Wrist & Hand

1. BONES
(Use articulated skeletons & bone sets)

Extra:(Ellipsoid joint: Condylar joint)
Bicipital Aponeurosis : Will cause biceps to flex when the forearm supinates
Volar palmar
(Pertaining to the palm)

1.1. Identify the parts of the upper (proximal) radius.
Radial tuberosity, head and neck of radius

1.2.Identify the bone that articulate with the radial head .
Radial notch on ulnar, round capitulum of the humerus

1.2.1.Identify the ligament that surrounds the radial head.
Annular ligament retain radial head along with radial notch of ulnar

1.2.1.1. What is its shape and why is its lower margin free?
Ring shape, partial loss of flexion and extension of elbow and total loss of pronation and supination of arm

Ans feedback: adult- funnel shaped; children- vertical
To allow rotation of the radius

1.3. Identify and give the important relations of the radial neck
It is easily fractured
Inferior to radial head

Ans feedback: Posterior interossues nerve

1.3.1.Identify and list the structures attached to the radial styloid
The radial styloid process projects obliquely downward from the distal end of the radius. It serves as the point of attachment for the brachioradialis muscle, radial collateral ligament and extensor retinaculum.

1.4. Identify the important parts of the upper (proximal) ulna.
Olecranon, trochlear notch, coronoid process, ulnar tuberosity, radial notch

1.4.1.What does the olecranon articulate with?
Olecranon fossa of Humerus

1.4.2.What is attached to the coronoid process?
Pronator teres (Ulnar head) , flexor digitorum superficialis,

1.4.3.What does the ulnar head articulate with?
Ulnar notch of radius

1.4.4.Demonstrate the carrying angle.
The lateral angle made by axis of the extended forearm with axis of the arm


1.4.4.1. What are the anatomical factors responsible for producing the carrying angle?
Superior articular surface of coronoid process of ulna is placed obliquely to long axis of ulna
Medial flange of trochlea is 6 mm below the lateral flange

1.4.4.2. What is the function of the carrying angle?
Avoid rubbing of the hip by the forearm during carrying weight or swinging arms- the angle is wider in females because of their wider pelvis


1.4.4.3. What is its clinical importance?
To determine degree of fracture

1.4.5.What is “Student’s elbow?
Olecranon bursitis- because you rest on your coronoid process


2. FUNCTIONAL ORGANIZATION OF THE FOREARM
(Use articulated skeletons & bone sets,plastinated cross section)

2.1.Draw a labeled cross section of the upper third of the forearm showing the
following:
2.1.1. Radius, Ulna and the Interosseous membrane
2.1.2. Superficial and deep fascia
2.1.3. Anterior and posterior compartments
2.1.4. Neuro-vascular structures





2.2. Identify the interosseous membrane
Between the radius and the ulnar

2.2.1. What are its functions?
Divides the forearm into anterior and posterior compartments
Site of attachment for muscles (FDP, FPL, EI)
Allows supination and pronation of forearm
Transmission & dissipation of force
Accessory ligament of radioulnar joints
Transfers load from distal radius to proximal ulna

3.1. Identify the distal attachments of the biceps
Radial tuberosity, Bicipital aponeurosis

3.1.1.What is the function of the bicipital aponeurosis.
Inserts into the deep fascia + ulna giving increased & more even forearm flexion; protects median nerve and brachial artery

Protect the components in the cubital fossa
Reduce the pressure between the bicep and radial tuberosity during pronation and supination

3.1.2.How does the other attachment enable it to act as a supinator?
Biceps brachii main function is at the elbow where it flexes the forearm and supinates the forearm.

3.1.2.1. What is the anatomical basis that we tighten screws clockwise?
Inserts into the posterior aspect of the radial tuberosity
Biceps is a powerful muscle hence supination is more powerful than pronation

3.1.2.2. Which type of lever mechanism does the biceps form?
Class 3 lever


3.2. Identify and list the boundaries of the cubital fossa.
Lateral border- medial border of the brachioradialis muscle, medial border- lateral border of the pronator teres muscle, superior border- hypothetical line between the epicondyles of the humerus

3.2.1.Identify the contents and show their relationship to each other
Lateral of the cubital fossa is the tendon of the biceps brachii muscle followed by the brachial artery and at medial of the cubital fossa is the median nerve.
Also contain the radial nerve and accompanying veins

3.2.2.What is the clinical importance of the fossa?
Common site for venipuncture (the superficial veins)
Site for recording blood pressure
Contents are jeopardized in supracondylar fracture of the humerus

When taking blood pressure reading from a patient, the clinician places the stethoscope over the brachial artery in the cubital fossa.

