Human Anatomy Vol 1

UPPER LIMB

The ulna is the medial bone of the forearm, and is

homologous with the fibula of the lower limb. It has

upper end, shaft and a lower end.

Side Determinolion

1 The upper end is hook-like, with its concavity

directed forwards.

2 The lateral border of the shaft is sharp and crest-like.

3 Pointed styloid process lies posteromedial to the

rounded head of ulna at its lower end.

Feotules

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The upper end presents the olecranon and coronoid

processes, and the trochlear and radial notches (Fig. 2.30).

1 The olecranonprocess projects upwards from the shaft.

It has superior, anterior, posterior, medial and lateral

surfaces.

. The anterior surface is articular, it forms the upper
part of the trochlear notch (Fig. 2.31a)
. The posterior surface forms a triangular
subcutaneous area which is separated from the
skin by a bursa, Inferiorly, it is continuous with
the posterior border of the shaft of the ulna (Fig.
2.32).Theupper part forms the point of the elbow.

Olecranon process

Radial notch

Head

Radial tuberosity

Trochlear notch

Coronoid process

Anterior surface

of coronoid process

Ulnar tuberosity

Nutrient foramen

Medial surface

Anterior surface

Sharp atera

border

Epiphyseal line

Capsular line

I nterosseous

membrane

lnferior radioulnar

joint

Styloid process

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Figs 2.28a and b: (a) Colles' fracture with dinner fork

deformity, (b) Smith's fracture

Ulna

Radius

Head of radius

pulled out of

annular

ligament

Lower end

of humerus

Figs2.29a and b: Pulled elbow

Fig.2.30: Anterior surfaces of radius and ulna