Unit 1

Question 1

Biceps Brachii (All Heads)

Answer 1

Origin:

Short head: Coracoid process of the scapula

Long head: Supraglenoid tubercle of the scapula

Insertion:

Radial tuberosity

Bicipital aponeurosis into the fascia of the forearm

Innervation:

Musculocutaneous nerve (C5, C6)

Action:

Supinates the forearm

Flexes the forearm (especially when supinated)

Assists in flexing the arm at the shoulder

Question 2

Brachialis

Answer 2

Origin:

Distal half of the anterior surface of the humerus

Insertion:

Coronoid process and tuberosity of the ulna

Innervation:

Musculocutaneous nerve (C5, C6)

Radial nerve (C7)

Action:

Flexes the forearm at the elbow joint (a primary flexor)

Question 3

Coracobrachialis

Answer 3

Origin:

Coracoid process of the scapula

Insertion:

Middle third of the medial surface of the humerus

Innervation:

Musculocutaneous nerve (C5, C6, C7)

Action:

Flexes and adducts the arm at the glenohumeral (shoulder) joint

Question 4

Triceps (All Heads)

Answer 4

Origin:

Long head: Infraglenoid tubercle of the scapula

Lateral head: Posterior surface of the humerus, superior to the radial groove

Medial head: Posterior surface of the humerus, inferior to the radial groove

Insertion:

Olecranon process of the ulna

Innervation:

Radial nerve (C6, C7, C8)

Action:

Extends the forearm at the elbow joint (chief extensor)

Long head: Assists in extension and adduction of the arm at the shoulder joint

Question 5

Anconeus

Answer 5

Origin:

Lateral epicondyle of the humerus

Insertion:

Lateral surface of the olecranon process and posterior ulna

Innervation:

Radial nerve (C7, C8, T1)

Action:

Assists the triceps brachii in extending the forearm

Stabilizes the elbow joint

Question 6

Pectoralis Major

Answer 6

Origin:

Clavicular head: Medial half of the clavicle

Sternocostal head: Sternum, upper six costal cartilages, and aponeurosis of the external oblique muscle

Insertion:

Lateral lip of the bicipital groove of the humerus

Innervation:

Lateral and Medial pectoral nerves (C5, C6, C7, C8, T1)

Action:

Adducts and medially rotates the humerus

Draws scapula anteriorly and inferiorly

Clavicular head alone: Flexes the humerus

Sternocostal head alone: Extends the humerus from a flexed position

Question 7

Pectoralis Minor

Answer 7

Origin:

Anterior surfaces of the 3rd to 5th ribs

Insertion:

Coracoid process of the scapula

Innervation:

Medial pectoral nerve (C8, T1)

Action:

Stabilizes the scapula by drawing it inferiorly and anteriorly against the thoracic wall

Assists in elevating the ribs during forced inspiration

Question 8

Subclavius M.

Answer 8

Origin:

Junction of the first rib and its costal cartilage

Insertion:

Inferior surface (subclavian groove) of the middle third of the clavicle

Innervation:

Nerve to subclavius (C5, C6)

Action:

Depresses the clavicle

Stabilizes the sternoclavicular joint

Question 9

Serratus Anterior M

Answer 9

Origin:

External surfaces of the lateral parts of the 1st to 8th ribs

Insertion:

Anterior surface of the medial border of the scapula

Innervation:

Long thoracic nerve (C5, C6, C7)

Action:

Protracts the scapula (pulls it forward around the ribcage)

Upwardly rotates the scapula

Stabilizes the scapula by holding it against the thoracic wall

Question 10

Subscapularis M

Answer 10

Origin:

Subscapular fossa on the anterior surface of the scapula

Insertion:

Lesser tubercle of the humerus

Innervation:

Upper and Lower subscapular nerves (C5, C6)

Action:

Medially (internally) rotates the arm

Adducts the arm

Helps stabilize the head of the humerus in the glenoid cavity (part of the rotator cuff)

Question 11

Latissimus Dorsi M

Answer 11

Origin:

Spinous processes of T7-L5 vertebrae

Thoracolumbar fascia

Iliac crest

Inferior 3 or 4 ribs

Insertion:

Floor of the intertubercular (bicipital) groove of the humerus

Innervation:

Thoracodorsal nerve (C6, C7, C8)

Action:

Extends, adducts, and medially rotates the arm

Depresses the shoulder girdle

Nickname & Mnemonic
This muscle is often called the “swimmer’s muscle” because of its powerful action in movements like the freestyle stroke. 🏊

A classic mnemonic to remember its insertion in the bicipital groove is “A Lady Between Two Majors,” where the latissimus dorsi tendon (Lady) inserts between the pectoralis major and teres major tendons.

