nerves and vessels of lower limb Flashcards

1
Q

what spinal levels supply which region *

A

c1-4 neck

c5-t1 upper limb

t2-l1 trunk

l2-s3 lower limb

s2-c1 perineum

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2
Q

what are teh 2 types of innervation *

A

segmental - dermatomes

peripheral - nerves to muscles and cutaneous nerves

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3
Q

where do peripheral nerves emerge from *

A

nerve plexuses

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4
Q

what is a nerve plexus *

A

it is formed when peripheral spinal nerve roots merge and split to produce a network of nerves from which new multi-segmental peripheral nerves emerge

multi-segmental means that fibres come from >1 spinal root

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5
Q

what are the 3 main nerves that supply the lower limb that come off the lumbosacral plexus *

A

femoral

obturator

sciatic

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6
Q

summarise the organisation of the lumbosacral plexus *

A

come of levels L2-S3

derived from the anterior rami of the spinal nerves

terminal branches have fibres off different roots

the lumbar plexus is derived from L1-L4, branches are:

  • iliohypogastric and ilioinguinal nerves
  • genitofemoral nerve
  • lateral cutaneous nerve of thigh
  • femoral nerve
  • obturator nerve
  • lumbosacral trunk

sacral plexus is derived from lumbosacral trunk and s1-4 anterior rami

  • sciatic nerve
  • nerve to piriformis
  • posterior cutaneous nerve of the thigh
  • pelvic splanchnic nerves - pns
  • pudendal nerves
  • nerve to obturator internus
  • superior gluteal nerve
  • inferior gluteal nerve
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7
Q

describe the anatomy of the gluteal region and the course of the sciatic nerve through it *

A

piriformis is one of the lateral rotator cuff muscles - important landmark

superior to piriformis have the superior gluteal nerve and vessels

inferior to the piriformis have the inferior gluteal nerve and vessels, and large nerves - the sciatic and posterior cutaneous nerve of thigh

sciatic then passes posterior in thigh and divides into tibial and common peroneal nerve

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8
Q

describe the femoral nerve *

A

L2-4

supplies - anterior compartment of the thigh and iliacus (hip flexor in pelvis - L1-4) [psoas and iliacus, pectineus, sartorius, rectus femoris, vastus medialis, vastus intermedius, vastus lateralis]

from lumbosacral plexus, passes under the inguinal canal, enters the femoral triangle and branches

it is a posterior division of the plexus but supplies anterior muscles because of the pronation that occurs in development

sensory to front of thigh and anteromedial knee

terminal branch is saphenous nerve - sensory to medial leg and foot

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9
Q

describe teh obturator nerve *

A

L2-4

supplies the medial - adductor compartment of thigh [obturator externus, adductor brevis and longus, part of adductor magnus, gracilis]

sensory to pelvis and upper medial aspect of thigh

comes off the lumbrosacral plexus and emerges on medial border of psoas muscle, runs inferiorly and anteriorly on pelvis and passes through the obturator foramen by piercing the fibrous membrane and muscle covering

is anterior division of the plexus

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10
Q

describe the sciatic nerve *

A

L4-S3

2 nerves that are stuck together - 1 anterior and 1 posterior division

passes through the greater sciatic foramen, behind the hip, then passes in posterior part of thigh

sciatic nerve proper supplies hamstring muscles in posterior part of thigh [biceps femoris, semimembranosus and semitendinosus, part of adductor magnus]

also has some sensory branches to back of thigh, lateral side of leg and foot, dorsal surface of foot

nerve divides just above the knee

branches are tibial and common peroneal branches

supply posterior thigh, anterior and posterior leg and foot ie all muscles in leg and foot

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11
Q

describe the tibial nerve *

A

l4-s3

branch of the sciatic nerve

stays posteriorly, runs on teh surface of the tibialis posterior and supplies posterior leg [gastrocnemius and soleus, plantaris, popliteus, tibialis posterior]

runs posterior to the medial malleolus, passes under the plantar aporneurosis where it divides into medial (L4 5)and lateral (S1 2) plantar nerves - supplies all muscles of the foot [flexor hallucis longus, flexor digitorum longus and brevis, abductor hallucis, fkexor hallucis brevis, interossei and lumbricles]