3.3. Identify the brachioradialis


3.3.1.What is its action?
Accessory flexor of the elbow joint when forearm is mid pronated

Elbow flexion; brings pronated/supinated forearm to mid-position

3.3.2.What is odd about its nerve supply and why?
It is innervated by the radial nerve even though the bulk of the muscle body is visible from the anterior aspect of the forearm.

Radial nerve; flexor muscle supplied by extensor nerve; muscle is on border between 2 compartments means may have components of both

3.4. Identify the pronator teres


3.4.1.What is its nerve supply?
It is innervated by the median nerve

3.4.2.What is its action?
It pronates the forearm (weak flexor)

3.5. List the muscles of the Anterior (flexor-pronator) compartment.
Do a virtual dissection in 4 D Anatomy (http://4danatomy.com/modules )to explore the muscles of the elbow region : Right cubital fossa (anterior-medial view)

3.6. From lateral to medial, identify the muscles originating from the common flexor origin. (medial epicondyle)
Humeral head of pronator teres, Flexor Carpi Radialis, Palmaris Longus, Humeral head of Flexor Carpi Ulnaris Deep: Flexor digitorum superficialis

3.6.1. What is Golfer’s elbow?
Golfer's elbow (medial epicondylitis) causes pain and inflammation in the tendons that connect the forearm to the elbow.

3.7.Which muscles have 2 heads ?
Pronator teres (deep head from coronoid process), Flexor Carpi Ulnaris (fibrous arch to subcutaneous border of ulna), Flexor Digitorum Superficialis (ulnar collateral ligament, coronoid process, fibrous arch to radial shaft origin)

3.7.1.Which main nerves enter the forearm by passing between the 2 heads of each of these muscles?
Pronator teres (Median), Flexor Carpi Ulnaris (Ulnar), Flexor Digitorum Superficialis (Median), Supinator (radial nerve- deep)

3.7.2.What structures pass under the FDS arch?
Ulnar artery and median nerve

Deep and intermediate flexor muscles

3.8.Which nerve supplies the muscles with the common flexor origin?
Median nerve except for flexor carpi ulnaris (ulnar nerve)

3.9. Identify and list the deep forearm flexor muscles.
Flexor digitorum profundus, Flexor pollicis longus, Pronator quadratus

3.9.1.What is their nerve supply?
Flexor digitorum profundus (Medial: Ulnar nerve, Lateral: Median nerve) , Flexor pollicis longus (Median, Anterior interosseous nerve ), Pronator quadratus (Median, Anterior interosseous nerve )

3.10. Identify pronator quadratus.


3.10.1.  What are its functions?
Pronates the forearm

Distal radioulnar joint stability (fixator)


3.10.2.  What is its nerve supply?
A branch of medial nerve- anterior interosseous nerve

3.10.2.1. From which branch is this nerve derived?
Median Nerve (C8, T1) (C7/8)


3.11. Identify the muscles of the Posterior (extensor- supinator) compartment of the forearm.
Extensor forearm muscles- abductor pollicis longus, extensor pollicis brevis, extensor pollicis longus, extensor indicis

3.11.1. What are the nerve supplies of these muscles?
Radial nerve

3.12. List the muscles originating from the common extensor origin.
Extensor carpi radialis brevis, extensor digitorum, extensor digiti minimi, extensor carpi ulnaris

3.12.1. Which nerve supplies the muscles with the common extensor origin?
Extensor Carpi Radialis brevis, Extensor digitorum (Posterior interosseous nerve) , Extensor digiti minimi (Posterior interosseous nerve)
General:(Deep branches of radial nerve)


3.12.2.  Which of these muscles have second heads?
Extensor carpi ulnaris- humeral head: lateral epicondyle of humerus and posterior border; ulnar head- olecranon
Supinator

3.12.3.  What is ‘tennis elbow’?
Tennis elbow is an inflammation of the tendons that join the forearm muscles on the outside of the elbow. The forearm muscles and tendons become damaged from overuse — repeating the same motions again and again. This leads to pain and tenderness on the outside of the elbow.

