TBL 7 The Forearm and Hand
Describe the fascia of the forearm and hand
Well the brachial fascia starts at the biceps which then becomes the antebrachial fascia of the forearm --> which eventually leads to the palmar fascia of the palm. the palmar fascia is thickened centrally as the palmar aponeurosis (layers of flat, broad tendons)
Do the FCR and FCU work together?
YES they work synergistically in flexing the hand at the wrist.
What is the most common cause of Colles fracture?
a complete transverse fracture of the distal 2cm of the radius, is called a Colles Fracture, and is the most common fracture of the forearm. The distal fragment is displaced dorsally and is often comminuted (broken into pieces). The fracture results from a forced extension of the hand, usually as the result of trying to easy a fall by outstretching a limb. --> characterized by displacement of the hand dorsally and radially when fractured at the radius' distally end.
What does the thick shaft of the ulna taper off to? What does the thin shaft of the radius thicken distally to?
the thick shaft of the ulna tapers distally into the head of the ulna. the thin shaft of the radius thickens distally to meet its styloid process, which extends farther than the ulnar head and contributes to the wrist joint.
What do the scaphoid and lunate bones of the proximal row articular with? And the distal row?
they articulate with the radius at the wrist joint and the distal row articulates with the 5 metacarpal bones that articulate with the proximal phalanges of the five digits at the metacarpophalangeal MCP joints.
the proximal phalanx of the thumb articulates with the ______ via a single _________. Two inter-phalangeal (IP) joints accommodate the _______________ ____________ of the fingers.
The proximal phalanx of the thumb articulates with the distal phalanx via a single interphalangeal (IP joint) and two Interphalangeal (IP) joints accommodate the middle phalanges of the fingers.
What is the median cubital vein ?
The medial cubital vein interconnects the cephalic and basilic veins in the cubital fossa. Both veins eventually join the axillary vein. the cubital fossa is a depression on the anterior aspect of the elbow.
What is the flexor digitorum superficialis? (FDS)
- it attaches to the middle phalanges of the fingers; enabling flexion of the proximal IP joints ( the tips of the fingers are controlled) It flexes the proximal interphalangeal joints, and flexes the hand and forearm.
What does the wrist consist of?
8 small carpal bones arranged in articulated proximal and distal rows of four.
What do muscles of anteromedial forearm contribute to? What does removal of palmaris longus tendon for grafting result in?
flexion of the wrist and IP joints. Removal of the palmaris longus tendon for grafting does NOT copromise flexion of the hand at the wrist.
What is the fibrous interosseous membrane?
forces received by the radius from the hand are distributed to the ulna and humerus by the fibrous interosseous membrane.
Why is fracture separation of the distal radius common in children and what is the prognosis for normal bone growth?
fracture-separation of the distal radial epiphysis is common in children because of frequent falls in which forces are transmitted from hand to the radius. When the epiphysis is placed in its normal position during reduction, the prognosis for normal bone growth is good.
what is the flexor capri ulnaris (FCU)
it attaches to the 5th metacarpal; and enables the hand to ADDUCT (lower) at the wrist. it flexes the forearm and flexes and ADDUCTS the hand.
What is the flexor pollicis longus (FPL)
it attaches to the anterior surface of the radius proximally and its distal tendinous attachment enables flexion of both phalanges of the thumb.
What does the median nerve descend from?
it descends from the midline of the fossa to innervate the superficial and intermediate muscle layers, except the FCU.
What is the ulnar nerve?
it descends posterior to the medial epicondyle of the humerus into the forearm; it innervates the FCU and the portion of the FDP that acts on the 4th and 5th digits.
What does the median nerve generate?
it generates the anterior interosseous nerve to supply the FPL, the pronator quadratus, and the portion of the FDP that acts on the 2nd and 3rd digits.
What is the palmar carpal ligament?
it is an anterior thickening of the antebrachial fascia. The median nerve and tendons of the FDS, FDP, and FPL traverse the underlying carpal tunnel into the palm.
