202- Upoer Limb(Forearm And Arm Muscles) And Nerve InJuries Flashcards
(28 cards)
Look at a picture of the medial epicondyle. What important tendon is there that holds all the tendons of the four superficial muscles of the anterior compartment of the forearm? Look at a picture to understand.
State the four superficial muscles of the anterior compartment of the forearm.
Why isn’t the brachioradialis considered part of the superficial Muscles even though it’s at the anterior compartment of the forearm and is a flexor?
Note that: the muscles in the anterior compartment of the forearm are divided into three:
Superficial layer
Intermediate layer
Deep layer
What muscle is in the intermediate layer?
What about the deep layer?
All muscles in the anterior compartment are supplied by what nerves?
The common flexor tendon.
The four superficial muscles are the :
Pronator teres
Flexor carpii radialis
Palmaris longus
Flexor carpii ulnaris
(Remember pass fail pass fail)
So the beachioradialis muscle is part of the posterior compartment but is seen in the anterior because it rotates anteriorly to fall on the humerus . Or The brachioradialis is not considered part of the superficial anterior forearm muscles because:
• Functionally and developmentally, it belongs to the posterior compartment (the extensor group), even though it lies on the lateral side of the forearm, which makes it look like it’s in front.
The flexor digitorum superficialis is in the intermediate layer. Note: Flexor digitorum superficialis: ulnar artery is under it. That muscle too is right under the Palmaris longus
Deep: pronator quadratus,flexor pollicis longus,flexor digitorum profundus)
Most are supplied by median nerve and only the flexor carpii ulnaris is supplied by the ulnar nerve. The brachioradialis too is supplied by the radial nerve since it’s actually considered part of the posterior not the anterior thought it’s in the anterior.
What muscle is an exception to the rule that;
(1) the radial nerve supplies only extensor muscles and
(2)that all flexors lie in the anterior (flexor) compartment.
The long flexors of the digits are the flexor digitorum superficialis (FDS) and flexor digitorum profundus(FDP) muscles. How many tendons does the FDS have? These tendons lie between what two structures?
What phalanges of the digits do these tendons attach to?
What are the actions of these two muscles,origin,insertion,innervation
The heads of the FDS form an arch. What two structures pass under that arch?
FDS is the largest superficial muscle in the forearm.
Note: The median nerve and ulnar artery enter the forearm by passing between its humero-ulnar and radial heads
Brachioradialis. Cuz it’s a flexor but it’s not in the anterior compartment and it’s a flexor but it’s not supplied by the median or ulnar nerve but by the radial nerve. So, although it looks anterior, the nerve supply and origin show it’s part of the posterior/extensor group.
4 tendons of the FDSmuscle.
the four tendons of the flexor digitorum superficialis muscle lie between the median nerve (laterally) and the ulnar artery and nerve. They enter into the carpal tunnel to get to the fingers. The four tendons are enclosed in a synovial common flexor sheath.
The phalanges Attaches to middle phalanges of digits 2 and 5.
FDS:
Origin-has 2 heads and 3 proximal attachments. Attachments (medial epicondyle of the humerus via the common flexor tendon), coronoid process of ulna and the anterior oblique line on the shaft of the radius)
Heads(1. Humeroulnar head – comes from the medial epicondyle of the humerus and the coronoid process of the ulna
2. Radial head – comes from the anterior surface of the radius
These two heads form an arch, and the median nerve and ulnar artery pass beneath it.
Look at the picture in the grants.
Insertion- uses the four tendons to insert at the shaft of the middle phalanges of digits 2-5(the medial four digits)
Action-The flexor digitorum su-perficialis muscle flexes the middle phalanx of digits 2 to 5.
Or
Flexes middle phalanges at proximal interphalangeal joints of middle four digits; acting more strongly, it also flexes proximal phalanges at metacarpophalangeal joints. It can flex each finger it serves individually
Innervation- median nerve(C7,8. T1)
FDP:(also has 4 tendons)
Origin- has two parts. Medial and lateral parts. So the origin is the Proximal three quarters of medial and anterior surfaces of ulna and interosseous membrane or from the grants, (proximal attachment of the flexor digitorum profundus muscle is on the anterior surface of the ulna and interosseous membrane)
Insertion: uses four tendons to insert at the bases of the distal phalanges of digits 2-5(note that FDS does at the shaft of the middle phalanges of 2-5).
In the distal forearm, its four tendons lie deep to the four tendons of the flexor digitorum superficialis muscle.
Action: since it attaches to the bases of the distal phalanges of 2-5, it’ll flex those distal phalanges. The lateral part will flex 2-3 at the distal interphalangeal joints since it’s arttached to the bases of the distal phalanges of the 2nd and 3rd digits and the medial part will flex 4-5 at the distal interphalangeal joints since it’s attached to bases of the distal phalanges of the 4th and 5th digits
Innervation: it has two motor nerves: the lateral half of the muscle is innervated by the anterior interosseous nerve that is from the median nerve(C8,T1) and the medial half is innervated by the ulnar nerve(C8,T1)
Brachioradialis and pronator teres are fusiform shaped
. The pronator teres, is the most lateral of the superficial forearm flexors. Its lateral border forms the medial boundary of the cubital fossa.
This muscle has two heads. Name them.
What nerve passes between these two heads?
What’s the origin
Insertion and action is this muscle
Note; the pulse of the radial artery between the abductor pollicis longus and flexor carpi radia-lis tendons. Note that the median nerve is superficial at the wrist and can be easily injured. distal attachment of the flexor carpi ulnaris tendon on the pisiform bone.
the ulnar nerve and artery, which lie immediately lateral to the pisiform bone
The pronator teres muscle has two proximal heads-
a superficial (humeral) head and a deep (ulnar) head. The median nerve passes between these two heads.
Origin-ulnar head originated from coronoid process of ulnar
Huméral head: medial epicondyle of humerus.
Insertion- both insert at the middle of the lateral surface of the radius.
