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Lower Extremity Anatomy II > Lecture 2 > Flashcards

Lecture 2 Flashcards

1
Q

Limb bud

A
  • Appear in the 4th week as small elevations on the ventrolateral body wall
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2
Q

Limb bud are derived from

A
  • Somatic body wall (lateral plate mesoderm)
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3
Q

Ectoderm covers

A
  • Mesenchyme (embryonic tissue)
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4
Q

Upper limb buds

A
  • Visible in the cervical region ~ 24
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5
Q

Lower limb buds

A
  • Visible in the lumbar region ~ day 28
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6
Q

Limb axis formation

A
  • Directional axes of limb
  • Proximal/Distal
  • Dorsal/Ventral
  • Cranial/Caudal
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7
Q

Proximal/Distal limb axis formation applies to

A
  • Thigh
  • Leg
  • Foot
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8
Q

Dorsal/Ventral limb axis formation applies to

A
  • Anterior vs. posterior thigh/leg

- Dorsum vs. plantar foot

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9
Q

Cranial/Caudal limb axis formation applies to

A
  • Big toe (cranial, preaxial) to little toe (caudal, postaxial)
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10
Q

Limb bud contains mesenchyme that will form

A
  • Cartilage/bone

- Dermis of the lower extremity

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11
Q

Muscles are derived from

A
  • Somites

- Myoblast migrate into developing limb

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12
Q

Motor neurons are derived from

A
  • Spinal cord
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13
Q

Structures derived from neural crest cells

A
  • Schwann cells
  • Melanocytes
  • Sensory neurons
  • Sympathetics
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14
Q

Limb elongation

A
  • Progresses from proximal to distal

- Thigh (stylopod), leg (zeugopod), foot (autopod)

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15
Q

Early stage of limb elongation

A
  • Limbs appear as flippers on the ventrolateral wall
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16
Q

Ectoderm over distal tip of limb

A
  • Condenses, forming apical ectodermal ridge (AER)

- Represents the dorsal/ventral boundary

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17
Q

Underlying mesenchyme

A
  • Induces the formation of the AER
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18
Q

Apical ectodermal ridge (AER) induces

A

P-roliferation of underlying mesenchyme

- Elongation of the limb (progress zone)

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19
Q

Mesenchyme obtains

A
  • Positional information about future proximal/distal location
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20
Q

Studies that removed the AER showed

A
  • Formation of a truncated limb
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21
Q

Mesenchyme will differentiate into

A
  • Cartilage (cartilage model precursor to bone)
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22
Q

Pre-axial and post-axial borders

A
  • Location where flexor and extensor compartments of the limb meet in fetal development
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23
Q

Pre-axial (cranial) border

A
  • Medial side (tibial side) of the limb

- Demarcated by the great saphenous vein

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24
Q

Post-axial (caudal) border

A
  • Lateral side (fibular side) of the limb

- Demarcated by the small saphenous vein

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25
Q

Bone formation

A
  • Mesenchyme –> cartilage
  • Ossification from cartilage template (most bones) or connective tissue
  • Once ossifying, visible on radiograph
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26
Q

Ossification from cartilage template/connective tissue

A
  • Tips of distal phalanges (ungal tuberosity, tufts)

- Develops from intramembranous ossification

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27
Q

Joint formation

A
  • Forms from mesenchyme between cartilage templates of future bone
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28
Q

Mesenchyme between cartilage templates of future bone can differentiate into

A
  • Collagen (fibrous)
  • Hyaline cartilage (synchondrosis)
  • Joint cavity (synovial)
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29
Q

Synovial joint

A
  • Development of an interzone between cartilage templates (trilaminar)
  • Cavitation develops within interzone
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30
Q

Limb muscles

A
  • Derived from hypaxial myogenic precursors
  • Migrate ventrally along dorsolateral body wall
  • Migration starts week 4/5
  • Muscle mass increases by mitosis until mid-fetal period
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31
Q

2 condensations formed by myoblast

A
  • Dorsal mass (extensors)

- Ventral mass (flexors)

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32
Q

Dorsal mass (extensors) initially located

A
  • Posteriorly (dorsally) before limb roation
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33
Q

After limb rotation, dorsal mass (extensors) located

A
  • Posterior in upper limb
  • Anterior in lower limb
  • Not lower limb girdle (pelvic girdle)
34
Q

Ventral mass (flexors) initially located

A
  • Anteriorly (ventrally) before limb rotation
35
Q

After limb rotation, ventral mass (flexors) located

A
  • Anterior in upper limb
  • Posterior in lower limb
  • Not lower limb girdle
36
Q

Innervation of developing limb

A
  • Ventral rami from spinal cord segments migrate into developing limb
  • Axons innervate muscle masses before they split into individual muscle
37
Q

Dorsal branches (divisions) of ventral rami innervate

A
  • Dorsal muscle mass
38
Q

Ventral branches (divisions) ventral rami innervate

A
  • Ventral muscle mass
39
Q

Subcostal nerve

A
  • Ventral rami T12

- Cutaneous supply to superior anterolateral thigh

40
Q

Lumbar plexus branches

A
  • Iliohypogastric (ventral division of L1)
  • Ilioinguinal (ventral division of L1)
  • Genitofemoral (ventral divisions of L1,2)
  • Lateral femoral cutaneous (dorsal divisions of L2,3)
  • Nerves to psoas major muscle (dorsal divisions of L2-4)
  • Femoral (dorsal divisions of L2-4)
  • Nerve to iliacus muscle
    Obturator (ventral divisions of L2-4)
  • Accessory obturator (ventral divisions of L3,4)
41
Q

