ANATOMY: The Forearm 2

8/8/2019 ANATOMY: The Forearm 2

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FOREARM 2

MEDIAN NERVE - You have to know the main nerves and main action for theory exam. (He

said something about exam. I cant understand. Then he said, trust me, I will ask you in the

exam. Please study well this part I think). Now we gonna talk about nerves and arteries that

pass through the forearm. What is that? Now in the forearm, we have median nerve, ulnar

nerve & radial nerve. And 1 nerve musculocutaneous nerve that does not complete the

journey along the forearm because it terminates within the arm. So the forearm we have

only the median nerve, the ulnar nerve and the radial nerve.

Look at this picture the cubital fossa is the main landmark to start. Now start talking about

the forearm, the median nerve is the control of the cubital fossa and median nerve is the

most median content, so we have medial collateral, median nerve, brachial artery soon

divides into 2 arteries and tendons of biceps brachialis muscle. It is not apparent in this

picture. So, the arrangement is like this nerve, artery and tendon. Okey?

So it passes posterior to the flexor digitorum superficialis muscle. Notice that this is NOT themost superficial muscle of the anterior compartment of forearm. Because we have 3 layer of

flexor muscles on top of it. This is intermediate layer which is the flexor digitorum

superficialis. The median nerve is pass beneath this muscle. So, the median nerve is

sandwiched between flexor digitorum superficialis and flexor digitorum profundus.

Then, median nerve continues until it reach the wrist. The floor of the wrist, we have

structure called flexor retinaculum. Do u remember in the introduction we said about the

deep fascia that undergo modifications, sometimes it is thickened to take the shape or band

that hold the tendons of muscle, so this is one example; flexor retinaculum - is a band of

fascia that holds the tendon of flexor of the forearm.

SPECIAL THANKS TO:

AINAA SYAHIRAH ROSLAN

ZULFADHLI MARHALIM

ROSHALIYANA JAFFAR

NOR SHARINA SAHAK


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So what is the relation of these median nerve and flexor retinaculum? Median nerve goes

posterior to this flexor retinaculum (in carpal tunnel), it innervates all anterior muscle

except the half of flexor digitorum profundus and flexor carpi ulnaris because they are

supplied by ulnar nerve, okey? If u notice here we have carpal tunnel. Tunnel is a space

within the wrist region. That is made by carpal bone and flexor retinaculum.

ULNAR NERVE - Ulnar nerve it pass behind medial epicondyle. It runs between flexor carpi

ulnaris and flexor carpi digitorum profundus. This muscle here is pulled away to see the

nerve. The nerve continues its journey. Notice it is medial to ulnar artery, this relation is

important. At rest it doesnt pass beneath the flexor retinaculur but pass superficial to it.

What does it means by that? It means, ulnar nerve doesnt enter the carpal canal. Okey? The

innervations is the flexor carpi ulnaris and the medial half of flexor digitorum profundus.

RADIAL NERVE - Radial nerve passes anterior to lateral epicondyle and almost immediately

after it passes, it is split into 2 branches, superficial and deep. The deep will pierce the

supinator muscle (muscle of posterior compartment) and will enter the posterior

compartment. The name will become posterior interosseous nerve. And it will supply all

posterior compartment of forearm. Notice that arm and forearm, their posterior

compartment of both are supplied by radial nerve. Superficial branch are just sensory area

of forearm. (from the slide it said it pass beneath the brachoradialis muscle)

ARTERY - The main artery that enters the forearm is brachial artery. When entering cubital

fossa it will split into two main branches (you can see from Snell page 488). Ulnar and radial.

Ulnar is medial. Radial is lateral. Which is larger? Ulnar is larger than radial okey. Pleaseremember. Proximally it passes on the lateral aspect of the forearm, leaves brachioradialis

muscle. In the picture it has been cut so that u can see radial artery. Notice that this artery it

approaches the wrist, it winds back to enter the snuffbox, it doesnt continue its journey on

same plane. What is snuffbox? It is the lateral part of the wrist. (it is appear bellow you

thumb, you can look from the slide where it is)

[slide 36] Snuffbox has lateral and medial border. Lateral border is made by tendon of

extensor pollicis* brevis (EPB) and abductor pollicis longus (AbPL). Medial boundary is made

by the tendon of extensor pollicis longus (EPL). The floor of this snuff box is made byscaphoid and trapezium. We talk about the snuffbox because this is the area where the

radial artery are passing.(refer page 498;Clinical Notes:Anatomic Snuffbox)

*slide 37+Lets go to anterior supply for the forearm. We are going to talk about ulnar artery.

