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MSK 💪🏾 > Development of the Upper and Lower Limb > Flashcards

Development of the Upper and Lower Limb Flashcards

1
Q

When do Upper limb buds + lower limb buds appear

A

Upper limb buds-day 26 or 27,

lower limb buds- 1 or 2 days later.

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2
Q

Upper limb buds develop opposite -

A

he caudal cervical segment,

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3
Q

lower limb bud develop opposite-

A

lumbar and upper sacral segment.

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4
Q

Limb buds consist of-

A

– A mesenchymal core

– Covered by ectoderm

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5
Q

wht starts off the process of limb

development ( elongation )

A

Activation of mesenchymal cells in the lateral

mesoderm

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6
Q

Paraxial mesoderm-

A

• Divides into 42-44 pairs

of somites

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7
Q

Intermediate mesoderm

A

• Urogenital system

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8
Q

Lateral plate mesoderm

A

– Subdivision of the intraembryonic(secondary) mesoderm

– Forms the connective tissue of the limbs

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9
Q

Somites give rise to-

A

Sclerotome,Myotome,Dermatome

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10
Q

The Homeobox (HOX) gene initiates

A

Limb development

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11
Q

Activation of mesenchyme induces formation-

A

of an apical ectodermal ridge (AER)

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12
Q

Mesenchyme condenses and gives rise to -

A

skeleton & connective tissue

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13
Q

Apical ectodermal ridge (AER)

A

– Ectodermal thickening at the apex of each limb bud

– Inductive influence on limb mesenchyme

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14
Q

Progress zone (AER)

A

Stimulates proliferation of mesenchyme

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15
Q

– Proximodistal axis (AER)

A

Growth and development of the limbs

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16
Q

Proximodistal Axis -

A

Signaling Center - (AER)
Molecular Signal-Fibroblast growth
factors (FGF-2,-4,-8)

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17
Q

Anteroposterior Axis

A

Signaling Center-Zone of polarizing
activity (ZPA)
Molecular Signal-Sonic hedgehog (Shh)

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18
Q

Dorsoventral Axis

A

Signaling Center-Dorsal ectoderm + Ventral ectoderm

Molecular Signal- Wnt-7a (dorsal)+ En-1 (ventral)

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19
Q

Limb Development – 28 days

A

Limb buds appear as small elevations of the ventrolateral body wall
– Upper limb buds appear by 26th – 27th day
• Opposite C5-T1 spinal segments (
– Lower limb buds appear ~2 days later
• Opposite L4–S3 spinal segments

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20
Q

Limb Development – 32 days

A

Formation of hand and foot plates

21
Q

Limb Development -Week 6

A

Mesenchymal tissue in the hand plates condense to form digital ray ( finger
buds ), outlines the pattern of the digits
-– Tissue between digital rays
undergoes apoptosis

22
Q

Limb Development -Week 7

A

– Mesenchymal tissue in the foot plates condense to form digital ray ( toe
buds ), outlines the pattern of the digits.
– Tissue between digital rays undergoes apoptosis (programmed cell death )
• Forming notches between the digit rays

23
Q

Limb Development -Week 8 (56 days)

A

– Fingers and toes are distinct and separated

24
Q

Positional Changes of Developing Limbs-48 days

A

Limbs extend ventrally
– Hand plates & foot plates
face each other

25
Q

Positional Changes of Developing Limbs-51 days

A

Upper limbs bent at elbows

– Hands curved over thorax

26
Q

Positional Changes of Developing Limbs-54th day

A

Soles of feet face medially

27
Q

Positional Changes of Developing Limbs-56th day

A

–Elbows point caudally

– Knees point cranially

28
Q

Development of Cartilaginous Bones- 5th week

A

Chondrification centers

29
Q

Development of Cartilaginous Bones- 6th week

A

6th week, the entire limb

skeleton is cartilaginous

30
Q

Development of Cartilaginous Bones- 7th week

A

Osteogenesis of the long
bones begins in the 7th
week
– Primary ossification centers

31
Q

Ossification of Appendicular Skeleton- Diaphysis

A

Formed by primary center of ossification

• Appear by 7th -8 th week

32
Q

Ossification of Appendicular Skeleton- Epiphysis

A

– Formed by secondary centers of ossification

• Appear during first 4 yrs

33
Q

Ossification of Appendicular Skeleton-Epiphyseal plate

A 
- Growth plate
between diaphysis
and epiphysis
– Adds length to the
bone
– Persist until growth
period is over
33
Q

Ossification of Appendicular Skeleton-Epiphyseal plate

A 
- Growth plate
between diaphysis
and epiphysis
– Adds length to the
bone
– Persist until growth
period is over
34
Q

Myotomes of Body Somites- Epaxial myotome

A

intrinsic muscles of back

35
Q

Myotomes of Body Somites- Hypaxial division

A

(ventral)

36
Q

when do the Sensory axons enter the limb buds-

A

Sensory axons enter limb buds after the motor axons , + Motor axons arise from the spinal cord & enter limb
bud during the 5th week

37
Q

• Neural crest cells

A

-Precursors of Schwann cells
– Surround motor and sensory nerve fibers in the limbs
– Form the neurolemma and myelin sheaths

38
Q

Development of Limb Arteries-intersegmental arteries

A

– Arise from dorsal aorta
– Form fine capillary network
throughout mesenchyme

39
Q

Cutaneous syndactyly

A

– Webbing of the digits – failure of webs to degenerate

between 2 or more digits

40
Q

Osseous syndactyly

A

– Fusion of the bones – failure of development of notches

between the digital rays

41
Q

Polydactyly

A
  • Supernumerary digits
  • Disruption of the anteroposterior pattern
  • Inherited as a dominant trait
42
Q

Club Foot (Congenital Talipes )

A

Talipes equinovarus ( is most common type )
• Twice more frequently in males as in females.
• Sole of foot is turned medially and the foot is inverted.
• Multifactorial pattern of inheritance.

43
Q

Amelia

A

Complete absence of limbs
– Suppression of limb bud
development in the 4th week

44
Q

Meromelia

A

Partial absence of limbs
– Disturbance of limb
development during 5th week

45
Q

Cleft Hand & Cleft Foot (Ectrodactyly)

A

Absence of one or more central digits
– Failure of development of one or more digital rays
• Remaining digits are partially or completely fused

46
Q

Amniotic Band Syndrome

A

ears in the amnion result in amniotic bands
• May encircle fetal limbs & digits
– Ring constrictions
– Amputations

47
Q

VACTERL Syndrome

A 
at least three of these characteristic features
– Vertebral defects
– Anal atresia
– Cardiac defects
– Tracheo-esophageal fistula
– Renal anomalies
– Limb abnormalities

MSK 💪🏾 (36 decks)

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