Innervation is median nerve(C6 and C7)
Action- pronates the hand and flexes the forearm at the elbow.
Flexor carpii radialis(FCR) is also fusiform (seems all the anterior compartment muscles are fusiform)
It’s located right beside or medial to the pronator teres or PT.
What artery lies lateral the the FCR?
State its origin insertion action innervation
The FCU(flexor carpii ulnaris) has 2 heads.
State its origin insertion action innervation
The radial artery.
Huméral and ulnar heads)
Origin-medial epicondyle of humerus
Insertion: tendon inserts at base of 2nd metacarpal
Innervation: median nerve(C6,7)
Action: flexes and abducts hand. (Abduction is away from the midline and the radius is also away from the midline so FCR will abduct or move away from the midline)
The FCR produces flexion (when acting with the flexor carpi ulnaris) and abduction of the wrist (when acting with the extensors carpi radialis longus and bre-vis). When acting alone, the FCR produces a combination of flexion and abduction simultaneously at the wrist so that the hand moves anterolaterally.
To reach its distal attachment, the FCR tendon passes through a canal in the lateral part of the flexor retinaculum, and through a vertical groove in the trapezium in its own synovial tendinous sheath of the flexor carpi radialis (Fig. 6.57C). The FCR tendon is a good guide to the radial artery, which lies just lateral to it
FCU:
Origin: has huméral and ulnar head. 1. Humeral head – from the medial epicondyle of the humerus
2. Ulnar head – from the olecranon and the posterior border of the ulna via an aponeurosis(using a flat sheet of tendon, instead of a narrow cord-like tendon. It’s not a separate named aponeurosis like the palmar aponeurosis — it’s just described that way to explain the wide, flat origin of the muscle from the ulna.)
Insertion: attaches to the pisiform bone, the hook of hamate bone, and the base of the fifth metacarpal bone.
Action: The flexor carpi ulna-ris muscle flexes and adducts the hand at the wrist with extensor carpii ulnaris. It also stablized wrist during finger extension. It flexes the wrist too
Innervation is ulnar nerve(C7,8) for both heads. Not just the ulnar head.
Or Che flexor carpi ulnaris (FCU)
is the most medial of the super
al flexor muscles. The FCU
simultaneously flexes and adducts the hand at the wrist if acting alone. It flexes the wrist when it acts with the FCR and adducts it when acting with the extensor carpi ulnaris.
The tendon of the FCU is a guide to the ulnar nerve and artery, which are on its lateral side at the wrist
Flexor carpii ulnaris has the ulnar artery and nerve under it
Not everyone has Palmaris longus. It’s absent in one or both sides(usually the left side) in some people.
The tendon of fhis muscles passes over what flexor?
State its origin action insertion innervation
has a short belly and a long, cord-like tendon that passes superficial to the flexor retinaculum and attaches to it and the apex of the palmar aponeurosis.
It is a useful guide to the median nerve in the wrist. The tendon lies deep and slightly
Medial to the wrist until it passes deep and superficial to the flexor retinaculum.
Origin: medial epicondyle of humerus
Insertion: attaches to the Distal half of flexor reti
-naculum and apex of the palmar aponeurosis.
Action: The palmaris longus muscle flexes the hand at the wrist and tenses the palmar aponeurosis. When you grip or hold something, it helps resist shear stress (side-to-side forces), keeping the skin and soft tissue stable.The palmaris longus helps tighten this aponeurosis, improving grip strength and stability.
Innervation:median (C7,8)
What muscle is the only
Muscle that can flex the distal interphalangeal joints of the fingers and clothes the anterior aspect of the ulnar bone?
What’s the function of this muscle ?
Why can fingers be flexes independently at the proximal but not at the distal
Interphalangeal joints?
What flexor is called the long flexor of the thumb?
State the origin insertion action innervation of this muscle.
The FDP flexes the distal phalanges of the medial four fingers after the FDS has flexed their middle phalanges (i.e., it curls the fingers and assists with flexion of the hand, making a fist).
Each tendon is capable of flexing two interphalangeal joints, the metacarpophalangeal joint and the wrist joint.
Each tendon enters the fibrous sheath of its digit, posterior to the FDS ten-dons. Unlike the FDS which can flex all the fingers it attaches to independently, the FDP can flex only the index finger independently; thus the fingers can be independently flexed at the proximal but not the distal interphalangeal joints.
Flexor pollicis longus is called that and is part of the muscle sin the deep layer of the anterior
Compartment of the forearm. It is lateral to the FDP and clothes the anterior aspect of the radius distal to the attachment of the supinator. It’s enclosed in its own sheath. synovial tendinous sheath of the flexor pol-licis longus on the lateral side of the common flexor sheath (Fig. 6.57C).
Origin: The proximal attachment or the origin of the flexor pollicis longus muscle is on the anterior surface of the radius and interosseous membrane.
Insertion: The distal attachment or insertion point of the flexor pollicis longus tendon is the base of the distal phalanx of digit 1 (thumb).
Innervation: anterior interosseous nerve which also comes from the median nerve(C8,T1)
Action: The FPL primarily flexes the distal phalanx of the thumb at the interphalangeal joint and, secondarily, the proximal phalanx and 1st metacarpal at the metacarpopha-angeal and carpometacarpal joints, respectively. The FPL is the only muscle that flexes the interphalangeal joint of the thumb. It also may assist in flexion of the wrist joint.
The flexor pollicis longus muscle flexes digit 1.
Sure! Here’s a simple version:
The flexor pollicis longus (FPL) bends the tip of the thumb (at the interphalangeal joint).
It can also help bend the base of the thumb and even the wrist a little.
It’s the only muscle that bends the thumb’s tip joint.
Yes, you’re absolutely right!
Let’s clear it up in simple terms:
• The thumb has only two bones (phalanges):
• Distal phalanx (tip)
• Proximal phalanx (base of the thumb)
The joints:
1. Interphalangeal (IP) joint – between the distal and proximal phalanx
→ FPL mainly acts here to bend the tip of the thumb.
