Development 1 Flashcards
Multicellular life
cells, tissues, organs, systems, organisms
Stages of Development
- fertilization
- cleavage
- gastrulation
- organogenesis
Fertilization stage
Haploid egg + sperm fuse into a diploid zygote
1. Sperm contacts outer jelly coat
2. acrosomal reaction
3. bindins bond to receptors on egg
3b. sperm fuses with egg
4. cortical reaction
polyspermy
when more than 1 sperm nucleus enters the egg.
If happens it leads to wrong # of chromosomes.
Egg activation & Cleavage
Egg is activated & ready for cell division after fertilization.
Sperm & nucleus rapidly merges with the egg nucleus & the new zygote begins rapid cell division
Blastomeres
new cells created by rapid divisions
Blastula
resulting hollow ball of cells in cleavage
Yolk
When eggs are fertilized externally they have yolk. A viscous fluid containing nutrients for the embryo
blastocoel
hollow fluid filled space needed for gastrulation to occur
Gastrulation
Formation of the gut tube that has 3 layers in the embryo called the embryonic germ layer (ectoderm, endoderm, mesoderm).
Ectoderm
forms skin epithelium & nervous tissue. (Jaws, teeth epidermis of skin)
Endoderm
forms the lining of the digestive tract & related organs (liver, pancreas), thymus, throid
Mesoderm
a looser tissue that forms in the space between the endoderm & ectoderm (the coelom), skeletal & muscular systems
Protostomes (molluscs, annelids)
Spiral & determinate cleavage patter.
Mouth develops from blastopore.
Deuterostomes (echinoderms, chordates)
Radial & indeterminate cleavage patters.
Anus develops from blsatopore.