Lecture 8 - Cubital fossa & forearm Flashcards
What is the forearm?
From elbow to wrist
What bones are found in the forearm?
- radius
- ulna
What joins are found in the forearm?
- elbow joint
- proximal and distal radioulnar joints
Muscles act on elbow, wrist and digital joints
What are the 2 compartments of the forearm?
- Anterior - flexor - 8 muscles
- Posterior - extensor - 12 muscles
What are the blood vessels found in the forearm?
From arch of the aorta: L/R subclavian artery (until 1st rib) –> axillary artery –> brachial artery –> radial & ulnar arteries
What is the venous system of the forearm - from the wrist?
cephalic + basilic veins (superficial) + radial & ulnar veins (deep) –> brachial vein (deep) –> axillary vein –> L/R subclavian vein –> L/R brachiocephalic vein –> L/R brachiocephalic vein –> SVC (superior vena cava)
What are the roots of the brachial plexus?
From the spinal cord in the neck:
- C5
- C6
- C7
- C8
- T1
What is the brachial plexus
The brachial plexus is a network of nerves that comes from the spinal cord in your neck and controls the movement and feeling in your shoulder, arm, and hand.
How is the brachial plexus broken down?
- Roots
- Trunks
- Divisions
- Cords
- Nerves
What are the terminal branches of the nerves in the forearm?
- Median nerve
- Ulnar nerve
- Radial nerve
What are features of the radius?
- on lateral side
- head, neck, radial tuberosity, styloid process, ulnar notch
What are features of the ulna?
- on medial side
- olecranon, coronoid process, trochlear notch, styloid process, head
What is the interosseous membrane?
The interosseous membrane is a fibrous connective tissue structure that connects the radius and ulna (the two bones of the forearm) along their lengths.
What are the elbow joints?
- synovial hinge joint
- flexion & extension of forearm
What are radioulnar joints?
- Pivot joints
- Proximal & distal
- Pronation & supination of forearm
What are digits?
Fingers
What are movement of the forearm?
- Elbow flexion / extension
- Supination / pronation
- Wrist flexion / extension
- Wrist abduction / adduction
How many muscles in the forearm anterior compartment - superficial?
4 muscles - 3 innervated by median nerve
- Pronator teres
- Flexor carpi radialis
- Palmaris longus
- Flexor carpi ulnaris (innervated by ulnar nerve)
What are features of the Pronator teres?
Origin - medial epicondyle of humerus
Insertion - mid-shaft of radius
Action - pronation of forearm, flexes elbow
What are features of flexor carpi radialis?
Origin - medial epicondyle of humerus
Insertion - base of metacarpals 2-3
Action - flexion & abduction at wrist
What are features of the Palmaris longus?
Origin - medial epicondyle of humerus
Insertion - flexor retinaculum and palmar aponeurosis
Action: Flexes wrist
What are features of the flexor carpi ulnaris?
Origin - medial epicondyle of humerus
Insertion - pisiform, hook of hamate and base of metacarpal 5
Action - flexion & adduction of wrist
What is the muscle found in the forearm anterior compartment - intermediate
Flexor digitorum superficialis
Origin - medial epicondyle of humerus, anterior radius & anterior ulna
Insertion - middle phalanges 2-5
Action - flexor of digits 2-5 (primarily at proximal interphalangeal joints
What are the muscles found in the forearm anterior compartment - deep?
(innervation - median nerve)
- flexor pollicis longus (*pollux = thumb)
- pronator quandratus
(innervation - median/ulnar nerve)
- flexor digitorum profundus
What are features of Flexor pollicis longus?
Origin - anterior surface of radius and interosseous membrane
Insertion - base of distal phalanx of thumb
Action - flexion of thumb
What are features of pronator quadratus?
Origin - distal anterior surface of ulna
Insertion - distal anterior surface of radius
Action - pronates the forearm
What are features of the flexor digitorum profundus?
Origin - anterior surface of ulna and interosseous membrane
Insertion - distal phalanges 2-5
Action - flex hand and both interphalangeal joints
What are the muscles of the forearm posterior compartment - mobile wad (superficial)?
(innervated by radial nerve)
(blood supply - ulnar artery)
- brachioradialis
- extensor carpi radialis longus
- extensor carpi radialis brevis
What are features of the brachioradialis?
