osteology

Humerus

Plan

· shaft

· upper end with articular head

· anatomical neck is at articular margin of head

· surgical neck is at narrower shaft

· lower end with epicondyles

Head

· forms 1/3 of sphere

· 4 times area of glenoid fossa

· capsule attached at articular margin

· except medially where extends down shaft 2 cm

· synovial membrne attached to articular margin

Lesser tuberosity

· projects forwards

· continued downwards as medial lip of bicipital groove

· subscapularis inserts into lesser tuberosity

· teres major inserts into medial lip for 5 cm below

Bicipital groove

· lies on anterior surface

· bridged by transverse ligament

· transmits long head of biceps

· latissimus dorsi inserts into floor of bicipital groove

Greater tuberosity

· three smooth facets

· supraspinatus inserts into superior facet

· infraspinatus inserts into intermediate facet behind this

· teres minor inserts into inferior facet posteriorly

· axillary nerve in contact with bone below this

· anterior margin continues downwards as lateral lip of bicipital groove

· attaches trilaminar tendon of pectoralis major

· posterior lamina extends up to anatomical neck

· anterior lamia extends up to surgical neck

· lateral lip continues downwards as anterior margin of deltoid tuberosity

Shaft

· greater tuberosity continues down into deltoid tuberosity

· V-shaped prominent ridge

· smaller ridge in between

· on lateral side of shaft halfway down

· gives rise to fibrous septae of deltoid

· radial groove below deltoid tuberosity

· spirals down posteriorly from medial to lateral

· superior lip is posterior part of deltoid tuberosity

· inferior margin runs down as lateral supracondylar ridge

· lateral supracondylar ridge

· gives attachment to lateral IM septum

· becomes lateral epicondyle

· medial supracondylar ridge

· gives attachment to medial IM septum

· becomes medial epicondyle

· coracobrachialis arises from medial shaft

· opposite deltoid tuberosity

· near nutrient foramen

· lateral head of triceps arises from superior lip of radial groove

· extends up to surgical neck

· medial head of triceps arises from inferior lip of radial groove

· then from whole shaft below and both MI septae

· radial groove bare between origins of lateral and medial heads

· radial nerve comes into contact with it at lowest part

Lower end

· articular surface is conjoined capitellum and trochlea

· capitellum

· for articulation with radius

· section of sphere

· projects forwards and inferiorly

· prominent nonarticular lateral ridge

· trochlea

· extends to posterior surface

· medial margin is high ridge

· lateral margin is low ridge on capitellum

· coronoid fossa

· on anterior surface laterally

· above trochlea

· for coronoid process of ulna

· radial fossa

· on anterior surface medially

· above capitellum

· for radial head

· olecranon fossa

· on posterior surface

· bounded by peripheral ridges of trochlea and capitellum

· for olecranon of ulna

· capsule attached to

· marginal ridges of trochlea and capitellum

· shaft of humerus above fossae

· synovial membrane

· attached to articular margins

· clothes floors of fossae

Medial epicondyle

· more prominent than lateral

· points in same direction as head

· facet on anterior surface for common flexor origin

· pronator teres arises from medial supracondylar ridge above this

· groove posteriorly between epicondyle and ridge of trochlea

· for ulnar nerve

· facet on epicondyle for attachment of ulnar collateral ligament

Lateral epicondyle

· smooth surface on anterior surface for common extensor origin

· brachioradialis arises from upper 2/3 of lateral supracondylar ridge

· ECRL arises from lower 1/3 of ridge

· facet on epicondyle for radial collateral ligament

· superficial fibres of supinator arise around this facet

· anconeus arises from pit behind origin of supinator