8 - Anatomy of the Forearm Flashcards
Where is the forearm?
Between the elbow and the wrist
How can you describe which side of the forearm you are looking at?
Using the terms radial and ulnar sides (not proximal and lateral as these are easily confused with movement).
Which end of the radius articulates with the elbow?
The proximal end
Which end of the radius articulates with the wrist?
The distal end
How many radio-ulnar joints are there?
Two - a distal and a proximal one
What does the radius articulate with proxmially?
The lateral condyle of the humerus (capitulum)
What does the radius articulate with distally?
The scaphoid and lunate bones
Where is the head of the ulna?
At the distal (lower) end
What attaches to the ulna tuberosity?
The brachial muscle
What do the coronoid process and olecranon process articulate with?
The medial humeral condyle (trochlear)
Does the distal ulna articulate with the carpal bones?
No - it articulates with a piece of fibrocartilage.
What is the fibrous sheet between the radius and ulna called?
Interosseus membrane
Which spaces in the forearm allow vessels to pass through?
Free upper margin
Circular aperture
What is the function of the interosseous membrane?
Provides attachment for muscles
Aids transmission of forces from radius to ulna
Useful for rotation - allows the radius to rotate around the ulna
How many compartments of the forearm are there?
What are they?
Are they divided equally?
2
Anterior (Flexor) and Posterior (Extensor)
Not divided equally - some of the posterior compartment sits around the radius and extends into the anterior part of the forearm.
What structures form the division between the anterior and posterior compartments of the forearm?
Radius & ulna
Interosseous membrane
Lateral intermuscular septum
Deep fascia - posterior border of ulna
What is the function of the muscles in the anterior compartment of the forearm?
Wrist & digit flexors
Forearm pronators
What is the function of the muscles in the posterior compartment of the forearm?
Wrist and digit extensors
Forearm supinators
Which muscle in the forearm is found in the posterior compartment anatomically but in the anterolateral aspect of the forearm clinically?
Brachioradialis
How many layers does the anterior compartment of the forearm have? What are they?
Three
Superficial, intermediate & deep
How many muscles are found in the SUPERFICIAL LAYER of the anterior compartment of the forearm?
What are they?
4
Flexor Carpi Ulnaris
Palmeris Longus
Flexor Carpi Radialis
Pronator Teres
What is the motor innervation to the superficial anterior compartment?
All motor function supplied by Median nerve (C6 & C7)
EXCEPT - Flexor Carpi Ulnaris - supplied by Ulnar nerve (C7, C8 & T1)
What do all the muscles in the superficial anterior compartment cross and where do they all attach?
All cross the elbow (this means they can flex the elbow).
Attach to the medial aspect of the distal humerus (the medial epicondyle).
What is the medial epicondyle known as? Why?
The common flexor origin
Because all the muscles which attach here can flex the elbow.
What is the lateral epicondyle known as? Why?
The common extensor origin
Because all the muscles which attach here can extend the elbow.
What percentage of the population do not have a palmaris longus muscle?
10%
What is the latin term for wrist?
Carpi
What is the function of flexor carpi ulnaris?
Flexes the ulnar side of the wrist & the forearm at the elbow joint.
What is the function of palmaris longs?
Flexes the wrist
What is the function of flexor carpi radialis?
Attaches to the radial side of the wrist and flexes the wrist.
What is the function of Pronator Teres?
Pronation of the forearm - turns it from anatomical position to pronation.
Which muscle is found in the intermediate layer of the anterior compartment of the forearm?
Flexor Digitorum Superficialis
How many heads does Flexor Digitorum Superficialis have?
What are they?
Two
Humero-ulnar head
&
Radial head
What is there function of Flexor Digitorum Superficialis?
Flexes the digits
What does Flexor Digitorum Superficialis arise from and attach to?
Arises from humerus & ulna
Attaches to - middle phalanges of the digits.
What is the motor nerve supply to Flexor Digitorum Superficialis?
C8 & T1
What are the muscles of the deep anterior compartment of the forearm?
Flexor Digitorum Profundus
Flexor Pollicis Longus
Pronator Quadratus
What is the function of flexor digitorum profundus?
Flexes the distal phalanges (fingertips)
What is the function of flexor pollicis longus?
Flexes the thumb
What is the function of pronator quadratus?
Assists the pronator teres to pronate the forearm.
What is the motor nerve supply to the deep anterior compartment of the forearm?
Median (C7 & C8). except for ulnar half of FDP (Flexor Digitorum Profundus) - which is the ulnar nerve (C8 & T1).
