Ulna bone structure

Ulna bone structure

1. + The ulna bone is the medial bone of the fore arm,and is

homologous with the fibula of the lower limb.
+ It has an upper end ,lower end and a shaft.

The upper end presents the olecranon and coronoid
process and the trochlear and radial notch.

1. Olecranon process: It projects upwards from the shaft .It has

- Anterior surface( articular surface and forms upper part of
trochlear notch)

2. - Posterior surface (forms a triangular subcutaneous
area)

- Medial surface

- Lateral surface

- Superior surface( posterior part shows roughned
area).

3. 2. It projects forwards from the shaft just below the
olecranon process and had four surfaces viz

- superior surface (forms the lower part of the trochlear notch)

- Anterior surface( triangular and rough and its lower corner forms the
ulnar tuberosity).

- Lateral surface.
- Medial surface.

4. 3. It forms an articular surface that
articulated with the trochlea of the humerus to form

the elbow joint.

4. It lies on the upper part of the lateral
surface and articulates with the head of the radius to
form the superior radio-ulnar joint.

5. « The shaft has three borders and three surfaces.

1,

Introsseous or lateral border: It is the sharpest in the
middle two- fourth.superiorly ,it is continuous with the
supinator crest.

. Anterior border: Thick and round.lt begins above on the
medial side of the ulnar tuberosity and terminates below at
the medial side of styloid process.

6. 3. Pos It begins above at the apex of triangular
area ar the back of the olecranon and terminates at the base
of the styloid process.

surfaces:-
lies between the anterior and

introsseous borders

2. E
borders
3. Posterior border: lies between the posterior and lateral
borders.

lies between the anterior and posterior

7. Lower End: Lower end is made up of the head and the styloid
process.

. It articulates with the ulnar notch of the radius to form the
inferior radio- ulnar joint.

It projects downwards from the posteriomedial side
of the lower end of ulna.posteriorly,between the styloid process and
the head ,there is a groove for the tendon of the extensor carpi
ulnaris.

8. «Side determination of ulna
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 medial to the rounded head of ulna.

9. Front view

Va

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Ulna bone

Back view

Trochlear Y
notch — HA
coronota ZA
seas €

Rodiaı / WM

notch

Head

Styloid
process

scanned with CamScamner