Anatomy 28 Flashcards
What are the radius and ulna bones connected by?
Interosseous membrane
What does the trochlea notch of the ulna articulate with?
The trochlea of the humerus
What does the radial head articulate with?
Capitellum of the humerus
What movements occur at the elbow joint?
Flexion and extension
Where do the radius and ulna articulate with each other at?
Proximal and distal radioulnar joints
What movement do the radioulnar joints allow?
Pronation and supination of the forearm and hand
What types of muscles does the anterior compartment of the forearm contain?
2 muscles that act as pronators
What forms the radiocarpal joint?
The radius articulates with two of the small bones of the wrist, or carpus
What movements occur at the wrist joint?
Flexion, extension, abduction and adduction
What muscles help achieve movements at the wrist joint?
Muscles in the anterior and posterior forearm
What is the carpus comprised of?
8 small bones that articulate with each other at small
joints
What are the bones in the carpus arranged in?
2 rows of 4 bones, one proximal, one distal
What forms the radiocarpal joint?
The distal radius articulates with two of the bones in the proximal row – the scaphoid and lunate
What bones does the proximal row of the carpal comprise of?
From lateral to medial:
the scaphoid, lunate, triquetral and the pisiform
What is the pisiform?
Not a true carpal bone, but rather is a small bone that develops in the tendon of flexor carpi ulnaris
What bones does the distal row of the carpal comprise of?
Form lateral to medial:
the trapezium (base of the thumb), trapezoid, capitate (located centrally and is the largest carpal bone) and the hamate.
What is the hamate?
Bears a bony process anteriorly (the hook), which is obvious on the bone and is palpable on examination
What is the most commonly fractured carpal bone?
Scaphoid – usually by a fall on to an outstretched hand.
A scaphoid fracture has potentially serious consequences
Where do the metacarpals lie?
Distal to the carpus
What are the bones of the digit?
Phalanges; there are three phalanges in each finger and two phalanges in the thumb.
What is the cubital fossa and what is it bounded by?
Triangular-shaped region anterior to the elbow, bounded by brachioradialis laterally and pronator teres medially
What is the pronator teres?
Anterior forearm muscle which we’ll look at in the next section
What is the superior border of the cubital fossa formed by?
A line drawn between the medial and lateral epicondyles of the humerus
What 4 important structures are found in the cubital fossa?
- Biceps tendon
- Median nerve
- Brachial artery which bifurcates into the radial and ulnar arteries
- Superficial veins lie in the subcutaneous tissue over the cubital fossa and are key sites for IV access
What are some features of the anterior compartment of the arm?
- They are arranged in three layers: superficial, middle and deep
- Most of them act as flexors of the wrist, fingers or thumb
- Most of them are innervated by the median nerve
What are the 4 muscles in the superficial layer of the anterior compartment of the arm?
From lateral to medial these are:
* Pronator teres
* Flexor carpi radialis
* Palmaris longus
* Flexor carpi ulnaris
What are the superficial muscles on the anterior compartment of the arms attached to?
Proximally to the medial epicondyle of the humerus.
For this reason, this region of the humerus is also commonly referred to as the ‘common flexor origin’.
What is the pronator teres?
Pronator (of the proximal radioulnar joint), rather than a flexor.
What is the flexor carpi radialis (FCR)?
Flexes and abducts the wrist.
It inserts onto the radial ‘side’ of the wrist, hence “flexor carpi radialis”.
What is the palmaris longus?
Has a small muscle belly but a long, thin, easily recognised tendon when present
Its tendon inserts into the fascia of the palm of the hand.
What is the flexor carpi ulnaris (FCU)?
Flexes and adducts the wrist. It inserts onto the ulnar
‘side’ of the wrist, hence “flexor carpi ulnaris”.
What nerve innervates the flexor capi ulnaris (FCU)?
Ulnar nerve
What does the flexor digitorum superficialis (FDS) give rise to?
4 tendons
What nerve innervates the flexor digitorum superficialis (FDS)?
Median nerve
What are the 3 muscles found in the anterior compartment of the arm?
- Flexor digitorum profundus
- Flexor pollicis longus
- Pronator quadratus
What is the Flexor digitorum profundus (FDP)?
Is a flexor of the digits, and lies deep to flexor digitorum superficialis
What does the Flexor digitorum profundus (FDP) give rise to?
