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Clinical Morphology > Embryology > Flashcards

Embryology Flashcards

1
Q

When do limb buds appear?

A

At 4 weeks

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2
Q

3 planes of limb bud development

A

Proximal-distal, dorsal-ventral, anterior-posterior

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3
Q

What gene regulates proximal-distal limb development

A

FGF

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4
Q

Describe production of FGF

A

Initially produced by mesoderm which causes the AER to form, then produced by AER to signal proliferation in mesoderm

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5
Q

Describe how digits form

A

Apoptosis of cells in the AER to separate it into five digits

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6
Q

Wnt-7a

A

Signalling protein expressed by AER that activates LMX-1 in the mesoderm to form dorsal structures

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7
Q

LMX-1

A

Activated by Wnt-7a, responsible for forming dorsal structures

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8
Q

Deletion of LMX-1 causes

A

both sides to be ventral

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9
Q

Engrailed1

A

Activated by the ectoderm on the ventral side of the limb to repress WNT-7a, to create a ventral and dorsal side

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10
Q

Shh

A

Signalling protein produced at posterior base of limb buds

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11
Q

Zone of Polarizing Activity

A

Area that produces Shh

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12
Q

Placing Shh or ZPA to anterior limb bud would cause

A

mirror duplication of structures

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13
Q

Hox genes

A

Activated by Shh diffusing across limb bud, responsible for differentiation pattern of anterior-posterior digits and segmental organization of entire embryo cranial-caudal

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14
Q

Gene responsible for proximal-dorsal limb development

A

FGF

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15
Q

Genes responsible for dorsal-ventral limb development

A

Wnt-7a, LMX-1, engrailed1

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16
Q

Genes responsible for anterior-posterior limb development

A

Shh, Hox

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17
Q

Genes responsible for cranial-caudal segmental organization of embryo

A

Hox

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18
Q

Ossification type used for long bones

A

Endochondral ossification

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19
Q

Ossification type used for flat bones of skull and face

A

Intramembranous ossification

20
Q

Mesenchyme

A

Loosely organized, mesodermal tissue that develops into connective and skeletal tissues

21
Q

Process of intramembranous ossification

A

Mesenchyme cells differentiate directly into osteoblasts

22
Q

Process of intramembranous ossification

A

Mesenchyme differentiates into chondroblasts which produce a cartilage model that then becomes vascularized, introducing osteoblasts. Chondrocytes get stuck at the epiphyses.

23
Q

Layers of epiphyseal plate

A

Resting, proliferation, hypertrophy, calcification, ossification

24
Q

Zone of calcification

A

where chondroblasts mineralize the surrounding matrix

25
Q

Zone of hypertrophy

A

where chondroblasts undergo apoptosis

26
Q

Zone of ossification

A

where osteoblasts bind to mineralized matrix and deposit bone matrix

27
Q

What area of trilaminar embryo becomes skeletal muscle?

A

Paraxial mesoderm (closest to notochord and neural tube)

28
Q

Somites

A

Segments in a cranial-caudal sequence in the trunk

29
Q

Somites differentiate into

A

Axial skeleton, some dermis, all skeletal muscle

30
Q

When do axons of motor neurons enter the limb bud

A

During 5th week

31
Q

When do axons of sensory neurons enter the limb bud

A

Soon after the motor neuron axons enter

32
Q

Dermatome

A

Area of the skin innervated by one spinal nerve

33
Q

When do limbs rotate?

A

6-8 weeks

34
Q

In what way do limbs rotate?

A

Arms laterally and legs medially

35
Q

When are embryos susceptible to limb malformations?

A

4-5 weeks

36
Q

Reduction deficit

A

All or part of limb is missing

37
Q

Types of reduction deficit

A

Meromelia, amelia, phocomelia

38
Q

Thalidomide effects

A

Amelia at week 4, meromelia at week 5

39
Q

Mechanism of thalidomide

A

Disrupts AER and its production of FGF

40
Q

Duplication defect

A

Extra limb elements are present

41
Q

Example of duplication defect

A

Polydactyly

42
Q

Polydactyly

A

Shh is expressed in anterior limb bud, causing mirror extra digits. Caused by ZPA duplication

43
Q

Dysplasia

A

Malformation of part of limb

44
Q

Example of dysplasia

A

Syndactyly

45
Q

Syndactyly

A

Abnormal fusing of the digits from reduced apoptosis in AER

Clinical Morphology (18 decks)

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