Embryological Development Ch 38.2 & Page 698 Early Animal Development

I 1.Development Cell division Growth Differentiation From embryonic tissues to Specialized tissues & organs

Embryological Development

Meiosis in the Gonads Sperm Meiotic cell division Egg

2. Fertilization of egg in fallopian tube by sperm

3. Zygote formation Fertilized Egg 2n Chromo- some # Union of sperm & egg 1N Sperm + 1N Egg = 2N Zygote

4.Implantation of egg in uterus Fertilization Implantation

5. Cleavage = Splitting by mitosis

3 rd Cleavage= 8 balls “cleave” = To cut Division of embryonic tissue From the zygote to a Multi-ball stage

6.Blastula Hallow “ball” After cleavage Signals the onset of Differentiation of embryo 5 th day blastocyst

Hallow Ball or Blastula

7. Gastrula Infolding of cells Follows Blastua stage Forms ? the digestive tract

7.Differentiation “differ” Specialization of embryonic tissue Orders cells into tissues & organs

Experimental Studies: DiffeDiffe Cell Differentiation

Embryonic Development & the “gray crescent” DiffeDiffe

9.Three cell layers 1. Ectoderm= outer 2. Mesoderm= middle 3. Endoderm= inner Ecto= Skin & nervous Meso= Muscles Bones Endo= Digest. Bladder

Neural Tube Development “ Neural”= nervous “tube” = spinal column

10-11.Mammal fetus & uterus Placenta= uterine lining Umbilical cord=connects to uterus Amnion= sack with fluid Fetus = baby

Placenta & Umbilical Cord

Fetal & Mother’s Blood Mother’s Blood is Separate from the baby! What passes across the placenta? Food, drugs, wastes, alcohol, oxygen What stays behind? Red blood cells How are wastes removed? Diffuse across the placenta (CO2, etc.)

Marsupial Pouch

Fetus Development

4 Week Embryo

Ultra sound scanning

Amniocentesis Sampling the amnionic fluid Check for chromosome abnormalities