Superficial Back Muscles

Question 1

Trapezius:

1. How many origin points does the trapezius have? List them.
2. How many main insertion points does the trapezius have? List them.
3. What are the actions of the upper fibers, middle fibers, and lower fibers of the trapezius?
4. What is the Innervation of the trapezius?
5. Is the trapezius a superficial, intermediate, or deep muscle in the back?

Answer 1

Origins:

1. External Occipital Protuberance: A bony prominence at the base of the skull.
2. Nuchal Ligament: A ligament that runs along the back of the neck.
3. Spinous Processes of C7: The vertebra at the base of the neck.
4. Spinous Processes of T1–T12: The thoracic vertebrae (upper and middle back).

Insertions:

1. Lateral third of the clavicle: The upper fibers of the trapezius insert here, helping with elevation and rotation of the scapula (shoulder blade).
2. Acromion: The middle fibers insert into this bony process on the top of the scapula, assisting with scapular retraction (pulling the shoulder blades together).
3. Spine of the scapula: The lower fibers insert here, helping with the depression and upward rotation of the scapula.

Action:

1. Upper Fibers: Elevates the scapula and rotates it during abduction of the arm.
2. Middle Fibers: Retract the scapula.
3. Lower Fibers: Pull scapula inferiorly.

Innervation:

1. Accessory nerve (cranial nerve XI)
2. Anterior rami of the C3 and C4 spinal nerves.

Question 2

Latissimus Dorsi:

1. How many origin points does the latissimus dorsi have? List them.
2. How many main insertion points does the latissimus dorsi have? List them.
3. What are the actions of the latissimus dorsi?
4. What is the Innervation of the latissimus dorsi?
5. Is the latissimus dorsi a superficial, intermediate, or deep muscle in the back?

Answer 2

Origins:

1. Broad origin arising from the spinous processes of T6-T12.
2. Thoracolumbar fascia.
3. Iliac crest.
4. Inferior three ribs.

Insertions:

1. The fibers converge into a single tendon that attaches to the intertubercular sulcus of the humerus.

Actions:

1. Extension of the arm (pulling the arm backward).
2. Adduction of the arm (pulling the arm toward the body).
3. Internal rotation of the shoulder joint.

Innervation:

1. Thoracodorsal nerve.

Question 3

Levator Scapulae:

1. How many origin points does the levator scapulae have? List them.
2. How many main insertion points does the levator scapulae have? List them.
3. What is the action of the levator scapulae?
4. What is the Innervation of the levator scapulae?
5. Is the levator scapulae a superficial, intermediate, or deep muscle in the back?

Answer 3

Origin:

1. Transverse processes of the C1-C4 vertebrae.

Insertion:

1. Medial border of the scapulae.

Action:

1. Elevates the scapula.

Innervation:

Dorsal scapular nerve.

Question 4

Rhomboid Major:

1. How many origin points does the rhomboid major have? List them.
2. How many main insertion points does the rhomboid major have? List them.
3. What is the action of the rhomboid major?
4. What is the Innervation of the rhomboid major?
5. Is the rhomboid major a superficial, intermediate, or deep muscle in the back?

Answer 4

Origin:

1. Spinous processes of the T2-T5 vertebrae

Insertion:

1. Attaches to the medial border of the scapula, at the level of the spine scapula.

Action:

1. Retracts and rotates the scapula.

Innervation:

1. Dorsal scapular nerve.

Question 5

Rhomboid Minor:

1. How many origin points does the rhomboid minor have? List them.
2. How many main insertion points does the rhomboid minor have? List them.
3. What is the action of the rhomboid minor?
4. What is the Innervation of the rhomboid minor?
5. Is the rhomboid minor a superficial, intermediate, or deep muscle in the back?

Answer 5

Origin:

1. Spinous processes of the C7-T-1 vertebrae.

Insertion:

1. Attaches to the medial border of the scapulae, at the level of the spine scapula.

Action:

1. Retracts and rotates the scapula.

Innervation:

1. Dorsal scapular nerve.