Anatomy - Lecture 18: Forearm joints and muscles

What are the boundaries of the cubital fossa?

• lateral

  • lateral epicondyle

  • brachioradialis

• medial

  • medial epicondyle

  • pronator teres

What are the components of the cubital fossa roof?

• skin, superficial fascia

• bicipital aponeurosis

• median cubital vein

• medial cutaneous nerve of forearm

• lateral cutaneous nerve of forearm

Which nerve is preferred in blood donation, withdrawing blood for investigations and intravenous infusions?

venipuncture to the median cubital vein

What is the role of the bicipital aponeurosis?

• covers and protects brachial artery

• separates medial cubital vein (superficial) from deeper brachial artery

• prevents artery from being injured during withdrawing blood from median cubital vein

What makes the floor of the cubital fossa?

• brachialis

• supinator

What are the contents of the cubital fossa?

• TAN

  • tendon of biceps

  • artery

    • brachial artery and its branches:

      • radial artery

      • ulnar artery

  • nerve → median nerve

Where can the brachial artery be palpated?

medial to tendon of biceps, useful for measuring blood pressure

What are the properties of the elbow joint?

• synovial uniaxial joint with a compound hinge

  • compound hinge:

    • humero-ulnar

    • humero-radial

• continuous with proximal radioulnar joint cavity

• articulating bones:

  • humerus → trochlea & capitulum

  • ulna → trochlear notch

  • radius → head

What are the ligaments of the elbow joint?

• medial (ulnar) collateral

• lateral (radial) collateral

Which muscles facilitate flexion of the elbow?

• BBB

  • brachialis → prime flexor

  • biceps brachii

  • brachioradialis → in midprone position

Which muscles facilitate extension of the elbow?

• triceps

• gravity

• helped by extensors of the forearm. their common origin is the lateral epicondyle of humerus

How is the elbow joint normally aligned?

• flexion

  • medial and lateral epicondyles and olecranon form the sides if an equilateral triangle

• extension

  • medial and lateral epicondyles and olecranon lie in a straight line

What are the radioulnar joints?

• proximal

  • synovial

  • uniaxial

  • pivot

• middle

  • fibrous syndesmosis: interosseous membrane between radius and ulna

• distal

  • synovial

  • uniaxial

  • pivot

What are the stabilizing factors of the radioulnar joints?

• bony factors

• ligaments

  • proximal → annular ligament around neck of radius

  • middle → interosseous membrane

  • distal → articular disc (fibrocartilage)

Which muscles produce pronation of the radioulnar joints?

• pronator quadratus

• pronator teres

supplied by median nerve

Which muscles produce supination of the radioulnar joints?

• supinator

• biceps brachii

more powerful because of biceps brachii

What is the subluxation of the radioulnar joints?

head of radius slides out of the annular ligament on being pulled downwards

more common in children because head of radius is small and annular ligament is cylindrical in a child compared to being cone-shaped in adults

What are the muscles in the anterior (flexor) compartment of the forearm?

• Superficial → common flexor origin → medial epicondyle of humerus

  • pronator teres

  • flexor carpi radialis

  • palmaris longus

  • flexor carpi ulnaris

  • flexor digitorum superficialis

• Deep

  • flexor pollicis longus

  • flexor digitorum profundus

  • pronator quadratus

nerve supply from the median nerve except:

• medial half of flexor digitorum profundus

• flexor carpi ulnaris

blood supply from the radial and ulnar arteries

What are the muscles in the posterior (extensor) compartment of the forearm?

• Superficial

  • brachioradialis

  • extensor carpi radialis longus and brevis

  • extensor digitorum'

  • extensor digit minimi

  • extensor carpi ulnaris

  • anconeus

• Deep

  • supinator

  • abductor pollicis longus

  • extensor pollicis longus and brevis

  • extensor indicis

nerve supply by radial nerve

blood supply by radial artery and ulnar artery (anterior and posterior interosseous branches)

Where can the pulsations of the radial and ulnar artery be felt?

• radial → lateral to tendon of flexor carpi radialis

• ulnar → lateral to tendon of flexor carpi ulnaris