The ulna (''pl''. ulnae or ulnas) is a
long bone
The long bones are those that are longer than they are wide. They are one of five types of bones: long, Short bone, short, Flat bone, flat, Irregular bone, irregular and Sesamoid bone, sesamoid. Long bones, especially the femur and tibia, are subj ...
found in the
forearm
The forearm is the region of the upper limb between the elbow and the wrist. The term forearm is used in anatomy to distinguish it from the arm, a word which is most often used to describe the entire appendage of the upper limb, but which in anat ...
that stretches from the
elbow
The elbow is the region between the arm and the forearm that surrounds the elbow joint. The elbow includes prominent landmarks such as the olecranon, the cubital fossa (also called the chelidon, or the elbow pit), and the lateral and the media ...
to the smallest finger, and when in
anatomical position
The standard anatomical position, or standard anatomical model, is the scientifically agreed upon reference position for anatomical location terms. Standard anatomical positions are used to standardise the position of appendages of animals with r ...
, is found on the
medial side of the forearm. That is, the ulna is on the same side of the forearm as the little finger. It runs parallel to the
radius
In classical geometry, a radius ( : radii) of a circle or sphere is any of the line segments from its center to its perimeter, and in more modern usage, it is also their length. The name comes from the latin ''radius'', meaning ray but also the ...
, the other long bone in the forearm. The ulna is usually slightly longer than the radius, but the radius is thicker. Therefore, the radius is considered to be the larger of the two.
Structure
The ulna is a long bone found in the forearm that stretches from the elbow to the smallest finger, and when in anatomical position, is found on the medial side of the forearm. It is broader close to the elbow, and narrows as it approaches the wrist.
Close to the elbow, the ulna has a bony
process
A process is a series or set of activities that interact to produce a result; it may occur once-only or be recurrent or periodic.
Things called a process include:
Business and management
*Business process, activities that produce a specific se ...
, the
olecranon process
The olecranon (, ), is a large, thick, curved bony eminence of the ulna, a long bone in the forearm that projects behind the elbow. It forms the most pointed portion of the elbow and is opposite to the cubital fossa or elbow pit. The olecranon ...
, a hook-like structure that fits into the
olecranon fossa
The olecranon fossa is a deep triangular depression on the posterior side of the humerus, superior to the trochlea. It provides space for the olecranon of the ulna during extension of the forearm.
Structure
The olecranon fossa is located on th ...
of the
humerus
The humerus (; ) is a long bone in the arm that runs from the shoulder to the elbow. It connects the scapula and the two bones of the lower arm, the radius and ulna, and consists of three sections. The humeral upper extremity consists of a roun ...
. This prevents
hyperextension
Motion, the process of movement, is described using specific anatomical terms. Motion includes movement of organs, joints, limbs, and specific sections of the body. The terminology used describes this motion according to its direction relative ...
and forms a
hinge joint
A hinge joint (ginglymus or ginglymoid) is a bone joint in which the articular surfaces are molded to each other in such a manner as to permit motion only in one plane. According to one classification system they are said to be uniaxial (having ...
with the
trochlea of the humerus
In the human arm, the humeral trochlea is the medial portion of the articular surface of the elbow joint which articulates with the trochlear notch on the ulna in the forearm.
Structure
In humans and apes it is trochleariform (or trochleiform), ...
. There is also a
radial notch
The radial notch of the ulna (lesser sigmoid cavity) is a narrow, oblong, articular depression on the lateral side of the coronoid process; it receives the circumferential articular surface of the head of the radius.
It is concave from before bac ...
for the
head of the radius
The head of the radius has a cylindrical form, and on its upper surface is a shallow cup or fovea for articulation with the capitulum of the humerus. The circumference of the head is smooth; it is broad medially where it articulates with the radi ...
, and the
ulnar tuberosity
The tuberosity of the ulna is a rough eminence on the proximal end of the ulna. It occurs at the junction of the antero-inferior surface of the coronoid process with the front of the body. It provides an insertion point to a tendon of the brachial ...
to which muscles attach.
