Anatomy and Physiology 2e · The Appendicular Skeleton
Bones of the Upper Limb
On this page 9 sections
In 30 seconds
Each upper limb contains 30 bones arranged in three segments: the arm (brachium) with a single bone, the Humerus The single long bone of the arm (brachium) Full entry →; the forearm (antebrachium) with two parallel bones, the Radius The lateral forearm bone (thumb side), with a disc-shaped head and distal styloid process Full entry → and Ulna The medial forearm bone (pinky side) with the olecranon and trochlear notch Full entry →; and the hand, which holds 27 bones — 8 Carpals The 8 small wrist bones in two rows of four Full entry → in the wrist, 5 Metacarpals The 5 palm bones, numbered 1–5 from the thumb Full entry → in the palm, and 14 Phalanges The finger bones — 14 total (thumb has 2, others 3) Full entry → in the fingers. The limb hangs from the pectoral girdle (Topic 1) and is built for mobility and fine manipulation rather than weight bearing.
The bones are not just a stack of parts; they are organized around two engineering ideas. First, two-bone segments create rotation: the radius can pivot around the ulna, which is what lets you turn your palm up (supination) and down (pronation). Second, a chain of small bones makes a flexible platform: the carpals, metacarpals, and phalanges convert a single forearm into a hand that can grip, pinch, and feel. Learning them in proximal-to-distal order matches how clinicians palpate the limb and how fractures are described.
Why this matters
The upper limb is the most frequently injured part of the body, and nearly every common injury is named after a bone landmark you are about to learn:
- A fall on an outstretched hand (the classic "FOOSH") can fracture the distal radius (Colles' fracture Fracture of the distal radius from a fall on an outstretched hand Full entry →), the Scaphoid Lateralmost proximal carpal, between thumb and wrist Full entry → carpal bone, or the surgical neck of the humerus — three different injuries from the same mechanism.
- The "funny bone" tingle you feel when you hit your elbow is the ulnar nerve passing behind the medial epicondyle of the humerus, not a bone.
- Wrist pain after a fall that "just hurts" may be an undetected scaphoid fracture, which has a poor blood supply and can fail to heal if missed.
For nurses, therapists, and clinicians, being able to name and palpate these bones is the foundation of assessment — describing where pain is, where a deformity is, and where to expect nerve problems. For students, the humerus, radius, ulna, carpals, metacarpals, and phalanges are among the most heavily tested structures in any anatomy course.
The college version
Core Concepts
The humerus: the arm bone
The humerus is the long bone of the arm. Its proximal end has a smooth head that fits the glenoid cavity of the scapula, separated from the shaft by the anatomical neck. Just below it, the surgical neck is the fracture-prone region of the proximal humerus (the axillary nerve runs near it). Two rounded tubercles — the greater (lateral) and lesser (anterior) — provide muscle attachments, and the intertubercular (bicipital) groove between them carries the tendon of the long head of the biceps brachii. Halfway down the shaft, the deltoid tuberosity marks where the deltoid muscle attaches, and the shallow radial groove on the back of the shaft carries the radial nerve.
The distal end widens into the elbow: the capitulum (lateral) articulates with the head of the radius, the trochlea (medial) articulates with the ulna, and the medial and lateral epicondyles are the knobs you can feel on either side of the elbow. The Olecranon The ulna's proximal hook that fits the olecranon fossa Full entry → fossa on the posterior side receives the ulna's olecranon when the elbow straightens; the coronoid and radial fossae on the anterior side receive the coronoid process and radial head when the elbow bends.
The radius and ulna: the forearm pair
The radius is the lateral bone of the forearm — the thumb side. Its disc-shaped head pivots against the capitulum and the radial notch of the ulna, allowing pronation and supination. Below the head, the radial tuberosity anchors the biceps brachii. Distally, the radius widens and its styloid process (the thumb-side wrist bump) is part of the wrist joint; the radius articulates with the scaphoid and lunate carpals, making it the main bone connecting the forearm to the wrist.
