ANAT:Lecture Note Forearm1

8/8/2019 ANAT:Lecture Note Forearm1

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FOREARM 1

BONES OF THE FOREARM

The forearm consist of two bones, RADIUS and ULNA.

RADIUS

First, we will be talking about the radius.We have an area, we call it Radial tuberosity. What is

this area for? Its for articulation with the ulna. So the two bones (radius and ulna), they

articulate with the humerus superiorly and they make up articulation with each other.

SPECIAL THANKS TO:

ZILLE ZAHRA MALIK

QURRATU AINI KHAIRUDDI

HANISAH SHAHRIR


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(A student asked the doctor about the position of ulna and radius in supination and pronation)

FRACTURES OF DISTAL END OF RADIUS

Now, forearm, like the rest of the bone in the body are subjected to fractures. One of the

common fracture in the radius called COLLES FRACTURE. The radius will break near the distal

end. It wont break at the wrist joint, but just before the joint. And the fracture process will

move posteriorly and superiorly. So the hand will be shaped like the dinner fork. And this is

one of the most common fracture. If the movement of the fracture bone is reversed, we call it

SMITHS FRACTURE or REVERSE COLLES FRACTURE.

ELBOW JOINT

Now we will start talking about the elbow joint, which is formed by the bone we have just

discussed and the humerus. Its a synovial hinge joint. What movement involve in this joint? Its

the FLEXION and the EXTENSION. What are the articular surfaces? The articular surfaces within

the humerus is the capitulum and the trochlea. If the articular surface within the forearm, it is

the head of radius and olecranon socket called trochlea notch. Also, we have joints related to

the elbow joint , related to radius and ulnar, we said they articulate with each other. And the

ligament of that articulation is continous with the ligaments of the elbow joints.

Now, lets talk about the supporting ligaments of elbow joints. By end synovial joint, we have

synovial membrane covered by the fibrous capsule, now this fibrous capsule is even

strengthened by ligament laterally and medially.

We have 2 ligaments. One is on the lateral that is called the Radial Collateral Ligament

(RCL) and on the medial will be called the Ulna Collateral Ligament (UCL). Well, ligaments are

just like a thickening of the elbow capsule. The thickening is thick enough to be called as a

ligament.

What are the attachments of this RCL ? Its from the lateral epicondyle of humerus and

until it blends with annular ligament. Annular ligament is the ligament that surrounds the headof the radius cause the articulation with ulna. Is it complicated? No. So thats on the radial side.

On the ulna side, we have the UCL which is from the medial epicondyle until it attaches

to the coronoid and olecranon process of ulna. Now this ligament has 3 bands. Anterior,

posterior and oblique (pointing to the slide). The oblique one has the function similar to the

glenoid lambrum (glenoid ligament). Remember that we talk about the glenoid in the shoulder


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joint. Glenoid lambrum increase the depth of glenoid cavity for the shoulder joint. This oblique

band of UCL also has the same function for the elbow joint. It increases the depth of the socket

that is made within the ulna.

Now, we move to the elbow movements, Flexion and Extension. Flexion is done mainly

by 3 muscle that are arrange according to its strength, which are the brachialis, the strongest

flexor of the elbow joint, followed by biceps brachii and brachioradialis. While extension, it is

done by 2 muscles which are triceps brachii and anconeus. Triceps is the strongest of the two.

We have 4 important relations, anterior, posterior, lateral and medial. The anterior of

the elbow joint, we can see the median nerve as well as the brachial artery. Also next to the

brachial artery, we have the biceps tendon and parts of brachialis muscle. What about the

posterior? It is a bit similar, just the triceps muscle. Medially, we have the ulnar nerve and

laterally, we have the radial nerve. The ulnar nerve, it passed behind the medial epicondyle

and subcutaneous. Subcutaneous means, if your medial side of elbow head touches or hitssomething, you will have a tickling sensation called the funny elbow. So how this term come to

existence? Its because of the anatomical track*[Im not sure about this]. The ulnar nerve is

subcutaneous behind the medial epicondyle, ok? This is why we have this incidence, which is

called funny elbow.

The doctor is explaining about the picture on the slides.

Now we go to the pathological condition regarding the elbow joint. Subluxation or

dislocation of radial head. Subluxation is like a mild dislocation, we can say that. Means that the

annular ligaments that surrounds the radial head, the radial head slips from the ligament. In

severe condition, we call it dislocation. Most commonly it happens in children when you are


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pulling one arm of the childrens arm (usually,it is sudden pull that exerted by an adult to

prevent the child from falling). Subluxation is used to be called Nursemaid dislocation or

Nursemaids elbow.