Question 12

Teres Major

Answer 12

Origin:

Posterior surface of the inferior angle of the scapula

Insertion:

Medial lip of the intertubercular (bicipital) groove of the humerus

Innervation:

Lower subscapular nerve (C5, C6)

Action:

Adducts and medially rotates the arm

Assists in extending the arm from a flexed position

Nickname & Mnemonic
Teres major is often called “Lat’s Little Helper” because its actions (adduction and medial rotation) are identical to those of the much larger latissimus dorsi.

It is the “Major” in the mnemonic “A Lady Between Two Majors,” referring to its insertion on the medial lip of the bicipital groove, next to the latissimus dorsi.

Question 13

Pronator Teres M

Answer 13

Origin:

Humeral head: Medial epicondyle of the humerus

Ulnar head: Coronoid process of the ulna

Insertion:

Middle of the lateral surface of the radius

Innervation:

Median nerve (C6, C7)

Action:

Pronates the forearm

Weakly flexes the elbow

Clinical Note
The median nerve passes between the two heads of the pronator teres. If this muscle becomes tight or inflamed, it can compress the nerve, leading to a condition called Pronator Teres Syndrome, which causes pain and numbness in the forearm and hand, mimicking some symptoms of carpal tunnel syndrome.

Question 14

Brachioradialis M

Answer 14

Origin:

Proximal two-thirds of the lateral supracondylar ridge of the humerus

Insertion:

Styloid process of the radius

Innervation:

Radial nerve (C5, C6, C7)

Action:

Flexes the forearm, especially in the neutral (“thumb-up” or handshake) position

Nickname
The brachioradialis is famously known as the “beer-drinking muscle” 🍺 because its strongest line of pull for elbow flexion is when the forearm is in that neutral position, just like when lifting a mug.

Question 15

Extensor Carpi Radialis Longus M

Answer 15

Origin:

Lateral supracondylar ridge of the humerus

Insertion:

Dorsal base of the 2nd metacarpal bone

Innervation:

Radial nerve (C6, C7)

Action:

Extends the wrist

Abducts (radially deviates) the wrist

Memory Tip
The name of this muscle tells you its story:

Extensor: It extends the wrist.

Carpi: It acts on the wrist (carpals).

Radialis: It’s on the thumb/radius side and helps with radial deviation.

Longus: It’s the longer of the two “extensor carpi radialis” muscles.

Question 16

Supinator M

Answer 16

Origin:

Lateral epicondyle of the humerus

Supinator crest of the ulna

Insertion:

Lateral, posterior, and anterior surfaces of the proximal third of the radius

Innerve:

Deep branch of the Radial nerve (C7, C8)

Action:

Supinates the forearm (turns the palm up or forward ✋)

Clinical Note
The deep branch of the radial nerve passes through the supinator muscle. This passageway is known as the supinator canal (or arcade of Frohse). If the muscle becomes tight or inflamed, it can compress the nerve, leading to weakness in the wrist and finger extensor muscles.

Question 17

Flexor Carpi Radialis M

Answer 17

Origin:

Medial epicondyle of the humerus (common flexor origin)

Insertion:

Base of the 2nd metacarpal bone

Innervation:

Median nerve (C6, C7)

Action:

Flexes the wrist

Abducts (radially deviates) the wrist

Memory Tip
Just like its extensor counterpart, the name tells you exactly what it does and where it is:

Flexor: It flexes the wrist.

Carpi: It acts on the wrist (carpals).

Radialis: It’s on the thumb/radius side and helps with radial deviation.

Question 18

Palmaris Longus M

Answer 18

Origin:

Medial epicondyle of the humerus (common flexor origin)

Insertion:

Palmar aponeurosis

Innervation:

Median nerve (C7, C8)

Action:

Weakly flexes the wrist

Tenses the palmar aponeurosis

Fun Fact
This muscle is one of the most variable in the human body and is completely absent in about 15% of the population (on one or both arms)!

You can test if you have it: touch your pinky finger to your thumb and then slightly flex your wrist. If you see a tendon “pop out” in the middle of your wrist, that’s your palmaris longus. Because it’s a weak flexor, it’s often harvested by surgeons for tendon grafts without causing any significant loss of function.

Question 19

Palmar Aponeurosis

Answer 19

Structure and Location
It originates from the tendon of the palmaris longus muscle (when present) and the flexor retinaculum at the wrist. It then fans out across the palm and inserts into the bases of the fingers, anchoring the skin and protecting the underlying tendons, nerves, and blood vessels.

Function
The primary functions of the palmar aponeurosis are:

Protection: It acts like a shield for the important structures passing through the palm, such as the flexor tendons and the median and ulnar nerves.

Grip: It firmly attaches to the skin of the palm, preventing it from sliding around and significantly improving our ability to grip objects securely. 🤝

Clinical Significance
The palmar aponeurosis is most famously associated with a condition called Dupuytren’s contracture. In this condition, the aponeurosis thickens and shortens, forming nodules and cords that can pull the fingers (most commonly the ring and little fingers) into a permanently flexed position, making it difficult to straighten them.