Lateral epicondylitis

3.12.4.  Identify the Lister’s tubercle
Lister's tubercle or dorsal tubercle of radius is a bony prominence located at the distal end of the radius, palpable on the dorsum of the wrist.



3.13. Identify and list (lateral to medial) the extensor tendons running in compartments over the distal forearm.
Extensor carpi ulnaris, extensor digiti minimi, extensor digitorum, extensor carpi radialis brevis, extensor carpi radialis longus


4. JOINTS (Use articulated skeletons, joint models & bone sets)
Do a virtual dissection in 4 D Anatomy (http://4danatomy.com/modules ) to explore the deepest layer and the elbow joint : Right cubital fossa (anterior-medial view)

4.1.Identify the three articulations of the elbow joint:
4.1.1.Humeroulnar
Trochlea of the humeral condyle and the trochlear notch of the ulna
4.1.2.Humeroradial
Head of the radius and the capitulum of the humerus
4.1.3.Superior radioulnar
Pivot joint- head of radius articulate with radial notch of ulna
4.1.4.What type of synovial joint is each of these joints?
Humeroulnar (simple hinge)
Humeroradial (Ball and socket joint)
Superior radioulnar (pivot joint)




4.2.Why does an elbow joint effusion become distended posteriorly ?
A joint effusion is the increased intra-articular fluid in a joint which causes swelling. In elbow joint effusion its is usually due to the cause of occult fracture (hidden fracture).  The joint capsule at the posterior and the anterior of the elbow joint are less dense and are prone to become distended if there is a joint effusion, especially at the olecranon fossa where the larger recess is distended easily.

The capsule is weak anteriorly and posteriorly. Hence, it wil be distended at these sites, especially posteriourly as there is loose capsule posteriorly and the antererior aspect is covered by muscles and deep fascia.

5. VESSELS
 5.1. List the blood and nerve supply to each of the compartments of the forearm.

Compartments of the forearm
Arteries blood supply
Nerve supply
Anterior (has 3 layers:
superficial, intermediate, and deep layer)
Radial and ulnar artery
Median nerve (mostly) and Ulnar nerve- flexor carpi ulnari and medial part of flexor digitorum profundus
Posterior (has 2 layers: superficial and deep layer)
Radial artery and posterior and anterior interosseous arteries
Radial nerve
Posterior interosseus nerve

 5.2. Identify the origin of the radial artery and its pathway in the forearm.
ORIGIN PATHWAY
Begins at level of radial neck and passes over pronator teres to run deep to brachioradialis to the wrist.


6. NERVES
6.1. Identify the ULNAR NERVE and trace it in the forearm and wrist



PART B: CLINICAL ANATOMY

7. CLINICAL/SURFACE ANATOMY
 {Where possible palpate on yourself or on your willing and consenting peers or models/ plastinated specimens the following:}

 Palpate/surface mark the following:
 7.1. Palpate the following ARTERIES:
• Axillary a. (3rd part) in the axilla (in front of teres major muscle)
• Brachial a. in the cubital fossa (just medial to tendon of biceps brachii)
• Radial pulse (between FCR & brachioradialis, against the radial styloid)
• Ulnar pulse ( Front of wrist, lateral to tendon of FCU)


7.2. Palpate and describe the normal relationship of these 3 bony points:
• Olecranon process
• Medial epicondyle of the humerus
• Lateral epicondyle of the humerus
In a supra condylar # the triangle relationship is maintained as the # lies above these points


 7.2.1.What is the clinical importance?
To check if there are golfer and tennis elbow
In elbow dislocation, the olecranon shift posterolaterally and comes to lie in line with the epicondyles which is fixed in flexion.

I do until here ni

7.3. Palpate the head of the radius

7.3.1.Demonstrate the ROM of :
• supination and pronation
• Flexion and extension
7.3.2.Demonstrate the axis of their movements
7.3.3.Which joints are involved?
7.3.4.Which muscles are involved?