Now we talk about the special structure of the elbow joint which is the cubital fossa.

Cubital fossa is a triangular depression that is made between 2 epicondyle in both side.

Superior to it is an imaginary line, laterally, a complete brachioradialis and medially, pronator

teres muscle and it lies posterior to the median cubital vein. This is clinically important because

when you go the clinic and you need a blood sample, you need to draw your blood, you will use

the median cubital vein to insert the needle which lies not inside the cubital fossa but anterior

to it. This triangular impression looks like triangular but its actually 3 dimension. So, it has a

floor and a roof. The floor is made by the brachialis muscle and supinator muscle. The roof is

made from the skin and because the skin is continuous fascia, a deep fascia, takes a special case

and we call it bicipital aponeurosis

The biceps have 2 attachments distally.

-1 to the biceps tendon

-1 to the biciptal aponeurosis.

It reinforces the roof of the cubital fossa. Now what is located in the cubital fossa?

Mainly 3 structures :

-median nerve

-brachial artery

-biceps tendon.

If you want to examine the layers. The most superficial is going to the level of the cubital fossa.

1) Skin2) Superficial fascia : within the superficial fascia we can find the median cubital vein.

Why? Because its one of the superficial vein of the forearm and arm. So thats the

location within the superficial fascia.3) Deep fascia : and specially to be more accurate, the biciptal aponeurosis.4) 3 structures within the cubital fossa (Below the deep fascia) : median nerve,

brachial artery, biceps tendon.

5) Brachialis muscle & supinator. (which is the floor)


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In this lecture i will just introduce the muscles of the forearm. We will complete them in the

next lecture.

Muscles of the Forearm

We have 3 groups. If you remember when we talk about the arm, we have 2 groups orcompartments. The anterior and posterior.

Anterior for flexors.

Posterior for extensors.

(NOT CLEAR)...instead we have an extra 3rd

group which is the lateral.

First, the radius and ulna. The fibrous membrane between them we call it interrosseous

membrane. It separates the forearm to anterior compartment and to a posterior compartment.

In addition to that, we have two muscles that by themselves we consider them a lateral

compartment.

So we have 8 muscles in the anterior compartment. They are either flexors or pronators.

2 muscles in the lateral compartment.

10 muscles in the posterior compartment.

How do we name the muscles of the forearm? In the name of each muscle, you will find either

flexor or extensor, pronator or supinator. You cant find both because it refers to the action. So

the actions can originate from the action or the attachment.

Flexor carpi ulnaris attach to the carpal bones. Or sometimes the length of the tendon whether

it is short or long. Palmaris longus it means the tendon is long.

Anterior muscles

Lets start with the anterior muscles of the forearm as we just mention to you it is the flexors of

the hand, pronator in the hand of forearm. It has one common insertion into the medial

epicondyle. So the medial epicondyle is the common attachment of flexors. The anterior

compartment of the forearm is either innervated by the median or ulnar nerves.

So the anterior compartment is inserted to the medial epycondyle and it has 3 layers :

- Superficial (4 muscles) : Flexor carpi ulnaris, Palmaris longus, Flexor carpi radialis and

pronator teres


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-Intermediate (1 muscle) : Flexor digitorum superficialis. It is a large muscle that should be easy

to be identified. This large muscle here if we move this muscle we will uncover the deep layer.

-Deep layer (3 muscles) : The flexor digitorum profundus, abductor pollicis longus, plus small

muscle that runs transverse direction which is the pronator quadrates

And of course you will identify these muscles in the lab.

Lateral muscles

The lateral group has only 2 muscles.

The brachioradialis muscle and extensor carpi radialis longus.

The origin is from the humerus. Which part of humerus? The lateral supracondylar ridge. And

they are innervated by the radial nerve.

Posterior Muscles

Posterior muscles of the forearm. We have the common origin, the lateral epicondyle. Function

to extend the hand at the wrist joint.

What you need to know about these muscles is the innervations and main action. That is the

task for you to find that in the text book. Plus, anything else mentioned in the slides. So the

origin, attachment, insertion is not mentioned in the slide you dont need to know. Your job is

to find the innervations and main action in the textbook (written in the table only) . Next

lecture we talk more about them, about the nerves in the forearm.

-END-

SPECIAL THANKS TO THOSE WHO INVOLVE IN THE MAKING OF THIS LECTURE NOTE.

MAY ALL OF YOU THAT READ THIS NOTE PRAY FOR THEIR SUCCESS NOW AND

HEREAFTER.

(SORRY FOR ANY MISTAKES.)

ANAT:Lecture Note Forearm1

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