2. Metacarpophalangeal (MCP) joint – between the proximal phalanx and the 1st metacarpal
→ FPL can help a little to bend here too.
3. Carpometacarpal (CMC) joint – between the 1st metacarpal and the wrist bones
→ FPL may assist in flexing this joint as well.
So yes, they’re different joints, and the FPL acts mainly at the IP joint, but can also assist at the MCP and CMC joints.
Would you like a labeled thumb diagram to help visualize this?
What nerve and artery pass posterior to the pronator quadratus?
Pronator quadratus origin action insertion innervation
The PG is quadrangular shape.its the deepest muscle in the anterior compartment of the forearm.
Note: The pronator quadratus (PQ) covers the lower part or distal fourth of the radius and ulna, and the membrane between them.
It’s the only muscle that connects the ulna on one side and the radius on the other—nothing else. But other muscles cover either only the ulna or the radius
The pronator quadratus muscle lies posterior to the tendons of the deep flexor muscles in the distal one-fourth of the forearm. The fibers of the pronator quadratus muscle run transversely from the ulna to the radius.
the anterior interosseous artery and nerve pass deep (posterior) to the pronator quadratus muscle (i.e., between the pronator quadratus muscle and the interosseous membrane).
Origin: distal quarter of anterior surface of the ulnar
Insertion;distal quarter of anterior surface of radius.
Innervation: Anterior interosseous nerve, from median nerve (C8, T1)
Action: Pronates forearm; deep fibers bind radius and ulna together.
The PQ is the prime mover for pronation. The muscle initiates pronation, and is assisted by the PT (pronator Teres) when more speed and power are needed. The pronator quadratus also helps the interosseous membrane hold the radius and ulna together, particularly when upward thrusts are transmitted through the wrist (e.g., during a fall on the hand).
all the muscles in the posterior compartment are innervated by the radial nerve. They are the extensors and supinators.
State the arrangement of these muscles laterally to medially across the posterior forearm.
These muscles can be organized physiologically into three functional groups:
1. Muscles that extend and abduct or adduct the hand at the wrist joint
2. Muscles that extend the medial four fingers
3. Muscles that extend or abduct the thumb
For each group, state the muscles involved.
The extensor tendons are held
in place in the wrist region by what muscle?
The extensor muscles of the forearm are organized anatomically into superficial and deep layers. State the muscles in the superficial and the ones in the deep.
Which of the 6 muscles in the superficial part are attached proximaly or originate at the common extensor tendon at the lateral epicondyle of the humerus?
The muscles in the posterior compartment from lateral to medial:
Superficial-brachioradialis, ECRL,ECRB,ED,EDM,ECU,Anconeus
These muscles can be organized physiologically into three funct nal groups:
1. Muscles that extend and abduct or adduct the hand at the wrist joint (extensor carpi radialis longus, extensor carpi radialis brevis, and extensor carpi ulnaris).
2. Muscles that extend the medial four fingers (extensor digi-torum, extensor indicis, and extensor digiti minimi).
3. Muscles that extend or abduct the thumb (abductor pollicis longus, extensor pollicis brevis, and extensor pollicis longus).
The extensor tendons are held
in place in the wrist region by the extensor retinaculum, which prevents bowstringing of the tendons when the hand is extended at the wrist joint. As the tendons pass over the dorsum of the wrist, they are provided with synovial tendon sheaths
Superficial: these 4 (extensor carpi radialis brevis, extensor digitorum, extensor digiti minimi, and extensor carpi ulnaris) are attached proximally by a common extensor tendon to the lateral epicondyle.
The other 2 (brachioradialis and extensor carpi radialis longus) ) are originated or have The proximal attachment as the proximal 2/3rds of the supra-epicondylar ridge of the humerus and adjacent lateral intermuscular septum and the lateral supra-epicondylar ridge of the humerus for the extensor carpii radialis longus
Note: The four flat tendons of the extensor digi-torum pass deep to the extensor retinaculum to the medial four fingers (Fig. 6.62). The common tendons of the index and little fingers are joined on their medial sides near the knuckles by the respective tendons of the extensor indicis and extensor digiti minimi (extensors of the index and little fingers, respectively).
What muscle forms the lateral border of the cubital fossa?
Apart from the supinator, which other muscle do not cross in the posterior compartment and that’s why they don’t act on the wrist ?
When a weight is lifted or in the presence of resistance during flexion, what muscle are you using?
How does the brachioradialis act as a shunt muscle resisting sublaxation of the head of the radius
Brachioradialis. This muscles rotates to the anterior aspect of the humerus so its flexes the forearm at the elbow.
. It is especially active during quick movements or in the presence of resistance during flexion of the forearm (e.g., when a weight is lifted), acting as a shunt muscle resisting subluxation of the head of the radius. The brachioradialis and the supinator are the only muscles of the compartment that do not cross and therefore are incapable of acting at the wrist.
Great question! Let’s break it down simply:
Brachioradialis as a shunt muscle:
• A shunt muscle mainly stabilizes a joint by pulling the two bones closer together, rather than moving them a lot.
• The brachioradialis runs from the humerus (above the elbow) to the distal radius (near the wrist).
• Because of its direction, when it contracts, it pulls the radius upward, helping hold the head of the radius in place against the humerus at the elbow joint.
• This helps resist subluxation (partial dislocation) — especially during forceful pulling or weight-bearing actions.
So, even though it flexes the elbow, one of its key roles is stabilizing the elbow joint, like a strap that holds things together.
Would you like a diagram to help visualize this?
Note: As it descends, the brachioradialis overlies the radial nerve and artery where they lie together on the supinator, pronator teres tendon, FDS, and FPL. The distal part of the tendon is covered by the abductors pollicis longus and brevis as they pass to the thumb (Fig. 6.61B).
