Bones of the forearm - Radius and ulna (preview) - Human Anatomy | Kenhub

ever ended up with one of these well I

hope not but chances are that you

actually have or at least know someone

who's experienced what many people might

refer to as a broken wrist but did you

know that more often than not injuries

like this are actually isolated to the

bones of the forearm rather than to the

wrist itself yes really

in fact fractures of the distal forearm

are almost three times more common in

children than fractures to the actual

bones of the wrist so if you're

interested to find out more about the

anatomy of these bones then this is the

tutorial for you today we're going to be

finding out all there is to know about

the radius and the ulna but before we

begin looking at the bones of interest

today I want to take a moment to remind

ourselves of the orientation of the

bones of the upper limb if you can think

back to your very first anatomy lessons

we always consider the body in the same

position regardless of the actual

position of the patient in question in

this position of course is known as the

anatomical position and when it comes to

the forum it's important to remind

ourselves of a few important details in

the anatomical position the palm of the

hand is facing forwards or anteriorly

with the thumb pointing outwards or

laterally when we look at the bones at

the forearm and the hand we can now see

that this bone here which is the ulna is

found along the medial or honor aspect

of the forearm while its partner the

radius is over here on the lateral or

the radial side this of course means

that we're looking at the anterior

aspect of the bones from this

perspective fortunately for us today the

surface anatomy of the two bones of the

forearm is relatively uncomplicated and

straightforward so rest easy there's

nothing to fear about these bones you'll

know them top to bottom pretty soon so

let's waste no time and get straight

into business beginning first with the

lateral bone of the forearm the radius

so the radius is the shorter of the two

bones of the forearm and it is so called

due to its ability to rotate relative to

its neighbor which is the ulna as you

can see in the illustration it

articulates proximally with the humerus

specifically at the capitulum and it

also articulates both proximally and

distally with the ulna at its distal end

it articulates with the two lateral

bones of the proximal carpal row which

are the scaphoid and the

eight bones so let's take a closer look

now at the parts surfaces and other

points of interest of the radius

regaining approximately with the head of

the radius which is the cylindrical

structure seen here it has a concave or

cupped proximal articular surface which

articulates with the capitulum of the

humerus which its outer border known as

the articular circumference articulates

with the ulna at the radial notch

forming the proximal radioulnar joint

there are two important ligaments to be

aware of in relation to the proximal end

of the radius and the first one of these

is this one here which works to

reinforce the proximal radioulnar joint

and it's known as the annular ligament

the term annular comes from the Latin

term annulus which means ring and as you

can see in the illustration this

ligament forms a ring around the

articular circumference of the radial

head ensuring the head of the radius

remains in position within the radial

notch of the ulna the second ligament of

interest is known as the radial

collateral ligament whose fibers extend

between the lateral epicondyles of the

humerus and the annular ligament around

the head of the radius this video is not

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