Its upper half is rounded and indistinctly marked, serving for the attachment of the lower part of the insertion of the teres minor muscle, and below this giving origin to the lateral head of the triceps brachii muscle; its center is traversed by a broad but shallow oblique depression, the spiral groove (musculospiral groove). The radial nerve runs in the spiral groove. Its lower part forms a prominent, rough margin, a little curved from backward, forward the lateral supracondylar ridge, which presents an anterior lip for the origin of the brachioradialis muscle above, and extensor carpi radialis longus muscle above, a posterior lip for the triceps brachii muscle, and an intermediate ridge for the attachment of the lateral intermuscular septum. Medial: the medial border extends from the lesser tubercle to the medial epicondyle. Its upper third consists of a prominent ridge, the crest of the lesser tubercle, which gives insertion to the tendon of the teres major muscle. About its center is a slight impression for the insertion of the coracobrachialis muscle, and just below this is the entrance of the nutrient canal, directed downward; sometimes there is a second nutrient canal at the commencement of the radial sulcus.
The inferior third of this border is raised into a slight ridge, the medial supracondylar ridge, which became very prominent below; it presents an anterior lip for the origins of the brachialis muscle and the pronator teres muscle, a posterior lip for the medial head of the triceps brachii muscle, and an intermediate ridge for the attachment of the medial intermuscular septum. The Deltoid tuberosity is a roughened surface on the lateral surface of the shaft of the Humerus and acts as the site of insertion of deltoideus muscle. The posterorsuperior part of the shaft has a crest, beginning just below the surgical neck of the humerus and extends till the superior tip of the deltoid tuberosity. This is where the lateral head of triceps brachii  is attached. The radial sulcus, also known as the spiral groove is found on the posterior surface of the shaft and is a shallow oblique groove through which the radial nerve passes along with deep vessels. This is located posteroinferior to the deltoid tuberosity. The inferior boundary of the spiral groove is continuous distally with the lateral border of the shaft. The nutrient foramen of the humerus is located in the anteromedial surface of the humerus. The nutrient arteries enter the humerus through this foramen. Distal humerus
The distal or lower extremity of the humerus is flattened from before backward, and curved slightly forward; it ends below in a broad, articular surface, which is divided into two parts by a slight ridge.