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Developmental Biology > M2. development of xenopus laevis > Flashcards

M2. development of xenopus laevis Flashcards

1
Q

the vertebrate body plan

A

-similar basic body plan

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2
Q

vertebral column

A

segmented backbone surrounding the spinal cord

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3
Q

anterior-posterior axis

A
  • head - trunk - tail

- head end enclosed in a skull (bone or cartilage)

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4
Q

dorsal-ventral axis

A
  • spinal cord (d)

- mouth (v)

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5
Q

bilateral symmetry

A

dorsal midline

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6
Q

phylotypic stage

A

-all chordate embryos pass through the phylotypic stage
(embryos are similar in appearance)
-common features : head, notochord, neural tube (earliest appearance of nervous system), somites (blocks of mesoderm)

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7
Q

all vertebrate embryos undergo a similar pattern of development

A
  • gametogenesis
  • fertilization
  • cleavage
  • gastrulation
  • notochord formation
  • neurulation
  • somitogenesis
  • organogenesis
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8
Q

cleavage

A

earliest cell division, rapid cell division through which embryo becomes divided into smaller cells

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9
Q

gastrulation

A

dynamic process through three germ layeter (ectoderm, mesoderm, endoderm) organize themselves

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10
Q

notochord formation

A

column of mesoderm located just ventral to neural tube

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11
Q

neurulation

A

formation of the neural tube - precursor to nerve cord

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12
Q

somitogenesis

A

formation of regularly spaced blocks of mesoderm (somites) flaking notochord that give rise to skeleton and muscle

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13
Q

organogenesis

A

development of organs

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14
Q

model amphibian embryo: xenopus laevis

A
  • basis for what we know about early development of the embryo
  • embryos are large (scaled bar 0.5mm) - allowed for dissection of the early embryo
  • dissected tissues easy to culture
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15
Q

xenopus laevis: egg

A
  • egg has a distinct polarity –> animal to vegetal axis (bar 1mm)
  • dark pigmented animal region and heavier yolk vegetal region
  • sperm enters animal region
  • zygote is diploid (2N)
  • first cleavage along animal -vegetal axis
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16
Q

xenopus blastulation: cleavage of the embryo to form blastomeres

A
  • first cleavage along A/V axis, divides egg in left -right
  • second cleavage 90 degrees to first cleavage
  • third cleavage equatorial and asymmetric - four small animal and four small vegetal cells, eight total blastomeres
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17
Q

blastula

A

germ layers start to form
(ectoderm, endoderm, mesoderm)

an animal embryo at the early stage of development when it is a hollow ball of cells.

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18
Q

blastula stage :

A
  • reached after 12 divisions (~4096 cells)
  • has radial symmetry (ie. no visible sign of A/P or D/V axis)
  • has blastocoel
  • marginal zone
19
Q

blastocoel

A

a fluid filled cavity in animal region

20
Q

marginal zone

A

equatorial ring around embryo separating animal and vegetal region

21
Q

ectoderm

A

animal region- epidermis and nervous system

22
Q

mesoderm

A

marginal zone - muscle, bone, blood, heart

23
Q

endoderm

A

vegetal zone - intestine , lungs, liver, pancreas

24
Q

xenopus laevis : gastrulation

A

the morphogenic process occurring in three dimensions where endoderm and mesoderm are internalized
-blastopore

25
Q

blastopore

A

small slit like in folding of marginal zone on dorsal side, site of embryonic organizer (i.e. Spemann-Mangold organizer)
-organized dorsal development and antero-posterior axis

26
Q

gastrula mesoderm and endoderm

A

enter blastopore and migrate (via involution) to the future anterior of the embryo
-first tissues to enter the embryo are most anterior

27
Q

involution

A

germ layer migrate as a coherent sheet of cells

28
Q

gastrula : ventral and dorsal

A

ventral side initiates involution after dorsal side - delayed but similar cell movement occur on ventral side

  • epiboly
  • all three layers change shape and elongate
29
Q

epiboly

A

ectoderm spreads to cover embryo

30
Q

gastrula: archentron

A

a second cavity forms during gastrulation (future gut cavity) –> blastocoel reduces in size
-mesoderm and endoderm spread to the left and right of the midline

-lateral mesoderm spreads ventrally to cover inside of archenteron

31
Q

late gastrulation

A
  • blastopore closed (future anus)
  • the mesoderm contacts both the ectoderm and endoderm along the antero -posterior axis
  • mesoderm is patterned along its antero-posterior axis via the action of the organizer
  • ectoderm covers embryo
  • yolk cells remain as food source
32
Q

neurulation

A
  • dorsal mesoderm starts to develop into notochord (rod along dorsal midline) and somites (segmented blocks of mesoderm along notochord)
  • lateral mesoderm (lateral plate mesoderm) will form mesoderm derived organs (i.e. heart (A) kidneys (P))
33
Q

neurulation: neurula stage

A

formation of the neural tube (precursor to central nervous system)

34
Q

neurulation: nerual plate

A

is the ectoderm located above notochord and somites

  • edge of the neural plate forms neural folds which rise towards midline and fuse to form neural tube
  • the neural tubes sinks below epidermis
  • the anterior neural tube becomes brain- middle and posterior neural tube becomes spinal cord
35
Q

early tail bud stage: dorsal part of somites

A

become dermatome (future dermis)

36
Q

early tail bud stage : ventral somite

A

becomes vertebrae, trunk and limb muscles

37
Q

early tail bud stage : lateral plate mesoderm

A

heart, kidney, gonads and gut muscles

38
Q

early tail bud stage: ventral mesoderm blood

A

forming tissues

39
Q

early tail bud stage : endoderm

A

lining of the intestine, liver, pancreas, and lungs

40
Q

early tail bud stage: after neurulation

A

neural tube closure, the tail bud stage occurs

41
Q

early tail bud stage: the brain

A

anterior neural tube, is divided into forebrain, midbrain and hindbrain

42
Q

early tail bud stage: organogenesis initiates

A

eyes and ears start to develop

43
Q

early tail bud stage: three branchial arches form

A

form jaws and bones of the face

44
Q

early tail bud stage: neural crest cells

A

come from the edges of the neural folds after neural tube fusion
-they detach and migrate as single cells b/w the mesodermal tissues to become the sensory and autonomic nervous system pigment cells and some cartilage of skull

Developmental Biology (9 decks)

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