The ulna is the medial bone — the pinky side. Its proximal end forms the olecranon (the point of the elbow), the coronoid process, and the trochlear notch that grips the humerus's trochlea. The radial notch accepts the radial head. Distally the ulna narrows to a head with a small styloid process (the pinky-side wrist bump). The ulna does most of the elbow's hinge work; the radius does most of the wrist's work.
The two bones are joined by the Interosseous membrane Tough sheet of connective tissue joining the radius and ulna Full entry → and articulate at the proximal and distal radioulnar joints; when you pronate or supinate, the radius rotates around the relatively fixed ulna.
The carpals: eight bones in two rows
The wrist has 8 carpal bones in two rows of four. Proximal row (lateral to medial): scaphoid, lunate, triquetrum, pisiform. Distal row (lateral to medial): trapezium, trapezoid, capitate, hamate. Mnemonics like "So Long To Pinky, Here Comes The Thumb" preserve the order. Two clinical heavyweights: the scaphoid is the most commonly fractured carpal bone, and because its blood supply enters distally (a "retrograde" supply), a missed fracture can lead to avascular necrosis and nonunion; the lunate is the carpal most often dislocated.
The metacarpals and phalanges: palm and fingers
The palm contains 5 metacarpals, numbered 1–5 starting at the thumb. Each has a base, shaft, and rounded head that forms a knuckle. The first metacarpal is the most mobile — it sits in a saddle joint with the trapezium, which is what makes the thumb opposable. The fingers contain 14 phalanges: the thumb has 2 (proximal and distal), and each of the other four fingers has 3 (proximal, middle, distal).
A memory strategy that works
Name each bone with its neighbor and its joint: humerus meets radius and ulna at the elbow; radius and ulna meet the carpals at the wrist; carpals meet metacarpals in the palm; metacarpals meet phalanges at the knuckles. When you can say what articulates with what, you also know where fractures and dislocations are described — and which nerve or vessel is nearby.
Common Confusions
| Do not confuse | With | Difference |
|---|---|---|
| Radius | Ulna | Radius is lateral/thumb side and rotates at the wrist; ulna is medial/pinky side and forms the elbow's hinge |
| "Arm" | "Forearm" or "upper limb" | Anatomically, arm = humerus only; forearm = radius + ulna; upper limb = everything from shoulder to fingertips |
| Capitulum | Trochlea | Capitulum (lateral) meets the radial head; trochlea (medial) meets the ulna's trochlear notch |
| Olecranon | Styloid process | Olecranon is the proximal ulna (elbow point); styloid processes are the distal wrist bumps (radial and ulnar) |
| Carpals | Metacarpals or phalanges | Carpals = 8 wrist bones; metacarpals = 5 palm bones; phalanges = 14 finger bones |
| Scaphoid (wrist) | Navicular (foot) | Scaphoid is a carpal; the navicular is a tarsal — similar names, different limbs |
| Hitting your "funny bone" | Hitting a bone | The tingle is the ulnar nerve being bumped behind the medial epicondyle — no bone is hit |
| Colles' fracture | Scaphoid fracture | Colles' = distal radius (dinner-fork deformity); scaphoid fracture = one specific carpal, often with persistent wrist pain and risk of nonunion |
Eli explains
The same idea, in plain words
Explain it like I’m 10
Your arm bones are like a robot arm built from Lego. One big bone (humerus) is the upper arm. Two bones side by side (radius and ulna) make the forearm, and the radius spins around the ulna so you can turn your palm over like a screwdriver. Then comes a pile of small bones — 8 in the wrist, 5 in the palm, and 14 in the fingers — like a flexible chain that lets your hand bend, grip, and pinch. The thumb is special: its base is a loose saddle joint, which is why you can touch it to every other finger.
Worked example
A 68-year-old woman slips on ice and catches herself with her right hand, landing hard on the extended wrist. She feels immediate wrist pain and notices the wrist looks bent backward like a fork. Walking through the anatomy: the force traveled up the hand into the distal radius — the bone that carries most of the load at the wrist — and broke it near its articulation with the scaphoid and lunate. This is the classic Colles' fracture; the "dinner fork" shape comes from the distal fragment being displaced backward and upward. In the emergency department, the provider will confirm the fracture and alignment with imaging, and treatment (casting or surgery) depends on the displacement. But notice what the anatomy predicts: the same fall in a younger person might instead fracture the scaphoid (which needs follow-up imaging because it can hide on initial X-rays and its blood supply is fragile) or, with force transmitted higher, the surgical neck of the humerus in an older person. Knowing the bone-by-bone chain of the upper limb is what lets a clinician anticipate the possible injuries from one mechanism — and lets a student answer the exam question "what else could this fall have broken?"
