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Flashcards in Animal Development Deck (23):
1

Fertilization steps

1. Acrosome fuses with membrane and releases enzymes that eat through jelly coat of egg
2. Species-specific signals are recognized
3. Contact and fusion of sperm and egg membranes
4. Depolarization of membrane: fast block to polyspermy (non-mammals only)
5. Cortical reaction: cortical granules fuse with plasma membrane and secreted contents clip off sperm-binding receptors and strip vitelline layer away, forming fertilization envelope (slow block to polyspermy)
6. Entry of sperm nucleus

2

Role of Ca+2 in cortical reaction

High concentration of Ca+2 in the egg triggers cortical reaction
Ca+2 spread across the egg correlates with the appearance of the fertilization envelope

3

Activation of egg

Rise in Ca+2 increases rate of cellular respiration and protein synthesis of egg cell
Haploid nuclei fuse and cleavage begins

4

Fertilization in mammals

1. Sperm travel through outer layer of cells to reach zona pellucida (glycoprotein coat; jelly layer)
2. Sperm bind to receptor in zona pellucida
3. Acrosomal reaction
4. Sperm membrane fuses with oocyte
5. Slow block to polyspermy
6. Meiosis II resumes
7. Sperm nucleus is taken into egg
8. Sperm and egg chromosomes are organized onto a single mitotic spindle

5

Blastomeres

Small cells that make up the cytoplasm of one large cell during cleavage

6

Holoblastic cleavage

Complete division of egg
Occurs in species whose eggs have little or moderate amounts of yolk (sea urchins and frogs)

7

Meroblastic cleavage

Incomplete division of egg
Occurs in species with yolk-rich eggs (reptiles and birds)

8

Blastula

Hollow ball of cells
Produced by first several cleavage divisions

9

Blastocoel

Space in blastula
Separates cells: don't want neighboring cells communicating with each other until proper time

10

Gastrulation

Rearrangement of cells of blastula into 3-layered embryo

11

Gastrula

3-layered embryo formed by gastrulation

12

Germ layers

3 layers produced by gastrulation
Endoderm (lines digestive tract), mesoderm (partially fills space between endoderm and ectoderm), and ectoderm (forms outer layer)

13

Parts of body that ectoderm gives rise to

Epidermis
Nervous and sensory systems
Jaws and teeth

14

Parts of body that mesoderm gives rise to

All other systems that ectoderm and endoderm don't produce
Skeletal and muscular systems, circulatory and lymphatic systems, excretory and reproductive systems

15

Parts of body that endoderm gives rise to

Digestive tract

16

Organogenesis

Various regions of germ layers develop into rudimentary organs
Mesoderm forms notochord (gives rise to part of spinal cord) and somites (give rise to skeletal muscles and bone among other things)
Ectoderm forms neural plate (turns into neural tube, which gives rise to central nervous system)
Endoderm forms archenteron (gives rise to digestive tract)

17

Induction

One cell population influences development of neighboring cells via interactions at close range

18

Pattern formation

Development of organization of organs and tissues inside embryo's body

19

Positional information

Molecular cues that control pattern formation

20

Limb buds

Precursors of vertebrate limbs in embryo

21

Apical ectodermal ridge (AER)

Thickened ectoderm at limb bud's tip
Releases signals that cause limb to extend outward

22

Zone of polarizing activity (ZPA)

Mesodermal tissue where the bottom of the limb bud is attached to the body
Releases signals that differentiate anterior from posterior

23

Sonic hedgehog

Molecule that diffuses out from ZPA providing anterior-posterior positional information to the growing limb