Anatomy dissection 12 & 13

Question 1

What are the carpal bones ?

Answer 1

So long to pink here comes the thumb

Question 2

What is the flexor and extensor retinaculum ?

Answer 2

• Flexor retinaculum - thick strip of connective tissue forms the roof of the carpal tunnel, attaches medially to the piriformis and hamate, then laterally to the scaphoid and trapezium
• Extensor retinaculum - thickening of the fascia on the dorsum of the hand

Question 3

What is the function of the flexor and extensor retinaculum ?

Answer 3

Prevents bowstringing of the tendons which pass under it

Question 4

What is the carpal tunnel ?

Answer 4

It is a combination of the carpal bones (posteriorly) and the flexor retinaculum (anteriorly)

Question 5

What are the contents of the carpal tunnel ?

Answer 5

Flexor muscles (FDS, FDP and FPL) and the median nerve

Question 6

Describe the blood supply to the hand in general terms

Answer 6

The ulnar and radial arteries interconnect to form two arches from which branches emerge to the digits

Question 7

Describe the route of the ulnar artery into the hand

Answer 7

It passes anteriorly over the flexor retinaculum and divides two branches:

• The superficial palmar arch
• And the deep palmar branch

Question 8

Describe the route of the radial artery into the hand

Answer 8

Enters the hand dorsally crossing the floor of the anatomical snuffbox

It then anastomoses with the deep palmar branch of the ulnar artery to form the deep palmar arch

Question 9

What branches does the superficial and deep palmar arches give off ?

Answer 9

• Superficial - gives off common palmar digital arteries arise, supplying the digits
• Deep - gives off gives rise to five arteries supplying the digits.

Question 10

Where is the superficial palmar arch found in the hand ?

Answer 10

Found anterior to the superifical to the flexor tendons and deep to the palmar aponeurosis

Question 11

Appreciate that each finger has four neurovascular bundles supplying it: Medial palmar, lateral palmar, medial dorsal and lateral dorsal.

Answer 11

This is important in the next card

Question 12

What technique is used to anaesthetise a finger and how is it done ?

Answer 12

• Ring block technique
• This is done by depositing local anaesthetic in a “ring” around the base of the finger to anaesthetise all four proper digital nerves

Question 13

What must not be used in the finger and why ?

Answer 13

Adrenaline - because the digital arteries are end arteries

Question 14

What are the 3 main nerves which provide the innevation of the hand ?

Answer 14

The ulnar, radial and median nerve

Question 15

Describe the sensory innervation of the hand

Answer 15

Ulnar nerve supplies:

• Medial part of the palm
• Little finger and medial half of ring finger

Median nerve supplies:

• Central & lateral palm
• Lateral half of ring finger, middle and index finger
• Thumb - excluding its base

Radial nerve supplies:

• Skin over base of the thumb

(hint for the palmar side simmply think in relation to the sides you would palpate the ulnar or radial artery)

Question 16

Describe what the palmar aponeurosis is and its function ?

Answer 16

The palmar fascia thickens centrally forming the palmar aponeurosis - protects the underlying muscles and then fans out into four digital rays which become the fibrous digital sheaths

Question 17

What are the flexor tendon sheaths ?

Answer 17

• The fibrous digital sheaths are continuous with the longitudinal digital bands of the palmar aponeurosis.
• The sheaths attach to both sides of the phalanges and form a secure tunnel through which the FDS, FDP and FPL tendons and their synovial sheaths travel distally.
• The tendons attach to the middle (FDS) and distal (FDP & FPL) phalanges respectively.

Question 18

Describe the innervation of the dorsal aspect of the hand

Answer 18

Ulnar nerve supplies:

• Medial part of dorsum of hand
• Little finger and medial half of ring finger

Median nerve supplies:

• Skin over the phalanges/nail beds of the thumb, index finger, middle finger and lateral half of ring finger

Radial nerve supplies:

• Skin over anatomical snuffbox
• Lateral part of dorsum of the hand
• Proximal part of index and middle finger

Question 19

What are the lumbricles and where are they found ?

Answer 19

Muscles of the hand, originates from a tendon of the flexor digitorum profundus. They pass dorsally and laterally around each finger, and inserts into the extensor hood

In pic the lumbricles are in purple

Question 20

What is the function of thel lumbricles ?

Answer 20

Flex the MCP and extend the PIP joints

Question 21

What is the innervation of the lumbricles ?

(hint think about the innervation of the hand they correspond to that)

Answer 21

• Medial 2 lumbircles (of the little finger and ring finger) supplied by ulnar nerve
• Lateral 2 lumbircles (of the middle and index) supplied by the median nerve

Question 22

Where are the interossei muscles located ?

Answer 22

• Located between the metacarpals
• Can be divided into palmar and dorsal interossei

Question 23

What is the function of the interossei muscles in the hand ?

Answer 23

• The palmar interossei adduct the digits (PAD)
• And the dorsal interossei abduct the digits (DAB).

Think PAD and DAB

Question 24

What nerve supplies the interossei muscles of the hand?

Answer 24

The ulnar nerve