Humerus bone Anatomy and Muscles Attachments, Lecture notes of Anatomy

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H U M E R U S

Anatomy & Applied

Humerus

• (^) The humerus is the longest and largest bone of the upper limb. It consists of a proximal end, a shaft and a distal end. It extends between the shoulder and the elbow.
• (^) The humerus is connected with the scapula at its proximal end, and with both forearm bones (radius and ulna) at its distal end.
• (^) The proximal end of the humerus articulates with the glenoid cavity of the scapula. At the distal end, the humerus articulates with the head of the radius and the trochlear notch of the ulna, forming the elbow joint.

Humerus

• (^) Like other long bones, the humerus is

made of three main parts

• (^) A proximal end or epiphysis
• (^) A shaft or diaphysis and
• (^) A distal end or epiphysis
• (^) All of these parts contain important

anatomical landmarks.

Proximal end of humerus

• (^) The anatomical neck of the humerus is a circular and oblique narrowing below the articular surface of the head. It encircles the head of the humerus. The joint capsule of the shoulder joint is attached to the sides of the anatomical neck.
• (^) The greater tubercle is the most lateral part of the proximal end. The upper posterior aspect of this tubercle presents with three impressions ( upper, middle and lower ) all of which serve as attachment sites for muscles.
• (^) Morphological neck lies 0.5cm below surgical neck. Its shows the position of the epiphyseal line.

Proximal end of humerus

• (^) The intertubercular sulcus or bicipital groove separates the lesser tubercle medially from the anterior part of greater tubercle. The sulcus has medial and lateral lip.
• (^) The narrow line separating the upper end of the humerus from the shaft is called the surgical neck.

Digital ( lower ) end of humerus

• (^) Lower end: consists of articular and non -articular parts.
• (^) Articular parts are - rounded capitulum laterally (articulates with head of radius) and pully like trochlea (articulates with ulna).
• (^) Non-articular parts are - medial and lateral epicondyles, radial fossa ( above the capitulum), coronoid fossa ( above the trochlea) and olecranon fossa on the posterior surface.
• (^) The sharp lateral margin just above the lower end is called the lateral supracondylar ridge.
• (^) The medial supracondylar ridge is similar ridge on medial side.

Borders of humerus

• (^) Lateral border - Its begins just distal to the greater tubercle of the humerus. It thickens distally to form the lateral supracondylar ridge. The middle portion of the lateral border has rough V shaped area referred to as the deltoid tubercle/tuberosity.
• (^) Medial border - The upper part of the medial border forms the medial lip of the intertubercular sulcus. About its middle, it presents a rough strip. It is continuous below the medial supracondylar ridge.

Surfaces of humerus

• (^) Surfaces of humerus -
• (^) The shaft of the humerus presents with three surfaces:
• (^) Anterolateral surface
• (^) Anteromedial surface
• (^) Posterior surface  (^) Anterolateral surface - The anteromedial surface is the area between the anterior and medial borders. a little above the middle, it is marked by a V- shaped deltoid tuberosity. Behind the deltoid tuberosity, the radial groove downwards and forwards across the surface.

Attachments

 Insertion -

 (^) Subscapularis - it is multipennate and inserted into the lesser tubercle.  (^) Supraspinatus - is inserted into the uppermost impression the greater tubercle.  (^) Infraspinatus - is inserted into the middle impression on the greater tubercle.  (^) Teres minor - is inserted into the lower impression on the greater tubercle.  (^) Pectoralis major - is inserted into the lateral lip of intertubercular sulcus.  (^) Latissimus dorsi - is inserted into the floor of the intertubercular sulcus.

Attachments

 (^) Insertion -  (^) Teres major - is inserted into the medial lip of the intertubercular sulcus.  (^) Deltoid - is inserted into the deltoid tuberosity.  (^) Coracobrachialis - is inserted into the rough area on the middle of the medial border.

 (^) AttachmentsOrigin -  (^) Superficial flexor muscles - arises from a common origin from the anterior aspect of the medial epicondyle. This is called common flexor origin.  (^) Superficial extensor muscles - supinator have a common origin from the lateral epicondyle. This is called common extensor origin.  (^) Anconeus - arises from the posterior surface of the lateral epicondyle.  (^) Triceps brachii - arises from the oblique ridge on the upper part of the posterior surface above the radial groove, while its medial head arises from the posterior surface below the medial groove.

Attachments

 Ligaments -

 Upper end : coracohumeral ligament

and transverse humeral ligament.

 Lower end : Radial and ulnar

collateral ligaments attached to

lateral and medial epicondyle

respectively.

Articulations

 (^) Head of the humerus : articulates with the glenoid cavity of the scapula  (^) The condyle of the humerus :  (^) Trochlea : articulates with the trochlear notch of the ulna  (^) Radial fossa : receives the anterior border of the radial head in forearm flexion  (^) Capitellum : articulates with the head of the radius  (^) Olecranon fossa : receives the olecranon process of the ulna with forearm extension  (^) Coronoid fossa : receives the coronoid process of the ulna with forearm flexion

Ossification

 (^) The humerus ossifies from the one primary center and seven secondary centers.  (^) The primary center appears in the middle of the diaphysis during the eight week of life.  (^) The upper end ossifies from three secondary centers -  (^) one for the head ( 1st year )  (^) One for the greater tubercle ( 2nd year )  (^) One for the lesser tubercle ( 5th year )  (^) The lower end ossifies from four centers which from two epiphysis. Three centers include -  (^) One for the capitulum and lateral flange of the trochlea ( 1st year )  (^) One for the medial flange of the trochlea ( 9th year )  (^) One for the lateral epicondyle ( 12th year )  (^) The center for the medial epicondyle appears during 4-6 years.