Key takeaways
- Upper limb = 30 bones: 1 humerus + 2 forearm bones (radius, ulna) + 8 carpals + 5 metacarpals + 14 phalanges.
- Radius = lateral (thumb side), ulna = medial (pinky side). The radius rotates around the ulna for pronation/supination.
- Humerus: head → anatomical neck → surgical neck (fracture site) → greater/lesser tubercles → intertubercular groove → deltoid tuberosity → capitulum (with radius) + trochlea (with ulna) + epicondyles + olecranon fossa.
- Ulnar nerve behind the medial epicondyle = "funny bone"; radial nerve runs in the radial groove of the humeral shaft.
- Elbow point = olecranon of the ulna; the ulna does the elbow hinge, the radius leads at the wrist (scaphoid + lunate).
- 8 carpals in two rows; scaphoid = most commonly fractured carpal with tenuous blood supply; lunate = most commonly dislocated carpal.
- 5 metacarpals (1 = thumb); 14 phalanges (thumb 2, other fingers 3 each); thumb's saddle joint with the trapezium enables opposition.
- Classic injury: Colles' fracture = distal radius fracture from a fall on an outstretched hand, often with a "dinner fork" deformity.
Check yourself
6 review questions from the chapter. Try each one, then open the answer.
How many bones are in each upper limb, and how do they break down by region?
Show answer
30 bones: 1 humerus, 2 forearm bones (radius and ulna), 8 carpals, 5 metacarpals, and 14 phalanges.
Which forearm bone is lateral, and which bone "leads" at the wrist joint?
Show answer
The radius is lateral (thumb side). The radius articulates with the scaphoid and lunate and is the main bone at the wrist; the ulna dominates the elbow hinge.
What movement does the radius perform around the ulna, and what structure connects the two bones?
Show answer
Pronation and supination — the radius rotates around the relatively fixed ulna; the interosseous membrane binds the two bones.
Name the 8 carpal bones by row, and identify the two clinically important ones.
Show answer
Proximal row: scaphoid, lunate, triquetrum, pisiform. Distal row: trapezium, trapezoid, capitate, hamate. The scaphoid (most commonly fractured) and lunate (most commonly dislocated) are the key clinical ones.
Where does the ulnar nerve pass at the elbow, and what does that explain?
Show answer
The ulnar nerve runs behind the medial epicondyle of the humerus — bumping it produces the "funny bone" tingling.
A fall onto an outstretched hand is classically associated with which three upper-limb fractures?
Show answer
Distal radius (Colles' fracture), scaphoid fracture, and fracture of the surgical neck of the humerus.
Study tools & related lessonsKey vocabulary · Related
Key vocabulary
- Humerus
- The single long bone of the arm (brachium)
- Radius
- The lateral forearm bone (thumb side), with a disc-shaped head and distal styloid process
- Ulna
- The medial forearm bone (pinky side) with the olecranon and trochlear notch
- Interosseous membrane
- Tough sheet of connective tissue joining the radius and ulna
- Capitulum / trochlea
- Lateral and medial articular surfaces at the distal humerus
- Olecranon
- The ulna's proximal hook that fits the olecranon fossa
- Carpals
- The 8 small wrist bones in two rows of four
- Scaphoid
- Lateralmost proximal carpal, between thumb and wrist
- Metacarpals
- The 5 palm bones, numbered 1–5 from the thumb
- Phalanges
- The finger bones — 14 total (thumb has 2, others 3)
- Colles' fracture
- Fracture of the distal radius from a fall on an outstretched hand
Sources & references
This lesson was adapted from the open educational references above; their licenses and attributions are preserved. See Copyright & Licensing.
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