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Palm of the Hand Lab Manual
|Topic and Text Reference | Learning Objectives | Special Instructions | Clinical Exercises | Key Structures
TOPIC AND TEXT REFERENCE: PALM OF THE HAND, PP. 30-35
LEARNING OBJECTIVES: (Click on a Learning Objective to go to the relevant section of the Study Module.)Obtain a bone model of the hand and study the bony landmarks. Include the names of the wrist bones (mnemonic= SLTPTTCH).
Trace the ulnar and radial artery into the palm. Identify which arteries form the superficial and deep palmar arches.
Examine the thenar and hypothenar group of muscles and learn how they are innervated.
Observe the relationship of the flexor digitorum profundus tendons and the flexor digitorum superficialis tendons.
Review and understand the actions of the fingers and the thumb - abduction, adduction, flexion, extension and opposition.
Learn the sensory innervation to the hand.
Observe the lumbricals and the interossei and compare their innervations and functions.
Learn the borders of the carpal tunnel and the structures that run through it.
SPECIAL INSTRUCTIONS FOR LAB TODAY:Pg.30: If you do not see the palmaris brevis muscle, check the undersurface of the skin that was removed. It may be there.
Pg.31: Take care not to sever any other structures while cutting the palmar aponeurosis.
Pg. 33: The recurrent branch of the median nerve is small, delicate, and difficult to isolate. Use your scissor technique.
To verify the function of the muscles, it is useful to pull on them and see which digit(s) move.
CLINICAL EXERCISES:
1. Perform an Allen test on yourself or your lab partner. What is the importance of this test?The ulnar and radial arteries both contribute to the superficial and deep palmar arches. However they contribute differently. The radial artery contributes mostly to the deep palmar arch and the ulnar artery to the superficial ulnar artery. The Allen test is a way of assessing how competent one artery is to take over for the other artery. For example if one artery is going to be used for blood sampling, an Allen test can be done by stopping all the blood flow to the hand by pressing on the volar side of the wrist until the hand looks pale. Then the artery that will not be used for the test is released to see if the hand now pinks up. If it does then that tells you that if the other artery were damaged during the blood sampling, the blood supply to the hand would not be compromised.
2.Why is the recurrent branch of the median nerve also known as the million dollar nerve?
Injury to it drastically affects the action of the thumb particularly opposition which separates us from the apes. If it gets cut, one has a potential “million dollar” case.
3.Why are scaphoid bone fractures so problematic?First of all these fractures often don ’t show on x-rays immediately. Secondly, there is a high degree of nonunion due to two reasons. The blood supply to this bone can be limited. In some individuals the blood supply comes from a single branch of the radial artery that enters the bone at its distal end and supplies the entire bone. In these individuals a fracture will interrupt the blood flow to the proximal end of the bone and cause a condition know as avascular necrosis. In addition, it is an interarticular bone and therefore bathed by synovial fluid. One of the purposes of synovial fluid is to keep the bones moving and if a bone is in two pieces, this may contribute to its difficulty to fuse.
KEY STRUCTURES:
You should be able to identify in a cadaver all the structures listed under key words unless they have an asterisk.
Click "I" for images and drawing from our lab, from Netter's, and Gold Standard. Click "S" for relevant pages in the Study Module.
Arteries flexor digitorum superficialis N1 G1 ulnar artery N1 G1 flexor pollicis brevis N1 G1 Bones - Carpal bones - (anterior/palmar view) flexor pollicis longus N1 G1 capitate N1 G1 interossei muscles, dorsal N1 G1(1st) hamate N1 G1 interossei muscles, palmar N1 G1 lunate N1 G1 lumbrical muscles N1 G1 pisiform N1 G1 opponens digiti quinti (aka minimi) N1 G1 scaphoid N1 G1 opponens pollicis N1 G1 trapezium N1 G1 palmaris brevis G1 trapezoid N1 G1 palmaris longus G1 triquetrum N1 G1 pronator quadratus N1 G1 Bones - Carpal bones - (posterior/dorsal view) Nerves capitate G1 median nerve, N1 G1 hamate G1 median nerve, common palmar branch G1 lunate G1 median nerve, recurrent branch N1 G1 pisiform G1 ulnar nerve N1 G1 (probe) scaphoid G1 ulnar nerve, deep branch N1 G1 trapezium G1 ulnar nerve, superficial branch N1 G1 trapezoid G1 Tendons triquetrum G1 flexor digitorum profundus tendon G1 Muscles flexor digitorum superficialis tendon G1 abductor digiti quinti (aka abductor digiti minimi) G1 Other structures abductor pollicis brevis N1 G1 superficial palmar arch adductor pollicis muscle N1 G1 deep palmar arterial arch G1 flexor digiti quinti (aka flexor digiti minimi brevis) N1 G1 flexor retinaculum (carpal tunnel) G1 flexor digitorum profundus N1 G1 palmar aponeurosis
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