7.4.Demonstrate on yourself, the following movements of the elbow joint and identifying its attachments, verbalise all the muscles involved for each of the following movements:
• Flexion • Extension • Supination • Pronation

 7.5. When a surgeon want to operate on the forearm he needs to have a knowledge of the safe zones for the surgical approach to the bones of the forearm. Give the anatomical basis of the following safe zones of the forearm: https://www2.aofoundation.org/wps/portal/surgery?showPage=approach&contentUrl=srg/21/04-Approaches/21-Safezones.jsp&bone=Radius&segment=Proximal&approach=Safe%20zones%20for%20pin%20insertion&Language=en • Zones in the ulna • Zones in the proximal radius • Zones in the distal radius

7.6. Demonstrate the biceps jerk, triceps jerk, brachioradialis jerk
Biceps jerk
This is most easily done with the patient seated.
Identify the location of the biceps tendon. To do this, have the patient flex at the elbow while you observe and palpate the antecubital fossa. The tendon will look and feel like a thick cord
Support the arm in yours, such that your thumb is resting directly over the biceps tendon (hold their right arm with your right; and vice versa)
Make sure that the biceps muscle is completely relaxed.
It may be difficult to direct your hammer strike such that the force is transmitted directly on to the biceps tendon, and not dissipated amongst the rest of the soft tissue in the area. If you are supporting the patient's arm, place your thumb on the tendon and strike this digit. If the arm is unsupported, place your index or middle fingers firmly against the tendon and strike them with the hammer.
Make sure that the patient's sleeve is rolled up so that you can directly observe the muscle as well as watch the lower arm for movement. A normal response will cause the biceps to contract, drawing the lower arm upwards


Triceps jerk
This is most easily done with the patient seated.
Identify the triceps tendon, a discrete, broad structure that can be palpated (and often seen) as it extends across the elbow to the body of the muscle, located on the back of the upper arm. If you are having trouble clearly identifying the tendon, ask the patient to extend their lower arm at the elbow while you observe and palpate in the appropriate region
The arm can be placed in either of 2 positions:
Gently pull the arm out from the patient's body, such that it roughly forms a right angle at the shoulder. The lower arm should dangle directly downward at the elbow.
Have the patient place their hands on their hips
Either of these techniques will allow the triceps to completely relax.If you are certain as to the precise location of the tendon, strike this area directly with your hammer. If the target is not clearly apparent or the tendon is surrounded by an excessive amount of subcutaneous fat (which might dissipate the force of your strike), place your index or middle finger firmly against the structure. Then strike your finger.
Make sure that the triceps is uncovered, so that you can observe the response. The normal reflex will cause the lower arm to extend at the elbow and swing away from the body. If the patient's hands are on their hips, the arm will not move but the muscle should shorten vigorously


Brachioradialis jerk
This is most easily done with the patient seated. The lower arm should be resting loosely on the patient's lap.
The tendon of the Brachioradialis muscle cannot be seen or well palpated, which makes this reflex a bit tricky to elicit. The tendon crosses the radius (thumb side of the lower arm) approximately 10 cm proximal to the wrist
Strike this area with your reflex hammer. Usually, hitting anywhere in the right vicinity will generate the reflex
Observe the lower arm and body of the Brachioradialis for a response. A normal reflex will cause the lower arm to flex at the elbow and the hand to supinate (turn palm upward)

7.6.1.What are the root values of these reflexes?
Biceps jerk and brachioradialis jerk = C5/C6 Musculotaneous for biceps, radial for brachioradialis
Triceps jerk= C6/C7/C8 (Radial nerve)
 7.6.2.What muscles do these correspond to?
 Biceps = flexion of forearm
Triceps= extension of forearm
Brachioradialis = flexion of elbow




7.7. What is a “pulled elbow?” Under what circumstances does it occur?
Also known as nursemaid’s elbow where the radius is dislocated,  The medical term for the injury is "radial head subluxation and is a common injury of early childhood. Because a young child's bones and muscles are still developing, it typically takes very little force to pull the bones of the elbow partially out of place, making this injury very common. It occurs when a child's hand or wrist and pulls suddenly on the arm. rarely caused by a fall. If a child injures the elbow when falling onto an outstretched hand or directly onto the elbow, it may be a broken bone


7.8. Regarding pronator quadratus.
7.8.1.What is the space of Parona?= mid palmar space
The midpalmar space contains the 2nd, 3rd, and 4th lumbrical muscles and lies posterior to the long flexor tendons to the middle, ring and little fingers. It lies in front of the interossei and the 3rd,  4th and 5th metacarpal bone.


