Animal development-lower vertebrates

Question 1

General overview if animal development

fertilization

Answer 1

fusion of egg and sperm (formation of the zygote)

Question 2

cellular cleavage

Answer 2

• formation of blastula
• Under maternal control (especially in lower vertebrates)

Question 3

Gastrulation

Answer 3

formation of the three germ layers-ectoderm, mesoderm, endoderm

Question 4

Organogenesis

Answer 4

• organ formation
• Under zygotic control

Question 5

Maternal sygotic transition (MZT)

Answer 5

• activation of zygoticgene expression
• cell cycle slows down
• Tissue movements initiate

Question 6

Descruptive enbryology terms

Answer 6

• The animal- vegetak axis

Question 7

Early Xenopus

Answer 7

Zygote-8 cell- mid blastula- early gastrula- mid gastrula- early neurula- late neurula

Question 8

Mid blastula

Answer 8

Actication of zygotic gene expression

Question 9

Cleavage stage

Answer 9

• 1st and 2nd cleavage= vertical
• 3rd cleavage= equatorial (closer to animal pole)
• cells of the blastula= blastomeres
• cavity that form at the center of the blastula= blastocoel

Question 10

Notice the cells at the vegetal poel are larger why is this so?

Answer 10

• more cells

Question 11

It is not bith, marriage or death is the most important them in your life, but gastrulation

Answer 11

• lewis wolpert

Question 12

What is gastrulation?

Answer 12

• Formation of the three primary germ layers
• Ectoderm, Mesoderm, and Endoderm

Question 13

The nechanism of gatrulation can vary among species

Answer 13

• Invertebrates
• lowe invertebrates (frogs and fish)
• higher vertebrates (birds and mammals)

Question 14

Important tissue movements involved in gastrulation

Answer 14

Invagination: Inforlding of cell sheet into embryo
- Sea urchins
- fruit dlies

Question 15

Involution:

Answer 15

• Inturning of cell sheet over the basal surface of an outer layer
• Frogs
• fish

Question 16

Ingression

Answer 16

• Migration of individual cells into the embryo
• Amniotes
• birds and mammals

Question 17

Apical construction of epithelial cells lead to tissue invagination

Answer 17

• note: this involves the actin cytoskeleton at apicla face (red)

Question 18

Fate map of the frog (xenopus) blastula

Axial

Answer 18

• notochord (important signaling tissue for inducing the CNS and somites)

Question 19

Paraxial

Answer 19

• somites
• 9form segmented strictures- vertebrae, musculature, dermis)

Question 20

Fate map of the frog (xenopus) blastula

Intermediate

Answer 20

kidneys, gonads

Question 21

Fate map of the frog (xenopus) blastula

Lateral plate

Answer 21

• body wall, limb buds (presursors to the limbs)

Question 22

Fate map of the frog (xenopus) blastula

Ventral

Answer 22

blood cells and vessels

Question 23

Fate map of the frog (xenopus) blastula

Much happens during gastrulation (frog example)

Answer 23

• cells of the animal hemisphere migrate over the whole embryonic surface in a process known as epiboly lower vertebrates)
• ## marginal zone cells involute to form the archenteron (develping gut)

Question 24

During involution

Answer 24

• The mesoderm separates from the endoderm and involutes as a separate tissues layer between the ectoderm and endoderm
• towards the end the dorsal axial mesoderm elongates in the anteroposterior direction faciliated by convergent extension:
• The ventrolateral mesoderm moves towards the dorsal midline (converges) and the dorsal midline elongates (extends)

Question 25

Gatrulation:

Answer 25

- formation of the three germ layers

Question 26

Initiation of gastrulation

Answer 26

- marked by the formation of the dorsal lip in the dorsal vegetal quadrant

Question 27

The gastrulating cells interact with

Answer 27

- fibronectin tracks secreted into the ECM b y the lastocoel roof

Question 28

Fibronenic

Answer 28

tracks promote the migraHng of involuted deep cells to the animal pole

Question 29

The dorsal lip elongates

Answer 29

laterally and then ventrally encircling the whole embryon forming the blastopore

Question 30

# The fates of the three gern layers Ectoderm

Answer 30

- epidermis - Cenetral nervous system - lens - neural crest: - melanocytes - craniofacial cartilage and bone - smooth muscle - peripheral neurons - some glial cells

Question 31

Mesoderm

Answer 31

- heaed mesoderm - notochord - somites - kidneys - limbs - blood vessels - skeletal muscle - heart

Question 32

Endoderm

Answer 32

- Epithelial linings of: - liver - gut - pancreas - bladder - lungs

Question 33

Neurolation:

Answer 33

The ectoderm on the dorsal side becomes the centrao nervous system

Question 34

Notochord

Answer 34

- Signals to the overlying ectoderm to become the neural plate

Question 35

Neural folds

Answer 35

form on the outer edges of the neural plate

Question 36

Neural folds

Answer 36

fuse at the dorsal midline forming the neural tube and the overlying epidermis

Question 37

Neural crest cells form

Answer 37

at the end of neurulation

Question 38

Neural crest forms:

Answer 38

- Melanocytes - craniofacial cartilage and bone - smooth muscle - peripheral neurons - some glial cells

Question 39

Tissue

Answer 39

Tissue invaginates all around the circumference of the embryo forming the blastopore

Question 40

During and after neurulation

Answer 40

there is significant elongation of the body

Question 41

Somites

Answer 41

are segmented pairs of paraxial mesodermal 1ssue that give rise to a variety of structures

Question 42

Subdivisions and Bssues derived from

Answer 42

the somite

Question 43

Somites are composed of:

Answer 43

* Sclerotome * Epaxial myotome * Hypaxial myotome * dermatome

Question 44

the vertebrae are formed initially of

Answer 44

cartilage-> which is later replaced by bone

Question 45

Epaxial myotome

Answer 45

forms the segmental muscles of the main body axis

Question 46

Dermatome

Answer 46

Forms the dorsal dermis