I just mentioned before ulnar artery is larger than radial artery. Its division from the brachial

artery is located opposite to neck of radius.


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Q: Where does it passes?

A: It passes (proximally) superficial to the flexor digitorum profundus (FDP) and deep to the

flexor digitorum superfiscial (FDS). Distally it runs between flexor digitorum superfiscial

(FDS) and the tendon of the flexor carpi ulnaris (FCU)

You dont need to go to deep detail consider that you are a dentist and just need to know

the general view.

*slide 39+ Lets talk about the hand. Hand has two surfaces; the anterior surfaces which is

the palm and the posterior surfaces which is the dorsum. It consist of 3 region, the wrist,

hand proper and the fingers. We gonna talk about the skeletal component at this region. In

the wrist we have carpal bone and in the hand proper we have metacarpal bones and

phalanges bone here (the fingers).

[slide 40]Each finger we have distal phalanges, middle phalanges and proximal phalanges.

So three phalanges each, except the thumb, it has only two.

*slide 41+Lets we proceed to carpal bones. In dorsal view we have 7. So, in dorsal view I can

only see 7 bones.

Q:Which one is missing??

A: The pisiform (The pisiform can only be seen in anterior view)

The carpals have two rows; (anterior view) distal row and proximal row. Scaphoid is themost commonly fracture. We have lunate, triquetral and small carpal bone which is the

pisiform (anterior to triquetral)

[slide 42] In second(distal) row we have trapezium, trapezoid, capitates and hamate.

Capitate is the largest of this bones.

[slide 43] Fracture of scaphoid. We are talking about this because this is the most common

fracture within the carpal bone. The symptoms are pain on lateral side (this is the location of

the scaphoid) of the wrist and deep tenderness** in Snuffbox. As we said, the floor of the

snuff box is made by the scaphoid bone, so when you press your Snuffbox, there is a pain

means that the scaphoid is fractured.

[slide 44] Q: Now how metacarpal attach to the forearm?

A: Through radiocarpal joint

Notice that the ulna is exluded in lateral. It is condyloid (ellipsoid) synovial joint. It

articulates between distal end of radius (lateral) and scaphoid, lunate. We also have

articular disc (medial). Articular disc is from wrist joint and articulate to triquetral joint. So

articulation for this joint are made proximally by radius and distal by schapoid, lunate and


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triquetral. Ulnar is not involve. All movements are possible except rotation. You only can

rotate your forearm.

Nota kaki:-

*pollicis = going to the thumb

**tenderness = sensitivity of pressure

[slide 45] At the rest of the joint in our body sometimes we have supporting ligaments,

many ligaments here. We dont need to worry about most of them. You only need to know

the anterior radiocarpal ligament and the dorsal radiocarpal ligament ,the palmar on the

anterior aspect of the wrist,the dorsal on the posterior aspect. These ligaments are just

thickening of the capsule,this is the sinovial joint so we have capsule, fibrous capsule. So

this attach to ligament are just a thickening of the capsule. We also have ulna collateral

ligament and it will be attach from the styloid process of ulna to trapezium. We have radial

collateral ligament, the attachment from styloid process of radius to scaphoid bone.

*slide 47+ Now well talk about flexor and extensor retinacula. Why? Because the flexor

retinacula is anterior to the rest joint whereas the extensor retinaculum is posterior to the

rest joint. The attachments, (refes Snell page 484) This is the flexor retinacula, notice that it

stretches from the hamate , the hook of hamate, the triquetrum, and the pisiform until it

reaches the trapezium and scaphoid. So the attachment for the flexor retinaculum, median

hamate and pisiform(cant see it in this pic)and laterally the trapezium and scaphoid.

Lets talk about the extensor retinaculum, extensor lies posterior to the rest joint. It has the

same median attachment which is the hamate and pisiform but the lateral attachment is

different because it is attach to the radius, to the distal part of the radius. Are we cool about

that? :D

Now we talk about tunnel. The tunnel is form by the carpal bones and flexor retinaculum.

Carpal tunnel is only a space. I have a structure inside it. It is in danger if we have condition

that is restricted the space, like inflammation for example edema, accumulation of fluid that

can happen in some injuries and can happen after a surgery in hand region for example.