Close to the wrist, the ulna has a
styloid process.
Near the elbow
![Gray212](https://upload.wikimedia.org/wikipedia/commons/6/60/Gray212.png)
Near the elbow, the ulna has two curved processes, the
olecranon
The olecranon (, ), is a large, thick, curved bony eminence of the ulna, a long bone in the forearm that projects behind the elbow. It forms the most pointed portion of the elbow and is opposite to the cubital fossa or elbow pit. The olecranon ...
and the
coronoid process; and two concave, articular cavities, the
semilunar
Semilunar can refer to:
* Semilunar valves
* Semilunar ganglion, or the trigeminal ganglion
* An older name for the Lunate bone
The lunate bone (semilunar bone) is a carpal bone in the human hand. It is distinguished by its deep concavity and ...
and
radial notch
The radial notch of the ulna (lesser sigmoid cavity) is a narrow, oblong, articular depression on the lateral side of the coronoid process; it receives the circumferential articular surface of the head of the radius.
It is concave from before bac ...
es.
The
olecranon
The olecranon (, ), is a large, thick, curved bony eminence of the ulna, a long bone in the forearm that projects behind the elbow. It forms the most pointed portion of the elbow and is opposite to the cubital fossa or elbow pit. The olecranon ...
is a large, thick, curved eminence, situated at the upper and back part of the ulna. It is bent forward at the summit so as to present a prominent lip which is received into the
olecranon fossa of the humerus in extension of the forearm. Its base is contracted where it joins the body and the narrowest part of the upper end of the ulna. Its posterior surface, directed backward, is triangular, smooth, subcutaneous, and covered by a bursa. Its superior surface is of quadrilateral form, marked behind by a rough impression for the insertion of the
triceps brachii
The triceps, or triceps brachii (Latin for "three-headed muscle of the arm"), is a large muscle on the back of the upper limb of many vertebrates
Vertebrates () comprise all animal taxa within the subphylum Vertebrata () ( chordates with ba ...
; and in front, near the margin, by a slight transverse groove for the attachment of part of the posterior ligament of the elbow joint. Its anterior surface is smooth, concave, and forms the upper part of the semilunar notch. Its borders present continuations of the groove on the margin of the superior surface; they serve for the attachment of ligaments: the back part of the ulnar collateral ligament medially, and the posterior ligament laterally. From the medial border a part of the
flexor carpi ulnaris
The flexor carpi ulnaris (FCU) is a muscle of the forearm that flexes and adducts at the wrist joint.
Structure Origin
The flexor carpi ulnaris has two heads; a humeral head and ulnar head. The humeral head originates from the medial epicondyle o ...
arises; while to the lateral border the
anconeus
The anconeus muscle (or anconaeus/anconæus) is a small muscle on the posterior aspect of the elbow joint.
Some consider anconeus to be a continuation of the triceps brachii muscle. Some sources consider it to be part of the posterior compartment ...
is attached.
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. Its apex is pointed, slightly curved upward, and in flexion of the forearm is received into the coronoid fossa of the humerus. Its upper surface is smooth, concave, and forms the lower part of the semilunar notch. Its antero-inferior surface is concave, and marked by a rough impression for the insertion of the
brachialis
The brachialis (brachialis anticus), also known as the Teichmann muscle, is a muscle in the upper arm that flexes the elbow. It lies deeper than the biceps brachii, and makes up part of the floor of the region known as the cubital fossa (elbow pi ...
. At the junction of this surface with the front of the body is a rough eminence, the tuberosity of the ulna, which gives insertion to a part of the brachialis; to the lateral border of this tuberosity the oblique cord is attached. Its lateral surface presents a narrow, oblong, articular depression, the
radial notch
The radial notch of the ulna (lesser sigmoid cavity) is a narrow, oblong, articular depression on the lateral side of the coronoid process; it receives the circumferential articular surface of the head of the radius.
It is concave from before bac ...