State the origin, insertion,innervation,action of the brachioradialis
What is the main function of the extensor carpii radialis longus? State its origin insertion and innervation
Do same for the extensor carpii radialis brevis
Why is ECRB shorter than ECRL?
Note: We have one radial nerve in each upper limb — so two radial nerves total in the body (one on the left, one on the right).
But the radial nerve has several branches, including:
• Deep branch → becomes the posterior interosseous nerve (motor)
• Superficial branch (sensory)
So: one main radial nerve per side, but it divides into different branches.
Brachioradialis
Origin:Proximal two thirds of supra-epicondylar ridge of humerus
Insertion:Lateral surface of distal end of radius proximal to styloid process
Innervation: Radial nerve
(C5, C6, C7)
Action: Relatively weak flexion of forearm; maximal when forearm is in mid-pronated position. Does something about subluxation or so. Check one of the cards
Main function of ECRL is when clenching the fist . Most important muscle in clenching the fist. The brachioradialis partly covers it.
Origin of ECRL: Supra condylar ridge of the humerus
Insertion; dorsal aspect of the base of the second metacarpal
Innervation: radial nerve(C6,7)
Action: extends and abducts hand at the wrist joint and active during fist clenching.
ECRB:
Origin- lateral epicondyle of the humerus via the common extensor tendon
Insertion: dorsal part of the base of the 3rd metacarpal
Innervation; deep branch of radial nerve(c7,8) this is the same as the other 3 muscles that originate from the lateral epicondyle. So from this, it means all the 4 muscles that originate from the lateral epicondyle are innervated by the deep radial nerve not the superficial one
Action is the same as the ECRL
The extensor carpi radialis brevis (ECRB), as its name indicates, is a shorter muscle than the ECRL because it arises distally in the limb, yet it attaches adjacent to the ECRL in the hand (but to the base of the 3rd metacarpal rather than the 2nd). As it passes distally, it is covered by the ECRL. The ECRB and ECRL pass under the extensor retinaculum together within the ten-dinous sheath of the extensor carpi radiales (Fig. 6.62).
The two muscles act together to various degrees, usually as synergists to other muscles. When the two muscles act by themselves, they abduct the hand as they extend it. Acting with the extensor carpi ulnaris, they extend the hand (the brevis is more involved in this action); acting with the FCR, they produce pure abduction. Their synergistic action with the extensor carpi ulnaris is important in steadying the wrist during tight flexion of the medial four digits (clenching a fist), a function in which the longus is more active.
What is known as the principal extensor of the medial four digits and occupies much of the posterior surface of the forearm and has four tendons?
Extensor digitorum(remember only the anterior compartment have the flexor digitorum superficialis and profundus. Extensor part is just digitorum)
- The following are observed in individuals with carpal tuanel syndrome
B and C
Reduction in sensation over central part of the palm
There is difficulty in adducting the thumb
There is difficulty in opposing the thumb
Which of the following forms part of the prosimal row of the carpal bones
Capitate
Hamate
Triquetrum
D. A and B
The following are observed in individuals with carpal tunnel syndrome:
Answer: B and C
(That is: Reduction in sensation over central part of the palm and Difficulty in opposing the thumb)
Explanation:
• Carpal tunnel syndrome affects the median nerve.
• It leads to sensory loss in the lateral palm and difficulty opposing the thumb.
• Adduction of the thumb is by the ulnar nerve, so it’s usually not affected.
- Which of the following forms part of the proximal row of the carpal bones?
Answer: Triquetrum
Explanation:
Proximal row of carpal bones (lateral to medial): Scaphoid, Lunate, Triquetrum, Pisiform
Capitate and Hamate are in the distal row.
Here’s a simple summary of the common nerves in the upper limb, their key motor and sensory innervations, and what happens when they are injured — especially in upper limb injuries and brachial plexus injuries:
- Musculocutaneous Nerve
• Root: C5–C7
• Motor: Anterior arm (biceps, brachialis, coracobrachialis)
• Sensory: Lateral forearm
• Injury Sign: Weak elbow flexion and supination
• Cause: Rare, but may occur in upper trunk or lateral cord injury. - Axillary Nerve
• Root: C5–C6
• Motor: Deltoid and teres minor
• Sensory: Skin over the deltoid (“regimental badge area”)
• Injury Sign: Shoulder abduction weakness (especially from 15–90°)
• Cause: Shoulder dislocation, surgical neck fracture of humerus - Radial Nerve
• Root: C5–T1
• Motor: Posterior arm and forearm (triceps, wrist/finger extensors)
• Sensory: Posterior arm, forearm, and back of hand (thumb side)
• Injury Sign: Wrist drop
• Cause: Midshaft humerus fracture, improper crutch use, Saturday night palsy - Median Nerve
• Root: C5–T1
• Motor: Most forearm flexors, thenar muscles, lateral 2 lumbricals
• Sensory: Lateral palm, palmar side of 3½ fingers
• Injury Sign:
• Hand of benediction when trying to make a fist
• Thenar wasting and loss of opposition
• Cause: Supracondylar humerus fracture, carpal tunnel syndrome - Ulnar Nerve
• Root: C8–T1
• Motor: Flexor carpi ulnaris, medial flexor digitorum profundus, most hand muscles
• Sensory: Medial palm and 1½ fingers (both palmar and dorsal)
• Injury Sign: Claw hand, especially 4th and 5th fingers
• Cause: Medial epicondyle fracture, wrist injuries, Guyon’s canal compression
Brachial Plexus Injury Patterns
Erb’s Palsy (Upper trunk: C5–C6)
• Affects: Musculocutaneous, Axillary, Suprascapular nerves
• Arm is: “Waiter’s tip” position (arm adducted, internally rotated, extended, pronated)
• Common Cause: Birth injury or trauma (fall on shoulder)
Klumpke’s Palsy (Lower trunk: C8–T1)
• Affects: Ulnar and part of median nerves
• Results in: “Claw hand” and possible Horner’s syndrome
• Common Cause: Sudden upward arm pull (e.g., pulling infant’s arm during delivery)
Would you like a printable summary chart or flashcards based on this info?