 7.8.1.1. What is its clinical application?
The space can be drained by an incision in either the 3rd or 4th web depending on where the pus points.
Infection of the midpalmar space may result from tenosynovitis of the middle and ring fingers or from a web infection which has spread proximally through the lumbrical canals.

7.8.1.2. What limits more proximal spread?
Flexor digitorum profundus, flexor pollicis longus

7.9. What is ‘Volkmann's contracture’?


 7.9.1. What is the pathology?
Volkmann’s contracture occurs when there is a lack of blood flow (ischemia) to the forearm. This occurs when there is increased pressure due to swelling, a condition called compartment syndrome (pressure increased, blood flow decreased, caused ischemia, lack of oxygen can supply to the muscle & nerve cells)

 7.9.2. Which muscles are involved?
Arm muscle: Superficial and deep flexor muscles on forearm

7.10. Identify the ventral structures at the wrist.


7.10.1. What is their order from medial to lateral?
Ulnar nerve, ulnar artery, flexor digitorum radialis, palmaris longus, median nerve, flexor pollicis longus, radial artery, brachioradialis, abductor pollicis longus, radial nerve (superficial branch)

7.10.2. List the key structures that may be damaged due to “suicide cuts”/deep lacerations of the:
• Radial side of the wrist
Radial artery, radial nerve

• Ulnar side of the wrist
Ulnar nerve, ulnar artery



7.11. How and why would you perform a venipuncture?
How: https://www.youtube.com/watch?v=Ie_nFCL5Hp0
https://phlebotomycoach.com/faqs/what-is-venipuncture
Most of the time, blood is drawn from a vein located on the inside of the elbow or the back of the hand.
The site is cleaned with germ-killing medicine (antiseptic).
An elastic band is put around the upper arm to apply pressure to the area. This makes the vein swell with blood.
A needle is inserted into the vein.
The blood collects into an airtight vial or tube attached to the needle.
The elastic band is removed from your arm.
The needle is taken out and the spot is covered with a bandage to stop bleeding.
In infants or young children, a sharp tool called a lancet may be used to puncture the skin and make it bleed. The blood collects onto a slide or test strip. A bandage may be placed over the area if there is any bleeding.
Why: For laboratory testing
Blood is made up of two parts:
Fluid (plasma or serum)
Cells
Plasma is the fluid part that contains substances such as glucose, electrolytes, proteins, and water. Serum is the fluid part that remains after the blood is allowed to clot in a test tube.
Cells in the blood include red blood cells, white blood cells, and platelets.
Blood helps move oxygen, nutrients, waste products, and other materials through the body. It helps control body temperature, fluid balance, and the body's acid-base balance.
Tests on blood or parts of blood may give your provider important clues about your health.

7.11.1. What procedures would you do to make the veins more visible /palpable for venepuncture?
An elastic band is put around the upper arm to apply pressure to the area. This makes the vein swell with blood.


7.12. By applying the same procedures as above on your consenting peer, identify and surface mark the following veins as well as the sites where the veins in the upper limb can be seen or palpated for venipuncture:


 • Region of the cubital fossa :




7.12.1. Cephalic vein : ant. to the lat. epicondyle along the anterolateral surface of the biceps brachii
7.12.2. Basilic vein: ant. to the medial epicondyle and medial to the biceps in the lower part of the arm
7.12.3. Medial cubital vein:
The cephalic vein at the lateral side of the forearm passes obliquely across the cubital fossa as the medial cubital vein then continues superiorly to become the basilic vein
7.12.3.1. Why is it commonly used for venipuncture?
-This is because it lies relatively close to the surface and is more prominent (visible) when pressure it’s applied.
-Large enough, can stay in place
(2nd choice is cephalic) (better not to use basilic because brachial artery and median nerve is close to it)

7.12.3.2. Why is the elbow kept extended during venipuncture?
Extension of elbow makes bicipital aponeurosis taut/stretched. Bicipital aponeurosis protects the medial nerve and brachial artery, preventing arterial haemorrhage.


 7.12.3.3. What are the common variations of this vein ?
In the cubital fossa, instead of having medial cubital vein, the median antebrachial vein will divide into median cephalic vein (connect to cephalic vein) and median basilic vein (connect to basilic vein). It has an M shape.