. Its medial surface, by its prominent, free margin, serves for the attachment of part of the
ulnar collateral ligament Ulnar collateral ligament (or UCL), may refer to:
* Ulnar carpal collateral ligament
* Ulnar collateral ligament of elbow joint
* Ulnar collateral ligament of thumb
The ulnar collateral ligament of the thumb runs along the ulnar side of the met ...
. At the front part of this surface is a small rounded eminence for the origin of one head of the
flexor digitorum superficialis
Flexor digitorum superficialis (''flexor digitorum sublimis'') is an extrinsic flexor muscle of the fingers at the proximal interphalangeal joints.
It is in the anterior compartment of the forearm. It is sometimes considered to be the deepest pa ...
; behind the eminence is a depression for part of the origin of the
flexor digitorum profundus
The flexor digitorum profundus is a muscle in the forearm of humans that flexes the fingers (also known as digits). It is considered an extrinsic hand muscle because it acts on the hand while its muscle belly is located in the forearm.
Together t ...
; descending from the eminence is a ridge which gives origin to one head of the
pronator teres
The pronator teres is a muscle (located mainly in the forearm) that, along with the pronator quadratus, serves to pronate the forearm (turning it so that the palm faces posteriorly when from the anatomical position). It has two attachments, to t ...
. Frequently, the
flexor pollicis longus
The flexor pollicis longus (; FPL, Latin ''flexor'', bender; ''pollicis'', of the thumb; ''longus'', long) is a muscle in the forearm and hand that flexes the thumb. It lies in the same plane as the flexor digitorum profundus. This muscle is uniqu ...
arises from the lower part of the
coronoid process by a rounded bundle of muscular fibers.
The
semilunar notch
The trochlear notch (), also known as semilunar notch and greater sigmoid cavity, is a large depression in the upper extremity of the ulna that fits the trochlea of the humerus (the bone directly above the ulna in the arm) as part of the elbow jo ...
is a large depression, formed by the olecranon and the coronoid process, and serving as articulation with the trochlea of the humerus. About the middle of either side of this notch is an indentation, which contracts it somewhat, and indicates the junction of the olecranon and the coronoid process. The notch is concave from above downward, and divided into a medial and a lateral portion by a smooth ridge running from the summit of the olecranon to the tip of the coronoid process. The medial portion is the larger, and is slightly concave transversely; the lateral is convex above, slightly concave below.
The
radial notch
The radial notch of the ulna (lesser sigmoid cavity) is a narrow, oblong, articular depression on the lateral side of the coronoid process; it receives the circumferential articular surface of the head of the radius.
It is concave from before bac ...
is a narrow, oblong, articular depression on the lateral side of the coronoid process; it receives the circumferential articular surface of the head of the
radius
In classical geometry, a radius ( : radii) of a circle or sphere is any of the line segments from its center to its perimeter, and in more modern usage, it is also their length. The name comes from the latin ''radius'', meaning ray but also the ...
. It is concave from before backward, and its prominent extremities serve for the attachment of the annular ligament.
Body
The body of the ulna at its upper part is prismatic in form, and curved so as to be convex behind and lateralward; its central part is straight; its lower part is rounded, smooth, and bent a little lateralward. It tapers gradually from above downward, and has three borders and three surfaces.
;Borders
* The volar border (''margo volaris; anterior border'') begins above at the prominent medial angle of the
coronoid process, and ends below in front of the
styloid process. Its upper part, well-defined, and its middle portion, smooth and rounded, give origin to the
flexor digitorum profundus
The flexor digitorum profundus is a muscle in the forearm of humans that flexes the fingers (also known as digits). It is considered an extrinsic hand muscle because it acts on the hand while its muscle belly is located in the forearm.
Together t ...
; its lower fourth serves for the origin of the
pronator quadratus
Pronator quadratus is a square-shaped muscle on the distal forearm that acts to pronate (turn so the palm faces downwards) the hand.
Structure
Its fibres run perpendicular to the direction of the arm, running from the most distal quarter of the ...