Here’s a simple summary of the common nerves in the upper limb, their key motor and sensory innervations, and what happens when they are injured — especially in upper limb injuries and brachial plexus injuries:
- Musculocutaneous Nerve
• Root: C5–C7
• Motor: Anterior arm (biceps, brachialis, coracobrachialis)
• Sensory: Lateral forearm
• Injury Sign: Weak elbow flexion and supination
• Cause: Rare, but may occur in upper trunk or lateral cord injury. - Axillary Nerve
• Root: C5–C6
• Motor: Deltoid and teres minor
• Sensory: Skin over the deltoid (“regimental badge area”)
• Injury Sign: Shoulder abduction weakness (especially from 15–90°)
• Cause: Shoulder dislocation, surgical neck fracture of humerus - Radial Nerve
• Root: C5–T1
• Motor: Posterior arm and forearm (triceps, wrist/finger extensors)
• Sensory: Posterior arm, forearm, and back of hand (thumb side)
• Injury Sign: Wrist drop
• Cause: Midshaft humerus fracture, improper crutch use, Saturday night palsy - Median Nerve
• Root: C5–T1
• Motor: Most forearm flexors, thenar muscles, lateral 2 lumbricals
• Sensory: Lateral palm, palmar side of 3½ fingers
• Injury Sign:
• Hand of benediction when trying to make a fist
• Thenar wasting and loss of opposition
• Cause: Supracondylar humerus fracture, carpal tunnel syndrome - Ulnar Nerve
• Root: C8–T1
• Motor: Flexor carpi ulnaris, medial flexor digitorum profundus, most hand muscles
• Sensory: Medial palm and 1½ fingers (both palmar and dorsal)
• Injury Sign: Claw hand, especially 4th and 5th fingers
• Cause: Medial epicondyle fracture, wrist injuries, Guyon’s canal compression
Brachial Plexus Injury Patterns
Erb’s Palsy (Upper trunk: C5–C6)
• Affects: Musculocutaneous, Axillary, Suprascapular nerves
• Arm is: “Waiter’s tip” position (arm adducted, internally rotated, extended, pronated)
• Common Cause: Birth injury or trauma (fall on shoulder)
Klumpke’s Palsy (Lower trunk: C8–T1)
• Affects: Ulnar and part of median nerves
• Results in: “Claw hand” and possible Horner’s syndrome
• Common Cause: Sudden upward arm pull (e.g., pulling infant’s arm during delivery)
Would you like a printable summary chart or flashcards based on this info?
What nerve injury is seen in waiters tip?
Erb’s palsy and Klumpke’s palsy are both types of brachial plexus injuries, but they affect different parts of the brachial plexus, leading to distinct symptoms. Erb’s palsy, also known as Erb-Duchenne palsy, affects the upper brachial plexus (C5 and C6 spinal nerves), causing paralysis or weakness in the shoulder, arm, and elbow. Klumpke’s palsy, on the other hand, affects the lower brachial plexus (C8 and T1 spinal nerves), resulting in paralysis or weakness in the hand, wrist, and forearm, potentially leading to a “claw hand” deformity.
In erb Duchene the arm hanging by the side and is rotated medially, the forearm or elbow is extended because the biceps brachii is paralyzed and pronated and the wrist flexed
In erb Duchene palsy, A. all parts of the brachial plexus is injured
B the arm is medially rotated
the elbow is flexed.
A and B.
31. The Lumbricals
3’* and 4*Lumbricals innervated by median nerve.
A and C.
attach to tendon of Flexor DigitorumSuperficialis.
flex the metacarpophalangeal joint.
32. The lateral cutaneous nerve of forearm
A. innervates the skin theloverlies the Brachioradialis muscle.
B, is a branch of the musculocutaneous nerve.
is a direct branch of the lateral cord of the brachial plexus.
B and C.
33. The Median nerve innervates the
elbow joint.
Flexor DigitorumSuperficialis.
skin of forearm.
B and C.
34. The Biceps Brachii muscle
attaches to the infraglenoid tubercle.
is a supinator of the forearm.
C, isparalysed in Erb-Duchenne palsy.
D. B and C.
Here are the answers with explanations for each question:
- In Erb-Duchenne palsy
Correct Answer: B. The arm is medially rotated.
Explanation:
• A. All parts of the brachial plexus are injured → Incorrect. Only the upper trunk (C5–C6) is affected.
• B. The arm is medially rotated → Correct. Due to paralysis of lateral rotators like infraspinatus.
• The elbow is flexed → Incorrect. In Erb’s palsy, the elbow is extended because biceps (C5-C6) is paralyzed.
• A and B → Incorrect because A is wrong.
- The Lumbricals
Correct Answer: flex the metacarpophalangeal joint.
Explanation:
• 3rd and 4th lumbricals innervated by median nerve → Incorrect. They’re innervated by the ulnar nerve.
• A and C → Incorrect, because A is wrong.
• Attach to tendon of Flexor Digitorum Superficialis → Incorrect. They attach to Flexor Digitorum Profundus.
• Flex the metacarpophalangeal joint → Correct. That is one of their key actions.
- You’re right — let’s go over Question 32 again carefully:
- The lateral cutaneous nerve of forearm
Options:
• A. Innervates the skin that overlies the brachioradialis muscle.
• B. Is a branch of the musculocutaneous nerve.
• C. Is a direct branch of the lateral cord of the brachial plexus.
• D. B and C.
Correct Answer: D. B and C
Explanation:
• A. Incorrect. While it may pass near the brachioradialis, the lateral cutaneous nerve of forearm mainly supplies skin on the lateral aspect of the forearm, not specifically the area over the brachioradialis.
• B. Correct. The lateral cutaneous nerve of the forearm is the terminal sensory branch of the musculocutaneous nerve.
