Wednesday, February 25, 2015
Humerus Anatomy
Other Terms:
Humérus, Húmero
IN THIS ARTICLE:
The Head (caput humeri) of the HUMERUS
Neck of the HUMERUS
The Greater Tubercle (tuberculum majus; greater tuberosity)
The Lesser Tubercle (tuberculum minus; lesser tuberosity) of the HUMERUS
The Body or Shaft (corpus humeri) of the HUMERUS
Capitulum of the HUMERUS
Coronoid fossa of the HUMERUS
Trochlea of the humerus
Deltoid tuberosity of the HUMERUS
Radial fossa of the HUMERUS
Medial supracondylar ridge of the HUMERUS
Lateral supracondylar ridge of the HUMERUS
Medial epicondyle of the humerus
Intertubercular groove of the HUMERUS
Borders of the HUMERUS
Ossification of the HUMERUS
Muscles of the HUMERUS
Nerves of the HUMERUS
Blood Supply to the Humerus
How To Determine Side of the HUMERUS ?
The humerus is the long bone in the upper arm, located between the elbow joint and the shoulder. At the elbow, it connects primarily to the ulna, as the forearms radial bone connects to the wrist. At the shoulder, the humerus connects to the body through the scapula. The humerus bone is the home of many muscular insertion and origination points, including the deltoid, the pectoralis major, and many others. The brachial artery travels most of the bones length, before it subdivides into the ulnar and radial arteries at the elbow. In the upper arm, the brachial branches into several arteries, transiting oxygenated blood from the lungs and heart. The radial nerve runs a similar course over the bone and into the forearm. Because it connects at the shoulder with a rotational joint, the humerus is instrumental in supporting many of the arms functions, including all lifting and physical activities. Since the humerus is one of the longest bones in the body, it is one of the most commonly broken or fractured.
The Head (caput humeri) of the HUMERUS
The head of the humerus is a smooth, dome-shape that lies at an angle to the shaft and fits into a shallow socket of the scapula (shoulder blade) to form the shoulder joint.
Anatomical Neck (collum anatomicum) of the HUMERUS
This is a slight constriction adjoining the edge of the humeral head. It serves as the attachment site for the glenohumeral capsular ligament.
Surgical neck of the HUMERUS
This is a constriction in the bone at the junction of the greater and lesser tubercles with the shaft. This is a common site of fracture, therefore its name.
The greater tubercle of the humerus is situated lateral to the head of the humerus and posterolateral to the lesser tubercle.
Its upper surface is rounded and marked by three flat impressions.
the highest of these gives ("superior facet") insertion to the Supraspinatus
the middle ("middle facet") to the Infraspinatus.
the lowest one ("inferior facet"), and the body of the bone for about 2.5 cm. below it, to the Teres minor.
The lateral surface of the greater tubercle is convex, rough, and continuous with the lateral surface of the body.
Between the greater tubercle and the lesser tubercle is the intertubercular sulcus (bicipital groove).
The Lesser Tubercle (tuberculum minus; lesser tuberosity) of the HUMERUS
The lesser tubercle of the humerus, although smaller, is more prominent than the greater tubercle: it is situated in front, and is directed medially and anteriorly.
Above and in front it presents an impression for the insertion of the tendon of the Subscapularis.
The Body or Shaft (corpus humeri) of the HUMERUS
The shaft of the humerus lies between the upper border of the pectoralis major insertion proximally and the supracondylar ridge distally. This constitutes the middle three fifths of the entire humerus. The anterior portion of the greater tuberosity extends into an anterior ridge that ends at the coronoid fossa distally. The posterior aspect of the greater tuberosity continues distally as a lateral ridge that ends in the lateral supracondylar ridge. The lesser tuberosity melds into a medially located ridge that forms the medial supracondylar ridge distally.The deltoid tubercle forms a lateral prominence just proximal to the midshaft. The shaft of humerus has a posterior, an anterolateral, and an anteromedial surface. The medullary canal of the humerus ends proximal to the olecranon fossa.The anatomy of humerus has important implications for internal and external fixation.The arm is divided into anterior and posterior compartments by fascial septae. Posterior compartmentcontains triceps muscle, radial nerve beteen the long and lateral heads of triceps. The anterior or flexorcompartment contains the flexors of the elbow, biceps brachii and brachialis, and the coracobrachialis. The brachialis has got two nerve supplies- one from musculocutaneous and other from radial nerve.
Capitulum of the HUMERUS
The capitulum of the humerus is an eminence in the human arm that is a smooth, rounded protuberance at the lateral portion of the humerus articular surface. It is pressed up against the depression at the head of the radius, and is located only on the lower front area of the bone. The capitulum of the humerus should not be confused with the trochlea, which is a pointed protuberance that is adjacent to the capitulum.
Coronoid fossa of the HUMERUS
This is the shallow concavity just superior to the trochlea on the anterior aspect of the distal humerus. This fossa receives the beak-like coronoid process of the ulna when the elbow is in full flexion.
Trochlea of the humerus
The trochlea of the humerus, or the humeral trochlea is a section on the humerus, at the articular surfaces medial portion. This is a deep depression in between two well-defined borders and covers the anterior, lower, and posterior parts of humerus. The trochlea of the humerus articulates with the ulnas trochlear notch and it is separated from the capitulum of the humerus by a shallow groove.
Deltoid tuberosity of the HUMERUS
This forms a roughened, vertically oblong area on the lateral surface of the mid-humeral shaft. It serves as the attachment site for the deltoid muscle.
Radial fossa of the HUMERUS
This fossa is the radial fossa because it receives the head of the radius when the elbow is in full flexion. It is a small, shallow fossa positioned medial and superior to the capitulum.