. This border separates the volar from the medial surface.
* The dorsal border (''margo dorsalis; posterior border'') begins above at the apex of the triangular subcutaneous surface at the back part of the
olecranon
The olecranon (, ), is a large, thick, curved bony eminence of the ulna, a long bone in the forearm that projects behind the elbow. It forms the most pointed portion of the elbow and is opposite to the cubital fossa or elbow pit. The olecranon ...
, and ends below at the back of the
styloid process; it is well-marked in the upper three-fourths, and gives attachment to an
aponeurosis
An aponeurosis (; plural: ''aponeuroses'') is a type or a variant of the deep fascia, in the form of a sheet of pearly-white fibrous tissue that attaches sheet-like muscles needing a wide area of attachment. Their primary function is to join musc ...
which affords a common origin to the
flexor carpi ulnaris
The flexor carpi ulnaris (FCU) is a muscle of the forearm that flexes and adducts at the wrist joint.
Structure Origin
The flexor carpi ulnaris has two heads; a humeral head and ulnar head. The humeral head originates from the medial epicondyle o ...
, the
extensor carpi ulnaris
In human anatomy, the extensor carpi ulnaris is a skeletal muscle located on the ulnar side of the forearm. The extensor carpi ulnaris acts to extend and adduct at the carpus/wrist from anatomical position.
Being an extensor muscle, extensor carpi ...
, and the
flexor digitorum profundus
The flexor digitorum profundus is a muscle in the forearm of humans that flexes the fingers (also known as digits). It is considered an extrinsic hand muscle because it acts on the hand while its muscle belly is located in the forearm.
Together t ...
; its lower fourth is smooth and rounded. This border separates the medial from the dorsal surface.
* The interosseous crest (''crista interossea; external or interosseous border'') begins above by the union of two lines, which converge from the extremities of the
radial notch
The radial notch of the ulna (lesser sigmoid cavity) is a narrow, oblong, articular depression on the lateral side of the coronoid process; it receives the circumferential articular surface of the head of the radius.
It is concave from before bac ...
and enclose between them a triangular space for the origin of part of the
Supinator
In human anatomy, the supinator is a broad muscle in the posterior compartment of the forearm, curved around the upper third of the radius. Its function is to supinate the forearm.
Structure
Supinator consists of two planes of fibers, between whi ...
; it ends below at the head of the ulna. Its upper part is sharp, its lower fourth smooth and rounded. This crest gives attachment to the
interosseous membrane
An interosseous membrane is a thick dense fibrous sheet of connective tissue that spans the space between two bones, forming a type of syndesmosis joint.
Interosseous membranes in the human body:
* Interosseous membrane of forearm
* Interosseous ...
, and separates the volar from the dorsal surface.
;Surfaces
* The volar surface (''facies volaris; anterior surface''), much broader above than below, is concave in its upper three-fourths, and gives origin to the
flexor digitorum profundus
The flexor digitorum profundus is a muscle in the forearm of humans that flexes the fingers (also known as digits). It is considered an extrinsic hand muscle because it acts on the hand while its muscle belly is located in the forearm.
Together t ...
; its lower fourth, also concave, is covered by the
pronator quadratus
Pronator quadratus is a square-shaped muscle on the distal forearm that acts to pronate (turn so the palm faces downwards) the hand.
Structure
Its fibres run perpendicular to the direction of the arm, running from the most distal quarter of the ...
. The lower fourth is separated from the remaining portion by a ridge, directed obliquely downward and medialward, which marks the extent of origin of the pronator quadratus. At the junction of the upper with the middle third of the bone is the
nutrient canal
All bones possess larger or smaller foramina (openings) for the entrance of blood-vessels; these are known as the nutrient foramina, and are particularly large in the shafts of the larger long bones, where they lead into a nutrient canal, which ex ...
, directed obliquely upward.
