Download Humerus

Humerus
Learning Objectives
• At the end of the lecture student should
– Recognize the bone.
– Identify the site of bone
– Mention the bony landmarks of bone like borders, surfaces & land
mark used for bone determination.
– Discuss the attachment of attachments of muscles
Introduction
• The longest and largest bone of the upper
extremity
•
Divisible into a shaft and two extremities
upper and lower end
•
Articulates with scapula at upper end to form
shoulder joint and at alower end with radius
and ulna to form elbow joint
The upper End
•
The head, nearly hemispherical in form
•
Directed upward, medially, and a little backward, and articulates with the
glenoid cavity of the scapula
Anatomical neck
• Line separating the head from the rest of the upper end
•
Obliquely directed, forming an obtuse angle with the body
•
Best marked in the lower half of its circumference
•
In upper half represented by a narrow groove separating the head from the
tubercles
•
•
•
•
•
•
•
•
•
The lesser tubercle (tuberculum minus; lesser tuberosity):
More prominent than the greater tubercle
Presents as an elevation on the anterior aspect of the upper end
The greater tubercle (tuberculum majus; greater
tuberosity):
An elevation that forms the lateral part of the upper end
Posterior aspect is marked by three impressions
Intertubercular sulcus or bicipital groove:
Separates the lesser tubercle medially from the anterior
part of the greater tubercle
Has two lips the medial and the lip
The Body or Shaft (corpus humeri)
•
Almost cylindrical in the upper half
of its extent
•
Prismatic and flattened in the lower
end
•
Compromised of three borders and three surface
Borders
1. Anterior border:
•
The upper 1/3rd forms the lateral lip of the
intertubercular sulcus
•
In middle part forms the anterior margin of the deltoid
tuberosity
•
The lower half is smooth and rounded
2. Lateral border:
•
The lateral border is prominent only at the lower end, where it forms the
lateral supracondylar ridge
•
In the middle part it is interrupted by the radial or spiral groove
3. Medial border:
•
The upper part of the medial border forms the medial lip pf the
intertubercular sulcus
•It is continuous below with the medial supracondylar ridge.
Surfaces
1. Anterolateral surface:
•
Lies between the anterior and the lateral
borders.
•
A little above the middle it is marked by a vshaped deltoid tuberosity.
•
Behind the deltoid tuberosity the radial groove runs downwards and forwards
across the surface
2. Anteromedial surface:
•
•
•
Lies between the anterior and medial borders.
Upper 1/3rd is narrow and forms the floor of the intertubercular sulcus.
A nutrient foramen is present on this surface.
3. Posterior surface:
•
•
•
Lies between the medial and lateral borders.
Its upper part is marked by an oblique ridge.
The middle 1/3rd is crossed by the radial groove.
The Lower end
•
•
•
•
Flattened from before backward, and curved slightly
forward
Ends below in a broad, articular surface, which is
divided into two parts by a slight ridge
Projecting on either side are the lateral and medial
epicondyles.
Capitulum
The rounded projection which articulates with the head of the radius
•
Trochlea:
•
•
•
A pulley shaped surface.
Articulates with the trochlear notch of the ulna.
The medial edge is responsible for forming the carrying angle.
•
Medial epicondyle:
A prominent bony projection on the medial side of the lower end.
•
Lateral epicondyle
Smaller than the medial one and its anterolateral part has a muscular impression.
•
Lateral supracondylar ridge.
Sharp lateral margin just above the lower end
• The medial supracondylar ridge is a similar ridge to the medial aspect.
•
Coronoid fossa
Depression just above the anterior aspect of the trochlea
•
Radial fossa
A depression that is present just above the anterior aspect of the
capitulum
•
Olecranon fossa
Lies just above the posterior aspect of the trochlea
Attachments on the Humerus:
Muscles attached on the upper end of humerus
 Insertion of muscle ON TUBEROSITIES
•
•
•
•
•
Subscapularis
Lesser tuberosity of the humerus.
Supraspinatus
Greater tuberosity of the humerus.
Infraspinatus
Greater tuberosity of the humerus.
Teres minor
Greater tuberosity of the humerus
Tendons of these four muscles form a cuff around
the anterior, posterior and superior aspect of shoulder joint and collectively
known as ROTATOR CUFF
Insertion in the region of bicipital groove
•
Latissimus dorsi
Floor of the intertubercular sulcus.
•
Pectoralis major
Lateral lip of the bicipital groove of the humerus.
•
Teres major
Medial lip of the bicipital groove of the humerus
Muscles attached on the shaft of Humerus
Origin of muscles:

Lateral head of the triceps
Upper half of posterior surface of shaft of humerus above
radial groove

Medial head of the triceps
Lower half of the posterior surface of the shaft of
humerus

Brachialis
Front of the lower half of the humerus i.e. from the
anteromedial and anterolateral surfaces of the shaft
Muscles attached on the shaft of Humerus
Insertion of muscle
• Deltoid
Middle of the lateral surface of the shaft of the humerus.
• Coracobrachialis
Into the rough area on the middle of the medial border.
Muscles attached on the lateral lower end of
Humerus
Origin of muscles from anterior surface:
•
Brachioradialis
Arises from the upper 2/3rd of the lateral supracondylar
ridge
•
Extensor carpi radialis longus
Arises from the lower 1/3rd of the lateral supracondylar ridge
Origin from posterior surface
•
Common Extensor Origin
The superficial extensor muscles of the forearm have a
common origin from the lateral epicondyle.
• Anconeus
Arises from the posterior surface of the lateral
epicondyle
Origin of muscle
•
•
Pronator teres (humeral head)
Arises from the lower 1/3rd of the medial supracondylar ridge medial
epicondyle of the humerus
Common Flexor Origin
The superficial flexor muscles of the forearm arise by a common origin from the
anterior aspect of the medial epicondyle
Attachment of capsular ligaments:
Capsular ligament of shoulder joint:
•
•
Attached to anatomical neck except on medial side
where it also includes a small area of shaft
Also provides an aperture for the tendon of long head of
biceps
Capsular ligament of elbow joint:
•
•
•
•
Anteriorly----- upper limit of cor onoid and radial fossa
Posteriorly-----upper limit of olecranon fossa
Medially between trochlea and epicondyle
Lateralry-between capitulum and epicondyle
Clinical correlates
•
Three nerves are liable to injury in fractures involving humerus
•
Axillary nerve is damaged in the fractures involving surgical neck of
humerus
•
Radial nerve in the radial groove
•
Ulnar nerve in the fractures involving fractures of medial epicondyle