The humerus extends from the shoulder to the elbow.

The humerus articulates with the scapula to form the shoulder joint and articulates with

the radius and ulna to form the elbow joint.

Movement of the humerus is essential to various daily activities involving the arm.

The humerus is classified as a long bone, meaning it has a shaft and two distinct ends.

The humerus has a proximal end, closer to the point of attachment to the body, and a

distal end.

At the proximal end of the humerus, a rounded structure, termed the head of the humerus,

can be seen.

The head articulates with the scapula at the glenoid cavity, to form the shoulder joint.

The anatomical neck lies just below the head of the humerus, in the same way the neck is

found below the head, hence the name.

The anatomical neck is an attachment point for the articular capsule, which is filled

with fluid, which lubricates the shoulder joint.

The anatomical neck separates the head of the humerus from the greater and lesser tubercles.

The greater tubercle is situated lateral to the head of the humerus.

The greater tubercle is a point of attachment for 3 of the rotator cuff muscles: the supraspinatus,

infraspinatus and teres minor.

The lesser tubercle is more distal and medial than the greater tubercle.

The lesser tubercle is a point of attachment for the fourth rotator cuff muscle, the subscapularis.

The intertubercular groove or sulcus is an indentation that lies between the greater

and lesser tubercles.

Moving distally from the tubercles, at the beginning of the shaft, the surgical neck

of the humerus is found.

Surgical neck fractures are the most common type of proximal humeral fractures, especially

in osteoporotic women after a fall.

It is called the surgical neck as it is the location of many fractures that require surgery.

The middle region of the humerus is identified as the shaft of the humerus.

About halfway down the shaft of the humerus, is a rough area on the lateral surface, the

deltoid tuberosity.

The deltoid tuberosity is the point of attachment for the deltoid muscle, which is a muscle

that acts in the movement of the humerus, specifically as a prime mover of arm abduction.

Moving distally from the middle region of the humerus is the distal end of the humerus.

The distal end of the humerus has two smooth, rounded articular surfaces.

The capitulum lies on the lateral side and the trochlea lies on the medial side.

The capitulum articulates with the head of the radius and is the structure that the head

rolls on when flexing the lower arm.

The trochlea articulates with the trochlear notch on the ulna in the forearm.

During flexion of the arm, the coronoid process of the ulna articulates with the coronoid

fossa of the humerus, rotating on the trochlea.

The head of the radius articulates with the radial fossa of the humerus, rotating on the

capitulum.

The lateral epicondyle is the rounded structure found at the distal end of the humerus on

the lateral side.

The lateral epicondyle is the point of attachment to the radial collateral ligament of the elbow

joint and some extensor muscles.

The extensor muscles include the extensor carpi ulnaris, extensor digitorum minimi,

extensor digitorum communis and extensor carpi radialis.

The medial epicondyle is the rounded structure found at the distal end of the humerus on

the medial side.

The medial epicondyle is larger and more prominent than the lateral epicondyle.

The medial epicondyle is the point of attachment for the ulnar collateral ligament of the elbow

joint.

While the lateral epicondyle is the attachment point for extensor muscles, the medial epicondyle

in the point of attachment for the flexor muscles of the forearm.

These muscles include the flexor carpi ulnaris, the palmaris longus, the flexor carpi radialis

and the pronator teres.

One of the main factors differentiating between a right or left humerus is the identification

of the olecranon fossa on the posterior side and the placement of the head.

Begin by identifying the olecranon fossa and orienting the fossa to be on the posterior

side.

Once the anterior and posterior sides have been identified, use the orientation of the

head of the humerus to determine right from left.

If the head is on the right side, it is the left humerus.

If the head is on the left side, as shown with this bone, it is the right humerus.

Due to the placement of the humerus connecting to both the elbow and the shoulder, it is

an essential bone involved in all arm motion.

This video was prepared as part of the course requirements of Human Anatomy at Saddleback

College.