* The dorsal surface (''facies dorsalis; posterior surface'') directed backward and lateralward, is broad and concave above; convex and somewhat narrower in the middle; narrow, smooth, and rounded below. On its upper part is an oblique ridge, which runs from the dorsal end of the radial notch, downward to the dorsal border; the triangular surface above this ridge receives the insertion of the
Anconæus, while the upper part of the ridge affords attachment to the
supinator
In human anatomy, the supinator is a broad muscle in the posterior compartment of the forearm, curved around the upper third of the radius. Its function is to supinate the forearm.
Structure
Supinator consists of two planes of fibers, between whi ...
. Below this the surface is subdivided by a longitudinal ridge, sometimes called the perpendicular line, into two parts: the medial part is smooth, and covered by the
extensor carpi ulnaris
In human anatomy, the extensor carpi ulnaris is a skeletal muscle located on the ulnar side of the forearm. The extensor carpi ulnaris acts to extend and adduct at the carpus/wrist from anatomical position.
Being an extensor muscle, extensor carpi ...
; the lateral portion, wider and rougher, gives origin from above downward to the
Supinator
In human anatomy, the supinator is a broad muscle in the posterior compartment of the forearm, curved around the upper third of the radius. Its function is to supinate the forearm.
Structure
Supinator consists of two planes of fibers, between whi ...
, the
abductor pollicis longus
In human anatomy, the abductor pollicis longus (APL) is one of the extrinsic muscles of the hand. Its major function is to abduct the thumb at the wrist. Its tendon forms the anterior border of the anatomical snuffbox.
Structure
The abductor p ...
, the
extensor pollicis longus
In human anatomy, the extensor pollicis longus muscle (EPL) is a skeletal muscle located dorsally on the forearm. It is much larger than the extensor pollicis brevis, the origin of which it partly covers and acts to stretch the thumb together with ...
, and the
extensor indicis proprius
In human anatomy, the extensor indicis roprius'' is a narrow, elongated skeletal muscle in the deep layer of the dorsal forearm, placed medial to, and parallel with, the extensor pollicis longus. Its tendon goes to the index finger, which it ex ...
.
* The medial surface (''facies medialis; internal surface'') is broad and concave above, narrow and convex below. Its upper three-fourths give origin to the
Flexor digitorum profundus
The flexor digitorum profundus is a muscle in the forearm of humans that flexes the fingers (also known as digits). It is considered an extrinsic hand muscle because it acts on the hand while its muscle belly is located in the forearm.
Together t ...
; its lower fourth is subcutaneous.
Near the wrist
The head of ulna presents an articular surface, part of which, of an oval or semilunar form, is directed downward, and articulates with the upper surface of the
triangular articular disc which separates it from the wrist-joint; the remaining portion, directed lateralward, is narrow, convex, and received into the
ulnar notch
The articular surface for the ulna is called the ulnar notch (sigmoid cavity) of the radius; it is in the distal radius
The radius or radial bone is one of the two large bones of the forearm, the other being the ulna. It extends from the latera ...
of the
radius
In classical geometry, a radius ( : radii) of a circle or sphere is any of the line segments from its center to its perimeter, and in more modern usage, it is also their length. The name comes from the latin ''radius'', meaning ray but also the ...
.
Near the wrist, the ulnar, with two eminences; the lateral and larger is a rounded, articular eminence, termed the head of the ulna; the medial, narrower and more projecting, is a non-articular eminence, the
styloid process.
* The ''head'' presents an articular surface, part of which, of an oval or semilunar form, is directed downward, and articulates with the upper surface of the triangular articular disk which separates it from the wrist-joint; the remaining portion, directed lateralward, is narrow, convex, and received into the
ulnar notch of the radius
The articular surface for the ulna is called the ulnar notch (sigmoid cavity) of the radius; it is in the distal radius, and is narrow, concave, smooth, and articulates with the head of the ulna forming the distal radioulnar joint
The distal rad ...
.
* The ''styloid process'' projects from the medial and back part of the bone; it descends a little lower than the head, and its rounded end affords attachment to the ulnar collateral ligament of the wrist-joint.
