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Ulna

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.

Radius

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

what is hypoxia
Akas Reply
I guess it's low supply the oxygen to the tissues
famuyiwa
yup
Natalie
A condition in which tissues (especially the blood) are deprived of an adequate supply of oxygen
Panthera
hanifa pia uko hapa
Panthera
where is present Glenoid Cavity ?
A- Reply
what is the muscular tissue
Md Reply
muscular tissue is a type of tissue that provide to help in cotraction to aur body.
A-
What's the difference in epithelial, connective, muscular and muscle tissue
Gifty
and it's similarities
Gifty
what is limb bone
Akshu Reply
this are bone attaching or joining to the axial bone.axial bone including skull,vertebrate and ribcage
Eliasi
how many bones make up the skull?
Matthew
22 bones
Husna
22bones
Bhanu
where is present Glenoid cavity ?
A-
how many bone in skull
Md
Explain the stages of mitosis and cell division
Bella Reply
systems of human body
Udezue Reply
define lymphatic system And give the composition of lymphatic fluid
sakshi Reply
the network of vessels through which lymphatic drains From the tissue into blood.lymph contain variety of substance like salts, glucose, proteins and fatsand water, white blood cells
Bhanu
yeah
Hassan
what is lymphatic system
Adie Reply
the network of vessels through which lymph drains from tissue into the blood
Bhanu
to describe the boundaries of four cavity
Pius Reply
homeostatic variables such as body temperature fluctuates within a normal range around the set point, or ideal, for a given homeostatic condition. for example, 98.6°F is a set point for body temperature. The response of the effector determines whether or not the homeostatic variable remains in the n
Chidinma Reply
why rbc is biconcave?
Sudhakar Reply
to carry oxygen easily
anwaar
What part of the brain controls the body temp
Ridwan
hypothalamus
JAYESH
what are epithelial tissues
Sachibu Reply
epithelial tissue that cover overall parts of the body and it's free from blood and nerves
Bhanu
Epithelial tissues are composed of cells laid out in sheets with strong cell-to-cell attachments.
Duah
Epithelial tissues perform a variety of functions that include; protection, secretion, filtration, diffusion, absorption, etc.
Duah
what control the flow of the blood ?
Donkor Reply
the pumping action of the heart
Holly
what is bony promises on the human body
Kelly Reply
what is the bony promises on human body
Kelly
what are bony prominences on human body
Kelly
support of the body
Bhanu
what are the characteristics of blood
yeboah Reply
they are red in colour
Tawoi
why blood is red in color?
Sudhakar
blood is red because it contains hemoglobin
Abena

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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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