wrist / endocrine / renal / balance Flashcards
WRIST BONE
1- radius 8- carpals 5- metacarpals 14- phalanx 28 total wrist bones
Radius – The most proximal (to the midline of the body) part of the wrist is distal end of the radius. It articulates with all but one of the bones in a proximal row of bones called the carpals. A distal feature of the radius that is important is its widening and thickening towards the distal end, thus providing a larger surface for muscular attachments. At the distal end the radius is at least double the size as the ulna. Both the radius and ulna have defined pointy distal ends. The points are the radial and ulnar styloid processes
There are eight carpal bones, or carpi, arranged in two curved asymmetrical rows; a
(1) proximal row = scaphoid / lunate / triquetrum / pisiform,
(2) distal row = trapezium / trapezoid / capitate/ hamate
The proximal carpal row forms a sort of an arch that articulates with the radius, forming the wrist joint. The distal row forms the transition from wrist to hand.
Scaphoid – The scaphoid bone is the largest and most lateral (thumb side) of the carpals in the proximal row. It articulates with the radius proximally and with the trapezium and trapezoid bones in the distal row of carpals. The scaphoid can be palpated fairly easily. It is the bone on the lateral side of the wrist immediately distal to the end of the radius. It is flanked, to the anterior and posterior, by two tendons at the base of the thumb. Spread the fingers and lift the thumb to make the tendons prominent, then relax them in order to palpate the lateral surface of the bone. As an aside here, when the two tendons at the base of the thumb were tense and prominent, there was a small depression in between them. This little fossa is historically known as the anatomical snuff box.
Pisiform – The pisiform is the fourth and most medial bone of the proximal row of carpals. It is a very small bone that articulates only with the triquetrum. In fact, it is classified as a sesamoid bone, situated in the ligament of the truiquetrum. The most proximal prominence is the triquetrum, the most distal and anterior (in front of the triquetrum) is the pisiform.
Trapezium – The first bone in the second (distal) row of carpals is the trapezium. It sits between the scaphoid and the base of the first metacarpal (base of the thumb). It articulates with the first and second metacarpals, scaphoid, and trapezoid bones. The anterior surface of the trapezium presents the tubercle of the trapezium, which can be palpated on the palmar side of the wrist, just proximal to the base of the thumb.
Trapezoid – On a skeleton the trapezoid is an easy bone to identify. It is the smallest in the distal row of carpals. While easy on a skeleton, its size and location make in unpalpable on a living human. It articulates with four bones; the scaphoid and the second metacarpal along the longitudinal axis and the flanking trapezium and capitate bone.
Capitate – The capitate is the largest of all the carpal bones and physically occupies the center space of the wrist. With firm pressure applied just proximal to the posterior base of the third metacarpal (middle one), a portion of the capitate can be palpated. Aside from it being the largest, it has more articulations than all of the other carpals, having seven articulations with the surrounding bones; the scaphoid, lunate, trapezoid, hamate, and the second, third, and fourth metacarpals.
Capitate – The capitate is the largest of all the carpal bones and physically occupies the center space of the wrist. With firm pressure applied just proximal to the posterior base of the third metacarpal (middle one), a portion of the capitate can be palpated. Aside from it being the largest, it has more articulations than all of the other carpals, having seven articulations with the surrounding bones; the scaphoid, lunate, trapezoid, hamate, and the second, third, and fourth metacarpals.
Metacarpals – The metacarpals are the long bones of the hand running between the distal carpals and the phalanges. They form the palm and what we call the back of the hand. Their distal ends are the knuckles when we make a fist. There is a general characteristic shape to a metacarpal; concave proximal end, arched anterior surface, fairly straight posterior surface, and convex distal end (the head). The metacarpals are numbered, lateral to medial (thumb side to pinky side), from one to five. All five can be palpated from the posterior aspect
Capitate – The capitate is the largest of all the carpal bones and physically occupies the center space of the wrist. With firm pressure applied just proximal to the posterior base of the third metacarpal (middle one), a portion of the capitate can be palpated. Aside from it being the largest, it has more articulations than all of the other carpals, having seven articulations with the surrounding bones; the scaphoid, lunate, trapezoid, hamate, and the second, third, and fourth metacarpals.