Medial supracondylar ridge of the HUMERUS
This is the medial ridge extending from the cylindrical shaft toward the medial epicondyle. The pronator teres muscle attaches to the distal aspect of it.
Lateral supracondylar ridge of the HUMERUS
The lateral epicondyle of the humerus is an attachment for muscles and ligaments of the elbow. It is on the side (the one toward the center is the medial epicondyle).This is the lateral ridge extending from the cylindrical shaft toward the lateral epicondyle. The brachioradialis and extensor carpi radialis longus muscles attach along the ridge.
Medial epicondyle of the humerus
This is the medial nonarticular process of the knuckle-like distal end of the humerus. It forms a prominent projection from the distal border of the medial supracondylar ridge. Its posterior surface forms a shallow groove for the ulnar nerve (this is the nerve, that when bumped, is referred to as "hitting the funny bone"), while its anterior aspect serves as the muscle attachment site for the superficial flexor muscles of the anterior antebrachium. It is subcutaneous in position and easily palpable.
Intertubercular groove of the HUMERUS
This is the medial nonarticular process of the knuckle-like distal end of the humerus. It forms a prominent projection from the distal border of the medial supracondylar ridge. Its posterior surface forms a shallow groove for the ulnar nerve (this is the nerve, that when bumped, is referred to as "hitting the funny bone"), while its anterior aspect serves as the muscle attachment site for the superficial flexor muscles of the anterior antebrachium. It is subcutaneous in position and easily palpable.
Borders of the HUMERUS
The anterior border runs from the front of the greater tubercle above to the coronoid fossa below, separating the antero-medial from the antero-lateral surface. Its upper part is a prominent ridge, the crest of the greater tubercle; it serves for the insertion of the tendon of the Pectoralis major. About its center it forms the anterior boundary of the deltoid tuberosity; below, it is smooth and rounded, affording attachment to the Brachialis.
The lateral border runs from the back part of the greater tubercle to the lateral epicondyle, and separates the anterolateral from the posterior surface. Its upper half is rounded and indistinctly marked, serving for the attachment of the lower part of the insertion of the Teres minor, and below this giving origin to the lateral head of the Triceps brachii; its center is traversed by a broad but shallow oblique depression, the radial sulcus (musculospiral groove). Its lower part forms a prominent, rough margin, a little curved from behind forward, the lateral supracondylar ridge, which presents an anterior lip for the origin of the Brachioradialis above, and Extensor carpi radialis longus below, a posterior lip for the Triceps brachii, and an intermediate ridge for the attachment of the lateral intermuscular septum.
The medial border extends from the lesser tubercle to the medial epicondyle. Its upper third consists of a prominent ridge, the crest of the lesser tubercle, which gives insertion to the tendon of the Teres major. About its center is a slight impression for the insertion of the Coracobrachialis, and just below this is the entrance of the nutrient canal, directed downward; sometimes there is a second nutrient canal at the commencement of the radial sulcus. The inferior third of this border is raised into a slight ridge, the medial supracondylar ridge, which becomes very prominent below; it presents an anterior lip for the origins of the Brachialis and Pronator teres, a posterior lip for the medial head of the Triceps brachii, and an intermediate ridge for the attachment of the medial intermuscular septum.
Ossification of the HUMERUS
The humerus ossifies endochondrally from eight centers. The first center appears during the eighth fetal week as an artery penetrates the diaphysis of the cartilage anlage or model. This establishes the primary center for the shaft of the femur. By birth ossification of the diaphysis is complete. Seven additional centers of ossification appear after birth. During the first year an ossification center appears in the head. This is followed by the greater tubercle center during the third year and the lesser tubercle center during the fifth year. By the sixth year these three epiphyseal centers have fused and cap the shaft with a growth plate. This growth plate remains until the twentieth year when fusion occurs. At the distal end a secondary center of ossification emerges in the capitulum during the first year quickly establishing the articular surface. In the fourth year a center for the medial epicondyle arises. During the tenth year a center appears for the trochlea. The final center arises in the lateral epicondyle during the twelfth year. All these centers, except the medial epicondyle, converge at puberty and the consolidated epiphysis fuses with the shaft around the fifteenth year. The medial epicondyle remains as a separate extracapsular epiphysis fusing during the twentieth year.
Muscles of the HUMERUS
MUSCLES THAT ACT ON ANTERIOR ARM (HUMERUS):
- DELTOID
- PECTORALIS MAJOR
- BICEPS BRACHII
- CORACOBRACHIALIS
- SUBSCAPULARIS
- TERES MAJOR (shown from the back)
- LATISSIMUS DORSI (shown from the back)
- DELTOID
- SUPRASPINATUS
- INFRASPINATUS
- TERES MINOR
- TRICEPS BRACHII (LONG HEAD)
The axillary nerve is located at the proximal end, against the shoulder girdle. Dislocation of the humeruss 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 anteriorly to the medial epicondyle, and is easily damaged in elbow injuries.
Blood Supply to the Humerus
Main blood supply to humeral head arises from anterolateral branch of anterior humeral circumflex artery; this vessel passes laterally to long head of biceps & forms arcuate artery;
Arcuate artery: arises from ascending branch of anterior humeral circumflex artery as it penetrates bone;
it enters into humeral head in area of intertubicular groove & gives branches to lesser and greater tuberosities;perfuses the entire epiphysis of the humeral head;
Posterior circumflex artery supplies only a small area in posteroinferior aspect of the humeral head
How To Determine Side of the HUMERUS ?
1. The upper end is rounded to form the head. The lower end is expanded from side to side and flattened from before backwards.
2. The head is directed medially and backwards.
3. The lesser tubercle projects from the front of the upper end and is limited laterally by the intertuberacular sulcus (bicipital groove).
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