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The ulna is the medial bone of the forearm. It runs parallel to the radius, which is the lateral bone of the forearm ( [link] ). The proximal end of the ulna resembles a crescent wrench with its large, C-shaped trochlear notch    . This region articulates with the trochlea of the humerus as part of the elbow joint. The inferior margin of the trochlear notch is formed by a prominent lip of bone called the coronoid process of the ulna    . Just below this on the anterior ulna is a roughened area called the ulnar tuberosity    . To the lateral side and slightly inferior to the trochlear notch is a small, smooth area called the radial notch of the ulna    . This area is the site of articulation between the proximal radius and the ulna, forming the proximal radioulnar joint    . The posterior and superior portions of the proximal ulna make up the olecranon process    , which forms the bony tip of the elbow.

Ulna and radius

This figure shows the bones of the lower arm.
The ulna is located on the medial side of the forearm, and the radius is on the lateral side. These bones are attached to each other by an interosseous membrane.

More distal is the shaft of the ulna    . The lateral side of the shaft forms a ridge called the interosseous border of the ulna    . This is the line of attachment for the interosseous membrane of the forearm    , a sheet of dense connective tissue that unites the ulna and radius bones. The small, rounded area that forms the distal end is the head of the ulna    . Projecting from the posterior side of the ulnar head is the styloid process of the ulna    , a short bony projection. This serves as an attachment point for a connective tissue structure that unites the distal ends of the ulna and radius.

In the anatomical position, with the elbow fully extended and the palms facing forward, the arm and forearm do not form a straight line. Instead, the forearm deviates laterally by 5–15 degrees from the line of the arm. This deviation is called the carrying angle. It allows the forearm and hand to swing freely or to carry an object without hitting the hip. The carrying angle is larger in females to accommodate their wider pelvis.


The radius runs parallel to the ulna, on the lateral (thumb) side of the forearm (see [link] ). The head of the radius    is a disc-shaped structure that forms the proximal end. The small depression on the surface of the head articulates with the capitulum of the humerus as part of the elbow joint, whereas the smooth, outer margin of the head articulates with the radial notch of the ulna at the proximal radioulnar joint. The neck of the radius    is the narrowed region immediately below the expanded head. Inferior to this point on the medial side is the radial tuberosity    , an oval-shaped, bony protuberance that serves as a muscle attachment point. The shaft of the radius    is slightly curved and has a small ridge along its medial side. This ridge forms the interosseous border of the radius    , which, like the similar border of the ulna, is the line of attachment for the interosseous membrane that unites the two forearm bones. The distal end of the radius has a smooth surface for articulation with two carpal bones to form the radiocarpal joint    or wrist joint ( [link] and [link] ). On the medial side of the distal radius is the ulnar notch of the radius    . This shallow depression articulates with the head of the ulna, which together form the distal radioulnar joint    . The lateral end of the radius has a pointed projection called the styloid process of the radius    . This provides attachment for ligaments that support the lateral side of the wrist joint. Compared to the styloid process of the ulna, the styloid process of the radius projects more distally, thereby limiting the range of movement for lateral deviations of the hand at the wrist joint.

Questions & Answers

1. Chemical level 2. Cellular level 3.Tissue level 4. Organ level 5.Organ system level 5.Organismal level
Jamela Reply
why there is bleeding in menstruation?
no one ready to help me
name temporary endocrine gland in female.
when does 1st meiotic division occur in male ?
) Which of the following best describes the human body's defense mechanism against environmental bacteria?
What the answer plz
Kuheli but I think skin is an organ not defence mechanism
Homeostasis is the system responsible for body response to external changes
what is an inflammation
Lodrick Reply
it's a reaction from a body tissue
is the body own mechanism of fighting against disease especially infections or injuries.
Inflammation is a tissue response to damage tissues
which cells are responsible for bone formation?
Richard Reply
which muscles are innervated by the lateral plantar nerve?
Tinyiko Reply
what book should i read for my Msc exam (physiology)
zeleke Reply
let ask u aquiz where bones live in a body
Lowyer Reply
306 bones in a human body
Netope Reply
206 bones in a human body
there are 206 bones in human body and a baby's body has about 300 bones at birth
what is anatomy?
Nuwagaba Reply
anatomy is the study of the internal structure of a living organism
can be define as the Scientific Study Of internal structure of the body Some of this Structures are Very tiny they can only be seen by The assistance of a microscope, While other structures can be seen manipulated and Weighted
Anatomy is the scientific study of the body and the physical relationship between systems
Scientific study of body structure and function
study of body functions of living organisms and organs
gross anatomy is the study of the internal structure of a living organism at a visible or macroscopic level
Favour Reply
homeostasis is the steady maintenance of the internal system
study of the structure of cells,tissue using a microscope
is the study of how the human body works and relates
i cannot understand this please explain how to calculate
Sania Reply
I don't get it either
How to calculate what exactly?...
be clair
where are bones lived
name of all the bones and eg
Shantal Reply
treatment for hereditary diseases
With gene therapy, the treatment or elimination of inherited diseases or physical conditions due to these mutations could become a reality. Gene therapy involves the manipulation of genes to fight or prevent diseases. Put simply, it introduces a "good" gene into a person who has a disease caused by

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Source:  OpenStax, Anatomy & Physiology. OpenStax CNX. Feb 04, 2016 Download for free at http://legacy.cnx.org/content/col11496/1.8
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