• Precedes from simple undifferentiated state to more complex, differentiated condition
• Occurs b/c of reg. of gene activity
• Homeoboxes
• The life- long interaction w/ the environment
• Life-long

• Set of genes- control expression of other genes during development
• General property

• Ends in gene science- breakdown of the body in old age
• General Property

• General Property
• Breakdown of the body in old age
• Due to accumulation of free radicals from metabolism
• Antioxidants

• General property
• Eliminate free radicals

• Trimesters
• 1st-all major organs appears
• 2nd- complete organ development
• 3rd- rapid fetal growth

• Fertilization
• 8 weeks
• Cleavage
• Blastocyst Formation
• Implantation

• 8 weeks
• Usually ocurs w/i 24hrs of ovulation
• Usually in the Fallopian tubes
• Sperm
• 200 mil. in vagina
• 2mill- cervix
• 200 at 2° oocyte
• Prostaglaglandins- contractions in females
• Move sperm
• Sperm acrosomis enzymes allow penetration of 2 layers around oocyte
• Oocyte finishes meiosis II
• Forms ovum & 2 polar bodies

• Cell division w/ no inc. in size
• Occurs in the Fallopian tube
• Monozygotic twinning may occur 1st-8 days
• Dizygotic twins from fertilization of > 1 egg
• Results in morula comprised of blastomeres

• Cleavage
• Identical

• Cleavage
• Non- identical

• Occurs in Fallopian tubes
• Morula enlarges & becomes a hollow ball of cells
• Trophoblast
• Blastocoel
• Embryoblast
• Approximately 6-7 days post fertilization
• Blastocyst attaches to endometrium
• Embryoblast move towards wall
• Endometrium- more vascularized
• Trophoblast
• Secretion of hCG-
• Maintains corpus luteum anf prevent menstruation
• Gastrulation
• Occurs during embryonic prd
• Embryonblast fold in on itself (blastopore), creating 3 layers
• Endoderm
• Mesoderm
• Ectoderm
• Coelom also forms

outer lyer of cells

eventually become placenta

• Inner
• Forms gut, digestive, urinary, respiratory sys.

• Middle
• Forms muscular, skeletal, cardio sys

• Outer layer
• Hair, skin, Nervous sys.

• Yolk sac
• Amnion
• Chorion
• Allantois

• Forma. of Embryo. Membr.
• Site of fetal BL formation, also provides nourishment

• Form. of Embryo. Membr.
• Surrounds embryo, keep amniotic fluid in place
• Shock absober

• Embryo. Membr.
• Formerly trophoblast, becomes placenta

• Embryo. Membr.
• Umibilical cord