Embryology (Lecture 2) Flashcards

(117 cards)

1
Q

Limb bud appear in the __ week

A

4th

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2
Q

limb bud appear as

A

as small elevations on the ventrolateral body wall

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3
Q

limb buds are derived from

A

the somatic body wall (lateral plate mesoderm)

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4
Q

Mesenchyme (embryonic tissue) covered in

A

ectoderm

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5
Q

upper limb buds are visible in the

A

cervical region ~day 24

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6
Q

lower buds are visible in the

A

lumbar region ~day 28

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7
Q

limb bud contains MESENCHYME that will form ____ of the lower extremity

A

cartilage/bone and dermis

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8
Q

muscles are derived from

A

somites, myoblasts migrate into developing limb

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9
Q

where are motor units derived from?

A

spinal cord

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10
Q

schwann cells,
melanocytes,
sensory neurons
and sympathetics are derived from

A

neural crest cells

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11
Q

proximal/distal directional axes of limb

A

thigh,leg,foot

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12
Q

dorsal/ventral directional axes of limb

A

anterior vs posterior thigh/leg

dorsum vs plantar foot

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13
Q

cranial/caudal directional axes of limb

A

big toe (cranial,preaxial) to little toe (caudal, postaxial)

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14
Q

limb elongation progresses from `

A

proximal to distal

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15
Q

stylopod

A

thigh

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16
Q

zeugopod

A

leg

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17
Q

autopod

A

foot

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18
Q

in early stages of limb elongation the limbs appear as

A

flippers on the ventrolateral wall

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19
Q

ectoderm over distal tip of limb condenses to form

A

the apical ectoderm ridge (AER)

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20
Q

what represents to dorsal/ventral boundary

A

apical ectoderm ridge (AER)

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21
Q

underlying mesenchyme induces

A

the formation of AER

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22
Q

AER induces the proliferation of

A

the underlying mesenchyme and elongation of the limb (progress zone)