Metacarpals – The metacarpals are the long bones of the hand running between the distal carpals and the phalanges. They form the palm and what we call the back of the hand. Their distal ends are the knuckles when we make a fist. There is a general characteristic shape to a metacarpal; concave proximal end, arched anterior surface, fairly straight posterior surface, and convex distal end (the head). The metacarpals are numbered, lateral to medial (thumb side to pinky side), from one to five. All five can be palpated from the posterior aspect.
Wrist – The wrist is the articulation of the radius, scaphoid, lunate, and triquetrum bones into a joint complex. It can also be called the radiocarpal joint. The wrist is capable of moving in two anatomical axes, the sagittal and frontal – a biaxial joint. If you consider the kinetic chain of the wrist, the wrist is an intermediary that transfers force from the hand to the radius when lifting (pulling) an object OR transfers force from the radius to the hand when pushing objects. It is important to note that those forces are also transferred, by physical necessity, to the ulna through engagement of ligamentous tissues.
The major ligaments of the wrist are the radial collateral and ulnar collateral ligaments. The radial collateral ligament lies laterally in the ligament complex and attaches to the radial styloid process and to the scaphoid bone of the proximal row of carpals. It is a ‘collateral’ ligament, so a second strand that attaches to the trapezium and base of the first metacarpal is also present. It engages to limit ulnar deviation (adduction of the hand at the wrist). The ulnar collateral ligament is medial (on the ulnar side) and the two strands attach the ulnar styloid process to the triquetrum and pisiform carpals. This particular ligament acts to limit radial deviation. Both the radial and ulnar collaterals can be palpated with firm pressure during repeated deviation/relaxation cycles. Radial deviation will reveal the ulna collateral ligament and ulnar deviation will reveal the radial collateral ligament.
Posterior aspect of the wrist there is a group of deep and unpalpable ligaments call the dorsal radiocarpal ligament. There are four defined segments of the ligament, all arising from the posterior lip of the radius just proximal to the joint. They will attach distally to the scaphoid, triquetrum, lunate, and capitate bones.
Anterior aspect of the wrist there is a group of deep and unpalpable ligaments collectively called the palmar radiocarpal ligament. There are six defined segments of the ligament, all arising from the anterior lip of the radius just proximal to the joint. They will attach distally to the scaphoid, triquetrum, lunate, and capitate bones.
Wrist – The wrist is the articulation of the radius, scaphoid, lunate, and triquetrum bones into a joint complex. It can also be called the radiocarpal joint. The wrist is capable of moving in two anatomical axes, the sagittal and frontal – a biaxial joint. If you consider the kinetic chain of the wrist, the wrist is an intermediary that transfers force from the hand to the radius when lifting (pulling) an object OR transfers force from the radius to the hand when pushing objects. It is important to note that those forces are also transferred, by physical necessity, to the ulna through engagement of ligamentous tissues.
The major ligaments of the wrist are the radial collateral and ulnar collateral ligaments. The radial collateral ligament lies laterally in the ligament complex and attaches to the radial styloid process and to the scaphoid bone of the proximal row of carpals. It is a ‘collateral’ ligament, so a second strand that attaches to the trapezium and base of the first metacarpal is also present. It engages to limit ulnar deviation (adduction of the hand at the wrist). The ulnar collateral ligament is medial (on the ulnar side) and the two strands attach the ulnar styloid process to the triquetrum and pisiform carpals. This particular ligament acts to limit radial deviation. Both the radial and ulnar collaterals can be palpated with firm pressure during repeated deviation/relaxation cycles. Radial deviation will reveal the ulna collateral ligament and ulnar deviation will reveal the radial collateral ligament.
WRIST
Posterior aspect of the wrist there is a group of deep and unpalpable ligaments call the dorsal radiocarpal ligament. There are four defined segments of the ligament, all arising from the posterior lip of the radius just proximal to the joint. They will attach distally to the scaphoid, triquetrum, lunate, and capitate bones.