sensory to the back of teh leg and the sole of the foot and lateral side of foot

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12
Q

describe the common peroneal nerve *

A

L4-S2

branch of the sciatic nerve in posterior compartment of thigh/popliteal fossa

follows the medial margin of the biceps femoris tendon over the lateral head of the gastrocneumius to the fibular (here gives off sural nerve)

passes laterally round neck of fibular

give off deep (L5-S2) and superficial (L4-S1) peroneal nerves

superficial descends in lateral compartment, deep to fibularis longus and brevis

superficial supplies the lateral compartment of the leg ie the peroneus longus and brevis

a branch of superficial emerges just superior to the ankle joint where it divides into medial and lateral branches that supply cutaneous dorsum of foot - except for the web space between digits 1 and 2 (supplied by deep peroneal) and lateral side of little toe (supplied by tibial)

deep passes anteromedially from lateral part of leg through the intermuscular septum into the anterior compartment of the leg the passes deep to the extensor digitorum longus, reaches the nterosseous membrane where it meets and descends with the tibial artery

the deep supplies the anterior compartment of the leg [tibialis anterior, extensor hallucis longus, peroneus tertius, extensor digitorum longus], the goes to dorsal foot - innervates extensor digitorum brevis, contributes to innervation of the 1st two dorsal interossei muscles

deep supplies skin between teh 1st adn 2nd digits

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13
Q

where is the common peroneal nerve suseptible to damage *

A

round teh neck of the fibula

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14
Q

describe the saphenous nerve *

A

it is a branch of the femoral nerve

accompanies femoral artery through adductor canal but doesnt pass through adductor hiatus; instead it penetrates through connective tissue in canal - appears between sartorius and gracialis muscles on medial side of knee

here penetrates deep facia and continues down medial side of leg to foot

it a cutanous nerve of medial knee, leg and foot

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15
Q

what does the femoral nerve supply *

A

anterior compartment of thigh - motor

medial leg and foot - sensory via the saphenous nerve

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16
Q

describe the sural nerve *

A

formed from branches of the common peroneal nerve and tibial nerve

tibial part originate between heads of gastrocnemius, descends superficially to gastrocnemius, penetrates the deep fascia

here joined by sural communicating nerve from common peroneus

passes down leg and round the lateral malleolus and into the foot

it is a cutanous nerve of the lateral leg and foot and little toe

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17
Q

describe the superior gluteal nerve *

A

L4-S1

pass into gluteal region via the greater sciatic foramen superior to piriformis

supplies glut med and min and tensor fascia lata

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18
Q

describe inferior gluteal nerve *

A

L5-S2

pass into the gluteal region via greater sciatic foramen inferior to the piriformis

supplies glut max

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19
Q

summarise the segmental supply to the limbs *

A

groups of motor nerve cell bodies in teh spinal cord

plexi for each limb

anterior division/rami - flexor muscles which are posterior

posterior division/rami - extensor muscles which are anterior

muscles are supplied by 2 adjacent segments

if muscles have the same action on a joint - have same nerve supply

opposing muscles have supply from 1-2 segments above/below

the more distal the muscle, the more caudal in spine the segment

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20
Q

spinal segments that are involved in movementof the limbs *

A

hip - flex L2-3, extend L4 5

knee extend l3 4 flex l5 s1

ankle dorsiflex (extension) - l4 5, plantarflex s1-s2

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21
Q

what are dermatomes *

A

fields of the cutaneous surface whose sensation is supplied by a single spinal nerve

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22
Q

what is an axial line in reference to dermatomes *

A

boundary between lower and higher spinal roots

where the dermatomes are not linked at the spinal level eg s2 and l2 lie next to each other in posterior thigh

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23
Q

who is the peripheral nerve supply different to the dermatomes *

A

peripheral supply refers to peripheral nerves not the spinal roots

not all fibres from 1 spinal root go via 1 peripheral nerve

also, peripheral nerves contain fibres from >1 spinal roots

for example posterior cutaneous nerve comes from S1 2

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24
Q

what are autonomous sensory zones *

A

dermatomes overlap - so difficult to know what has been affected in spinal root damage

autonomous sensory zones are zones taht if you have abnormal sensation in them, it is indicative of spinal root damage for a particular dermatome

eg L3 region on thigh, L4 knee, S1 back of calf

obturator nerve enters medially and supplies muscle and skin of medial thigh - autonomous sensory zone

deep fibular nerve supplies cleft between 1st and 2nd digit - autonomous sensory zone

