1. Chick Embryo Development Dr. Douglas Rhoads Professor Biological Sciences Affiliated Faculty Center of Excellence for Poultry Science Director of Graduate Program in Cell and Molecular Biology University of Arkansas drhoads@uark.edu http://biscweb.uark.edu/drhoads

2. The Egg http://www.enchantedlearning.com/ subjects/birds/info/chicken/egg.sht ml http://www.ehow.com/how_4715979_ tell-chicken-eggs-fertile.html

3. The Life of an Egg Male inseminates female Female stores sperm for up to 2 weeks Female has one ovary (left side) Ovary has multiple follicles in hierarchy –One ovulation every 25 hours –timed to light cycle

4. Ovulation Primary Follicle ruptures –Sperm attach to germinal disk over egg –Acrosome reaction –One sperm penetrates egg membrane –Zygote begins development Transiting the oviduct –Egg white albumen deposited –Egg membrane deposited –Shell added in Shell gland Oviposition –about 22-24 hours after ovulation –Embryo already at about 1000 cells

5. Embryo Growth Embryo on side of yolk –Floats up (hen rocks and reorients) –Incubation temperature of 39 to 40 C Embryo divides into Embryo and Extra-embryonic tissue Extra-embryonic tissue –Blood cell production Blood islands >> Blood ring Fuses with embryo circulatory system –Grows out around yolk Heart pumps blood out around yolk and back to embryo –Absorbs yolk and albumen Eventually, chick grows around and encompasses last of yolk through cloacal opening Chick emerges from egg after 21 days

6. H&H chart

7. The First Three Days http://geisha.arizona.edu/geisha/stages.jsp

8. Day 4 to 8 http://geisha.arizona.edu/geisha/stages.jsp

9. Embryo Dissection