• C. Correct. The musculocutaneous nerve is a direct branch of the lateral cord, so by extension, the lateral cutaneous nerve (a branch of it) originates from the lateral cord.
• D. B and C → Correct.
Thank you for catching that! Let me know if you’d like the rest reviewed in a similar way.
- The Median Nerve Innervates the
Correct Answer: B. Flexor Digitorum Superficialis.
Explanation:
• Elbow joint → Incorrect. It’s innervated by nerves like the musculocutaneous, not directly by the median nerve.
• Flexor Digitorum Superficialis → Correct. It’s a forearm flexor innervated by the median nerve.
• Skin of forearm → Incorrect. Mostly covered by medial, lateral, and posterior cutaneous nerves, not the median nerve.
• B and C → Incorrect due to C.
Your Answer: A. Elbow joint
Let’s evaluate each:
• A. Elbow joint → Correct.
The median nerve does give articular branches to the elbow joint during its course in the arm — so this is correct.
• B. Flexor Digitorum Superficialis → Correct.
The median nerve innervates this muscle in the anterior forearm.
• C. Skin of forearm → Incorrect.
The skin of the forearm is innervated by:
• Lateral cutaneous nerve of forearm (from musculocutaneous)
• Medial cutaneous nerve of forearm (from medial cord)
• Posterior cutaneous nerve of forearm (from radial)
Median nerve does not supply the skin of the forearm.
• D. B and C → Incorrect, because C is wrong.
Correct Answer: A is correct, but B is also correct.
So the most accurate answer should actually be “A and B”, but that was not an option.
So if A is the only choice that was clearly correct on its own, and the question only offered A, B, C, and “B and C” — then yes, A is the best available ans
- The Biceps Brachii Muscle
Correct Answer: D. B and C.
Explanation:
• A. Attaches to the infraglenoid tubercle → Incorrect. That’s the origin of the long head of triceps brachii. Biceps originates from supraglenoid tubercle (long head) and coracoid process (short head).
• B. Is a supinator of the forearm → Correct.
• C. Is paralyzed in Erb-Duchenne palsy → Correct, because it is supplied by C5–C6.
• D. B and C → Correct.
Let me know if you’d like these in flashcard format or a printable summary.
- The following nerves arise from the posterior cord of the brachial plexus EXCEPT:
• Correct Answer: B) Suprascapular nerve
Explanation:
• The suprascapular nerve arises from the upper trunk of the brachial plexus, not the posterior cord.
• The posterior cord gives rise to:
• Axillary nerve
• Radial nerve
• Thoracodorsal nerve
• Upper and lower subscapular nerves - The rotator cuff muscles include the following muscles EXCEPT:
• Correct Answer: D) Teres major
Explanation:
• The rotator cuff consists of the following muscles:
• Supraspinatus
• Infraspinatus
• Teres minor
• Subscapularis
• The teres major is a muscle that helps with shoulder movement, but it is not part of the rotator cuff. - Which of the following muscles has its insertion on the lateral lip of the intertubercular sulcus of the humerus?
• Correct Answer: B) Pectoralis major
Explanation:
• The pectoralis major inserts on the lateral lip of the intertubercular sulcus (also known as the bicipital groove) of the humerus.
• Other muscles involved in shoulder movement, such as latissimus dorsi, teres major, and teres minor, insert in different regions of the humerus. - In an 18-degree abduction of the shoulder, the glenohumeral joint accounts for how many degrees of the movement?
• Correct Answer: B) 4
Explanation:
• During shoulder abduction, the glenohumeral joint is responsible for the majority of the movement. However, at around 18 degrees of abduction, the glenohumeral joint contributes about 4 degrees of movement. The rest is contributed by the scapulothoracic joint and the movement of the scapula.
State the cords and the nerves they give rise to
The brachial plexus is organized into roots, trunks, divisions, cords, and branches. The cords are named based on their position relative to the axillary artery. There are three cords: lateral, medial, and posterior, and each cord gives rise to specific nerves. Here’s a breakdown of the cords and the nerves they give rise to:
- Lateral Cord (formed by the anterior divisions of the upper and middle trunks)
• Musculocutaneous nerve: Innervates the coracobrachialis, biceps brachii, and brachialis muscles.
• Lateral root of the median nerve: Contributes to the formation of the median nerve, which innervates most of the anterior forearm muscles and some hand muscles. - Medial Cord (formed by the anterior division of the lower trunk)
• Ulnar nerve: Innervates most of the intrinsic muscles of the hand and some forearm muscles.
• Medial root of the median nerve: Contributes to the formation of the median nerve, which innervates most of the anterior forearm muscles and some hand muscles.
• Medial cutaneous nerve of the arm: Provides sensory innervation to the skin of the medial side of the arm.
• Medial cutaneous nerve of the forearm: Provides sensory innervation to the skin of the medial side of the forearm. - Posterior Cord (formed by the posterior divisions of all three trunks)
• Radial nerve: Innervates the triceps brachii, anconeus, and muscles of the posterior forearm.
• Axillary nerve: Innervates the deltoid and teres minor muscles and provides sensory innervation to the skin over the shoulder.
• Upper subscapular nerve: Innervates the subscapularis muscle.
• Thoracodorsal nerve: Innervates the latissimus dorsi muscle.
• Lower subscapular nerve: Innervates the subscapularis and teres major muscles.
Summary:
• Lateral cord: Musculocutaneous nerve, Lateral root of the median nerve.
• Medial cord: Ulnar nerve, Medial root of the median nerve, Medial cutaneous nerves (arm and forearm).
• Posterior cord: Radial nerve, Axillary nerve, Upper subscapular nerve, Thoracodorsal nerve, Lower subscapular nerve.
These nerves innervate various muscles and provide sensory functions in the upper limb.
All the following muscles are medial rotators of the humerus EXCEPT the infraspinatus.
B latissimus dorsi. . pectoralis major.
