The bones

The bones of the arm and shoulder

Five bone names carry you from the center of the chest to the wrist: clavicle, scapula, humerus, radius, and ulna. The clavicle and scapula make the shoulder girdle, which attaches the upper limb to the trunk. The humerus fills the upper arm, and the radius and ulna run side by side through the forearm.

Anatomy draws its boundaries carefully, so the counts change with the question. The arm strictly means shoulder to elbow and contains one humerus. The whole upper limb has 30 bones, but 27 of them are in the wrist and hand. The shoulder girdle sits outside that 30, even though it is the structure that lets the limb hang from the rest of the skeleton. On this page, left and right copies of the five named bones account for ten of the 206.

There is one familiar impostor in the room. Your funny bone is the ulnar nerve passing behind the inner bump of the humerus at the elbow, where a knock can catch it against the bone. The actual humerus is far less mysterious: it is the largest bone of the upper limb, meeting the scapula at the shoulder and the radius and ulna at the elbow.

These 5 entries account for 10 of the 206.How the 206 is counted.

On this page: Try one · Questions · The plates · The specimens · Nearby

01 · Try one

Can you name this one?

This is how the lab asks. A bone you name today comes back a week later to be named again, and that is how it stays known.

Identify the specimen

S-shaped strut connecting the breastbone to the shoulder blade. You can feel it just under the skin.

2 (left + right)

clavicle

plural: clavicles

“collarbone”

In the body2 (left + right)

DescriptionS-shaped strut connecting the breastbone to the shoulder blade. You can feel it just under the skin.

Field noteOne of the most frequently fractured bones in the human body. Around 87 percent of the breaks come from landing directly on the shoulder, not from a fall on an outstretched hand.

02 · Questions

The questions people ask about these bones.

How many bones are in the arm?

The arm, in the strict anatomical sense, has one humerus. Add the forearm and there are three bones from shoulder to wrist. The whole upper limb has 30 once the wrist and hand are included, while the clavicle and scapula form the separate shoulder girdle. OpenStax, Bones of the Upper Limb and OpenStax, The Pectoral Girdle

Which is the largest bone in the arm?

The humerus is the largest bone of the upper limb. It is also the only bone in the upper arm, running from shoulder to elbow. StatPearls, Humerus

What is the funny bone?

It is the ulnar nerve, which passes beneath the medial epicondyle, the bony bump on the inner side of the elbow. A knock there can pinch the nerve and produce the familiar shock-like tingle. Cleveland Clinic, Ulnar Nerve

Is the collarbone the most commonly broken bone?

OpenStax describes the clavicle as the most commonly fractured bone in the body, though the Swedish Fracture Register gives that place to the distal radius. OpenStax, The Pectoral Girdle Swedish Fracture Register, distal radius fractures

Around 87 percent of clavicle fractures follow a fall directly onto the side of the shoulder; a fall on an outstretched hand accounts for about 6 percent. StatPearls, Clavicle Fracture Stanley and others, 1988

03 · The plates

Every specimen with a plate of its own.

An engraved plate of the clavicle — clavicle2 (left + right)

An engraved plate of the scapula — scapula2 (left + right)

An engraved plate of the humerus — humerus2 (left + right)

An engraved plate of the radius — radius2 (left + right)

An engraved plate of the ulna — ulna2 (left + right)

04 · The specimens

What each one is called, and how it is counted.

clavicle

plural: clavicles

“collarbone”

In the body2 (left + right)

DescriptionS-shaped strut connecting the breastbone to the shoulder blade. You can feel it just under the skin.

Field noteOne of the most frequently fractured bones in the human body. Around 87 percent of the breaks come from landing directly on the shoulder, not from a fall on an outstretched hand.

On record

The clavicle is the only long bone in the body that lies horizontally. OpenStax 8.1
One small joint at the breastbone is the upper limb’s only direct bony link to the axial skeleton. OpenStax 8.1
The clavicle is the first bone to begin ossifying during embryonic development. StatPearls

scapula

plural: scapulae

“shoulder blade”

In the body2 (left + right)

DescriptionFlat, triangular bone lying over the ribs on the upper back.

Field noteIt has no bony attachment to the rib cage at all. It floats on the back, held in place almost entirely by muscle.

On record

The scapula does not form a joint with the ribs; muscles hold it against the back of the chest. OpenStax 8.1
Seventeen different muscles attach to each scapula. StatPearls
The shoulder socket is only a shallow depression in the scapula called the glenoid cavity. OpenStax 8.1

humerus

plural: humeri

“upper arm bone”

In the body2 (left + right)

DescriptionThe single long bone of the upper arm, shoulder to elbow.

Field noteHitting your "funny bone" is actually the ulnar nerve getting pinched against the end of this bone. Not funny at all.

On record

The humerus is the largest bone of the upper limb. StatPearls
One humerus helps build two very different joints: a ball-and-socket shoulder and a hinge-like elbow. StatPearls
Your “funny bone” is not a bone at all: it is the ulnar nerve passing just behind the humerus at the elbow. StatPearls

radius

plural: radii

“forearm bone (thumb side)”

In the body2 (left + right)

DescriptionForearm bone on the thumb side. When you turn your palm down, it crosses over its neighbor.

Field noteIts name comes from the Latin word for a spoke of a wheel. When you turn your palm down, the radius crosses over the ulna.

On record

The radius meets the humerus and ulna near the elbow, then meets two wrist bones at its other end. OpenStax 8.2
The radius and ulna work as a pair to turn the palm up and down. StatPearls
The wrist connects directly to the radius, while the ulna is separated from the carpal bones by a cartilage pad. OpenStax 8.2

ulna

plural: ulnae

“forearm bone (pinky side)”

In the body2 (left + right)

DescriptionForearm bone on the pinky side. Its upper end forms the point of your elbow.

Field noteThe bony tip you lean on when you put your elbow on the table is this bone’s olecranon process.

On record

The hard point of your elbow is not the humerus; it is the ulna’s olecranon process. OpenStax 8.2
At the elbow, the ulna’s large notch fits around the humerus rather like the jaws of a wrench. OpenStax 8.2

05 · Learn them

Reading them is not the same as knowing them.

In the lab these are Case 01, The Arm & Shoulder, on the Explorer track, the first case file anyone opens.

It introduces bones a few at a time, asks where they are, and comes back days later to check they stayed.

Start with theseBegin with four bones. It’s free, and you don’t need an account.

Nearby: leg · rib cage · spine and pelvis · hand · wrist · foot and ankle · skull · ear · all nine