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25
Q

describe the cutanous innervation of foot *

A

saphenous nerve supply medial side of ankle and foot

deep and superficial peroneal nerves - become dorsal digital nerves

dorsal lateral cutaneous nerve - from sural nerve supplies lateral of foot

have common and proper plantar digital nerves and lateral and medial plantar nerve and medial calcaneal nerve on sole of foot

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26
Q

what do you assess in assessment of nerve function *

A

motor, sensory, reflex, autonomic and trophic

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27
Q

effect of prolapsed intervertebral disk at L5/S1 *

A

cause pressure on S1 nerve root - cause segmental loss

motor - loss of eversion and weakness elsewhere

sensory - loss of sensation on outer border of foot

reflex - loss of ankle jerk S1

autonomic - minimal - abnormalities in sweating in the S1 cutaneous nerve distribution

trophic - in long standing lesions there might be trophic changes in the lateral aspect of the foot

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28
Q

effect of lesion of common peroneal nerve at fibular neck *

A

peripheral nerve loss

motor - foot drop because of paralysis of anterior and lateral compartments of legs (cant raise toes so scuff front of shoes and have high stepping/swinging gait - can get springs to lift toes artificially iff long term)

sensory - dorsum of foot at least

reflex - none

autonomic - minimal - abnormalities of sweating in cutaneous distribution of the common preoneal nerve

trophic - in chronic cases may be damage to sole of foot due to pressure effects of foot drop

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29
Q

summarise the arterial anatomy *

A

aorta branches into common iliac arteries that branch into external and internal iliac arteries at pelvic brim - external is the main blood supply to lower limb (internal stays in pelvis exept for 1 branch is the obturator artery which passes through the obturator foramen into the thigh)

superior and inferior gluteal arteries are branches of the internal iliac

external pass under inguinal ligament at mid-inguinal point (halfway between syphysis pubis and ASIS) to become femoral which passes anteriorly in thigh

femoral has 4 branches below inguinal ligament - superficial circumflex iliac artery, superficial epigastric artery, superficial external pudendal artery, deep external pudendal artery

femoral gives off deep branch in the femoral triangle - the profunda femoris artery, this arises 4cm distal to the inguinal ligament - its branches are the perforating arteries and medial and lateral femoral circumflex arteries - they supply the distal head of the femer

femoral passes from anterior to posterior through the adductor hiatus to become the popliteal artery

popliteal artery gives off genicular (knee) branches

popliteal artery ‘‘trifurcates’’ - not true trifurcation

branches into anterior tibial artery and tibioperoneal artery

tibioperoneal then branches into peroneal and posterior tibial artery

anterior tibial pierces interosseous membrane then is deep in anterior compartment between bones running on the interosseous mem, becomes dorsalis pedis artery when it passes over the ankle, passing anteromediolaterally to turn laterally as the arcuate artery giving off the digital branches

perforating arteries communicate between the plantar arch adn arcuate artery

posterior tibial passes into posterior compartment of leg alongside the tibialis posterior around medial malleolus and branches into lateral and medial plantar arteries which form a plantar arterial arch, supplying sole of foot

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30
Q

what are the pulse points in the lower limb *

A

femoral artery

popliteal

posterior tuibial

dorsalis pedis

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31
Q

why are pulses important *

A

aging population

need to assess vascular health

lower limb is further away from heart so there are more issues

suseptible to PVD - need to know legs are being perfused

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32
Q

why is the femoral triangle important *

A

for access to the heart

femoral pulse important for cannulation

for cardiac arteriography access artery

for resuscitation - vein

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33
Q

describe the femoral artery and vein’s relation to adductor magnus *

A

they pass from anterior to posterior through teh adductor hiatus (of the adductor hiatus muscle)

the passing through the hiatus is a point where occlusion can occur

superficial short saphenous vein drains into the popliteal vein at the popliteal fossa