What is the pronator teres?
it is part of the superficial muscle layer. It originates at the medial epicondyle of the humerus and ulna and attaches to the radius, where it acts syngergistically when pronation requires more speed and power.
Where does the superficial muscle layer originate?
it originates at the lateral epicondyle of the humerus.
What is the bicipital aponeurosis?
it reinforces the brachial and antebrachial fasciae covering the cubital fossa, a depression on the anterior aspect of the elbow.
How are the median nerve and brachial artery somewhat protected when the mean cubital vein is used for venipuncture?
lots of accessible veins are found in the cubital fossa area (think where you get blood drawn). The veins lie directly on the deep fascia running diagonally from the cephalic vein of the forearm to the basilica vein of the arm. these veins crosses the bicipital aponeurosis which separates it from the underlying brachial artery and median nerve which provides some protection to both.
The pronator quadratus?
of the deep muscle layer originates at the ulna and attaches to the radius; it is the prime pronator of the forearm and hand.
How are syndactyly and polydactyly distinguished
syndactyly = 2 or more fingers or toes are fused. = caused when the mesencyhme between prospective digits in hand and footplates is not removed by apoptosis causing fusion of 2+ joints. polydactyly = presence of extra fingers or toes. Extra digits frequently lack proper muscle connections. extra digits frequently lack proper muscle connections --. abnormalities are usually bilateral, wheras absence of a digit (ectrodacylyl) such as the thumb, usually occurs unilaterally.
What is the flexor digitorum profundus? (FDP)
the FDP of the deep muscle layer attaches to the anterior surface of the ulna proximally and its distal tendinous attachments enable flexion of the distal IP joints of the fingers.
What do the median nerve and brachial artery enter?
the cubital fossa. At the cubital fossa the brachial artery bifurcates into the radial and ulnar arteries.
What is the dorsal venous network? Where do the lateral and medial portions drain?
the digital veins drain into the dorsal venous network in the superficial fascia on the dorsum of the hand. the lateral portion drains into the cephalic vein --> ascends laterally through the axillary fascia to join the axillary vein. the medial portion drains into the medial veins of the forearm --> basilic vein --> ascends medially through the brachial fascia to join the axillary vein.
Where do the digital veins drain into?
the dorsal venous network in the superficial fascia on the dorsum of the hand, and the network drains laterally into the cephalic vein and medially into median veins of the forearm that empty into the basilic vein ascends the arm to join the axillary vein.
What is the flexor carpi radialis (FCR)
the flexor carpi radialis (FCR) attaches tot he 2nd metacarpal and enables the hand ABDUCTION (Raising) at the wrist It also flexes the forearm, and flexes and abducts the hand.
What is the proximal radioulnar joint?
the proximal radioulnar joint is between the humerus and the radius/ulna. The head of the ulna articulates with the radius at the distal radioulnar joint.
Where do the superficial and intermediate muscle layers originate?
the superficial and intermediate muscle layers originate the medial epicondyle of the humerus proximally (closer to the body)
What do the tendons of the FPS and FDP enter?
they enter the common flexor sheath that originates at the wrist and extends through the carpal tunnel into the central palm where it unites with the 5th synovial digital sheath. The synovial digital sheaths enables the flexor tendons to slide freely over each other during movement of the fingers.
What do most muscles of the posterolateral forearm extend?
they extend the wrist, MCP and IP joints.
how do the brachialis and supinator relate to the cubital fossa?
they form the muscular floor of the cubital fossa.
how does the resulting dinner fork deformity occur?
when a Colles Fracture occurs, often the ulnar styloid process is avulsed (broken off). Under normal anatomical conditions, the radial styloid process projects farther distally than the ulnar syloid, yet when the Colles fracture occurs, the relationship is reversed due to shortening of the radius. A "Dinner form deformity" occurs because the posterior angulation occurs in the forearm just proximal to the wrist and the normal anterior curvature of the relaxed hand. The posterior bending is produced by the posterior displacement and tilt of the distal fragment of the radius.