Question 20

Flexor Carpi Ulnaris

Answer 20

Origin:

Humeral head: Medial epicondyle of the humerus

Ulnar head: Olecranon and posterior border of the ulna

Insertion:

Pisiform bone, hook of the hamate, and base of the 5th metacarpal

Innervation:

Ulnar nerve (C8, T1)

Action:

Flexes the wrist

Adducts (ulnarly deviates) the wrist

Memory Tip & Clinical Note
The name tells you its function and location: Flexor (it flexes), Carpi (acts on the wrist), Ulnaris (it’s on the ulna/pinky side and helps with ulnar deviation).

The ulnar nerve passes between the two heads of this muscle at the elbow, in a location called the cubital tunnel. Compression of the nerve at this site can cause numbness and tingling in the ring and little fingers. 🤏

Question 21

Flexor Digitorum Profundus M

Answer 21

Origin:

Anteromedial surface of the ulna and the interosseous membrane

Insertion:

Bases of the distal phalanges of the 2nd, 3rd, 4th, and 5th fingers

Innervation:

Dual Innervation:

Medial part (for 4th and 5th fingers): Ulnar nerve (C8, T1)

Lateral part (for 2nd and 3rd fingers): Anterior interosseous nerve (a branch of the Median nerve, C8, T1)

Action:

Flexes the distal interphalangeal (DIP) joints of the medial four fingers

Assists in flexing the other joints of the fingers and wrist

Nickname & Clinical Note
This muscle is the only one that can flex the distal interphalangeal (DIP) joint—the very last joint of your finger. Because of this, it’s often called the “fingertip flexor.”

A common test for FDP function is to hold the patient’s middle phalanx (the middle bone of the finger) steady and ask them to flex the tip of that finger. If they can, the FDP muscle and its nerve supply are intact. 💪

Question 22

Flexor Digitorum Superficialis M

Answer 22

Origin:

Humeroulnar head: Medial epicondyle of the humerus, ulnar collateral ligament, and coronoid process of the ulna

Radial head: Superior half of the anterior border of the radius

Insertion:

Bodies of the middle phalanges of the 2nd, 3rd, 4th, and 5th fingers. The tendon cleverly splits to allow the FDP tendon to pass through.

Innervation:

Median nerve (C7, C8, T1)

Action:

Flexes the proximal interphalangeal (PIP) joints of the medial four fingers

Assists in flexing the metacarpophalangeal (MCP) joints and the wrist

Clinical Note
To test the function of the FDS, a clinician will hold all the patient’s fingers in extension except for the one being tested. They will then ask the patient to flex that finger at the middle (PIP) joint. This isolates the FDS because the flexor digitorum profundus (FDP) cannot flex one finger independently without also flexing the others.

Question 23

Flexor Pollicis Longus M

Answer 23

Origin:

Anterior surface of the radius and the interosseous membrane

Insertion:

Base of the distal phalanx of the thumb

Innervation:

Anterior interosseous nerve (from the Median nerve, C8, T1)

Action:

Flexes the interphalangeal (IP) joint of the thumb 👍

Assists in flexing the metacarpophalangeal (MCP) and carpometacarpal (CMC) joints of the thumb

Memory Tip
The name perfectly describes the muscle:

Flexor: It flexes the thumb.

Pollicis: The Latin word for thumb is “pollex.”

Longus: It’s the long muscle that flexes the thumb, distinguishing it from the flexor pollicis brevis.

Question 24

Pronator Quadratus M

Answer 24

Origin:

Distal fourth of the anterior surface of the ulna

Insertion:

Distal fourth of the anterior surface of the radius

Innervation:

Anterior interosseous nerve (from the Median nerve, C8, T1)

Action:

Pronates the forearm (the prime mover for this action)

Binds the radius and ulna together

Memory Tip
This is one of the easiest muscles to remember because its name tells you its shape and function:

Pronator: It pronates the forearm.

Quadratus: It’s quadrilateral, or roughly square-shaped. 🟧

Question 25

Flexor Retinaculum

Question 26

Abductor Pollicis Longus m

Answer 26

Origin: Posterior surfaces of the ulna and radius Insertion: Base of the 1st metacarpal bone Innervation: Posterior interosseous nerve (a continuation of the deep branch of the Radial nerve, C7, C8) Action: Abducts the thumb Extends the thumb at the carpometacarpal (CMC) joint Assists in radially deviating the wrist Clinical Note The tendons of the abductor pollicis longus (APL) and the extensor pollicis brevis (EPB) travel together in the same sheath and form the anterior border of the anatomical snuffbox. Overuse can cause inflammation of these tendons, leading to a painful condition called De Quervain's tenosynovitis.

Question 27

Bicipital Aponeurosis

Question 28

Extensor Carpi Radialis Brevis

Question 29

Flexor Pollicis Brevis