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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

where can we find the short bones
Chidi Reply
Carpal bones are examples of short bones
during pregnancy which would more increase size the mothers abdominal or pelvic cavity?
Nurmalyn Reply
define the main directional terms of the body
cris Reply
during physical exercise respiratory rate increace two student are discussing the mechanisms involved. student A claim they are positive feedback and student B claim negative feedback do you agree with student A or B and why
during pregnancy, which would more size the mother's abdominal or pelvic cavity? explain
cris Reply
list and define the three plane of devision of the body
complete the following statements using correct directional terms for human being. 1. the navel is________to the nose 2. the heart is______to the breastbone(sternum) 3 the ankle is______to the knee 4 the ear is______to the eyes.
1. superior 2. posterior 3. superior 4. lateral
name the system of the body and its function
cris Reply
11 system are human body 1.integumentary system 2. skeletal system 3. muscular system 4. nervous system 5. endocrine system 6. cardiovascular system 7. lymphatic system 8. respiratory system 9. digestive system 10. urinary system 11. reproductive system male and female.
during pregnancy, which would more size the mother's abdominal or pelvic cavity? explain
how the body maintain hormeostasis in terms of bloodglucose level
cris Reply
It releases hormones from the pancreas insulin and glucagon
why human blood pressure high
amin Reply
What is red blood cell
A type of blood cell that is made in the bone marrow and found in the blood. Red blood cells contain a protein called hemoglobin, which carries oxygen from the lungs to all parts of the body. Checking the number of red blood cells in the blood is usually part of a complete blood cell (CBC) test. It
red blood cell are the most numerous blood cells.they comprise about 99% of all blood cells red blood cells are non nucleated it has red colour due to present to hemoglobin.
Thanks for the answers
how will you promote quality of life in ptb patient using the 14 basic needs and 21 nursing problems?
rOx Reply
coronary circulation ?
Juri Reply
Coronary circulation is the circulation of blood in the blood vessels that supply the heart muscle (myocardium). Coronary arteries supply oxygenated blood to the heart muscle, and cardiac veins drain away the blood once it has been deoxygenated. Because the rest of the body.
coronary circulation ,is flow of blood that supplies the heart tissue itself is the coronary circulation. the functional blood supply of the heart,is the shortest circulation in tha body.
what about the easy way to understand action potential
event of cardiac cycle
Juri Reply
kaso Reply
anatomy is the scientific way of studying the body structure.
the branch of science concerned with the bodily structure of humans, animals, and other living organisms, especially as revealed by dissection and the separation of parts.
what is means by LAPE and HAPE
guys i've question what occur when homeostasis balance mechanisms lost
cris Reply
Bladder is blank to the small intestine, what is the right directional term for that?
Julaika Reply
When peristaltic movement is correct.
what tissue that support body organ?
Sabrina Reply
the skeleton

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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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