Anatomy Test 8 (Muscular System 3/4)

What are the 4 muscles that have a large surface area and dominate the superficial musculature of the shoulder, chest, and upper back?

The pectoralis major, deltoid, trapezius, and latissimus dorsi

What is the main action of the muscles that move the pectoral girdle?

It is to stabilize the scapula so it can function as a stable base for most of the muscles that move the humerus

What can muscles that move the pectoral girdle be classified into?

2 groups based on their location in the thorax: anterior and posterior thoracic muscles

What are the anterior thoracic muscles?

The subclavius, the pectoralis minor, and the serratus anterior

What is the pectoralis minor?

A thin, flat, triangular muscle that is deep to the pectoralis major

What is the serratus anterior?

It is a large, flat, fan-shaped muscle between the ribs and the scapula

Why is it named the serratus antihero?

Because of the saw-toothed appearance of its attachment on the ribs

What is the serratus anterior an antagonist of?

It is an antagonist of the rhomboids

What lies superficial to the anterior part of the serratus anterior?

The lateral and inferior portion of the breast lies superficial to the anterior part of the serratus anterior

What are the posterior thoracic muscles?

The trapezius, the levator scapulae, the rhomboid major, and the rhomboid minor

What is the trapezius?

It is a large, flat, triangular sheet of muscle extending from the skull and the vertebral column medially to the pectoral girdle laterally

What is the most superficial back muscle?

The trapezius is the most superficial back muscle and it covers the posterior neck region and the superior portion of the trunk

What do the 2 trapezius muscles do?

They form a trapezoid shape which gives it its name

How many sets of fibers does the trapezium have? What are they?

3 sets:

1. Superior

2. Middle

3. Inferior

What do the 3 sets of fibers of the trapezium enable it to do?

It enables the trapezium to cause multiple actions

How much does the human head weigh?

About 12 pounds

What is the levator scapulae?

It is a narrow, elongated muscle in the posterior portion of the neck

What is the position of the levator scapulae?

It is deep to the sternocleidomastoid and trapezius muscles

What does the levator scapulae contain? What does this do?

A twist in the muscle belly which inverts the superior and inferior fibers as they approach the scapular attachment and ensures that the muscle willl elevate the scapula rather than rotating it

Where do the rhomboid major and minor lie?

They lie deep to the trapezius and are not always distinct from one another

How do the rhomboid major and minor appear?

They appear as parallel bands that pass inferiorly and laterally from the vertebrae to the scapula

How much wider is the rhomboid major than the rhomboid minor?

It is about 2 times wider

How many muscles cross the shoulder joint?

9

Where do the pectoralis major and latissimus dorsi attach? What are they called?

They are called axial muscles because they attach to the axial skeleton

What is the pectoralis major?

It is a large, thick, fan-shaped muscle that covers the superior part of the thorax and forms the anterior fold of the axilla

What is the latissimus dorsi?

It is a broad, triangular muscle located and the inferior part of the back that forms most of the posterior wall of the axilla

What is often called the “swimmer’s muscle”

The latissimus dorsi because its many actions are used while swimming

What is the teres major?

It is a thick, rounded muscle in cross-section that also helps form the posterior wall of the axilla

What is the deltoid?

It is a thick, powerful shoulder muscle that covers the shoulder joint and forms the rounded contour of the shoulder

What muscle is the frequent site for intramuscular injections?

The deltoid

How many sets of fibers does the deltoid have? What are they?

3 sets of fibers:

1. Anterior

2. Lateral

3. Posterior

What are the 4 deep muscles of the shoulder?

1. Subscapularis

2. Suprasinatus

3. Infraspinatus

4. Teres minor

What do the 4 deep muscles of the shoulder do?

They strengthen and stabilize the shoulder joint

What is the rotator cuff also known as?

The musculotendinous cuff

What forms the rotator cuff?

The flat tendons of the 4 deep shoulder muscles (subscapularis, supraspinatus, infraspinatus, and teres minor) fuse together to form the rotator cuff

What is the subscapularis?

It is a large triangular muscle that fills the subscapular fossa of the scapula and forms a small part in the apex of the posterior wall of the axilla

What is the supraspinatus?