4 tendons, which travel into the hand and to the fingers (digits 2-5)
What is the innervation of the Flexor digitorum profundus (FDP)?
- The lateral half of the muscle, which gives rise to the tendons that travel to the index and middle fingers, is innervated by the median nerve.
- The medial half of the muscle, which gives rise to the tendons that travel to the ring and little fingers, is innervated by the ulnar nerve.
What is the Flexor pollicis longus (FPL)?
Flexes the thumb (pollex = thumb). ‘Longus’ distinguishes it from another muscle, flexor pollcis brevis, which is much smaller and lies within the hand
What is the pronator quadratus?
Is the deepest forearm muscle (it is considered a fourth layer by some).
It is square-shaped (‘quadratus’) and lies over the distal ends of the radius and ulnar.
It pronates the distal radioulnar joint.
What is the carpal tunnel?
Narrow passageway at the wrist
- Its floor and sides are formed by the carpal bones.
- A fibrous band called the flexor retinaculum completes the tunnel, forming the roof.
It is attached to the scaphoid and trapezium laterally and to the hook of the hamate and pisiform medially
What tendons travel through the carpal tunnel?
- flexor digitorum superficialis
(4 tendons, to digits 2-5) - flexor digitorum profundus (4 tendons, to digits 2-5)
- flexor pollicis longus
(1 tendon, to the thumb [1st digit])
What nerve travels through the carpal tunnel?
Median nerve
What is carpal tunnel syndrome?
- impaired or altered sensation over the skin of the hand supplied by the median nerve - the patient may experience tingling, numbness or pain in the hand
- weakness of the hand muscles supplied by the median nerve – particularly the small muscles of the thumb.
What happens if carpal tunnel syndrome (CTS) is left untreated?
The small muscles of the thumb may atrophy and weakness may be permanent, which has serious consequences for a patient.
What does the brachial artery bifurcate in the cubital fossa into?
2 terminal branches
– the radial artery and the ulnar artery
Where does the radial artery travel along?
Travels along the lateral aspect of the forearm and it can usually be easily palpated at the wrist
Where does the ulnar artery travel along?
Travels along the medial aspect of the forearm
– it can also be palpated at the wrist, but it is often not as easy to palpate as the radial artery, as it may be partly covered by the tendon of flexor carpi ulnaris
Where do the radial and ulnar arteries anastomose?
Anastomose in the palm of the hand to form palmar arches
Where does all venous blood drain in the forearm?
Drains to the axillary vein
What are the 2 important superficial veins of the upper limb?
Cephalic vein (laterally) and the basilic vein (medially)
What are the cephalic and basilic vein connected to each other by?
Median cubital vein
What does the basilic vein receive deep veins of the arm to form?
Axillary vein
How is a fracture of the radial head usually sustained by?
Usually sustained by a fall onto the outstretched hand.
The tricky bit is that these fractures are not always apparent on X-ray images.
However, abnormal soft tissue signs on X-ray are often an indirect sign that a fracture is present, even if one cannot be seen.
What is a fracture of the distal radius?
Otherwise known as a Colles’ fracture, is very common in older people, especially females (in whom osteoporosis is more common).
It is usually caused by a fall onto an outstretched hand
What is medial epicondylitis?
Inflammation of the tendinous insertions of the superficial forearm flexors at the medial epicondyle.
It tends to be caused by repetitive use and strain of the muscles.
Pain is felt around the medial epicondyle and may radiate down the forearm.
Also called ‘Golfer’s elbow’, as it is seen in golfers
What are flexor tendons at risk from?
Lacerations over the anterior forearm and wrist.
In patients with such injuries, it is important to test the movements of the wrist and fingers to ascertain whether any tendons have been injured.
Patients with confirmed or suspected tendon injuries require a surgical assessment.
Failure to recognise tendon injuries may leave patients with permanent impairment.
What does injury of the ulnar nerve at the wrist impair?
Impairs the function of most of the small muscles of the hand
Where does the median nerve lie?
Lies deep in the forearm and so is fairly well protected, but it can be injured by deep lacerations.
At the wrist the nerve lies more superficially, so may be injured here
What can injury to the median nerve at the wrist impair?
Impairs the function of the small muscles of the thumb and sensation in the regions of the hand supplied by the median nerve.
What is a ganglion?
A ganglion is a cystic swelling that commonly appears on the dorsum of the wrist.
They feel soft and are typically non-tender.
They contain synovial fluid