Part of L4 joins with L5 ventral rami to form

A
  • Lumbosacral trunk
42
Q

Sacral plexus branches

A
  • Superior gluteal (dorsal divisions of L4-S1)
  • Inferior gluteal (dorsal divisions of L5-S2)
  • Nerve to piriformis (dorsal divisions of S1,2)
  • Perforating cutaneous nerve (dorsal divisions of S2,3)
  • Sciatic (dorsal divisions of L4-S2 and ventral divisions of L4-S3)
  • Posterior cutaneous nerve of thigh (dorsal divisions of S1,2 and ventral divisions of S2,3)
  • Nerve to quadratus femoris (ventral divisions of L4-S1)
  • Nerve to obturator internus (ventral divisions of L5-S2)
  • Pudendal (ventral divisions of S2-4)
43
Q

Digit formation

A
  • Zone of polarizing activity (ZPA)
  • Signaling center that forms in the dorsal mesenchyme just below AER
  • Controls pattern formation on an anterior/posterior axis
  • Hallux vs. little toe
44
Q

Axis artery (axial)

A
  • Primary vessel that supplies the developing limb
45
Q

Axis artery arises from

A
  • Dorsal root of umbilical artery
46
Q

Axis artery pathway

A
  • Passes along posterior aspect of developing limb to plantar foot
47
Q

External iliac forms from

A
  • Dorsal root of umbilical artery
  • Femoral artery then forms from external iliac artery
  • Travels to posterior thigh and communicates with axial artery
48
Q

Once femoral artery forms and communicated with axial artery

A
  • Axis artery proximal to this disappears

- Inferior gluteal and ischiadic artery persist

49
Q

Axial artery eventually becomes

A
  • Major supplier to lower extremity through its communication with popliteal artery
50
Q

Dorsal root of umbilical artery becomes

A
  • Common iliac
51
Q

Remnants of axis artery

A
  • Inferior gluteal
  • Popliteal
  • Ischiadic artery (sciatic artery)
  • Fibular
52
Q

5th week

A
  • Hand and foot plates develop (hands develop earlier)

- Flat and paddle shaped

53
Q

6th week

A
  • Joints become more observable
  • Digital rays of hand plate develop
  • Limbs move to a more ventral position
54
Q

7th week

A
  • Digital rays of the foot develop

- Limb rotation

55
Q

Limb rotation

A
  • Knee/elbows initially face laterally

- Upper/lower limbs rotate in opposite directions

56
Q

8th week

A
  • Fetal position is attained by the end of the week

- Mesenchyme between digits degenerates (apoptosis)

57
Q

Upper limb rotation (7th week)

A
  • Rotate laterally/externally to face caudally
58
Q

Lower limb rotation (7th week)

A
  • Rotate medially/internally so the knees face cephalically
59
Q

Tarsal coalition

A
  • Complete or partial union between 2 or more tarsal bones

- Developmental fusion that results from incomplete or faulty mesenchymal segmentation

60
Q

Tarsal coalition development

A
  • Genetically programed to develop

- Calcaneonavicular and talocalcaneal are most common

61
Q

Tarsal coalition classification

A
  • Classified by the type of tissue that bridges the bones
  • Fibrous (syndesmosis)
  • Cartilaginous (synchondrosis)
  • Bony (synostosis)
62
Q

Syndactyly

A
  • Congenital malformation caused by the the failure of differentiation of digits
  • Mesenchyme doesn’t separate
63
Q

Syndactyly effects

A
  • Fusion of toes (or fingers)
  • May be single or multiple
  • Can affect skin and soft tissue, or soft tissue and bone
64
Q

Cutaneous syndactyly

A
  • Failure of mesenchyme degeneration between digits
  • Causes webbing between digits
  • Can be complete or partial
    More of a functional problem in the hand
65
Q

Osseous syndactyly

A
  • Failure of mesenchyme to segment in the foot
66
Q

Amelia

A
  • Absence of an entire limb (failure of formation)

- Can be 1 or multiple

67
Q

Amelia is caused by

A
  • Interruption of the limb formation process (prevented or interrupted early on)
68
Q

Tetra-amelia

A
  • Absence of all limbs
69
Q

Meromelia

A
  • Partial absence of limb

- Can occur at any level of the limb

70
Q

Phocomelia (“seal limb”)

A
  • Type of meromelia where rudimentary hands or feet are attached to trunk
71
Q

The various types of missing limb or limb malformations can result from

A
  • Vascular interruption
  • Genetic
  • Teratogens
72
Q

Teratogens

A
  • Agents that can cause malformation of embryo

- Thalidomide, chemicals, radiation

73
Q

Congenital absence of bone

A
  • Fibula (fibular hemimelia)

- Can be partial or complete

74
Q

Cleft foot/hand (ectrodactylyl

A
  • “Lobster Claw Foot (hand)”
  • Rare anomaly
  • Central conical defect from periphery to tarsals
  • Presentation varies
  • Affects central rays
  • Surgically addressed early on to prevent pathological adaptation
75
Q

Polydactyly (“many digits”)

A
  • Formation of extra digits
  • Can be due to genetic defect or part of a syndrome
  • Different appearances
76
Q

Polydactyly in lower limb

A
  • Pre-axial
  • Post-axial
  • Centra
77
Q

Pre-axial polydactyly

A
  • Extra digit towards the hallux
78
Q

Post-axial polydactyly

A
  • Extra digit towards little toe
  • More common
  • Surgically corrected
79
Q

Central polydactyly

A
  • Extra digit involves digits 2, 3, or 4
80
Q

Macrodactyly (“large digits”)

A
  • Enlargment of digits

- Overgrowth of bone/tissue

Lower Extremity Anatomy II (9 decks)

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