S7) The Upper Arm

Question 1

Where is the upper arm?

Answer 1

The upper arm is located between the shoulder joint and elbow joint

Question 2

What are the muscles of the upper arm?

Answer 2

Question 3

Identify the 3 muscles in the anterior compartment of the upper arm

Answer 3

• Biceps brachii
• Coracobrachialis
• Brachialis

Question 4

Describe the neurovascular supply of the anterior compartment of the upper arm

Answer 4

• Innervated by the musculocutaneous nerve
• Arterial supply via muscular branches of the brachial artery

Question 5

Describe the structure and function of the biceps brachii muscle

Answer 5

• Structure: two-headed muscle, bicipital aponeurosis forms the roof of the cubital fossa and blends with the deep fascia of anterior forearm

- Function: supination, elbow flexion, shoulder flexion

Question 6

State the origin and attachment of the biceps brachii muscle

Answer 6

• Origin:

I. Long head – supraglenoid tubercle

II. Short head – coracoid process

• Attachment: radial tuberosity and the fascia of the forearm via the bicipital aponeurosis

Question 7

Describe the structure and function of the coracobrachialis muscle

Answer 7

• Structure: lies deep to biceps brachii

- Function: shoulder flexion

Question 8

State the origin and attachment of the coracobrachialis muscle

Answer 8

• Origin: coracoid process of the scapula
• Attachment: medial side of the humeral shaft, at the level of the deltoid tubercle

Question 9

Describe the structure and function of the brachialis muscle

Answer 9

• Structure: lies deep to biceps brachii, found more distally than the other and forms the floor of the cubital fossa

- Function: elbow flexion

Question 10

State the origin and attachment of the brachialis muscle

Answer 10

• Origin: medial and lateral surfaces of the humeral shaft
• Attachment: ulna tuberosity, distal to the elbow joint

Question 11

Identify the muscle in the posterior compartment of the upper arm

Answer 11

Triceps brachii

Question 12

Describe the neurovascular supply of the posterior compartment of the upper arm

Answer 12

• Innervated by the radial nerve
• Arterial supply via the profunda brachii artery

Question 13

Describe the structure and function of the triceps brachii muscle

Answer 13

• Structure: three heads; medial head lies deeper than the other two

- Function: elbow extension

Question 14

State the origin and attachment of the triceps brachii muscle

Answer 14

• Origin:

I. Long head – infraglenoid tubercle

II. Lateral head – above radial groove of humerus

III. Medial head – below radial groove of humerus

• Attachment: olecranon of the ulna

Question 15

What is the cubital fossa?

Answer 15

The cubital fossa is triangular depression on the anterior surface of the elbow joint as the anatomical arm transitions to become the forearm

Question 16

The cubital fossa is triangular in shape, and thus has three borders.

What are they?

Answer 16

Question 17

Describe the structure of the floor and roof of the cubital fossa

Answer 17

• The floor is formed proximally by the brachialis, and distally by the supinator muscle
• The roof is formed of skin and fascia and is reinforced by the bicipital aponeurosis

Question 18

Which structure runs in the roof of the cubital fossa?

Answer 18

Median cubital vein is located superficially within the roof of the cubital fossa and can be accessed for a venepuncture

Question 19

Identify and describe contents of the cubital fossa

Answer 19

• Radial nerve passes underneath the brachioradialis muscle

- Biceps tendon runs through to attach to the radial tuberosity

- Brachial artery bifurcates at the apex of the cubital fossa

- Median nerve leaves the cubital fossa between the two heads of the pronator teres

Question 20

Where can the brachial pulse be felt?

Answer 20

The brachial pulse can be felt by palpating immediately medial to the biceps tendon in the cubital fossa

Question 21

What is the humerus and what does it do?

Answer 21

• The humerus is the bone that forms the upper arm and joins it to the shoulder and forearm
• It acts as an attachment site for many muscles and ligaments

Question 22

Describe the proximal and distal articulations of the humerus

Answer 22

• The proximal region articulates with the scapula and clavicle to form part of the shoulder joint
• The distal region articulates with the radius and ulna to form the elbow joint.

Question 23

Identify the anatomical features observed in the proximal region of the humerus

Answer 23

Question 24

Describe the anatomical position of the head and anatomical neck of the humerus

Answer 24

• The head of the humerus projects medially and superiorly to articulate with the glenoid cavity of the scapula
• The anatomical neck is short in width and connects the head to the tubercles

Question 25

What is a tubercle?

