Humerus bone, its anatomy, and fractures

Humerus

In human anatomy, the humerus is a long bone that is present in the upper limb more specifically in the upper arm that runs from the shoulder of a person to the elbow. This bone connects the radius and ulna with the scapula. Humerus consist of three parts that are the upper part, body, and lower part. The upper part consists of a head, neck, and two tuberosities. The body is cylindrical in its upper part while prismatic in its below part. The lower part of the humerus consists of three fossae, two epicondyles, and two processes. The fossae that are present in the humerus are radial fossa, coronoid fossa and olecranon fossa.

Humerus anatomy

What is the structure of the humerus?

The Humerus consists of many parts such as head, necks, tubercles, foramen, epicondyles, and fossae, etc. Below we will discuss the parts one by one.

1.Head

The head is hemisphere in shape and faces medially. The head articulates with the glenoid fossa.

2. Neck

Two types of necks are present in this bone. One is the anatomical neck and the other is the surgical neck. The anatomical neck is a groove that is present around the articular surface of the head while the surgical neck is present inferior to the head.

3.  Greater tubercle

It is present on the posterior side. It is a large projection present laterally. A greater tubercle provides an attachment site to the supraspinatus, infraspinatus, and teres minor muscles. It’s crest form the lip of the bicipital groove.

4.  Lesser tubercle

It is a smaller project that is placed anterolaterally to the head. The subscapularis muscle attached to it and It’s crest form the medial lip of the bicipital sulcus.

5.  Bicipital groove

it is a deep groove present between the lesser and greater tubercle and extends down the proximal shaft of the humerus. A ligament called the transverse humeral ligament connects the tubercles and bridge this groove to form a canal.

6. The shaft of the humerus

The shaft consists of mainly three surfaces that are anteromedial, anterolateral, and posterior surface. The anteromedial surface is the area between the medial border, the anterolateral surface is the area between the lateral border and the posterior surface is the area between the lateral and medial borders.

7. Deltoid tuberosity

It is a roughened surface present on the lateral surface of the shaft. Deltoid muscle attached to it.

8.  Radial groove

The radial groove also called the spiral groove is present on the posterior surface through which blood vessels along with radial nerve passes. Its inferior boundary is continuous with the lateral border of the shaft.

9.Nutrient foramen

It is present in the anteromedial surface through which nutrient arteries enter the humerus.

10. Olecranon fossa

It is a hollow part present on the distal humerus and accommodates the olecranon process of the ulna.

11. Coronoid fossa

It is a hollow part present on the anterior surface of the distal humerus. It receives the coronoid process of the ulna.

12. Radial fossa

It is located laterally on the anterior surface of the distal humerus and receives the head of the radius.

13. Capitulum

It is a rounded eminence that forms the lateral part of the distal humerus. The capitulum articulates with the head of the radius bone.

14. Trochlea

The trochlea is a spool-shaped structure that forms the medial part of the distal humerus. It articulates with the ulna bone.

15. Lateral epicondyle

It is a lateral bulge that is present superior and lateral to the capitulum. Various tendons of the extensor muscles of the forearm originate from the lateral epicondyle. The radial collateral ligament also attached to it.

16. Medial epicondyle

It is a medial bulge that is present superior and medial to the trochlea. The ulnar collateral ligament is attached to it.

What are the articulations of the humerus?

The Humerus articulates with three bones that are the scapula, radius, and ulna. It articulates at the shoulder with the glenoid fossa of the scapula. At the elbow, the capitulum of this bone articulates with the head of the radius while its trochlea articulates with the trochlear notch of the ulna.

Ossification

During prenatal development, it is one of the first structures that ossifies. At birth, this bone is only ossified in the shaft and its epiphysis is cartilaginous. The ossification of this bone completes at the age of 13.

What are the muscles that attached to the humerus?

Attached muscles are

1.  Deltoid muscle
2.  Pectoralis major
3.  Teres major
4.  Lattisimus Dorsi

5.   Infraspinatus
6.   Teres minor
7.   Biceps brachii
8.   Coracobrachialis muscle
9.   Brachioradialis
10.   Triceps brachii
11.   Anconeus
12.  Flexor carpi ulnaris
13.  Palmaris longus
14.  Flexor carpi radialis

15.   Pronator teres
16.   Extensor carpi radialis longus
17.   Extensor carpi radialis brevis
18.   Extensor digitorium
19.   Extensor digiti minimi
20.   Extensor carpi ulnaris

Nerve

The major nerves that pass by the humerus are
1. Axillary nerve
2.  Radial nerve
3.  Ulnar nerve
4.  Median nerve

The fracture in humerus may damage these nerves.

Movements

The movements that are produced in the arm are
1. Arm flexion
2.  Arm extension
3.  Arm abduction
4.  Arm adduction
5.  Arm internal rotation
6.  Arm external rotation
7.  Circumduction

If you want to know these movements then check out our article the language of anatomy.

Humerus fractures

A humerus fracture is an injury to the bone in the upper arm that connects the scapula with the elbow. On the basis of their location, these fractures are divided into three types that are

1. Proximal fractures
2.  Midshaft fractures
3.  Distal fractures

Causes
Trauma
Sport injuries
Direct impact on the body

Symptoms
Severe pain
Swelling
Difficult to move the upper arm
Unusual sensations in the hand
Weakness in hand and wrist

Diagnosis
Diagnosis can be done through
1. history of the patient
2.  Physical examination
3.  By taking X-rays
4. computed tomography.

Does a humerus fracture require surgery?

the fractures In the humerus are common and its severity depends on the type and location of the fracture. Some of these fractures heal without surgery but some required surgery.

Surgery can be done in the case when the bone has moved out of its position. The types of fractures in which the surgery is used are proximal and distal fractures.

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