Humerus

Humerus


Parts of Humerus

1. Upper end
• Head 
Neck 
Greater tubercle
Lesser tubercle 
Intertubercular sulcus 

2. Lower end
- Articular part 
  • Capitulum 
  • Trochlea 

- Non-articular part 
  • Coronoid fossa 
  • Radial fossa 
  • Olecranon fossa 

3. Shaft 

 

Upper end of Humerus


Head 
Smooth and rounded.
Articular surface covered by hyaline cartilage.


Neck 
There are three types of neck.
1. Anatomical neck 
2. Surgical neck 
3. Morphological neck

 

Anatomical neck 

It is the constriction present at the margin of the rounded head.
Gives attachment to the Capsular ligament of the shoulder joint. 
Capsular ligament is deficient superiorly for the passage of the tendon of the long head of biceps brachii.
Capsular ligament extends medially from the anatomical neck to the shaft about 1-2 cm.

 

Surgical neck 

It is the constriction present between the upper end of the shaft and below the greater and lesser tubercle.
It is related to the axillary nerve and posterior and anterior circumflex humeral vessels.
It is the weakest part of the humerus where fracture commonly takes place.
Fractures at this point lead to damage to the axillary nerve and vessel associated with it.
That's why it is surgically important.


Morphological neck

It is the junction between epiphysis and diaphysis.
It is also the true junction of the head and shaft.

 

Greater tubercle 

It is the most lateral part located at the proximal end of the humerus.
Posterio-superior parts bears three flat impression 
Those flattened impressions give attachment to the supraspinatus, infraspinatus, and teres minor muscle to upper, middle, and lower impression respectively.


Lesser tubercle

Small elevation
Lie just above the surgical neck.
Give attachment to the subscapularis muscle.

Note:
Supraspinatus
Infraspinatus
Teres minor
Subscapularis
These are the muscles of rotator cuff

 

Bicipital groove/ Intertubercular sulcus 

It is a vertical groove between lesser tubercle and greater tubercle.
Content 
  1. Long head of biceps with enclosed synovial sheath 
  2. Ascending branch of anterior circumflex humeral artery.
Lateral lip
Gives attachment to the pectoralis major 
Medial lip
Gives attachment to the teres major
Floor of groove
Gives attachment to the Latissimus dorsi 

 

Shaft  of Humerus


Three border 
  1. Anterior border 
  2. Medial border 
  3. Lateral border 
Three surfaces 
  1. Anterior lateral surface 
  2. Anterior medial surface 
  3. Posterior surface 

 

Anterior border

It begins from the lateral lip of the bicipital groove and runs anteriorly.
It continues below the margin of the deltoid tuberosity. 
In the lower half it becomes smooth and rounded.
It ends in the radial fossa.


Medial border 

It begins from the medial lip of the bicipital groove and gives continuous with the medial epicondyle.
Rough area in the middle of this border provides insertion to the coracobrachialis muscle.
Lower area of this border above the medial epicondyle gives origin to the pronator teres.


Lateral border 

It is indistinct in the upper part but prominent in the lower part where it forms the lateral epicondyle.
Lower parts of this border gives attachment to the lateral intermuscular septum.

 

Anterolateral surface 

It is the area between the anterior and lateral border.
Deltoid tuberosity present in this surface which is V-shaped.
Deltoid tuberosity is the main characteristics features of this surface.


Anteromedial surface 

It is the area between the anterior and medial border.
Middle of this border nutrient foramen is present which is directed downward.

 

Posterior surface 

It is the area between the medial and lateral border 
An oblique ridge is present in the upper one-third of this surface that is directed downward and laterally.
Below the ridge there is the presence of a groove called radial groove which lodges radial nerve and profunda brachii vessels.
An oblique ridge
Give origin to the lateral head of triceps brachii
Below the radial groove
Gives origin to the medial head of triceps brachii

 

Lower end of Humerus


Articular part:

Capitulum
• It is a rounded projection and lies laterally.
• Articulates with head of the radius.


Trochlea 
• It is a pully shaped projection lies medially.
• Articulates with the trochlear notch of the ulna.


Non-articular part 

Radial fossa 
• Lies above capitulum.
• During the full flexion of the elbow joint, the head of the radius fits into the radial fossa.


Olecranon fossa 
• Lies posterior aspect above the trochlea.
• During the full extension of the elbow joint, the olecranon process of the ulna fits into the olecranon fossa.


Coronoid fossa
• It lies above the trochlea.
• During full flexion of the elbow joint, the coronoid process of the ulna fits into coronoid fossa.


Attachment of lower end 

Anterior surface of the medial epicondyle
Give the common origin of the superficial flexor of the forearm
Anterolateral part of the lateral epicondyle
Give common extensor muscles origin
Posterior surface of the lateral epicondyle
Gives origin to the anconeus muscle


Note:
Relation of the nerve 

Axillary nerve
→ It around the surgical neck 
Radial nerve
→ It passes through the radial groove 
Ulnar nerve
→ It lies behind the medial epicondyle