Superficial Back – Gross Anatomy Lecture

These flashcards review osteology, joints, scapular movements, fascia, muscle origins/insertions/actions/innervations, blood supply, and clinical correlations for the superficial (extrinsic) back lecture.

What distinguishes extrinsic from intrinsic back muscles?

Extrinsic muscles originate on the back but insert on and move another region (e.g., upper limb); intrinsic muscles both originate and insert on the back.

acromioclavicular joint

relatively weak plane joint with limited mobility some rotation of the acromion process occurs here accompanying scapular movements

sternoclavicular joint

mobile saddle joint surrounded by strong ligaments. all scapular motion is accompanied by movement of this joint

glenohumeral joint

extremely mobile and relatively weak. motion of this joint is often accompanied by motion at the sternoclavicular and acromioclavicular joints

superficial fascia

• Subcutaneous tissue

• Primarily adipose tissue

• Varies in thickness

deep fascia

• Dense connective tissue layer

• Lies deep to superficial fascia

investing fascia

Extensions of deep fascia surrounding muscles & neurovascular bundle

Name the five superficial (upper-limb moving) extrinsic back muscles.

Trapezius, Latissimus dorsi, Levator scapulae, Rhomboid major, Rhomboid minor.

Which two ‘deep-extrinsic’ (intermediate) muscles assist respiration?

Serratus posterior superior and Serratus posterior inferior.

What is the origin of the trapezius muscle?

Midline: external occipital protuberance, nuchal ligament, cervical and thoracic spinous processes.

Where does trapezius insert?

Spine of scapula, acromion process, lateral third of clavicle.

List the primary actions of the trapezius.

Elevates, depresses, retracts, and superiorly rotates the scapula; also extends/laterally flexes the neck.

What nerve innervates the trapezius?

Accessory nerve (cranial nerve XI).

Which artery runs with the accessory nerve to trapezius?

Transverse cervical artery (branch of subclavian).

A patient cannot shrug one shoulder and the scapula droops. Which nerve is likely injured?

Accessory nerve (CN XI).

What are the origins of latissimus dorsi?

Spinous processes of lower thoracic vertebrae (T7-T12), thoracolumbar fascia

Where does latissimus dorsi insert?

Intertubercular sulcus (anterior humerus).

Actions of latissimus dorsi on the humerus?

Adduction, extension, and medial rotation.

Which nerve and artery supply latissimus dorsi?

Thoracodorsal nerve and thoracodorsal artery (branches of brachial plexus and axillary artery respectively).

Origin and insertion of levator scapulae?

Origin: transverse processes of C1-C4; Insertion: superior part of medial border of scapula.

Main actions of levator scapulae.

Elevates and inferiorly rotates scapula; assists with neck extension.

Which nerve innervates levator scapulae and the rhomboids?

Dorsal scapular nerve (with dorsal scapular artery).

Origin of rhomboid minor vs. rhomboid major.

Minor: spinous processes C7-T1; Major: spinous processes T2-T5.

Common insertion of both rhomboids.

Medial border of scapula (minor at level of spine; major inferior to spine).

Primary actions of rhomboids.

Retract, elevate, and inferiorly rotate the scapula.

Origin & insertion of serratus posterior superior (SPS).

Origin: spinous processes C7-T3; Insertion: superior borders of ribs 2-5.

Action of serratus posterior superior.

Elevates ribs (accessory inspiration)

Origin & insertion of serratus posterior inferior (SPI).

Origin: spinous processes T11-L2; Insertion: inferior borders of ribs 8-12.

Action of serratus posterior inferior.

Depresses ribs (accessory expiration)

propioception

The body's ability to sense its position and movement in space, primarily through receptors in the muscles and joints.

What nerves innervate the serratus posterior muscles?

Intercostal nerves (ventral primary rami).

triangle of auscultation

lacts large muscles and is a good place for listening to lungs

lumbar triangle

gap in muscles of the lower back, bounded by the iliac crest, latissimus dorsi, and external oblique, facilitating access for auscultation and injections.

Name the three major shoulder joints discussed.

Sternoclavicular (saddle, strong), Acromioclavicular (plane, weak), and Glenohumeral (ball-and-socket, highly mobile).

Define scapular protraction and name a back muscle that performs it.

Anterior movement of scapula along thoracic wall; serratus anterior (not on back) is primary, no true superficial back muscle protracts.

Which superficial back muscles elevate the scapula?

Upper fibers of trapezius and levator scapulae; rhomboids assist.

Muscles responsible for scapular depression.

Gravity, lower fibers of trapezius, latissimus dorsi; also serratus anterior and pectoralis minor/major (anterior muscles).

Which muscles retract the scapula?

Middle fibers of trapezius, rhomboid major and minor, latissimus dorsi.

Name the two muscles that superiorly rotate the scapula.

Upper & lower fibers of trapezius and serratus anterior.

Name three muscles that inferiorly rotate the scapula.

Levator scapulae, rhomboids, latissimus dorsi.

What is the triangle of auscultation and its borders?

A thin-muscle area for lung auscultation; borders: latissimus dorsi (inferior), trapezius (medial), medial border of scapula (lateral).

Describe the lumbar triangle (of Petit) and its clinical importance.

Borders: iliac crest (inferior), latissimus dorsi (medial), external abdominal oblique (lateral); muscular gap prone to lumbar hernias.

Define superficial fascia.

Subcutaneous adipose tissue layer beneath skin; thickness varies.

Define deep fascia and investing fascia.

Deep fascia: dense CT layer deep to superficial fascia; investing fascia: extensions of deep fascia surrounding muscles and neurovascular bundles.

Which cutaneous nerves of the back arise from dorsal rami?

All cutaneous nerves that pierce the back midline skin are branches of dorsal rami, each representing one spinal nerve dermatome.

Which artery accompanies the transverse cervical nerve?

None—the accessory nerve accompanies the transverse cervical artery (branch of subclavian).