6: Bones Of Forearm Flashcards
The forearm skeleton is formed by …(a)…. (shorter bone) and …(b)…. (longer bone)
(a) radius (lateral)
(b) ulna (medial)
The ……. rotates medially over the ulna to produce pronation
radius
Joints between radius and ulna
- proximal radio ulnar joint
- interosseous membrane
- distal radio ulnar joint
The stabilizing bone of the forearm which has a bulky proximal end which gradually tapers distally
Ulna
Proximal end of ulna has an …….. process and a …… process, between them lie the trochlear notch
olecranon process and a coronoid process
The distal end of ulna has:
- head
- posteromedial extension called styloid process
Describe distal end of radius
- the distal end it is quadrangular in outline
- distal end presents ulnar notch for the ulnar head, and a styloid process
Where is the radial notch?
Superior end of ulna laterally shows the radial notch, supinator crest and fossa and tuberosity
Tubercle of lister, where?
The dorsal surface of inferior end of radius shows a dorsal tubercle of radius (of Lister) and grooves for tendons of extensor muscles.
(Know the muscles in picture attached)
What bones articulate to form the wrist joint?
radius articulates with scaphoid and lunate
(Note: inferior surface of ulna is also articular but does not articulate with any bone, instead with a fibrous articular disc)
The radius and ulna have three borders and three surfaces each (what are the surfaces of each?)
- ulna: anterior, posterior, medial surfaces
- radius: anterior, posterior, lateral surfaces
The fracture of one bone (radius or ulna) is bound to be associated with dislocation of a nearby joint. Explain why?
Bcz Radius and ulna are bound together by the interosseous membrane
How many carpal bones we have? How are they arranged?
Eight carpal bones arranged in proximal and distal rows of 4 bones each form the carpus, which is concave anteriorly and convex posteriorly
The concave anterior surface of the carpus forms the floor of the ……?
carpal tunnel (canal)
Carpal bones proximally articulate with the …(a)….. (scaphoid and lunate) but not with the ulna.
Carpal bones distally articulate with ….(b)….
(a) radius
(b) metacarpals
What is the largest carpal bone?
Capitate
What carpal bone is seen anteriorly only?
Pisiform bone
(Note: Pisiform bone is a sesamoid bone developing in the tendon of flexor carpi ulnaris and sitting on the palmar surface of triquetral)
A. …….. has a tubercle
B. …….. has a hook
C. ……… has a head
A. Scaphoid
B. Hamate
C. Capitate
What forms the knuckles?
The distal ends (heads) of metacarpals articulate with proximal phalanges to form metacarpophalangeal joints (knuckles)
Which metacarpal also has a styloid process projecting from its base?
Third
……. has two phalanges, and the four fingers have three phalanges each
Thumb
What is boxer’s fracture?
Fifth metacarpal fracture is called ‘boxer’s fracture’ as it happens in someone who punches with closed abducted fist & extended wrist (at neck of 5th metacarpal)
Phalangeal fractures are usually due to ……………, the distal phalanx fracture is highly painful as the tip of the finger has highly developed sensation
crushing injuries
Do Metacarpals heal quickly or not & why?
Metacarpals have rich blood supply, so fractures heal quickly
When ……. fractures, there will be pain in anatomical snuffbox
Scaphoid
What type of joint is the interosseous membrane?
Syndesmosis
Type of joint between carpals?
Plane synovial
Ulna doesn’t articulate with any carpal bone. Why?
Bcz there is an articular disc formed by fibrous cartilage between it and the pisiform & triquetral bones
What parts of carpals are not seen posteriorly?
Pisoform, hook of hamate, tubercle of trapezium
How are the metacarpals numbered?
Lateral to medial
What type of joint is metacarpophalangeal joint?
Condyloid
What type of joint is interphalangeal joint?
Hinge
What type of joints are the carpometacarpal?
plane synovial joint except the joint between the first metacarpal and the trapezium and it is a saddle joint.
Elbow joint (Type & articulations)
- Elbow joint is a hinge joint consisting of humero-ulnar and
humero-radial joints - Superior articular surfaces are provided by trochlea and capitulum on humerus, whereas the inferior articular surfaces are formed by the trochlear notch on ulna and radial head
Why is the elbow joint capsule weaker anteriorly and posteriorly?
Bcz on either side it’s supported by the collateral ligaments
RCL vs UCL
- The radial collateral ligament (RCL) extends from the lateral epicondyle and has two bands which merge with the anular ligament
- The (UCL) is stronger than the RCL
It has a stronger anterior band, a weaker posterior band and an oblique band which deepens the trochlear notch
What is the carrying angle?
The carrying angle is formed between the long axis of humerus and ulna (forearm), which is about 10-15
degrees in males and more than 15 degrees in females
Why is forearm in females more deviated than in males?
The more deviated forearm in females allows clearance of the upper limbs while swinging from the pelvis which is wider in females
What makes the carrying angle disappear?
Pronation of the forearm makes the angle to disappear
prime flexors of the elbow joint
Brachialis and biceps brachii
chief extensor of the elbow joint
Triceps brachii
Flex in absence of resistance?
Brachioradialis can also flex in the absence of resistance, but when there is resistance, brachioradialis and supinator help the prime flexors in flexing