:
Pectoralis Major Muscle
The Pectoralis Major (Sternocostal head) is a thick, fan-shaped muscle that extends from the anterior shoulder girdle and covers the upper chest. It assists in shoulder and arm movements, and it comprises three heads:
- Clavicular head
- Sternocostal head
- Abdominal head
17. Pectoralis Major (Sternocostal Head)
- Origin: Sternum and costal cartilages 2-4
- Insertion: The Lateral lip of the intertubercular groove of the humerus
- Innervation: Nerves C07-T01
- Action: Adduction, horizontal adduction, and medial (internal) rotation of the arm at the shoulder joint; depression, downward rotation, and abduction of the scapula
- Blood supply: Thoracoacromial trunk, pectoral branch
18. Pectoralis Major (Clavicular Head)
- Origin: Medial half of the clavicle
- Insertion: The Lateral lip of the intertubercular groove of the humerus
- Innervation: Nerves C05 and C06
- Action: The Flexion of the arm at the shoulder joint
- Blood supply: Thoracoacromial trunk, pectoral branch
19. Pectoralis Major (Abdominal Head) Muscle
- Origin: Distal sternum (ribs 5 and 6) and external oblique fascia
- Insertion: The Lateral lip of the intertubercular groove of the humerus
- Innervation: Nerves C08 and T01
- Action: Adduction and medial (internal) rotation of the arm at the shoulder joint
- Blood supply: Thoracoacromial trunk, pectoral branch
Pectoralis Minor Muscle
20. Pectoralis Minor Muscle
The Pectoralis Minor is a thin, and triangular muscle of the anterior thorax, situated beneath the pectoralis major in the upper part of the chest. It assists in shoulder movements and elevates the ribs during forced inspiration.
- Origin: Ribs 3-5
- Insertion: Coracoid process of the scapula
- Innervation: Medial pectoral nerve (C08 and T01)
- Action: Depression, downward rotation, and abduction of the scapula; elevation of the ribs
- Blood supply: Thoracoacromial trunk, pectoral branch
FAQs
What Are The 5 Main Functions of Muscles?
The 5 main actions of muscles are movement, blood circulation, protection, support, and heat generation.
What Is the Insertion and Action of a Muscle?
The origin of the muscle is the fixed attachment of it. The insertion is based on the movement based on the contraction. The action of a muscle works according to the movement of a muscle based on the way it moves with the joint and body.
What Are The 3 Sites of Muscle Attachment?
The three main sites of muscle attachments are Tendons, Aponeuroses and other Attachments.
What Are Muscle Attachments?
Muscle attachments are attachments to bones, muscles, or tissues where two or more points are connected. However, if the location is a bone that is immobile for a specific action, that type of attachment is called Origin. If the location is on the bone and moves through the action, that type of attachment is called an Insertion.
Final Thoughts
The human body is the pinnacle of biomechanics, and it all comes down to how muscles work with bones. So, knowing the relationship between muscles and how they attach, coupled with what ensuing actions occur, is key to understanding all these obstacles that throw the man off balance.
Taking a detailed look into 20 major muscle attachments and actions, we reveal the biomechanical composition of our vast repertoire for performing physical maneuvers. However, if you have any muscle pains, don’t hesitate to book your massage therapy to relieve the pain. Get to know more details here!
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