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34
Q

describe the arrangement of vessels in the popliteal fossa *

A

the artery is deeper than the vein

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35
Q

what bone do you press the femoral artery against for pulse *

A

pubic ramus

at mid-inguinal point it lies on the psoas tendon so can be palpated easily

36
Q

what bone do you press dorsalis pedis artery against for pulse *

A

tarsal bones and maybe metatarsal

37
Q

where do you feel the posterior tibial artery *

A

behind the medial malleolus

38
Q

describe the path of the superficial veins *

A

lie in the subcutaneous tissue, have valves to prevent the backflow of blood

great and short saphenous emerge from the dorsal venous arch

great emerges from medial portion of arch and passes 2cm anterior and posterior to medial malleolus - travels up medial of leg, skirts behind medial femoral condyle of knee, pass up medial thigh going more anteriorly - through the saphenous opening (the cribiform fascia) 3cm below and lateral to the pubic tubercle to join the femoral vein. a number of venous tributaries join the vein here

short saphenous drains the lateral part of arch, goes behind the lateral malleolus, up posterior of leg with the sural vein, pierces fascia over the popliteal fossa and drains into the popliteal vein

short and long vein communicate at many levels

the popliteal vein lays in fossa between popliteal artery and tibial nerve

the femoral vein passes behind the femoral artery and lies medial to it at inguinal ligament

just before the long saphenous joins femoral, profunda femoris vein joins the femoral

when femoral goes under the inguinal ligament it becomes the external iliac vein

39
Q

describe the depp veins of the lower limb *

A

they run alongside the arteries as venae comitantes

40
Q

describe venae comitantes *

A

they are accompanying veins

multiple veins form a network of smaller veins with arteries which they accompany

there are connections between the venae comitantes

this allows heat exchange - cooled blood in veins from peripheries is warmed by blood from the arteries

artery pulses promote venous return

41
Q

what is cut down of the long saphenous vein *

A

when patient in shock and all vessels have collapsed but you need to give them fluid

cut long saphenous vein 2cm lateral and proximal to the medial malleolus and get fluid in this way - small canular is inserted into vein

not used as much today - flouid given byu interosseous administration - a needle inserted into the bone marrow of anterior tibia

in well equipt fascilities US can be used tp find a patent vein

42
Q

describe arterial embolism *

A

caused by sudden occlusion of an atherosclerotic vessle or by a thrombus formed by afib

if a vessel is suddenly occluded with no time for a collateral circulation to develop = acute ischaemia

intermittent claudication is where there is gradula occlusion of arteries, usually atherosclerotic - the muscles distal to occlusion become deprived of blood on exercise muscle pain, commonly in calf during activity

43
Q

describe compartment syndrome *

A

the neuromuscular compartments of the limbs are enclosed in fibrous sheaths which confine them

compartment syndrome is where ischemia is caused by trauma induced increased in pressure in a confined limb compartment - commonly anterior, posterior and lateral compartments of the leg

normal pressure is 25mmHg - if rise to 50-60mmHg = collapse of small vessels, but BP is 120/80mmHg - so you can still feel pulse even though tissues are not being perfused

acute compartment syndrome is trauma associated eg fractures or muscle damage/inflammation

chronic - exercise induced - muscles get pumped up with increased pressure if built muscle mass quickly and the fascia hasnt had any time to adjust - exercise induced discomfort

44
Q

treatment of acute compartment syndrome *

A

emergancy fasciotomy to prevent the death of muscle

45
Q

descrive varicose veins *

A

perforating veins connect superficial and deep veins, they have a valve so blood only flows from superficial to deep - spheno-femoral junction is most important

if valve is comprimised - blood pushed into superficial = swelling of superficial veins - leading to varicose veins

valve may be comprimised if FH, lifestyle or multiple pregnancy

can get ulcers/pain

ulcers are important to consider in people with dm, older people and people who are less mobile

can get lipodermatosclerosis - skin thickening because of the increased pressure in the superficial circulation - possible chronic inflammatory cause

treatment involves tying off sapheno-femoral junction

46
Q

describe DVT *

A

clot in deep veins

mainly in lower limb

risk factors - inactivity, long haul flights, surgery in abdo, pelvis or limbs, the pill

often silent but can present with pain and swelling in calf or proximal thigh

DVT can be dislodged - travel in veins and cause PE = sudden death

a distal dvt occurs in calf, distal occurs in thigh/pelvis - prox is dangerous because high risk of PE

dvts treated with anti-coag to avoid this

can cause increased back pressure in the deep veins = venous insufficiency and leg ulcers - this is post-phlebitic syndrome

superficial veins may also clot or be infected causing superficial thrombophlebitis - painful, the treatment is rest, ice, analgesic - less dangerous than dvt

