Lecture 12: Hand

Question 1

What is the first carpometacarpal joint between, what type is it and what movements can it do

Answer 1

Between the metacarpal of the thumb and the trapezium. Its a saddle joint which allows flexion/extension, adduction/abduction and a small amount of rotation

Question 2

Compare the movements of the Metacarpophalangeal joints vs the interphalangeal joints

Answer 2

MCP joints are condyloid joints allowing flex/ext and abd/add (except for thumbs one which acts as IP joint).
IP joint is a hinge joint so only does flex/ext.

Question 3

What are the 2 ligaments of the hand, where are they attached and what do they do

Answer 3

Deep transverse metacarpal ligaments go between the the 4 metacarpals of the digits and stop the bones from spreading too widely. They are attached to sides of the Palmar ligaments which are at the MCP joint and the IP joints and form the floor of the fibro-osseus tunnels holding long flexor tendons

Question 4

What are the 3 major compartments of the palm and what forms the main boundaries of this

Answer 4

There is a lateral compartment with the thenar muscles and a medial compartment with the hypothenar muscles. These are separated from the central compartment by fibrous septa extending from the edges of the palmar aponeurosis. Central compartment has the long flexor tendons and the lumbricals

Question 5

What protects the long flexor tendons on the digits and at the flexor reticulum

Answer 5

There is a synovial sheath for each individual digit but at the flexor retinaculum there is a common sheath for the 4 digits (extending longer up the pinky) and a separate one for the flexor pollicis tendon. This lubricates the tendon. Under this is the fibrous digital sheath which just goes from the MCP joint to the distal phalanx. It stops tendons bow stringing

Question 6

What are the intrinsic muscles of the hand that cause abduction of the 2,3,4 fingers, _pennate and where do they insert/ act on

Answer 6

Dorsal interossei that are bipennate. They act on the index to ring finger and insert into the dorsal hood and base of P1 toward the midline of the digit that is closer to the midline of the hand out of the two digits that it has a origin from–> therefore has an origin on the thumb and pinky too.

Question 7

In what plane is abduction of the thumb in comparison to the fingers and so what action is the thumb doing when we naturally spread the fingers and which muscles do this

Answer 7

Abduction of the thumb is considered on a plane 90 degrees to the palm, so when we spread all fingers, we are extending the thumb and this uses Extensor pollicis longus and brevis

Question 8

What intrinsic muscles of the hand abduct the pinky

Answer 8

Abductor digiti minimi

Question 9

What are the intrinsic muscles of the hand that cause adduction of the 1,2,4,5 fingers, _pennate and where do they insert/ act on

Answer 9

Palmar interossei that are unipennate. They insert on the dorsal hood on the same finger on the side closer to the hand’s midline.

Question 10

What muscle gives some extra help to adduct the thumb and where does it insert

Answer 10

Adductor pollicis which inserts into sesamoid bone on the thumb and has two origins, one on the front of the 3rd metacarpal and one on the capitate.

Question 11

What causes the flexion of IP joints

Answer 11

The insertion of tendons of FDS and FDP into the bases of the middle and distal phalanges

Question 12

What causes the flexion at the MCP joint

Answer 12

Partially the maximal shortening of FDS and FDP with fine control brought by the interossei and lumbricals with their insertions into the edges of the dorsal digital expansion hood as this narrows over the proximal phalanx.

Question 13

Compare the lumbricals- (muscles that pass between flexor and extensor tendons) for the 2nd and 3rd finger to the 4th and 5th by insertion, _pennate and what is the special nerve supply

Answer 13

For 2nd and 3rd finger lumbricals are unipennate and innervated by the median nerve. They insert into the dorsal hood on the same digit it originated from, both insertion and origin on the side of the digit closer to the thumb.

For the 4th and 5th finger, lumbricals are bipennate and innervated by ulnar nerve. They have the two heads between 3rd and 4th and 4th and 5th. The insertion is on the side of the finger closest to the thumb.

