The longest bone of the upper limb, the single bone between shoulder and elbow
Humerus — the arm bone.
Anatomy · Bones
Humerus
Longest bone of the upper limb
Upper limb · arm
The humerus is the single long bone of the upper arm, running from the shoulder to the elbow. Its rounded head fits into the glenoid cavity of the scapula, and its lower end, shaped like a pulley and a small knob, forms the elbow joint with the ulna and radius. It is the longest and largest bone of the upper limb.
How to spot them
- ▸Long shaft with a smooth, ball-like head facing inwards and upwards to meet the shoulder blade
- ▸Greater and lesser tubercles on the upper end, separated by a groove that carries a biceps tendon
- ▸A V-shaped roughness (deltoid tuberosity) halfway down the outer side of the shaft
- ▸Flattened lower end with a pulley-shaped trochlea, a knob-like capitulum, and two epicondyles
What to know
Its rounded head sits in the shallow socket of the shoulder blade, and the groove between two tubercles below it carries the long tendon of the biceps
Humerus — the intertubercular (bicipital) groove.
A spiral groove winds down the back of its shaft, carrying a nerve whose damage in a mid-shaft break causes wrist drop
Humerus — the radial groove, with the radial nerve and the profunda brachii artery.
A break at the narrowing below its two tubercles endangers the axillary nerve, and is a common fracture in older people with fragile bones
Humerus — the surgical neck.
Its lower end carries a spool-shaped surface for one forearm bone and a small rounded knob for the other
Humerus — the trochlea (for the ulna) and capitulum (for the radius).
In children, a fall on the outstretched hand often breaks it just above the elbow, threatening the brachial artery
Humerus — the supracondylar fracture.
The 'funny bone' is not this bone at all, but the ulnar nerve where it passes behind the prominent inner knob at its lower end
Humerus — the medial epicondyle.
Key ideas
- The medial epicondyle is larger and stronger than the lateral one because the powerful grasping muscles of the front of the forearm arise from it.
- Three depressions at the lower end (coronoid fossa, radial fossa, olecranon fossa) accommodate the forearm bones when the elbow is fully bent or straightened.
Quick-fire facts
- •Its head, the anatomical neck, the greater and lesser tubercles and the surgical neck make up the upper end; the surgical neck, not the anatomical neck, is the common fracture site.
- •The deltoid tuberosity, a V-shaped roughening halfway down the outer shaft, is where the deltoid inserts.
- •The radial nerve and the profunda brachii artery run in the radial (spiral) groove on the back of the shaft, so a mid-shaft fracture can injure the radial nerve and cause wrist drop.
- •The axillary nerve wraps around the surgical neck and can be damaged by fractures or shoulder dislocations there.
- •The trochlea ('pulley') articulates with the ulna and the capitulum ('little head') with the radius.
- •The ulnar nerve runs in a groove behind the medial epicondyle; striking it gives the 'funny bone' sensation, and the name is commonly linked to a pun on 'humerus'.
- •Supracondylar fractures are the classic elbow fracture of childhood and can compress the brachial artery.
- •The word humerus is Latin for the upper arm or shoulder; the Latin word umerus also means shoulder.
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Sources
- OpenStax — Anatomy and Physiology 2e — 8.2 Bones of the Upper Limb
- TeachMeAnatomy — Humerus — Bones of the Upper Limb