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23
Q

mesenchyme obtains positional information about

A

future proximal/distal location

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24
Q

studies that removed the AER showed

A

the formation of truncated limb

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25
mesenchyme will differentiate into
cartilage as a cartilage precursor model to bone.
26
in fetal development where do the flexor and extensor compartments meet?
pre-axial (cranial) and post-axial (caudal) borders
27
Pre-axial (cranial) border
medial side of the limb (tibal side)
28
which border is demarcated by the great saphenous vein
pre axial (cranial) border
29
post-axial (caudal) border
lateral side (fibular side) of the limb
30
which border is demarcated by the small saphenous vein
the post-axial (caudal) boarder
31
mesenchyme differentiates into
cartilage
32
ossification occurs from
cartilage templates (most) or connective tissue
33
what develops from inter-membranous ossification
tips of distal phalanges (ungal tuberosity , tufts)
34
when does bone become visible on radiographs
once it begins ossification
35
joints form from
mesenchyme between cartilage templates of future bones
36
joints can differentiate into either
1. collagen (fibrous) 2. hyaline cartilage (synchondrosis) 3. joint cavity (synovial)
37
Synovial Joint
development of an interzone between cartilage templates
38
in a synovial joint where does the cavitation develop
within interzone
39
limb muscles are derived from
hypaxial myogenic precursors that migrate ventrally along dorsolateral wall
40
when does migration of the hypaxial myogenic precursors begin
week 4/5
41
muscle mass increases by __ until ___
mitosis until mid fetal period
42
myoblasts form 2 condensations
- dorsal mass (extensor) | - ventral mass (flexor)
43
dorsal mass is located ___ before limb rotation
posteriorly (dorsal)
44
After limb rotation, dorsal mass is located
- Posterior in upper limb - Anterior in lower limb - Not lower limb girdle (pelvic girdle)
45
Ventral mass is located ___ before limb rotation
anterior/ventrally
46
after rotation, ventral mass is located
- Anterior in upper limb - Posterior in lower limb - Not lower limb girdle
47
__ rami from spinal cord segments migrate into developing limb
Ventral
48
Dorsal branches (divisions) innervate
dorsal muscle mass
49
Ventral branches (divisions) innervate
ventral muscle mass
50
axons innervate muscle mass when?
before they split into individual muscles
51
lumbar plexus
ventral rami of L1-4
52
ventral rami have __ division
ventral and dorsal
53
subcostal nerve
- ventral rami T12 | - cutaneous supply to superior anterolateral thigh
54
Branches of the lumbar plexus
1. Iliohypogastric 2. Ilioinguinal 3. Genitofemoral 4. Lateral femoral cutaneous 5. Nerves to psoas major muscle 6. Femoral 7. Obturator 8. Accessory Obturator
55
Ventral Division of L1
Iliohypogastric and Ilioinguinal
56
Ventral division of L1,L2
Genitofemoral
57
dorsal divisions of L2,3
Lateral Femoral cutaneous
58
dorsal divisions of L2-4
- nerve to psoas major muscle | - Femoral, (nerve to iliacus muscle)
59
Ventral divisions of L2-4
Obturator
60
Ventral divisions of L3,4
Accessory Obturator
61
A part of L4 also contributes joints with L5 ventral rami to form
lumbosacral trunk
62
branches of the sacral plexus
``` Superior Gluteal Inferior Gluteal Nerve to Piriformis Perforating cutaneous nerve Sciatic Posterior cutaneous nerve to thigh Nerve to Quadratus femoris Nerve to obturator Internous Pudendal ```
63
dorsal divisions of L4-S1
Superior gluteal
64
dorsal divisions of L5-S2
inferior gluteal
65
dorsal divisions of S1,2
Nerve to piriformis
66
dorsal divisions of S2,3
Perforating cutaneous nerve
67
dorsal divisions of L4-S2 and ventral divisions of L4-S3
Sciatic
68
dorsal divisions of S1,2 and ventral divisions of S2,3
Posterior cutaneous nerve of thigh
69
ventral divisions of L4-S1
Nerve to quadratus femoris
70
ventral divisions of L5-S2
Nerve to obturator internus
71
ventral divisions of S2-4
Pudendal
72
Zone of polarizing activity (ZPA) is a signaing center that forms in
the dorsal mesenchyme just below AER (apical ectodermal ridge)
73
controls pattern formation on an anterior/posterior axis
zone of polarizing activity
74
the Hallux at the Cranial/anterior end is exposed to a __ amount of morphogen compared to the little toe
lesser
75
one of the important morphogens influencing the formation of the digits
Sonic Hedghog
76
Primary vessel that supplies the developing limb
axis (axial) artery
77
axis artery arises from
dorsal root of umbilical artery
78
the axis artery passes along
posterior aspect of developing limb in the plantar foot
79
external iliac forms from
dorsal root of umbilical artery
80
femoral artery forms from
exteral iliac artery
81
femoral artery travels to
posterior thigh where it then communicates with the axis artery
82
proximal to the femoral artery communicating the with axial artery
the axial artery will disappear
83
axis artery disappears but what arteries persist
inferior gluteal and ischiadic artery
84
___ eventually becomes major supplier to lower extremity through its communication with __
femoral artery; popliteal artery
85
Dorsal root of umbilical becomes
common iliac
86
Remnants of axis artery
- Inferior gluteal - Popliteal - Ischiadic artery (sciatic artery) - Fibular
87
5th week
- Hand and foot plates develop, hands develop earlier | - Flat and paddle shaped
88
6th week
- Joints become more observable - Digital rays of hand plate develop - Limbs move to a more ventral position
89
7th Week
- Digital rays of the foot develop | - Limb rotation
90
limb rotation initially the knees and elbows are facing
laterally
91
upper and lower limbs rotate in
oppositie directions
92
upper limbs rotate ___ to face caudally
laterally/exertnall
93
lower limbs rotate ___ to so knees face cephalically
medially/internally
94
8th week
- Fetal position is attained by the end of the week | - Mesenchyme between digits degenerates (apoptosis)
95
Complete or partial union between 2 or more tarsal bones
tarsal coalition
96
developemntal fusion that results from incomplete or faulty mesenchymal segmentation
tarsalcoalation; Genetically programed to develop
97
in tarsal coalition, ___ and __ are most common
Calcaneonavicular and talocalcaneal
98
tarsl coalition is classified by the type of tissue that bridges the bones
- fibrous (syndesmosis) - cartilaginous (Synchondrosis) - bony (synostosis)
99
syndactyly
congenital malformation caused by the the failure of differentiation of digits (mesenchyme doesn’t separate)
100
fusion of toes in syndactyly can be either __ and can effect __
single or multiple; skin and soft tissue OR soft tissue and bone
101
Cutaneous Syndactyly
- Failure of mesenchyme degeneration between digits - Causes webbing between digits - Can be complete or partial - More of a functional problem in the hand
102
Osseous Syndactyly
Failure of mesenchyme to segment in the foot
103
Amelia
lack of limb; absence/failure of formation of an entire limb
104
amelia is cause by
interruption of the limb formation process (prevented or interrupted early on
105
absence of all limbs
tetra-amelia
106
Meromelia
partial absence of a limb
107
where does meromelia occur
can occur at any level of the limb
108
phocomelia
seal limb | type of meromelia where rudimentary hands or feet are attached to trunk
109
amelia, meromelia, phocomelia can be cause by
vascular interuption, genetic, or caused by terogens (like thalidomide, chemicals, radiation)
110
congenital absence of bone example
fibula (fibular hemimelia) can be partial or complete absence
111
Cleft foot or hand (ectrodactyly)
- "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
112
Polydactyly (many digits) formation of extra digits that can be due to
genetic defect or part of a syndrome. can appear differently.
113
Polydactyly in lower limb types
pre axial post axial central
114
Pre-axial polydactyly:
extra digit towards the hallux
115
Post-axial:
- extra digit towards little toe - more common - Surgically corrected
116
central
extra digit involves digits 2,3, or 4
117
Macrodactyly
- Enlargment of digits | - Overgrowth of bone/tissue