Anatomy Notes Day 23-B: Palmer Hand 1. Slide 2 i. Digital flexion comes from 2 major muscles: the flexor digitorum superficialis (FDS) and the flexor digitorum profundus (FDP) ii. The FDS and FDP are located in the forearm, but their actions are carried out in the hand at the digits >The FDP attaches to the distal phalanx and can flex and all the interphalangeal and carpophalangeal joint >FDS attaches to the middle phalanx so it flexes the proximal interphalangeal joints and the metacarpal phalangeal joint iii. FDS and FDP can flex the wrist because they cross the wrist; “also observe the anatomical pattern of the FDP where the tendon pierces through the FDS to reach its target attachment points” 2. Slide 3 i. The tendons of the FDS and FDP (as well as flexor pollicis longus) are encased in synovial sheaths >These synovial sheaths are similar to synovial joints except these are membranes that wrap around the tendons that form a cavity filled with synovial fluid; the purpose behind this is to provide lubrication for the tendons as they slide in and around the joints of the hands in the fingers (this also keeps friction from building up) ii. The palmer aponeurosis covers all the structures and keeping them stable; the flexor retinaculum is another sheet that helps with stabilization; the digits also have annular and cruciform ligaments that function as to hold the tendons up against the fingers as well 3. Slide 4 i. Digital motion is described in reference to the hand itself rather than in reference to the body as a whole (i.e. abduction and adduction occur in reference to the 3rd digit/middle axis of the hand using the metacarpophalangeal joints) >Flexion and extension happens in the “palmer vs dorsal” direction from the standard anatomical position ii. The thumb rotates 90 degrees in reference to all the other digits for movement (i.e. abduction moves the thumb in a ventral direction, when you adduct you bring the thumb back to midline, when you flex the thumb you are moving it medially to the 5th digit, when you extend the thumb it moves in a lateral direction, and opposition) 4. Slide 5 i. The thumb can flex/extend, abduct/adduct, and do opposition/reposition because the 1st carpometacarpal joint is a saddle joint (the carpometacarpal joint is between the first metacarpal and the trapezium bone) >The saddle joint gives us two axes of rotation which allows for all those movements 5. Slide 6 i. *He didn’t make any comments for this slide, he just read the slide as is 6. Slide 7 i. The hand is complex in regards to its musculoskeletal components; this is because the hand is responsible for extremely fine motor movements (even microscopic movements) ii. Intrinsic Muscles of the Hand include 4 major groups of muscles a. Thenar Muscles: These are located under the thenar pad (pad of flesh at the base of the thumb) b. Hypothenar Muscles: These are located under the hypothenar pad (pad of flesh on the palm proximal to the pink finger) c. Lumbrical Muscles: Worm shaped muscles d. Interosseous Muscles: These are in-between the metacarpals >Palmar Interossei >Dorsal Interossei iii. There are two subdivisions of the interosseous muscles: the palmar interossei and dorsal interossei 7. Slide 8 i. Intrinsic Hand Muscles: T1 myotome (“myo” meaning muscle) ii. Skin on Hand: C6, C7, and C8 dermatomes (“derm” meaning skin) 8. Slide 10 i. Three Thenar Muscles: Flexor, Abductor, Opposer (“FAO”) a. Flexor pollicis brevis b. Abductor pollicis brevis c. Opponens pollicis (this muscle is deep to the flexor and abductor) ii. Pollux means “thumb” so anything with the name pollux/pollicus/ etc. means it is relating to the thumb iii. The FAO muscles are in the thenar pad and receive a common innervation >The Adductor pollicis is not part of the thenar group but it still acts on the thumb >The Adductor pollicis stands out on its own; it contains two heads but we won’t be distinguishing them for exam purposes (just know it attaches to the distal aspect of the metacarpal between the webs of digit one and digit two) >The Adductor pollicis is not part of the thenar pad and it’s innervation is different from the thenar muscles 9. Slide 11 i. Thenar Muscles: Abductor pollicis brevis, flexor pollicis brevis, opponens pollicis all receive innervation from the recurrent branch of the median nerve >This is called “recurrent median nerve” because it passes through the carpal tunnel and then heads back to where it came from (so it comes off the median nerve through the carpal tunnel and then flips back to innervate the thenar muscles) ii. It is important to note that the recurrent median nerve is located superficially to the muscles that it innervates iii.