A3 - Forearm Flashcards
What are the bones of the forearm?
the radius and ulna
What are the 3 articulations of the radius and ulna?
- proximally with the humerus at the elbow joint
- proximally with each other at the superior (proximal) radioulnar joint
- distally with each other at the inferior (distal) radioulnar joint
What does the radius articulate with distally?
the carpal bones to form the radiocarpal joint (wrist)
What is the interosseous membrane and what does it connect?
it is a thin, fibrous sheet that connects the medial border of the radius and the lateral border of the ulna
Label the components of the forearm
Label the components of the radius and the ulna
What are the 2 movements possible at the superior/inferior radioulnar joints?
supination and pronation
What is supination?
the action of turning the palm up to face you
(the palm and the pads of the fingers are visible)
What is the main muscle involved in supination of the forearm?
Supinator - this is a posterior forearm muscle
What is the second muscle involved in supination of the forearm?
Biceps brachii - an anterior arm muscle
using biceps increases the power of supination when the elbow is flexed
What is pronation?
the act of turning your palm down to face the ground
e.g. when typing at a keyboard
What are the 2 anterior forearm muscles involved in pronation?
- pronator teres
- pronator quadratus
Label the muscles involved in supination and pronation
Where is supinator located?
What is its origin?
It is in the posterior compartment of the forearm
It originates from:
- supinator crest of the ulna
- lateral epicondyle of the humerus
- ligaments associated with the elbow joint
What is the insertion of supinator?
it attaches to the shaft of the radius superior to the oblique line
Where are pronator teres and pronator quadratus located?
in the anterior compartment of the forearm
What is the origin and insertion of the pronator teres?
it runs from the medial epicondyle of the humerus to midway along the lateral surface of the radius
What is the insertion and the origin of the pronator quadratus?
It extends between the anterior surfaces of the distal ends of the radius and ulna
Label the 3 muscles involved in supination and pronation
Why is the cubital (antecubital) fossa clinically important?
- it contains several important neurovascular structures
- superficial veins overlying the cubital fossa are routinely used for venepuncture and intravenous cannulation
What are the 3 main contents of the cubital fossa?
- tendon of biceps brachii muscle
- brachial artery
- median nerve
What is the superior border of the cubital fossa?
a hypothetical line between the medial and lateral epicondyles of the humerus
What is the lateral border of the cubital fossa?
medial border of brachioradialis muscle
What is the medial border of the cubital fossa formed from?
lateral border of the pronator teres muscle
What forms the floor of the cubital fossa?
brachialis muscle
Label the borders of the cubital fossa
Label the muscles, arteries and nerves surrounding the antecubital fossa
At the level of the cubital fossa, which artery bifurcates?
What does it split into?
The brachial artery bifurcates into the radial and ulnar arteries
Label the vessels and nerves
Why must care be taken when inserting a needle into one of the superficial veins of the cubital fossa?
the brachial artery and the median nerve lie deeper than the superficial veins
How do the superficial veins drain the upper limb?
the basilic vein joins with the brachial vein to form the axillary vein
the cephalic vein drains into the axillary vein
as it passes under the clavicle, it becomes the subclavian vein
How can the muscles of the anterior compartment of the forearm be divided into 3 groups?
- superficial
- intermediate
- deep
What are the superficial muscles of the anterior compartment of the forearm?
- flexor carpi radialis
- flexor carpi ulnaris
- palmaris longus
- pronator teres
What are the deep muscles of the anterior compartment of the forearm?
- flexor digitorum profundus
- flexor pollicis longus
- pronator quadratus
What are the intermediate muscles of the anterior compartment of the forearm?
flexor digitorum superficialis
What is the alternative name for the anterior compartment of the forearm?
flexor compartment
all the muscles flex the wrist, fingers and thumb