Humerus


The humerus /ˈhjuːmərəs/, Plural: humeri is a long bone in the arm or forelimb that runs from the shoulder to the elbow It connects the scapula and the two bones of the lower arm, the radius and ulna, and consists of three sections The humeral upper extremity consists of a rounded head, a narrow neck, and two short processes tubercles, sometimes called tuberosities The body is cylindrical in its upper portion, and more prismatic below The lower extremity consists of 2 epicondyles, 2 processes trochlea & capitulum, and 3 fossae radial fossa, coronoid fossa, and olecranon fossa As well as its true anatomical neck, the constriction below the greater and lesser tubercles of the humerus is referred to as its surgical neck due to its tendency to fracture, thus often becoming the focus of surgeons

Contents

  • 1 Etymology
  • 2 Structure
    • 21 Articulations
    • 22 Nerves
  • 3 Function
    • 31 Muscular attachment
  • 4 Other animals
  • 5 Additional images
  • 6 See also
  • 7 References
  • 8 External links

Etymology

The word "humerus" is derived from Latin: humerus, umerus meaning upper arm, shoulder, and is linguistically related to Gothic ams shoulder and Greek ōmos[1]

Structure

Articulations

At the shoulder, the head of the humerus articulates with the glenoid fossa of the scapula More distally, at the elbow, the capitulum of the humerus articulates with the head of the radius, and the trochlea of the humerus articulates with the trochlear notch of the ulna

Diagram of the human shoulder joint 
The left shoulder and acromioclavicular joints, and the proper ligaments of the scapula 
Head of humerus 
The supinator 

Nerves

The axillary nerve is located at the proximal end, against the shoulder girdle Dislocation of the humerus's glenohumeral joint, has the potential to injure the axillary nerve or the axillary artery Signs and symptoms of this dislocation include a loss of the normal shoulder contour and a palpable depression under the acromion

The radial nerve follows the humerus closely At the midshaft of the humerus, the radial nerve travels from the posterior to the anterior aspect of the bone in the spiral groove A fracture of the humerus in this region can result in radial nerve injury

The ulnar nerve at the distal end of the humerus near the elbow is sometimes referred to in popular culture as 'the funny bone' Striking this nerve can cause a tingling sensation "funny" feeling, and sometimes a significant amount of pain It lies posterior to the medial epicondyle, and is easily damaged in elbow injuries[2]

Horizontal section at the middle of upper arm 
Horizontal section of upper arm 
Humerus 

Function

Muscular attachment

The deltoid originates on the lateral third of the clavicle, acromion and the crest of the spine of the scapula It is inserted on the deltoid tuberosity of the humerus and has several actions including abduction, extension, and circumduction of the shoulder The supraspinatus also originates on the spine of the scapula It inserts on the greater tubercle of the humerus, and assists in abduction of the shoulder

The pectoralis major, teres major, and latissimus dorsi insert at the intertubercular groove of the humerus They work to adduct and medially, or internally, rotate the humerus

The infraspinatus and teres minor insert on the greater tubercle, and work to laterally, or externally, rotate the humerus In contrast, the subscapularis muscle inserts onto the lesser tubercle and works to medially, or internally, rotate the humerus

The biceps brachii, brachialis, and brachioradialis which attaches distally act to flex the elbow The biceps do not attach to the humerus The triceps brachii and anconeus extend the elbow, and attach to the posterior side of the humerus

The four muscles of supraspinatus, infraspinatus, teres minor and subscapularis form a musculo-ligamentous girdle called the rotator cuff This cuff stabilizes the very mobile but inherently unstable glenohumeral joint The other muscles are used as counterbalances for the actions of lifting/pulling and pressing/pushing

Left humerus Anterior view
A Supraspinatus muscle
B Latissimus dorsi muscle
C Pectoralis major muscle
D Deltoid muscle
E Brachioradialis
F Extensor carpi radialis longus muscle
G Common extensor tendon
H Subscapularis muscle
I Teres major muscle
J Coracobrachialis muscle
K Brachialis muscle
L Pronator teres muscle
M Common flexor tendon
Left humerus Posterior view

Other animals

Primitive fossils of amphibians had little, if any, shaft connecting the upper and lower extremities, making their limbs very short In most living tetrapods, however, the humerus has a similar form to that of humans; connecting their extremities In many reptiles and some primitive mammals, the lower extremity includes a large foramen, or opening, which allows nerves and blood vessels pass through[3]

Additional images

See also

  • Humerus fracture

References

  1. ^ Harper, Douglas "Humerus" Online Etymology Dictionary Retrieved 6 November 2014 
  2. ^ "The Humerus" TeachMeAnatomynet 
  3. ^ Romer, Alfred Sherwood; Parsons, Thomas S 1977 The Vertebrate Body Philadelphia, PA: Holt-Saunders International pp 198–199 ISBN 0-03-910284-X 
  • This article incorporates text in the public domain from the 20th edition of Gray's Anatomy 1918

External links

  •  "Humerus" New International Encyclopedia 1905 


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