10-F Limb Development, Brachial Plexus

Question 1

Identify the spinal cord segments associated with each limb bud.

Answer 1

upper limbs C5-T1, lower limbs L2- S3

Question 2

When does embryonic limb development begin and end?

Answer 2

begins at 3-4 weeks and is finished in 8 weeks, note lower limb development is a “little behind” upper limb development

Question 3

The radius is comparable to which bone in the lower limb and why?

Answer 3

radius is comparable to the tibia and this is somewhat confusing because the lower limb undergoes 180 deg rotation associated with upright posture

Question 4

Nerves that supply the limbs come form what rami and carry what types of fibers?

Answer 4

ventral rami, carrying somatomotor, general sensory, post ganglionic sympathetic and proprioceptive

Question 5

Distinguish between pre axial and post axial aspects of the limb.

Answer 5

the upper/cranial border of the limb is called the pre axial border (thumb side) and the lower/caudal margin is called the post axial border (little finger side)– note in the lower limb, the groin side is considered the pre axial side because of the lower limb rotation

Question 6

Which vessels lay on the pre and post axial sides of the upper and lower limbs?

Answer 6

upper limb: cephalic vein is pre axial while basilica is post axial, note that the greater saphenous vein is pre axial

Question 7

The limb is a sack of ____ filled with _____ (developed from ____ ____ ____) which forms connective tissue elements of the limb.

Answer 7

The limb is a sack of ectoderm filled with mesoderm (developed from lateral plate mesoderm) which forms connective tissue elements of the limb.

Question 8

The ____ ____ ____ is important factor in outgrowth of the limb

Answer 8

apical ectodermal ridge

Question 9

Myogenic cells that migrate (dragging their nerve supply with them) comes from a specific part of the somite called the _____ which form the body wall and limb muscles (innervated by ventral rami.

Answer 9

hypo mere

Question 10

Preaxial masses are innervated by fibers “dragged” from _____ and post axial masses are innervated by fibers from _____

Answer 10

pre axial C5,6,7

post axial C8, T1

Question 11

Preaxial and post axial muscles split into two groups ___ and ___ which further develop how?

Answer 11

anterior and posterior which go on to fuse with its matching pair

Question 12

What are the general functions of the anterior compartment and posterior compartment?

Answer 12

anterior: flexion
posterior: extension

Question 13

T/F the flexor/extensor pattern can be seen in the arrangement of the motor neurons in the spinal cord?

Answer 13

true

Question 14

The prexial muscles tend to be innervated by the _____ segmental levels whereas the muscles closest to the post axial border tend to be innervated by the ____ levels

Answer 14

highest- pre axial, lowest- post axial

Question 15

Flexor muscles of the pectoral girdle are generally attached tot eh ____, _____ and ____ while extensor muscles are attached to the _____.

Answer 15

clavicle, coracoid and subraglenoid tubercle; scapula

Question 16

Which motor nerves serve the posterior/extensor vs. the anterior/flexor parts of the arm, forearm and hand

Answer 16

posterior/extensor: radial

Question 17

The dermatome of the thumb is ___ while the dermatome of the pinky finger is ____.

Answer 17

thumb C6, pinky C8 (first two fingers C7)

Question 18

Which are the anti or division nerves of the leg? Which are the posterior division nerves of the leg?

Answer 18

anterior division: tibial and obturator nerve; posterior division nerves: femoral and fibular nerve (peroneal)

Question 19

What is the dermatome of the little toe and the big toe?

Answer 19

little two S1, big toe, L4/5

Question 20

Brachial plexus is formed from the ____ rami.

Answer 20

ventral rami of the spinal nerves

Question 21

Describe which nerve innervates muscle at the shoulder, elbow, wrist and intrinsic muscles of the hands.

Answer 21

shoulder C5-6, elbow C6-7, wrist C7-8, hand C8-T1 (C5 and C6 innervated the muscles from the scapula)

Question 22

Movements of the shoulder girdle hinge on which joint?