Anterior aspect of the wrist there is a group of deep and unpalpable ligaments collectively called the palmar radiocarpal ligament. There are six defined segments of the ligament, all arising from the anterior lip of the radius just proximal to the joint. They will attach distally to the scaphoid, triquetrum, lunate, and capitate bones.
Intercarpal Joints – The intercarpal joints are the articulations between the individual carpal bones. Frequently you will see the intercarpal joints referred to as one of two collections of joints within the carpus, referring to the lateral and medial attachments between adjacent carpals. Midcarpal joints would then be attachments between the proximal and distal rows of carpals. These are planar synovial joints and although capable of limited movement between the carpals, they do contribute to wrist mobility. The carpals form an arch in the tranverse plane that is concave on the palmar side through which ligaments, nerves, and blood vessels pass. The arch deepens with flexion of the wrist and flattens with extension. This is why it is important to mildly extend the wrist when palpating for a radial pulse (checking the heart rate at the wrist).
The flexor retinaculum, also known as the transverse carpal ligament crosses over the carpal bones, forming a tunnel through which tendons and nerves can pass in a protected environment. As in the similar retinaculum in the ankle, it also prevents bowstringing of the tendons during contraction. It attaches to the pisiform and the hamate (along the hamulus) on the medial side and to the scaphoid the trapezium laterally. It is contiguous with the extensor retinaculum on the dorsum of the hand.
The extensor retinaculum, also known as the dorsal carpal ligament, lies at a downward angle, lateral to medial, across the carpal bones and forms a connective tissue bridge over the extensor tendons, helping to keep the tendons in place. It has an attachment to the lateral border of the distal radius and to the triquetrum and the pisiform bones of the medial side of the wrist. You can look at the retinaculi as a guide for tendons, one that keeps them in a location that facilitates appropriate and mechanically efficient transmission of force. Combined, the flexor and extensor retinaculum form a robust band around the wrist at roughly the level of where a watch is worn.
Carpometacarpal Joints – These joints are easy to identify and describe, five of them occur where the distal row of carpals articulate with the proximal end of the metacarpals. Each such articulation is a carpometacarpal joint. A small amount of pressure on a relaxed and flexed wrist joint allows palpation on the dorsal surface of hand. There is some debate regarding the number of ligaments present and their names.
The five that seem to be most accepted are the 1- anterior oblique 2- ulnar collateral 3- first intermetacarpal 4- posterior oblique 5- dorsoradial ligaments.
Metacarpophalangeal Joints – These are the condyloid joints or the ‘knuckles’ where the metacarpals meet the phalanges. The rounded end of the metacarpal sits in the shallow bowl of the proximal phalanx. These are biaxial joints allowing flexion, extension, abduction, and adduction of the phalanges. The exception here is the thumb which is a uniaxial joint, allowing flexion and extension. The joints are among the easiest to visualize and palpate. Simple make a fist to demonstrate the knuckles. One of the most interesting is the transverse metacarpal ligaments occurring between adjacent metacarpals (refer to Figure 16.14). These ligaments bind the heads of the metacarpals in close proximity, thus preventing excessive spreading and defining the maximum width of the distal palm. They can be palpated by gently squeezing the tissues just behind the webs between the fingers.
Interphalangeal Joints – The articulation of two sequential phalanx is an interphalangeal joint. There are two such joints in each phalange with the exception of the thumb which has but one interphalangeal joint between its proximal and distal phalanx. The interphalangeal joint closest to the metacarpals is termed the proximal interphalangeal joint. The one farthest away is the distal interphalangeal joint. Each joint can be easily identified by simple curling the fingers up making palpation elementary. Each interphalangeal joint has several ligaments surrounding it to include cruciate (cross the joints) and collateral (down the sides) ligaments.
There are a many many more small ligaments encasing the bones of the wrist, forming a network of interwoven connective tissue strands. This extensive system reinforces and holds the joints in close proximity while still allowing appropriate mobility.
WRIST MUSCLES
In general, there are two levels of stratification used to lay out the muscles of the wrist and hand.
1- The first strata is the division of the muscles into those that arise outside of the wrist and hand, the extrinsic muscles, and those that arise and end within the wrist and hand, the intrinsic muscles.
