Lower extremity of humerus
Encyclopedia
The lower extremity of the humerus
is flattened from before backward, and curved slightly forward; it 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 epicondyle
s.
The lateral portion of this surface consists of a smooth, rounded eminence, named the capitulum of the humerus; it articulates with the cup-shaped depression on the head of the radius, and is limited to the front and lower part of the bone.
On the medial side of this eminence is a shallow groove, in which is received the medial margin of the head of the radius.
Above the front part of the capitulum
is a slight depression, the radial fossa
, which receives the anterior border of the head of the radius, when the forearm is flexed.
, and presents a deep depression between two well-marked borders; it is convex from before backward, concave from side to side, and occupies the anterior, lower, and posterior parts of the extremity.
The grooved portion of the articular surface fits accurately within the semilunar notch
of the ulna; it is broader and deeper on the posterior than on the anterior aspect of the bone, and is inclined obliquely downward and forward toward the medial side.
of the ulna during flexion
of the forearm.
Above the back part of the trochlea is a deep triangular depression, the olecranon fossa
, in which the summit of the olecranon
is received in extension
of the forearm.
These fossæ are separated from one another by a thin, transparent lamina of bone, which is sometimes perforated by a supratrochlear foramen
; they are lined in the fresh state by the synovial membrane of the elbow-joint, and their margins afford attachment to the anterior and posterior ligaments of this articulation.
The epicondyles are continuous above with the supracondylar ridges.
Humerus
The humerus is a long bone in the arm or forelimb that runs from the shoulder to the elbow....
is flattened from before backward, and curved slightly forward; it 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 epicondyle
Epicondyle
Epicondyle may refer to:...
s.
Articular surface
The articular surface extends a little lower than the epicondyles, and is curved slightly forward; its medial extremity occupies a lower level than the lateral.The lateral portion of this surface consists of a smooth, rounded eminence, named the capitulum of the humerus; it articulates with the cup-shaped depression on the head of the radius, and is limited to the front and lower part of the bone.
On the medial side of this eminence is a shallow groove, in which is received the medial margin of the head of the radius.
Above the front part of the capitulum
Capitulum of the humerus
In human anatomy of the arm, the lateral portion of the articular surface of the humerus consists of a smooth, rounded eminence, named the capitulum of the humerus....
is a slight depression, the radial fossa
Radial fossa
Above the front part of the capitulum is a slight depression, the radial fossa, which receives the anterior border of the head of the radius, when the forearm is flexed....
, which receives the anterior border of the head of the radius, when the forearm is flexed.
Borders
The medial portion of the articular surface is named the trochleaTrochlea of humerus
The medial portion of the articular surface of the humerus is named the trochlea, and presents a deep depression between two well-marked borders; it is convex from before backward, concave from side to side, and occupies the anterior, lower, and posterior parts of the extremity...
, and presents a deep depression between two well-marked borders; it is convex from before backward, concave from side to side, and occupies the anterior, lower, and posterior parts of the extremity.
- The lateral border separates it from the groove which articulates with the margin of the head of the radius.
- The medial border is thicker, of greater length, and consequently more prominent, than the lateral.
The grooved portion of the articular surface fits accurately within the semilunar notch
Semilunar notch
The semilunar notch of the ulna is a large depression, formed by the olecranon and the coronoid process, and serving for articulation with the trochlea of the humerus....
of the ulna; it is broader and deeper on the posterior than on the anterior aspect of the bone, and is inclined obliquely downward and forward toward the medial side.
Fossae
Above the front part of the trochlea is a small depression, the coronoid fossa, which receives the coronoid processCoronoid process of the ulna
The coronoid process is a triangular eminence projecting forward from the upper and front part of the ulna.Its base is continuous with the body of the bone, and of considerable strength....
of the ulna during flexion
Flexion
In anatomy, flexion is a position that is made possible by the joint angle decreasing. The skeletal and muscular systems work together to move the joint into a "flexed" position. For example the elbow is flexed when the hand is brought closer to the shoulder...
of the forearm.
Above the back part of the trochlea is a deep triangular depression, the olecranon fossa
Olecranon fossa
The olecranon fossa is a deep triangular depression on the posterior side of the humerus, superior to the trochlea, in which the summit of the olecranon is received during extension of the forearm.-External links: *...
, in which the summit of the olecranon
Olecranon
The olecranon is a large, thick, curved bony eminence of the forearm that projects behind the elbow.It is situated at the upper end of the ulna, one of the two bones in the forearm...
is received in extension
Extension (kinesiology)
In kinesiology, extension is a movement of a joint that results in increased angle between two bones or body surfaces at a joint. Extension usually results in straightening of the bones or body surfaces involved. For example, extension is produced by extending the flexed elbow. Straightening of...
of the forearm.
These fossæ are separated from one another by a thin, transparent lamina of bone, which is sometimes perforated by a supratrochlear foramen
Supratrochlear foramen
The supratrochlear foramen is a small hole located above the trochlea of the humerus of larger dog species. It is covered by a layer of connective tissue....
; they are lined in the fresh state by the synovial membrane of the elbow-joint, and their margins afford attachment to the anterior and posterior ligaments of this articulation.
Epicondyles
- The lateral epicondyleLateral epicondyle of the humerusThe lateral epicondyle of the humerus is a small, tuberculated eminence, curved a little forward, and giving attachment to the radial collateral ligament of the elbow-joint, and to a tendon common to the origin of the Supinator and some of the Extensor muscles. In birds, where the arm is somewhat...
is a small, tuberculated eminence, curved a little forward, and giving attachment to the radial collateral ligament of the elbow-joint, and to a tendon common to the origin of the Supinator and some of the Extensor muscles.
- The medial epicondyleMedial epicondyle of the humerusThe medial epicondyle of the humerus, larger and more prominent than the lateral epicondyle, is directed a little backward. In birds, where the arm is somewhat rotated compared to other tetrapods, it is called ventral epicondyle of the humerus....
, larger and more prominent than the lateral, is directed a little backward; it gives attachment to the ulnar collateral ligament of the elbow-joint, to the Pronator teres, and to a common tendon of origin of some of the Flexor muscles of the forearm; the ulnar nerve runs in a groove on the back of this epicondyle.
The epicondyles are continuous above with the supracondylar ridges.