The head is separated from the styloid process by a depression for the attachment of the apex of the triangular articular disk, and behind, by a shallow groove for the tendon of the
extensor carpi ulnaris
In human anatomy, the extensor carpi ulnaris is a skeletal muscle located on the ulnar side of the forearm. The extensor carpi ulnaris acts to extend and adduct at the carpus/wrist from anatomical position.
Being an extensor muscle, extensor carpi ...
.
File:Gray336.png, Vertical section through the articulations at the wrist, showing the synovial cavities.
File:Gray213.png, Bones of left forearm. Anterior aspect.
File:Gray214.png, Bones of left forearm. Posterior aspect.
File:Gray334.png, Ligaments of wrist. Anterior view
File:Gray335.png, Ligaments of wrist. Posterior view.
Microanatomy
The ulna is a
long bone
The long bones are those that are longer than they are wide. They are one of five types of bones: long, Short bone, short, Flat bone, flat, Irregular bone, irregular and Sesamoid bone, sesamoid. Long bones, especially the femur and tibia, are subj ...
. The long, narrow
medullary cavity
The medullary cavity (''medulla'', innermost part) is the central cavity of bone shafts where red bone marrow and/or yellow bone marrow (adipose tissue) is stored; hence, the medullary cavity is also known as the marrow cavity.
Located in the m ...
of the ulna is enclosed in a strong wall of
cortical tissue which is thickest along the
interosseous border and dorsal surface. At the extremities the compact layer thins. The compact layer is continued onto the back of the olecranon as a plate of close spongy bone with lamellæ parallel. From the inner surface of this plate and the compact layer below it trabeculæ arch forward toward the olecranon and coronoid and cross other trabeculæ, passing backward over the medullary cavity from the upper part of the shaft below the coronoid. Below the coronoid process there is a small area of compact bone from which trabeculæ curve upward to end obliquely to the surface of the semilunar notch which is coated with a thin layer of compact bone. The trabeculæ at the lower end have a more longitudinal direction.
Development
The ulna is
ossified
Ossification (also called osteogenesis or bone mineralization) in bone remodeling is the process of laying down new bone material by Cell (biology), cells named osteoblasts. It is synonymous with bone tissue formation. There are two processes ...
from three centers: one each for the body, the wrist end, and the elbow end, near the top of the
olecranon
The olecranon (, ), is a large, thick, curved bony eminence of the ulna, a long bone in the forearm that projects behind the elbow. It forms the most pointed portion of the elbow and is opposite to the cubital fossa or elbow pit. The olecranon ...
.
Ossification begins near the middle of the body of the ulna, about the eighth week of fetal life, and soon extends through the greater part of the bone.
At birth, the ends are cartilaginous. About the fourth year or so, a center appears in the middle of the head, and soon extends into the
ulnar styloid process
The styloid process of the ulna is a bony prominence found at distal end of the ulna in the forearm.
Structure
The styloid process of the ulna projects from the medial and back part of the ulna. It descends a little lower than the head. The head ...
. About the tenth year, a center appears in the olecranon near its extremity, the chief part of this process being formed by an upward extension of the body. The upper
epiphysis
The epiphysis () is the rounded end of a long bone, at its joint with adjacent bone(s). Between the epiphysis and diaphysis (the long midsection of the long bone) lies the metaphysis, including the epiphyseal plate (growth plate). At the join ...
joins the body about the sixteenth, the lower about the twentieth year.
Function
Joints
The ulna forms part of the
wrist
In human anatomy, the wrist is variously defined as (1) the Carpal bones, carpus or carpal bones, the complex of eight bones forming the proximal skeletal segment of the hand; "The wrist contains eight bones, roughly aligned in two rows, known ...
joint and
elbow
The elbow is the region between the arm and the forearm that surrounds the elbow joint. The elbow includes prominent landmarks such as the olecranon, the cubital fossa (also called the chelidon, or the elbow pit), and the lateral and the media ...
joints. Specifically, the ulna joins (
articulates) with:
* trochlea of the
humerus
The humerus (; ) is a long bone in the arm that runs from the shoulder to the elbow. It connects the scapula and the two bones of the lower arm, the radius and ulna, and consists of three sections. The humeral upper extremity consists of a roun ...