2- The second strata is divided by function into flexors and extensors. Sometimes you will see further descriptions of these muscles as anterior/posterior or superficial/deep.
WRIST MUSCLES
Extensor muscles are found on the medial aspect of the forearm.
In general, there are two levels of stratification used to lay out the muscles of the wrist and hand.
1- The first strata is the division of the muscles into those that arise outside of the wrist and hand, the extrinsic muscles, and those that arise and end within the wrist and hand, the intrinsic muscles.
2- The second strata is divided by function into flexors and extensors. Sometimes you will see further descriptions of these muscles as anterior/posterior or superficial/deep.
Flexor carpi radialis – The name of this muscle can provide all you need to know. It is a flexor and since flexors are anterior, it must be on the anterior of the arm near the radius. It attaches distally to the second and third carpi (carpi is plural). It is attached proximally to the medial epicondyle of the humerus, on the radial side of the arm.
The basic actions driven by contraction of the muscle are flexion of the hand and – as the muscle angles across the forearm medial to lateral – it assists in abduction of the hand. Palpation of the tendon is fairly simple, flex the wrist and look for the closest tendon to the thumb on the radial side. By following the tendon back up toward the proximal attachment on the medial ulna, about half way up the forearm the cable-like tendon becomes softer – this is the beginning of the muscle.
Palmaris longus – This is a small muscle that may actually be absent in ten percent or more of the population. It has been reported in the clinical literature that its absence does not affect wrist flexion and grip strength. An interesting finding, as flexion of the wrist is its primary function. The muscle attaches proximally to the medial epicondyle of the humerus and distally to the proximal center of the palmar aponeurosis, a fanned sheet of fascia lying across the palm into which many ligaments and tendons invest themselves (Figure 16.19). The tendon running between muscle and the aponeurosis is quite long. When the muscle contracts, the palmar fascia is tensed. The tendon can be palpated by placing the tips of the thumb and pinky together while flexing the wrist. The tendon, if the muscle is present, will present as a prominent tendon running longitudinally through the center of the superficial wrist. The palmaris longus lies immediately lateral to the flexor carpi radialis.
Pronator quadratus – This is an anterior muscle that is not a flexor. It is, as the name implies, a pronator of the hand. It attaches along the distal aspect of the last few inches of both the radius and ulna (Figure 16.21). The direction of the fiber orientation is lateral, across the space between the two bones.
Flexor pollicus longus – Here is where the Latin nomenclature for the thumb comes into play. Pollux means thumb, so the flexor pollicis longus should be a flexor of the thumb. Attaching proximally to the upper half of the radius along with an attachment to the coronoid process of the ulna, the muscle attaches distally to the base of distal phalanx of the thumb (Figure 16.22). The muscle can be identified by palpating the lateral aspect of the upper forearm during repeated flexion/relaxation cycles of the thumb against the fore finger (pinching). The movement of the tendon and muscle should be visible and palpable.
Flexor digitorum profundus – The name flexor digitorum profundus suggests a flexor of the fingers. The other word in the name, profundus, sounds a lot like profound. A profound thought is a deep thought. The muscle has a long proximal attachment along the ulna, spanning from near the olecranon down about two thirds its length. The distal attachments of the profundus are interesting and relatively unique. Instead of a single tendon emerging from the muscle and then dividing into slips for multiple attachments, there are four tendons that arise independently along the distal border of the muscle belly. The tendons then continue on to attach distally to the bases of the distal phalanx of digits two through five (Figure 16.22).
Extensor carpi ulnaris – This extensor attaches proximally to the humerus at the lateral epicondyle. It then runs down the medial border of the forearm where it has a considerable attachment to the ulna, crosses the wrist, and attaches distally to the base of the fifth metacarpal. This orientation also makes it an adductor of the wrist and hand. Palpation is fairly easy by finding the two attachment sites and observing/ palpating the expected line of the muscle along the forearm while performing simultaneous wrist flexion and ulnar deviation. It should be visually apparent and palpable with repeated contraction-relaxation cycles.