Which nerve roots make up the median nerve?
C7 & C8
Which nerve roots make up the ulnar nerve?
C8 & T1
The whole anterior compartment is innervated by _________ nerve except for the muscles (?)_________. which are innervated by ___________ nerve.
Whole anterior compartment innervated by MEDIAN NERVE
except
FLEXOR CARPI ULNARIS & ulnar half of FLEXOR DIGITORUM PROFUNDUS
which are innervated by
ULNAR NERVE.
How many layers are found in the posterior compartment of the forearm?
Two - superficial and deep
How many muscles are found in the superficial layer of the posterior compartment of the forearm?
What are they called?
7
Brachioradialis
Extensor Carpi Radialis Longus
Extensor Carpi Radialis Brevis
Extensor Digitorum
Extensor Digiti Minimi
Eyesore Carpi Ulna’s
Anconeus
What is the motor nerve supply to the muscles in the superficial posterior compartment of the forearm?
Radial nerve (C5, 6, 7 & 8)
+
Deep and posterior interosseous branches
What compartment does brachioradialis appear to be in visually, and which compartment is it actually in anatomically?
Appears to be anterior but is anatomically in the posterior compartment.
What is the function of brachioradialis?
Helps to flex the elbow.
What is the common extensor origin of the muscles in the superficial posterior compartment of the forearm?
Lateral epicondyle
What happens to the radial nerve in the forearm?
After crossing the humerus it bifurcates into deep and superficial branches
How many muscles are found in the deep layer of the posterior compartment of the forearm?
What are they called?
5
Supinator
Abductor Pollicis Longus
Extensor Pollicis Longus
Extensor Pollicis Brevis
Extensor Indicis
Which is the only muscle in the deep layer of the posterior compartment of the forearm to cross the elbow?
Supinator
What do the pollicis muscles form between them?
The anatomical snuffbox
Which muscle in the deep posterior compartment of the forearm is closest to the radial shaft proximally that is responsible for turning the forearm from pronation to supination?
Supinator
What is the function of the supinator muscle?
Turns the forearm from pronation to supination.
How many pronators win the arm are there and how many supinators?
Two pronators
One supinator
What is the motor nerve supply to the deep layer of the posterior compartment of the forearm?
Posterior interosseous nerve (C6-8)
Which nerve roots form the posterior interosseous nerve?
C6-8
What type of joint is the elbow?
Synovial
x2 hinge joints
x1 pivot joint
How many articulations does the elbow comprise of?
What are they formed by?
3
Trochlea of humerus + trochlear notch of ulna
Capitulum of humerus + radial head
Radial + ulna joint
What type of joint is the trochlea of humerus with the trochlear notch of the ulna?
Hinge
What type of joint is the capitulum of the humerus with the radial head?
Hinge
What type of joint is the proximal radio-ulnar joint?
Pivot
Which joint is the main joint of the elbow?
Humerus and ulna joint
What gives stability to the elbow joint?
Shape of articular surfaces
Strong, thick capsule
Medial and lateral collateral ligaments
Which ligament goes from the radial head of the ulna, around the elbow joint, to join the posterior side of the ulna?
Anular ligament
What angle is the elbow hinge joint at when it is in
(a) Full Extension?
(b) Full Flexion?
Full Extension = 0 °
Full Flexion = 140 °
Why do we have a carrying angle of the elbow - what is this angle?
The axis of the hinge is not aligned straight with the humerus - is at approx 170 ° - greater in F than M.
Which joints of the forearm allow proximal and distal rotation? What are these movements known as?
Proximal and distal radio-ulnar joints
Pronation and supination
Which ligament supports the proximal radio-ulnar joint?
Anular ligament
How big is the arc through which the forearm can move through pronation and supination?
140 degrees
Which bones join to form the wrist?
The radius articulates with two carpal bones (scaphoid and lunate)
Which bone of the forearm does not form part of the wrist joint?
The ulna
What type of joint is the wrist?
Synovial condyloid joint
What is found between the ulna and the hand?
Which hand bones does it articulate with?
Fibrocartilaginous disc
Articulates with the triquetum and lunate bones
How much movement can the wrist do in abduction and adduction?
Abduction = 15 ° approx
Adduction = 45 ° approx
What is the term for abduction of the wrist?
Radial deviation
What is the term for adduction of the wrist?
Ulnar deviation
Which muscles are responsible for radial deviation of the wrist?
Flexor carpi radialis
Extensor carpi radialis longus
Extensor carpi radialis brevis
Which muscles are responsible for ulnar deviation of the wrist?
