Human Anatomy Vol 1

Olecranon process

Coronoid process

Apex of

articular disc

of inferior

radioulnar joint

Head of

ulna

Ulnar collateral ligament

on styloid process

Figs 2.31a and b: (a) Features of anterior aspect of ulna, and

(b) upper end of ulna

o The medial surface is continuous inferiorly with the

medial surface of the shaft.

o The lnteral surface is smooth, continues as posterior

surface of shaft.

. The superior surface in its posterior part shows a
roughened area.
2 The coronoid (Greek like crow's beak) process projects
forwards from the shaft justbelow the olecranon and
has four surfaces, namely superior/ anterior, medial
and lateral.
. The superior swface forms the lower part of the
trochlear notch.
. The anterior surface is triangular and rough. Its
lower corner forms the ulnar tuberosity.
. The upper part of its lateral surfnce is marked by
the radial notch for the head of the radius. The
annular ligament is attached to the anterior and
posterior margins of the notch. The lower part of
the lateral surface forms a depressed area to
accommodate the radial tuberosity. It is limited
behind by a ridge called the supinator crest.
. Medial surface is continuous with medial surface
of the shaft.
3 The trochlear notch forms an articular surface that
articulates with the trochlea of the humerus to form
the elbow joint (Fig. 2.31b).

BONES OF UPPEB LIMB

4 The radial notch articulates with the head of the radius

to form the superior radioulnar joint (Fig. 2.31b).

$tusff

The shaft has three borders and three surfaces

(Fig.2.23).

&orders

1 The interosseous or lateral border is sharpest in its

middle two-fourths. Inferiorly, it canbe traced to the

lateral side of the head. Superiorly, it is continuous

with the supinator crest.

2 The anterior border is thick and rounded. It begins

above on the medial side of the ulnar tuberosity,

passes backwards in its lower one-third, and

terminates at the medial side of the styloid process

(Fig.2.25).

3 Theposteriorborder is subcutaneous. Itbegins, above,

at the apex of the triangular subcutaneous area at

the back of the olecranon, and terminates at the base

of the styloid process.

Su ces

1 The anterior surface lies between the anterior and

interosseous borders. A nutrient foramen is seen on

the upper part of this surface. It is directed upwards.

The nutrient artery is derived from the anterior

interosseous artery (Fig. 2.30).

2 The medial surfaie lieJ between the anterior and

posterior borders (Fig. 2.30).

3 The posterior surface lies between the posterior and

interosseous borders. It is subdivided into three areas

by two lines. An oblique line divides it into upper

and lower parts. The lower part is further divided

by a vertical line into a medial and a lateral area

(Fig.2.32).

d"o r End

The lower end is made up of the head and the styloid

process. The head articulates with the ulnar notch of

the radius to form theinferior rndioulnar joint (Fig.2.30).

It is separated from the wrist joint by the articular disc

(seeFig. 10.24). Ulnar artery and nerve lie on the anterior

aspect of head of ulna.

The styloid process projects downwards from

posteromedial side of lower end of the ulna. Posteriorly,

between the head and the styloid process, there

is groove for the tendon of the extensor carpi ulnaris

(Fig.2.27).

Attochmenls

1 The tricepsbrachii is inserted into the rough posterior

part of the superior surface of the olecranon

(Fig.2.26). The anterior part of the surface is covered

by a bursa.

(a)

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c

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Olecranon process

Trochlear notch

Superior surface of

coronoid process

Radial notch on

lateral surface with

annular ligament

Lateral surface