Question 14

Describe the structure , location and function of the dorsal digital extension hood

Answer 14

The hood attaches to palmar ligament at the MCP joint and covers the Extensor digitorum which attaches to the base of distal phalanx to stop it from sliding off the back of the hand.

Question 15

What happens when FDP contracts while interossei and lumbricals relax compared to when the interossei and lumbricals contract

Answer 15

The MCP joint and the IP joint is flexed when they’re relaxed like a circle but when they’re contracting, there is flexion at the MCP joint but the flexor tendon past this joint is a bit loose and this lets the IP joints be extended like a duck hand.

Question 16

What innervates the Thenar muscles compared to the Hypothenar muscles and what digits are these muscles associated with

Answer 16

Thenar is by median nerve and is associated with pollux, hypothenar by deep branch of ulnar nerve and is associated with digiti minimi

Question 17

What is the arrangement of the abductor, flexor and opponens of pollicis (brevis cept opponens) and digiti minimi

Answer 17

The abductors are both on the most lateral edges in front. Next to it closer to the hand midline is the flexors and in the middle but behind both of those is the opponens

Question 18

What does the ulnar nerve innervate in the hand for motor

Answer 18

The ulnar nerve (next to the ulnar artery) goes over the flexor retinaculum and divides into superficial and deep branches in the hand. Superficial branch does the pinky and ulnar side of the ring finger. Deep branch does hypothenar muscles and crosses the palm with the artery to supply the interossei, two bipennate lumbricals and adductor pollicis.

Question 19

What does the median nerve innervate in the hand for motor

Answer 19

Median nerve travels in the carpal tunnel and the recurrent branch of the median nerve innervates the thenar muscles and two unipennate lumbricals

Question 20

Describe the cutaneous innervation of the palm

Answer 20

The palmar branch of the ulnar and median nerve innervate the palm. This branch splits into common plamar digital nerves which then go into proper palmar digital nerves which innervate the (relative to the hand midline) lateral side of one digit and the medial side of the other. The pinky and the lateral half of the 4th finger is done by the ulnar branch, while the rest is done by median nerve

Question 21

Describe the cutaneous innervation of the dorsal side of the hand

Answer 21

The dorsal branch of the ulnar nerve does the back of the 5th and lateral half of the 4th finger. The finger tips of the rest are done by the dorsal branches of the proper palmar digital nerves while the superficial branch of the radial nerve does the majority of the rest of the first 3 fingers + medial half of 4th

Question 22

Describe the arterial supply to the hand by the radial and ulnar arteries via the superficial branches

Answer 22

The arteries split into a deep branch and superficial palmar branch. The two superficial branches from both arteries meet up to form the superficial palmar arch. From this arch springs 3 common palmar digital arteries which go toward the 3 junctions between the 4 fingers. They then each split into two branches to supply the medial side of one finger and the lateral side of the adjacent finger (in relation to the hand midline). These two branches are Proper palmar digital arteries

Question 23

Describe the path of the radial and ulnar arteries via the deep branches to complete the Deep palmar arch

Answer 23

The deep branch of radial artery goes around the lateral aspect of the wrist under tendons of extensor muscles, through anatomical snuff box then through 2 heads of 1st DI and adductor pollicis into the palm to join up with the deep branch of ulnar artery which went between the hypothenar muscles.

Question 24

Describe what comes off the deep palmar arch

Answer 24

Metacarpal arteries which join the common palmar digital arteries from the superficial arch as well as perforating arteries which reach the dorsum.

Question 25

Describe the arterial supply to the dorsum to up to halfway up the proximal phalanges

Answer 25

The dorsal carpal branches of the radial and ulnar artery supply the dorsum of the hand via a dorsal rete. From this rete dorsal metacarpal branches are given off and reinforced by perforating artereis from the deep palmar arch.

Question 26

How is blood and lymph drained from the hand (where do the veins start )

Answer 26

Drained dorsally around the edges of the palm and fingers so its not compromised in a tight grip. The cephalic and basilic veins start on the lateral and medial sides of the back of the hand and eventually become the axillary vein.