Answer 25

A **tubercle** is a round nodule, and signifies an attachment site of a muscle or ligament

Question 26

Describe the anatomical position of the greater and lesser tubercles of the humerus

Answer 26

- The **greater tubercle** is located laterally on the humerus and serves as an attachment site for 3 rotator cuff muscles – supraspinatus, infraspinatus, teres minor - The **lesser tubercle** is located medially on the humerus and serves as an attachment site 1 rotator cuff muscle – subscapularis

Question 27

How are the the greater and lesser tubercles of the humerus separated?

Answer 27

Separating the two tubercles is a deep depression, called the **intertubercular sulcus/groove** and its edges are known as lips

Question 28

Describe the anatomical position of the surgical neck of the humerus

Answer 28

The **surgical neck** runs from the tubercles to the shaft of the humerus

Question 29

The shaft of the humerus contains some important bony landmarks. Identify and describe them

Answer 29

- **Deltoid tuberosity** is a roughened surface on lateral side of humeral shaft - **Radial groove** is a shallow depression running diagonally down the posterior surface of the humerus, parallel to the deltoid tuberosity

Question 30

Which structures run along the radial groove?

Answer 30

- Profunda brachii artery - Radial nerve

Question 31

Which muscles attach to the shaft of the humerus?

Answer 31

**- Anteriorly:** deltoid, coracobrachialis, brachialis, brachioradialis **- Posteriorly:** medial and lateral heads of the triceps

Question 32

Identify the anatomical features observed in the distal region of the humerus

Answer 32

Question 33

Describe the structure of the lateral and medial supraepicondylar ridges

Answer 33

- The **supracondylar ridges** are formed from the lateral and medial borders of the humerus - The lateral supraepicondylar ridge is more roughened as many **extensor muscles** in the posterior forearm attach there

Question 34

Describe the structure of the lateral and medial epicondyles

Answer 34

- The **lateral** and **medial epicondyles** are projections of bone immediately distal to the lateral and medial supracondylar ridges - The medial is much larger and can be palpated more easily

Question 35

What passes along the medial epicondyle?

Answer 35

The **ulnar nerve** passes into the forearm along the posterior side of the medial epicondyle, and can also be palpated there

Question 36

Describe the anatomical position and articulations of the trochlea and capitulum

Answer 36

- The **trochlea** is located medially and articulates with the ulna - The **capitulum** is located laterally and articulates with the radius

Question 37

Three depressions are also found on the distal portion of the humerus. Identify and describe them

Answer 37

The **coronoid, radial** and **olecranon fossae** are 3 depressions which accommodate the forearm bones during movement at the elbow

Question 38

What is a biceps tendon rupture?

Answer 38

**Biceps tendon rupture** is the complete rupture of the biceps brachii tendon after the very strong contraction of the muscle and presents with a characteristic Popeye sign on elbow flexion

Question 39

After the rupture of the biceps tendon, why would the patient not notice much weakness in the upper limb?

Answer 39

Due to the action of the **brachialis** and **supinator** muscles

Question 40

Which structures are at risk of damage in a mid-shaft humeral fracture?

Answer 40

- Radial nerve - Profunda brachii artery

Question 41

What is a mid-shaft humeral fracture?

Answer 41

- **Mid-shaft humeral fractures** are fractures within the shaft of the humerus, occuring from FOOSH, which damage the profunda brachii artery and radial nerve - It presents with the unopposed flexion of the wrist (wrist drop) due to paralysis of the extensor muscles of the wrist and some sensory loss over the dorsum of the hand

Question 42

Identify two common fracture types of the distal humerus

Answer 42

- Supracondylar fractures - Medial epicondyle fractures

Question 43

What is a supracondylar fracture?

Answer 43

- **Supraepicondylar fractures** are transverse fractures, spanning between two epicondyles, which occur by falling on a flexed elbow - It presents with Volkmanns ischaemic contracture which is ischaemia causing the uncontrolled flexion of the hand, as flexor muscles become fibrotic and short

Question 44

Which nerves might be damaged in a supracondylar fracture?

Answer 44

- Median nerve - Ulnar nerve - Radial nerve

Question 45

What is a medial epicondyle fracture?

Answer 45

- A **medial epicondyle fracture** is a fracture which damages the ulnar nerve producing a deformity known as ulnar claw due to the paralysis of the lateral lumbricals - It presents with a loss of sensation over the dorsal and palmar hand surfaces and the medial 1½ fingers