D. subscapularis.
48. During mastectomy, the long thoracic nerve must be protected. This nerve supplies the
sin usaunding the niple.
C pectoralis major muscle.
D. pectoralis minor.
In the cell cycle,
AM phase is the most complex and the longest phase.
quiescent cells cannot be induced to re-enter the cycle.
the order of phase is GI, G2, S and M.
there is a Go phase in equilibrium with the Gl phase.
Here are the correct answers with explanations:
- All the following muscles are medial rotators of the humerus EXCEPT —
Correct Answer: A. Infraspinatus
Explanation:
• Infraspinatus is a lateral rotator of the humerus.
• Latissimus dorsi, pectoralis major, and subscapularis are medial rotators.
- During mastectomy, the long thoracic nerve must be protected. This nerve supplies the —
Correct Answer: A. Serratus anterior
Explanation:
• The long thoracic nerve innervates the serratus anterior muscle.
• Damage to this nerve leads to winged scapula.
- In the cell cycle —
Correct Answer: D. There is a Go phase in equilibrium with the G1 phase.
Explanation:
• G0 phase is a resting phase; cells can re-enter the cycle via G1.
• The correct order of phases is G1 → S → G2 → M (not G1 → G2 → S → M).
• M phase is not the longest; interphase (G1, S, G2) is longer.
• Quiescent cells can be induced to re-enter the cycle under certain conditions.
Let me know if you want a summary or flashcards!
Which nerve is likely to be injured if in an attempt to make a fist there is ulnar deviation of the wrist?
Median nerve
Musculocutateous nerve
© Radial nerve
• D. Ulnar nerve
42. Which of the following is a branch of the 2”d part of the asillary artery?
Anterior circumflex humeral artery
Lateral thoracic artery
Posterior circumflex humeral artery
Superior thoracic artery
43. Inferior dislocation of the glenohumeral joint is most likely to injure the
axilary nerve.
median nerve.
musculocutaneous nerve.
radial nerve.
44. The following structures lie anterior to the Nexor retinaculum EXCEPT
Rexor carpi radialis.
palmar cutaneous nerve of median nerve.
tendon of Palmaris longus.
D whar anery.
45. In carpal tunnel syndrome there is reduced sensation in all the following areas of the hand EXCEPT
A. nails of middle finger.
® palmar surface of index finger.
palmar surface of thumb.
thenar eminence.
46. The axillary nerve innervates which of the following muscle?
A) Deltoid
3. Infraspinatus
wawNOP.Swpzarnatus
Methotrexate inhibits which part of the cell cycle?
Correct Answer: G1 phase
Explanation:
• Methotrexate inhibits dihydrofolate reductase, which prevents DNA synthesis by reducing purine and thymidine production.
• This affects the S phase, but the block starts in G1 as cells prepare for DNA synthesis.
So G1 phase is the best choice among the options (S phase would be ideal, but it’s not listed)
Primary function of intermediate filaments:
Correct Answer: C. Provide mechanical stability
Explanation:
• Unlike microfilaments (movement) and microtubules (transport and division), intermediate filaments provide tensile strength and structural support.
↓
Here are the correct answers with explanations:
- Which nerve is likely to be injured if in an attempt to make a fist there is ulnar deviation of the wrist?
Correct Answer: A. Median nerve
Explanation:
• The median nerve supplies the lateral flexors of the wrist (flexor carpi radialis).
• Injury causes weak flexion at the wrist, and the unopposed action of the ulnar nerve (flexor carpi ulnaris) pulls the hand into ulnar deviation when trying to make a fist.
- Which of the following is a branch of the 2nd part of the axillary artery?
Correct Answer: B. Lateral thoracic artery
Explanation:
• The 2nd part of the axillary artery lies posterior to the pectoralis minor and gives 2 branches:
• Thoracoacromial artery
• Lateral thoracic artery
- Inferior dislocation of the glenohumeral joint is most likely to injure the —
Correct Answer: A. Axillary nerve
Explanation:
• The axillary nerve runs below the shoulder joint and wraps around the surgical neck of the humerus, making it vulnerable during inferior dislocation.
- The following structures lie anterior to the flexor retinaculum EXCEPT —
Correct Answer: D. Ulnar artery
Explanation:
• The ulnar artery passes lateral to the pisiform bone, superficial to the flexor retinaculum, but it is still considered to pass through Guyon’s canal, not anterior to the flexor retinaculum directly like palmaris longus or the palmar cutaneous branch of the median nerve.
- In carpal tunnel syndrome there is reduced sensation in all the following areas of the hand EXCEPT —
Correct Answer: D. Thenar eminence
Explanation:
• The thenar eminence receives sensation from the palmar cutaneous branch of the median nerve, which does not pass through the carpal tunnel — so it is spared in carpal tunnel syndrome.
- The axillary nerve innervates which of the following muscle?
Correct Answer: A. Deltoid
Explanation:
• The axillary nerve supplies the deltoid and teres minor muscles.
• Infraspinatus is supplied by the suprascapular nerve.
Let me know if you want a one-liner summary or flashcards for revision!
For the muscles in the arm, they are five. State the them and whether they’re in the anterior or posterior compartment of the arm
What two structures divide the muscles of the arm into anterior and posterior compartments?
What nerve supplies the anterior compartment and which supplies the posterior compartment?
Which is the main flexor of the forearm?why is it the main flexor of the forearm?
Anterior: they’re all flexors
Biceps brachii(most powerful supinator of the forearm)
Brachialis( main flexor of forearm. The biceps only becomes the most powerful flexor when the elbow is flexed close to 90degrees and the forearm is supinated. )
Coracobrachialis
Note: Exactly! You’re spot on. Here’s a clear breakdown to help reinforce that concept:
Brachialis
• Function: Main (primary) flexor of the forearm at all positions of forearm rotation (neutral, pronated, supinated)
• Origin: Distal half of anterior humerus
• Insertion: Coronoid process and tuberosity of ulna
• Why it’s the main flexor:
• It inserts on the ulna, which doesn’t rotate during supination/pronation, so it always contributes to flexion, regardless of forearm position.