47
Q

describe muscle pump of deep veins *

A

valves mean blood only flows up leg

deep veins are sandwiched between layers of calf muscles

during movement - contraction of muscle squeeze veins and push blood up - they contract distal valve and open prox

immobility means less efficient venous return from foot/leg - sluggish return = dvt

elastic surgical socks compress superficial veins so more blood is pushed into deep system = more vigorous deep flow - redeuced chance of DVT

48
Q

describe venous grafts *

A

coronary artery bypass graft

this is arterial bypass surgery around an occlusion

have to put the valves the right way round so that blood flows in right dirn

because of the anastomoses in the leg, there is rarely a problem in removing a superficial vein

49
Q

what is included in the peripheral NS

A

cranial and spinal nerves

50
Q

what is a spinal nerve *

A

formed from the union between an anterior (motor) and a dorsal (sensory) root

the roots merge at the intervertabral foramen to form a spinal nerve

51
Q

where do autonomic fibres run

A

between t1-l2 and s2-4`

52
Q

describe path of spinal nerves *

A

as soon as pass through intervertebral foramen splits into anterior and posterior ramus

the anterior rami merge to form the major plexi of the limbs

the posterior rami are less significant and are mainly cutaneous nerves

53
Q

dermatomes of lower limb *

A

l3 front of thigh

l4 front of leg

l5 dorsum of great toe

s1 lateral aspect of foot

s2-s4 perineum and perianal region

54
Q

describe the sequence for the knee jerk reflex *

A

tap

stretch the patella tendon

stimulation of afferent (1a) fibres in quadriceps

passes to spinal cord through posterior root

synapse with a motor neuron in anterior horn of the spinal cord

efferent signal to quadriceps

quadriceps extend the knee joint

55
Q

reflexes in the lower limb*

A

stretch reflexes/deep tendon reflexes and are monosynaptic

knee jerk - L3

ankle jerk - S1

56
Q

what is the sympathetic outflow to the lower limb

A

t11-l2

57
Q

when can the femoral nerve be damaged *

A

iatrogenic - traction injuries via hip replacements and laproscopic repair of inguinal hernias

or in erroneus attempted cannulations of the femoral a or n

58
Q

how can the lateral cutaneous nerve of the thigh be damaged *

A

passes 2cm medial to the ASIS at level of inguinal ligament

can be comprimised causing meralgia parasthesia - burning pain, numbness, and tingling sensation in the outer thigh.

59
Q

describe damage to the obturator nerve *

A

rarely damaged

pain in the distribution of teh obturator nerve could be indicative of malignant disease in pelvis

60
Q

describe injury to the superior gluteal nerve *

A

results in Tredelenburg gait - pelvis lurches during gait

commonest injury is during hip replacement

nerve lies 5cm proximal to tip of greater trochanteur and approaches the hip joint - should not extend >5cm from tip of greater trochanteur

61
Q

describe injury to the sciatic nerve *

A

after hip replacement

trauma eg hip dislocations or acetbular fractures

pelvic disease

common peroneal division more vulnerable than tibial

62
Q

how do you prevent damaging the sciatic nerve*

A

give an intramuscular injection in upper lateral quadrant of buttock - nerve most likely situated in lower inner qudrant

63
Q

describe injury to the common peroneal nerve *

A

at level of hip and round fibular neck

from trauma, knee replacement, and external pressure - from plasters or during surgical procedures

64
Q

describe damage to the tibial nerve *

A

very deep so rarely damaged in isolation

65
Q

describe damage to the saphenous nerve *

A

common

at medial malleolus after varicose vein surgery or at knee after ACL surgery

66
Q

describe anaesthetic nerve blocks

A

aid or substitute GA in surgery

eg femoral, sciatic, ankle, lateral cut nerve blocks

67
Q

what is the location of the femoral canal *

A

medial to femoral vein at inguinla ligament - within the canal is a lymph node

68
Q

palpate the femoral artery *

A

in midinguinal point

69
Q

palpate the popliteal artery *

A

in inferior of popliteal fossa against posterior surface of tibia

70
Q

palpate posterior tibial artery *

A

behind medial malleolus

71
Q

palpate dorsalis pedis artery *

A

dorsum of foot

lateral to the extensor hallucis longus tendon

72
Q

what structures are at risk during venepuncture of femoral vein *

A

femoral n

femoral a

femoral canal

73
Q

palpate the popliteal lymph nodes *

A

only when enlarged

around popliteal fossa along small saphenous vein

74
Q

palpate superficial inguinal lymph nodes *

A

near the termination of long saphenous vein

(deep inguinal nodes are along the proximal part of the femoral vein)