It is a rounded muscle named for its location in the supraspinous fossa of the scapula, and it lies deep to the trapezius 

What is the infraspinatus?

It is a triangular muscle, also named for its location in the infraspinous fossa of the scapula. A portion of the muscle is superficial and other portions are deep to the trapezius and deltoid

What is the teres minor?

It is a cylindrical, elongated muscle, located between the teres major and the infraspinatus muscles. Its belly lies parallel to the inferior edge of the infraspinatus and is sometimes indistinguishable from it

What are the flexor muscles of the arm that move the forearm?

The biceps brachii, the brachialis, and the brachioradialis

What are the extensor muscles of the arm the extend the forearm?

The triceps brachii, and the anconeus

What is the biceps brachii?

It is the large muscle located on the anterior surface of the arm. It has 2 proximal heads (long and short), both from the scapula. It spans both the shoulder and elbow joint

What happens at the distal attachment of the biceps brachii?

At the distal attachment of the biceps brachii in the forearm, a thin flat tendon, the bicipital aponeurosis, splits away from the rest of the tendon. It depends medially across the brachial artery and vein and fuses with the fascia over the forearm flexor muscles

What is the brachialis?

It is deep to the biceps brachii muscle. It is the most powerful flexor of the forearm at the elbow joint. Its thick belly is wider than that of the biceps brachii

What is the brachialis also called?

The “workhorse” of the elbow flexors

Where can you feel the brachialis?

On the lateral aspect of the arm where it is sandwiched between the biceps brachii and triceps brachii muscles

What is the triceps brachii?

It is the large muscle located on the posterior surface of the arm. It is the more powerful of the extensors of the forearm at the elbow joint. It has 3 proximal heads… 1 from the scapula (long head) and 2 from the humerus (lateral and medial heads)

What is the anconeus?

It is a small muscle located on the lateral part of the posterior aspect the elbow that assists the triceps brachii

What are the pronators of the forearm?

The pronator teres and pronator quadratus muscles

What is the supinator of the forearm?

It is the supinator muscle

What are compartments?

They are when functionally related skeletal muscles and their associated blood vessels and nerves are grouped together by fascia into regions

What muscles compose the anterior compartment of the arm?

The biceps brachii, the brachialis, and the coracobrachialis

What muscles form the posterior component of the arm?

The triceps brachii muscle

What are extrinsic muscles of the hand?

Muscles of the forearm that move the wrist, and and digits that act on the digits because their proximal attachment is outside the hand but their distal attachment is within the hand

What muscle is missing in about 20% of individuals?

The palmaris longus

How are the superficial anterior compartment muscles of the forearm arranged from lateral to medial?

Pronator teres, flexor carpi radialis, palmaris longus, and flexor capri ulnairs. The flexor digitorum superficialis muscle is deep to the other 3 muscles and is the largest superficial muscle in the forearm

How are the deep anterior compartment muscles arranged from lateral to medial?

Flexor pollicis longus and flexor digitorum profundus

How are the superficial posterior compartment muscles arranged from lateral to medial?

Brachioradialis, extensor carpi radialis longus, extensor carpi radialis brevis, extensor digitorum, extensor digitorum minimi, and the extensor carpi ulnaris

How are the deep compartment muscles arranged from lateral to medial?

Abductor pollicis longus, extensor pollicis longus, extensor pollicis brevis, and extensor indicis

What is the retinacula?

It is deep fascia that is thickened into fibrous bands at the wrist

What is the flexor retinaculum?

It is located over the palmar surface of the carpal bones. The long flexor tendons of the digits and wrist and the median nerve pass deep to the flexor retinaculum

What forms the carpal tunnel?

The flexor retinaculum and the carpal bones

What is the extensor retinaculum?

It is located over the posterior surface of the carpal bones. The extensor tendons of the wrist pass deep to it

Where is the FCU (flexor carpi ulnaris) located?

In the left upper quadrant (My left)

Where is the FCR (flexor carpi radialis) loacted?

In the right upper quadrant (My right)

Where is the ECU (extensor carpi ulnaris) located?

In the left lower quadrant (My left)

Where is the ECRL/B (extensor carpi radialis longus/brevis) located?

In the right lower quadrant (My right)