, at the right side
elbow
The elbow is the region between the arm and the forearm that surrounds the elbow joint. The elbow includes prominent landmarks such as the olecranon, the cubital fossa (also called the chelidon, or the elbow pit), and the lateral and the media ...
as a
hinge joint
A hinge joint (ginglymus or ginglymoid) is a bone joint in which the articular surfaces are molded to each other in such a manner as to permit motion only in one plane. According to one classification system they are said to be uniaxial (having ...
with semilunar
trochlear notch
The trochlear notch (), also known as semilunar notch and greater sigmoid cavity, is a large depression in the upper extremity of the ulna that fits the trochlea of the humerus (the bone directly above the ulna in the arm) as part of the elbow jo ...
of the ulna.
* the
radius
In classical geometry, a radius ( : radii) of a circle or sphere is any of the line segments from its center to its perimeter, and in more modern usage, it is also their length. The name comes from the latin ''radius'', meaning ray but also the ...
, near the elbow as a
pivot joint
In animal anatomy, a pivot joint (trochoid joint, rotary joint or lateral ginglymus) is a type of synovial joint whose movement axis is parallel to the long axis of the proximal bone, which typically has a convex articular surface.
According to o ...
, this allows the radius to cross over the ulna in
pronation
Motion, the process of movement, is described using specific anatomical terms. Motion includes movement of organs, joints, limbs, and specific sections of the body. The terminology used describes this motion according to its direction relative ...
.
* the
distal radius
The radius or radial bone is one of the two large bones of the forearm, the other being the ulna. It extends from the lateral side of the elbow to the thumb side of the wrist and runs parallel to the ulna. The ulna is usually slightly longer than ...
, where it fits into the
ulnar notch
The articular surface for the ulna is called the ulnar notch (sigmoid cavity) of the radius; it is in the distal radius
The radius or radial bone is one of the two large bones of the forearm, the other being the ulna. It extends from the latera ...
.
* the radius along its length via the
interosseous membrane
An interosseous membrane is a thick dense fibrous sheet of connective tissue that spans the space between two bones, forming a type of syndesmosis joint.
Interosseous membranes in the human body:
* Interosseous membrane of forearm
* Interosseous ...
that forms a
syndesmosis
In anatomy, fibrous joints are joints connected by fibrous tissue, consisting mainly of collagen. These are fixed joints where bones are united by a layer of white fibrous tissue of varying thickness. In the skull the joints between the bones are ...
joint
Muscle attachments
Clinical significance
Fractures
Specific types of
ulna fracture
An ulna fracture is a broken bone, break in the ulna bone, one of the two bones in the forearm. It is often associated with a fracture of the other forearm bone, the radius fractures, radius.
An ulna fracture can be a single break as in a so cal ...
include:
*
Monteggia fracture
The Monteggia fracture is a fracture (bone), fracture of the Anatomical terms of location#Proximal and distal, proximal third of the ulna with dislocation of the proximal head of radius, head of the radius. It is named after Giovanni Battista Mont ...
- a fracture of the proximal third of the ulna with the dislocation of the
head of the radius
The head of the radius has a cylindrical form, and on its upper surface is a shallow cup or fovea for articulation with the capitulum of the humerus. The circumference of the head is smooth; it is broad medially where it articulates with the radi ...
*
Hume fracture
The Hume fracture is an injury of the elbow comprising a fracture of the olecranon with an associated anterior dislocation of the radial head which occurs in children. It was originally described as an undisplaced olecranon fracture, but more r ...