only palpable when enlarged

75
Q

what are the levels of the dermatomes in the lower limb *

A

l1 - inguinal region

l2- thigh-upper lateral

l3 - thigh- lower lateral

l4 - leg and great toe medial

l5 - leg anterolateral and foot and toes 2-4 dorsal

s1 - sole lateral margin and heel

s3-s4 buttock medial, intergluteal cleft and peineum

76
Q

how do you test the integrity of dermatomes *

A

touch in them with crude and light touch

77
Q

describe the principle of deep tendon reflexes *

A

when tendon is tapped and so stretched, there is involuntary contraction of that muscle

78
Q

test the patella tendon reflex - knee jerk *

A

ask subject to sit comfortably with legs dangling on edge of couch

examiner strike patella tendon with knee hammer

should see brisk extension of knee joint

palpate the contraction of the quadriceps

compare to opposite sife

79
Q

test the calcaneal tendon reflex *

A

ask pt to sit comfortably with legs dangling on edge of couch - examiner should strike calcaneal tendon with a knee hammer while holding foot slightly dorsiflexed with other hand

plantar flexion of ankle joint will occur

might be absent of S1 sopinal nerve root is affected or tibial nerve damage

80
Q

how would you test integrity of femoral nerve *

A

extension of the knee - test the quadriceps

sensation on anterior of thigh and medial side of leg and foot

81
Q

how would you test for integrity of the obturator nerve *

A

check adduction - medial compartment of thigh

sensation on medial compartment of thigh

82
Q

what is sciatica *

A

pain in the area of distribution of the sciatic nerve

l4 to s3 - over the buttock and in the posterolateral aspect of the leg

83
Q

what is the significance of anastomoses *

A

the femoral circumflex arteries, inferior and superior gluteal and obturator arteries, with branches from the internal pudnendal branches anastomose in gluteal and upper thigh region- these anastomoses can provide collateral circulation if one of the vessels becomes occluded

genicular branches from the femoral, popliteal and lateral circumflex arteries in thigh and the circumflex fibular artery and recurrent branches from the anterior tibial artery in leg form an anastomotic network around the knee joint

84
Q

describe the contents of the femoral triangle with regard to arterial sampling and catheter placement *

A

contents are: femoral nerve, artery, vein, lymph nodes (which are in femoral canal) from laterally to medially

radiological approaches involve catheterisation of fem a or v to get access to contralateral limb, ipsilateral limb, the vessels of the thorax and abdomen and the cerebral vessels

use the fem a to place catheters in vessels around the arch of the aorta and into coronary arteries to perform coronary angiography and angioplasty

access to fem v allows catheters to be manovered in renal and gonadal veins, the R atrium, R side of heart - pulmonary artery and distal vessels of the pulmonary tree

access to superior vena cava and great veins is also possible

85
Q

describe the lymphatic drainage of the lower limb *

A

most drain into superficial and deep inguinal lymph nodes located in the fascia just below the inguinal ligament

superficial inguinal nodes - approx 10 are in the superficial fascia and follow course of inguinal ligament; medially they extend inferiorly along terminal part of the great saphenous vein

superficial recieve lymph from gluteal region, lower abdo wall, perineum, and superficial regions of lower limb

superficial drain via vessels that accompany femoral vessels into external iliac nodes, associated with external iliac artery

deep inguinal - up to 3 in number, medial to femoral vein, recieve lymph from deep lymphatics associated with femoral vessels and glans penis/clitoris

deep interconnect with superficial and drain into external iliac nodes via vessels medial to femoral vein

popliteal nodes - deep nodes close to popliteal vessels - they recieve lymph from superficial vessels which accompany superficial saphenous vein, and deep areas of leg and foot

popliteal drain into superficial and deep inguinal

86
Q

describe how lymph drainage is related to tumour/infection spread *

A

lymph drains areas in the leg

if these areas are affected or have cancer - these cells will be drained to the nodes

this causes the node to be active - the rapid cell turnover and production of local inflammatory mediators cause node to enlarge and become tender

because the flow through the nodes is slow, cells metastisise away from primary tumours and enter lymphatic vessels - lodge and grow as secondary tumours in lymph nodes