Answer 22

the sternoclavicular joint

Question 23

Shoulder joint flexion and extension occurs at which joint?

Answer 23

glenohumeral joint

Question 24

What are the general movements at the shoulder girdle?

Answer 24

elevation/depression, retraction and protraction, lateral and medial rotation

Question 25

Actions at the shoulder joint

Answer 25

abduction/adduction; internal and external rotation, extension/flexion

Question 26

Action of the elbow/knee.

Answer 26

flexion and extension

Question 27

The roots are formed from what?

Answer 27

C5-T1 ventral roots (supply both the anterior and posterior compartments)

Question 28

Name the trunks and what contributes to the trunks.

Answer 28

upper (C5-6), middle (C7), lower (C8-T1)

Question 29

What are the cords and what contributes to their formation?

Answer 29

cords of the plexus result from separation of the anterior and posterior nerve fibers into three cords: lateral, posterior, and medial cord (named in relation to the axillary artery)

Question 30

Which nerves arise from the anterior cord?

Answer 30

(form an M) musculocutaneous, median and ulnar nerves

Question 31

What are the muscles of the flexor arm and how are they innervated

Answer 31

biceps brachia, bachialis and coracobrahcialis innervated by the musculocutaneous n. (C5-7) (musculocutaneuous also branches to the lateral ante brachial cutaneous nerve)

Question 32

What does the radial nerve innervate and what spinal cord levels contribute to this nerve?

Answer 32

radial nerve serves all of the posterior/extensor muscles supplied from C5-T1

Question 33

What does the median nerve innervate and what spinal nerves contribute to this nerve?

Answer 33

innervates most muscles of the anterior forearm and a couple of the hand, contributed to by C5-T1 **associated with carpal tunnel

Question 34

What does the ulnar nerve innervate?

Answer 34

couple of anterior forearm muscles and majority of muscles in the hand, some skin

Question 35

What nerve branches from the spinal roots right away?

Answer 35

long thoracic nerve from C5,6,7 caries fibers tot eh serratus anterior muscle (extensor) and the dorsal scapular n. (branch of C5)

Question 36

Name two ways the nerves of the brachial plexus can be damaged.

Answer 36

hyperextension of the head leading to evulsion of the rootlets or fractured vertebral body can crush the spinal cord at cervical levels

Question 37

Name nerves that branch off the trunks.

Answer 37

supra scapula (upper trunk), subclavius (upper trunk)

Question 38

Name the nerves that branch from the cords

Answer 38

medial and lateral pectoral n. (anterior and lateral cords), upper, middle and lower sub scapular (posterior cord) and medial ante brachial cutaneous (distal medial cord)

Question 39

What region does the superior (supreme) thoracic artery supply? (1st region axillary artery)

Answer 39

passes medially to supply the first two intercostal space

Question 40

What region does the lateral thoracic supply? (2nd region axillary artery)?

Answer 40

aries at the lateral border of the pectorals minor , supplies pectorals minor and serratus anterior muscles

Question 41

What area is served by the sub scapular?

Answer 41

the largest branch of the axillary artery, splits into the circumflex scapular and the thoracodorsal arteries

Question 42

What area is served by the circumflex scapular artery?

Answer 42

passes around the lateral border of the scapula to reach the posterior surface supply the infraspinatus and anastomosing with the subclavian artery

Question 43

What does the thoracodorsal supply?

Answer 43

latissimus dorsi muscle

Question 44

What does the anterior and posterior humeral circumflex serve?

Answer 44

passes around the surgical neck of the humorous beneath the deltoid, serves the deep surface of the humerus and surrounding muscle

Question 45

Name the three branches of the subclavian artery that supply the axillary region.

Answer 45

traverse cervical a. (anastomose with sub scapular), dorsal scapular and suprascapualr (anastomoses with the circumflex scapular

Question 46

What is one significant collateral route that can bypass a blockage in the first part of the axillary artery

Answer 46

anterior intercostals and lateral thoracic artery