Biceps Brachii
• Function:
• Powerful supinator of the forearm
• Strong flexor, but only when the forearm is supinated and elbow is at ~90°
• Insertion: Radial tuberosity (radius moves during pronation/supination)
• Why it’s not always dominant:
• Loses mechanical advantage when the forearm is pronated or when the elbow is fully extended.
Summary:
• Brachialis = consistent, powerful elbow flexor
• Biceps brachii = strongest only in supinated, flexed position
Posterior; triceps brachii with its three heads and the aconeus.
extensor in the arm
The medial and lateral intermuscular septa are strong, fibrous bands of fascia that divide the arm into anterior and posterior compartments
Medial Intermuscular Septum:
Extends from the deep surface of the brachial fascia to the medial supracondylar ridge of the humerus. It separates the anterior compartment (flexors) from the posterior compartment (extensors) of the arm.
Lateral Intermuscular Septum:
Extends from the greater tubercle of the humerus to the lateral epicondyle of the humerus, along the supracondylar ridge
Musculocutaneos nerve supplies the anterior
Radial nerve supplies posterior
Biceps brachii.
State the :
Origin
Insertion
Action
Innervation
What ligament converts the intertubecular sulcus into a canal?
What structure does it hold in the sulcus?
What is the function of the bicipital aponeurosis
Origin:
(More medial)short head- tip of coracoid process of the scapula
(More lateral) Long head: supraglenoid tubercle of the scapula
Insertion: tuberosity of radius and fascia of forearm via bicipital aponeurosis(it’s triangular).
Action: most powerful supinator of the forearm.
Innervation: musculocutaneous nerve c5,6,7
Transverse huméral ligament. It holds the tendon of the long head of the biceps brachii in the groove.
Function:
The proximal part of the aponeurosis can be easily felt where it passes obliquely over the brachial artery and median nerve (Figs. 6.47A and 6.52A). The aponeurosis affords protection for these and other structures in the cubital fossa. It also helps lessen the pressure of the biceps tendon on the radial tuberosity during pronation and supination of the forearm.
Brachialis:
State the origin, insertion,action,innervation
So from lateral to medial(we have the biceps brachii with the short head being more medial than the long head, then the Brachialis which is right under it and then we have the coracobrachialis which is the more medial muscle. It’s superomedial unlike the Brachialis which is posteriolateral when relative to the coracobrachialis)
Origin: distal half of the anterior surface of the humerus
Insertion: ulnar tuberosity(remember that the main flexor inserts here) and coronoid process of the ulnar.
Innervation is musculocutaneous but the lateral part is radial nerve cuz some of the lateral fibers are in the posterior compartment.
Action: flexes forearm in all positions
It lies behind the biceps brachii in the anterior compartment.
Main flexor of the forearm. Check the beginning card on muscles of the arm to explain why. But in summary, it flexes the forearm in all positions and is not affected by whether the forearm is pronated or supinated cuz of its attachment to the ulnar tuberosity (insertion) which isn’t involved in pronation and supination. The biceps brachii however only works when the forearm is in supination cuz it’s attached to the radius tuberosity (insertion)
Coracobrachialis :
Origin
Insertion
Action
Innervation
Origin:tip of coracoid process of scapula. Both the short head of the biceps brachii and the coracobrachialis originate from the coracoid process of the scapula. They share a common tendon of origin before separating into their respective muscle bellies
Insertion: middle third of the medial part of the humerus.
Innervation; musculocutaneous
Action: helps to flex and adduct the arm and resist dislocation of the shoulder.
The musculocutaneous nerve is right beside the coracobrachialis medially and pierces jt
Beside the musculocutaneous nerve is the median nerve
For example, the musculocutaneous nerve pientes to the the dist pato ts ate met in icate he
cobrachialis helps flex and adduct the arm and stabilize the glenohumeral joint. With the deltoid and long head of the triceps, it serves as a shunt muscle, resisting downward dislocation of the head of the humerus, as when carrying a heavy suitcase. The median nerve and/or the brachial artery may run deep to the coracobrachialis and be compressed by it.
The triceps which is the main extensor of the forearm has three heads name them
State their origins and insertions innervation and action
Long lateral and medial
So anteriorly: the long head is more lateral and the lateral is more medial to the long head. The medial head is under the long head.
Posteriorly, the long head is on top of the medial head and the medial head is more medial while the lateral is lateral
Look at the picture to understand
Long head origin: infraglenoid tubercle of scapula(not just infraglenoid tubercle)
Lateralhead:posterior surface of the humerus, superior to the radial groove on the humerus
Medial head: posterior surface of the humerus, inferior to the radial groove
Insertion: all insert at the proximal end of the olecranon on the ulna and the fascia of the forearm
Innervation: radial. C6-8
Note that the radial nerve and profunda brachii artery are between the lateral and medial heads and the axillary innervates the proximal part
Of the long head while the radial
Innervates the distal part of the long head
profunda brachii accompanies the radial nerve along the radial groove as it passes posteriorly around the shaft of the humerus
Action/Chief extensor of forearm; long head resists dislocation of humerus; especially important during adduction
Because its long head crosses the glenohumeral joint, the triceps helps stabilize the adducted glenohumeral joint by serving as a shunt muscle, resisting inferior displacement of the head of the humerus. The long head also aids in extension and adduction of the arm, but it is the least active head.
The medial head is the workhorse of forearm extension, active at all speeds and in the presence or absence of resistance.
The lateral head is the strongest but is it recruited into activity primarily against resistance (Hamill and Knutzen,
2008). Pronation and supination of the forearm do not affect triceps operation. Just proximal to the distal attachment of the triceps is a friction-reducing subtendinous olecranon bursa, between the triceps tendon and the olecranon.