The content of this tunnel its not written in the slide. We have the tendons of flexor

digitorum superficialis and flexor digitorum profundus. Are this the only muscles? NO, we

have also the tendons of flexor carpi radialis and the tendons of flexor pollicis longus. So we

have 4 muscles have tendons that pass through this tunnel, 4 muscles and one nerve which

is the median nerve. So usually when we have condition that restrict this space, the area

supplied by the median nerve will be affected, we lose sensation, we will feel paresthesia in

the region supplied by that nerve. (check out page 500 in Snell)

Extensor retinaculum, it holds the tendons extensor unlike the flexor it does not make atunnel,it make..??? Each tendon has its own .???? So usually we dont have


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problem with the extensor retinaculum. (I dont sure what Dr said. But you can read about it

from the Snell page 485 and 486)

[slide 51] Deep fascia of the palm, now we talk about the anterior surface of the hand, the

deep fascia of the palm it has 3 modifications, we have 3 different names, on the wrist

region we have flexor retinaculum. At the hand proper we have triangular shape

aponeurosis, we call it palmar aponeurosis. And distally when we reach the fingers, we have

tubular sheath for each finger. We call it fibrous digital sheaths. So fibrous digital sheaths

are modified deep fascia of the palm.

The proximal border is the distal transverse skin.???

(xfhm lps ni sbb campur ng bhs arab,sorry)

anteriorly will continue with palmar aponeurosis. (Please refer it from book). =.=

[Slide55] Carpal tunnel

Roof : Flexor retinaculum

Floor : Carpal bones.

The contents we already talk about it. Medical condition related to the anatomical carpal

tunnel we call it carpal tunnel syndrome. It is due to stress , we have pressure in this tunnel,

the median nerve will be affected and we will start losing sensation that are carried by the

median nerve. Where? In the hand. Treatment? We cut the flexor retinaculum, we makeincision to release the pressure.

[Slide 56] Palmar aponeurosis , as we can see it is triangular in shape. The apex is proximal

and the base is distal.

What comes after the deep fascia? The muscles. So we have 5 group within the hand. 1-

Thenar group that is related to thumb. 2- We have hypothenar group related to the middle

finger. 3- We have abductor pollicis muscle and it is related to thumb but it is not part of

the thenar group. We have 4- lumbrical and 5- interrossei muscle. You dont have to know

much about this muscle. Just know this are the muscle. Just know the number of each

group. (Refer to what written in slide i think)

This picture shows the 3 thumb muscle for thenar grup. This are thenar grup and this part

and this part is related to the muscle that i have talk about. Which is the part of thenar

group. So the 3 thumb muscle. We have adductor pollicis brevis. The adduct muscle that

usually become not clear is the flexor pollicis brevis. The muscle which was underneath both

of them is the opponens pollicis : sho opponens? Ya3ni ana bete3mal hek. This is mediated

by the opponent muscle. to oppose the thumb and middle (*not sure either middle or little)

finger. Nerve supply is upon the median nerve.


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Adductor pollicis which is related to the thumb but is not involved in thenar group. It is 2

parts. Tranverse head and oblique head and it is supplied by the ulnar nerve.

The hydrothenar group which is related to the little finger. We have 3 of them, the abductor

digiti minimi, the flexor digiti minimi and the opponent of digiti minimi that is supplied by

ulnar nerve. You are not required to identify these.

Now lets talk about arterial blood supply. within the hand,we have 2 blood arches. Simply,

one superficial and one deep. As the name implies,the superficial we call it superficial

palmar arch and the deep we call it deep palmar arch. The superficial palmar arch is a direct

continuation of ulnar artery. Where does it lies? It lies in between palmar aponeurosis and

the long flexor tendon. It anostomoses with the radial artery.

Lets talk about deep palmar arch. It is a continuation of radial artery and anostomose to

ulnar artery. So each each artery (ulnar or radial) give rise to an arch that will anostomosewith other one artery. It is to make sure the blood circulation available for the hand. So, the

deep palmar arch is in between long flexor tendons and metacarpal bones. So,we can know

the deep palmar arch is deep structure.

So what about venous drainage? We also have an arch but this time it is NOT in the palmar

side,it is in the dorsal side. Its name dorsal venous arch. It is subcutenous which mean

superficial, nearest the skin. It drains into 2 vein. Laterally it drains to cephalic vein and

medially into basilic vein.

And last slide we talk about sensation of the hand. Since you will be working with it for the

rest of you life ^.^ Unless you drop the dental school =.= Ok. The dorsal of the hand is

supplied by the median nerve. median nerve supply lateral 2/3. Sho ya3ni lateral 2/3? One

(thumb), two ,three and half of the next finger. So, these skin is supplied by the median

nerve (sambil menggayakan dgn tgn). What about the skin of little finger and half little

finger (jari manis) by the ulna nerve ok. Again we have in palm, lateral 2/3 supplied by the

median nerve and medial 1/3 by ulnar nerve. Always remember, medial 1/3 is supplied by

the ulna nerve on either side. (see Snell page 493. Bigger picture)

-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.

ANATOMY: The Forearm 2

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