Origin - lateral supracondylar ridge of humerus
Insertion - distal ends of radius
Action - flexion of elbow, supination & pronation to 90 degrees
What are features of the extensor carpi radialis longus?
Origin - lateral supracondylar ridge of humerus
Insertion - base of metacarpal 2
Action - extension and abduction of wrist, weak elbow flexor
What are features of the extensor carpi radialis brevis?
Origin - lateral epicondyle of humerus
Insertion - base of metacarpal 3
Action - extension and abduction of wrist, weak elbow flexor
What are parts of the forearm posterior compartment - superficial?
(blood supply - ulnar artery)
(innervated - radial nerve)
- Extensor digitorum
- Extensor digit minimi
- Extensor expansion
What are features of extensor digitorum?
Origin - lateral epicondyle of humerus
Insertion - extensor expansion digits 2-5
Action - extension of wrist and digits 2-5
What are features of extensor digit minimi?
Origin - lateral epicondyle of humerus
Insertion - extensor expansion digit 5
Action - extension of wrist and digit 5
What is Extensor expansion?
Flattened tendons (aponeurosis) of extensor muscles of phalanges. Also known as extensor hood, dorsal expansion, dorsal hood, dorsal aponeurosis
What are muscles in the forearm posterior compartment - innervated by radial nerve?
- Anconeus
- Extensor carpi ulnaris
What are features of anconeus?
Origin - lateral epicondyle of humerus
Insertion - olecranon and posterior surface of the ulna
Action - prevents the elbow joint capsule being pinched in the olecranon fossa during extension of the elbow
Blood supply - deep brachial artery
What are features of the extensor carpi ulnaris?
Origin - lateral epicondyle of humerus
Insertion - base of metacarpal 5
Action - extension and adduction of wrist
Blood supply - ulnar artery
What are muscles in the forearm posterior compartment - deep (index finger - digit 2)?
(blood supply - ulnar artery)
(innervation - radial nerve)
- supinator
- extensor indicis
What are features of the supinator?
Origin - lateral epicondyle of humerus
Insertion - radius
Action - supinates forearm
What are features of the extensor indicis?
Origin - posterior surface of ulna and interosseous membrane
Insertion - extensor expansion of digit 2
Action - extension of wrist & digit 2
What are muscles found in the forearm posterior compartment - deep (thumb - digit 1)?
(Blood supply - ulnar nerve)
(Innervation - radial nerve)
- Abductor pollicis longus
- Extensor pollicis brevis
- Extensor pollicis longus
What are features of abductor pollicis longus?
Origin - posterior ulna/radius and interosseous membrane
Insertion - base of metacarpal 1
Action - abduction of digit 1
What are features of extensor pollicis brevis?
Origin - posterior radius and interosseous membrane
Insertion - base of proximal phalanx digit 1
Action - extension of digit 1 gat metacarpophalangeal joint
What are features of extensor pollicis longus?
Origin - posterior ulna and interosseous membrane
Insertion - base of distal phalanx digit 1
Action - extension of digit 1 at MCP/interphalangeal joint
What is the cubital fossa?
- Triangular space/depression on anterior elbow
- transition between arm & forearm
What are the boundaries of the cubital fossa?
- 3 borders
- floor
- roof
What are the structures of the cubital fossa?
- 5 inside the space
- 3 on the roof
What are the borders?
- Lateral border - brachioradialis muscle
- Medial border - pronator teres muscle
- Superior border - epicondylar line
What is the roof of the cubital fossa?
Roof - bicipital aponeruosis (from biceps brachii muscle) fascia, subcutaneous fat & skin
What is the floor of the cubital fossa?
Brachialis muscle proximally and supinator muscle, distally
What makes up the lateral part of cubital fossa?
Radial nerve - divides into superficial and deep branches
Bicep tendon - passes centrally
Brachial artery - bifurcates into the radial and ulnar arteries
What makes up the medial part of the cubital fossa?
Brachial vein - union of radial and ulnar veins
Median nerve - exists between the 2 heads of the pronator teres muscle
Describe the order from lateral & medial
- Radial nerve
- Bicep tendon
- Brachial artery
- Brachial vein
- Median nerve
What is found in the roof of the cubital fossa?
Between bicipital aponeurosis and fascia
Several superficial veins
- easily accessible for venipuncture (taking blood)
- Median cubital vein - connects basilic & cephalic veins