- a fracture of the
olecranon
The olecranon (, ), is a large, thick, curved bony eminence of the ulna, a long bone in the forearm that projects behind the elbow. It forms the most pointed portion of the elbow and is opposite to the cubital fossa or elbow pit. The olecranon ...
with an associated
anterior
Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position prov ...
dislocation
In materials science, a dislocation or Taylor's dislocation is a linear crystallographic defect or irregularity within a crystal structure that contains an abrupt change in the arrangement of atoms. The movement of dislocations allow atoms to sl ...
of the
radial head
The head of the radius has a cylindrical form, and on its upper surface is a shallow cup or fovea for articulation with the capitulum of the humerus. The circumference of the head is smooth; it is broad medially where it articulates with the rad ...
Conservative management Conservative management is a type of medical treatment defined by the avoidance of invasive measures such as surgery or other invasive procedures, usually with the intent to preserve function or body parts. For example, in appendicitis, conservati ...
is possible for ulnar fractures when they are located in the distal two-thirds, only involve the shaft, with no shortening, less than 10° angulation and less than 50% displacement.
[Page 158]
/ref> In such cases, a cast
Cast may refer to:
Music
* Cast (band), an English alternative rock band
* Cast (Mexican band), a progressive Mexican rock band
* The Cast, a Scottish musical duo: Mairi Campbell and Dave Francis
* ''Cast'', a 2012 album by Trespassers William
* ...
should be applied that goes above the elbow.[
]
Other animals
In four-legged animals, the radius is the main load-bearing bone of the lower forelimb, and the ulna is important primarily for muscular attachment. In many mammals, the ulna is partially or wholly fused with the radius, and may therefore not exist as a separate bone. However, even in extreme cases of fusion, such as in horse
The horse (''Equus ferus caballus'') is a domesticated, one-toed, hoofed mammal. It belongs to the taxonomic family Equidae and is one of two extant subspecies of ''Equus ferus''. The horse has evolved over the past 45 to 55 million y ...
s, the olecranon process is still present, albeit as a projection from the upper radius.
In birds
Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweigh ...
and other dinosaurs
Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is t ...
the ulna forms a surface of attachment for the secondary feathers
Flight feathers (''Pennae volatus'') are the long, stiff, asymmetrically shaped, but symmetrically paired pennaceous feathers on the wings or tail of a bird; those on the wings are called remiges (), singular remex (), while those on the tail ...
. These often leave osteological evidence in the form of quill knobs, allowing for identification of feathers in fossils that otherwise lack integumentary information.
Gallery
File:Ulna - animation.gif, Position of ulna (red). Animation
File:Human ulna.stl, 3D image
File:RightHumanPosteriorRadiusUlna.jpg, Bones of the right arm, showing the ulna, radius, wrist and humerus
File:Gray417 color.PNG, Cross-section through the middle of the forearm, showing the two bones and the muscles, nerves and blood vessels surrounding them.
File:Ulna Anatomy by Jason Christian.webm, Ulna Anatomy
See also
*Anatomical terms of bone
Many anatomical terms descriptive of bone are defined in anatomical terminology, and are often derived from Greek and Latin. Bone in the human body is categorized into long bone, short bone, flat bone, irregular bone and sesamoid bone.
Types of ...
*Madelung's deformity
Madelung's deformity is usually characterized by malformed wrists and wrist bones and is often associated with Léri-Weill dyschondrosteosis. It can be bilateral (in both wrists) or just in the one wrist.
It has only been recognized within the pa ...
*Terms for anatomical location
Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position prov ...
*Ulnar artery
The ulnar artery is the main blood vessel, with oxygenated blood, of the medial aspects of the forearm. It arises from the brachial artery and terminates in the superficial palmar arch, which joins with the superficial branch of the radial ar ...
*Ulnar nerve
In human anatomy, the ulnar nerve is a nerve that runs near the ulna bone. The ulnar collateral ligament of elbow joint is in relation with the ulnar nerve. The nerve is the largest in the human body unprotected by muscle or bone, so injury is ...
References
External links
Bone and Spine : Musculoskeletal-Anatomy
{{Authority control
Long bones
Bones of the upper limb