7.12.3.4. What is the median vein of the forearm?
• The cephalic vein in the roof of the anatomical snuff box and just posterior to the radial styloid.
• Dorsal venous network on the dorsum of the hand
Median vein of the forearm (median antebrachial vein) begins at the base of the dorsum of the thumb, curves around the lateral side of the wrist, and ascends between the cephalic and basilic veins (sometimes divides into median cephalic and median basilic veins first before joining cephalic and basilic vein respectively)





7.13. How is an arteriovenous fistula created in the forearm for Haemodialysis?
When the surgeon connects an artery to a vein, the vein grows wider and thicker, making it easier to place the needles for dialysis. The AV fistula also has a large diameter that allows your blood to flow out and back into your body quickly. The goal is to allow high blood flow so that the largest amount of blood can pass through the dialyzer.When the surgeon connects an artery to a vein, the vein grows wider and thicker, making it easier to place the needles for dialysis. The AV fistula also has a large diameter that allows your blood to flow out and back into your body quickly. The goal is to allow high blood flow so that the largest amount of blood can pass through the dialyzer.




7.13.1. What vessels are involved?

When the surgeon connects an artery to a vein, the vein grows wider and thicker, making it easier to place the needles for dialysis. The AV fistula also has a large diameter that allows your blood to flow out and back into your body quickly. The goal is to allow high blood flow so that the largest amount of blood can pass through the dialyzer.

7.13.2. How would you check if the AV fistula is working properly?

7.14. What is the importance of ‘Allen’s test’ ?




8. RADIOLOGY {Refer to radiological images in textbooks, Student web resources in Moodle – Grants Atlas & 'Diagnostic Imaging Pathways' http://www.imagingpathways.health.wa.gov.au/index.php/image-galleries/normal-anatomy }



8.1.Study the following :
8.1.1.Elbow joint : AP and Lateral views

Right forearm, Anterior view






















Lateral view




8.1.2.Supracondylar fracture of humerus




8.1.2.1. What are the possible vascular complications? Injury to brachial artery and therefore the radial and ulnar arteries will also be affected. This can cause ischemia to the arm as well as the forearm within few hours.
8.1.2.2. How can median nerve palsy, mask a pending compartment syndrome ?
Median nerve palsy(paralysis) is caused by the entrapment/compression to the median nerve. The arteries that are near within the median nerve can also be trapped. Therefore, ischemia will occur. Muscles and nerves can tolerate to to 6 hrs of ischemia and after this fibrous scar tissue replaces the necrotic tissues and causes the involved muscles to shorten permanently producing the flexion deformity known as the ischemic compartment syndrome (Volkmann contracture).
8.1.3.Both Bone forearm fractures
8.1.3.1. What are Monteggia and Galeazzi fractures ?
Monteggia fracture of the Ulnar proximal (MU)
Galeazzi fracture of the Radius distal  (GR)



8.1.4.What is a Colles fracture?
Colles fracture is the  fracture of the distal forearm and usually the most common fracture is the transverse complete fracture of the distal 2 cm of radius bone. The fracture is the result of forced extension of the hand when person outstretched the upper limb during a fall.




http://www.radiologyassistant.nl/en/p476a23436683b/wristfractures.html#i476a24282794c 8.1.4.1. What deformity does it produce?

When colles fracture happens, the ulnar styloid process can be avulsed (broken off). Since the distal part of the radius is fractured, there is an shortening of the radius and without proper support of the ulnar styloid process. Dinner fork deformity can be seen.







8.4.Identify the hypothenar eminence and its muscles.
Opponens Digiti Minimi, Abductor Digiti Minimi, Flexor Digiti Minimi
8.4.1.What is their nerve supply?
Opponens Digiti Minimi, Abductor Digiti Minimi, Flexor Digiti Minimi (Deep Branch of Ulnar Nerve T1)
8.4.2.What other muscles does this nerve supply?
The deep head of flexor pollicis brevis, adductor pollicis, 3rd and 4th lumbricals, Dorsal and palmar interossei, hypothenar eminence




8.5. Identify the thenar eminence and its mucles.

Abductor pollicis brevis, flexor pollicis brevis, opponens pollicis.
8.5.1.What is their nerve supply and their root values?
Recurrent branch of median nerve (C8, T1) (opponens pollicis, Abductor pollicis brevis, Flexor pollicis brevis [Superficial head]).
Deep branch of ulnar nerve (C8, T1) (flexor pollicis brevis [big head]).