Flexor carpi ulnaris
Extensor carpi ulnaris
What degree of movement is permitted by the flexion and extension arcs of the wrist?
Flexion arc = approx 80 °
Extension arc = approx 60 °
Which muscles are responsible for flexion of the wrist?
Flexor carpi radialis
Flexor carpi ulnaris
Palmaris Longus
Which muscles are responsible for extension of the wrist?
Extensor carpi radialis longus
Extensor carpi radialis brevis
Extensor carpi ulnaris
Which artery supplies the forearm?
The brachial artery
In the cubital fossa - where is the brachial artery found?
Medial to the biceps tendon
What dos the brachial artery divide into?
Radial
Ulnar arteries
Where is the radial artery found in the forearm?
In the anterior compartment
Under brachioradialis & adjacent to the superficial branch of the radial nerve
What does the radial artery travel with in the forearm?
Radial nerve
What does the radial artery pass through to enter the back of the hand?
Anatomical snuff box
Which artery is the main supply to the deep palmar arch in the hand?
The radial artery
Where is the ulnar artery found?
Under Flexor Carpi Ulnaris, with the ulnar nerve on its medial side
What travels with the ulnar artery?
The ulnar nerve
What does the ulnar artery supply in the hand?
Is the major blood supply of medial three and 1/2 digits.
Is the main supply of the superficial palmar arch
Which artery is the main supply to the superficial palmar arch?
Ulnar artery
What branch does off the ulnar artery above the interosseous membrane?
The common interosseous artery
What does the common interosseous artery bifurcate into?
Where do they go?
The anterior and posterior interosseous arteries
Anterior interosseous = anterior compartment of the forearm
Posterior interosseous = posterior compartment of the forearm
What provides superficial venous drainage to the forearm?
Dorsal venous arch (from the hand)
Cephalic and Basilic veins
What provides deep venous drainage to the forearm?
Deep veins accompany every deep artery (same names) - these drain into brachial veins which are associated with the brachial artery in the cubital fossa.
Which veins are found in the cubital fossa?
Cephalic vein
Basilic vein
Median cubital vein
Which are the main nerves that supply the forearm?
Median
Radial
Ulnar
Superficial cutaneous
Which compartment is the median nerve found in the forearm?
Anterior compartment
What are the branches of the median nerve?
Anterior interosseous
Palmar branch
What innervation does the anterior interosseous supply?
Muscular innervation to entire anterior compartment - EXCEPT Flexor Carpi Ulnaris and the ulnar part of Flexor Digitorum Profundus
Where does the palmar branch of the media nerve arise? What does it supply?
Arises proximal to flexor retinaculum
Supplies skin over the base and central palm of the hand.
Where is the radial nerve found?
The posterior compartment (in the spiral groove).
What does the radial nerve divide into?
The deep posterior interosseous and the superficial
What does the deep posterior interosseous innervate?
Muscles in the extensor compartment
What does the superficial radial nerve innervate?
Skin over the 1st dorsal web space
What does the superficial radial nerve travel with?
Radial artery - along the forearm on the radial border
Where is the ulnar nerve found?
In the anterior compartment of the forearm
What are the branches of the ulnar nerve?
Muscular and cutaneous
What does the muscular branch of the ulnar nerve innervate?
Flexor carpi ulnaris
Medial half Flexor Digitorum Profundus
Deep Palmar muscles
What does the cutaneous branch of the ulnar never supply?
2 branches -
Palmar = supplies the skin on medial side of the palm
Dorsal = supplies the sin on the back of the posteriomedial hand and the medial one and one 1/2 digits
The musculocutaneous nerve supplies the anterior arm muscle and then becomes what in the forearm?
The lateral cutaneous nerve of the forearm
Where does the medial cutaneous nerve of the forearm arise from?
The medial cord of the brachial plexus
What is the name for the triangular area of transition anterior to the elbow joint which is formed by a depression between two forearm muscles?
The cubital fossa
What are the lateral, medial, base and floor boundaries of the cubital fossa?
Lateral = brachioradialis
Medial = pronator teres
Base - Imaginary line between humeral epicondyles
Floor = brachialis muscle
What is found in the cubital fossa?
TAN
Tendon (biceps)
Artery (brachial)
Nerve (median)
From lateral to medial (L-M)
What is found superficial to the cubital fossa?
Lateral cutaneous nerve of the forearm
Medial cutaneous nerve of the forearm
Median cubital vein
Cephalic vein
Basilic vein
