1. Ch. 46/47 Warm-Up
(Ch. 46) How do oogenesis and spermatogenesis differ?
(Ch. 46) How do these hormones affect the menstrual cycle? LH
FSH
Estrogen
Progesterone
(Ch. 47) Describe the process of fertilization.

2. Chapter 47 Animal Development

3. What you must know: The events that occur when a sperm contacts an egg
What occurs in cleavage, gastrulation, and organogenesis
Two structures derived from each germ layer

4. Mammalian Fertilization
Sperm binds to receptors in zona pellucida (extracellular matrix of egg)
Acrosomal reaction: sperm releases hydrolytic enzymes to digest z.p.
(Sea Urchins) Depolarization of membrane: prevent other sperm from binding = fast block to polyspermy
Sperm + Egg Fuse
Cortical reaction: sperm + egg fusion triggers release of Ca2+
cortical granules fuse with z.p.  z.p. hardens to form fertilization envelope = slow block to polyspermy
Ca2+ release also triggers activation of the egg

5. Fertilization in mammals

6. Cleavage: rapid mitotic cell division
Zygote cytoplasm partitioned into smaller cells (blastomeres)
Solid ball of cells = morula
Blastula (hollow ball of cells) filled with fluid (blastocoel)
Blastocyst (human)

7. Gastrulation: rearrange cells to form 3-layered embryo w/primitive gut
Three Embryonic Germ Layers*
Ectoderm
Mesoderm
Endoderm
Skin, nails, teeth
Lens of eye
Nervous system (brain, spinal cord)
Skeletal, muscular systems
Notochord
Excretory, circulatory
Reproductive system
Blood, bone, muscle
Epithelial linings of digestive, respiratory, excretory tracts
Liver, pancreas
* For AP Test, you should know at least 2 derivatives of each germ layer.

9. Organogenesis: development of 3 germ layers into organs
Notochord – stiff dorsal skeletal rod, forms from mesoderm
Neural plate  neural tube brain and spinal cord
Neurulation – forms hollow dorsal nerve chord
Somites – blocks of mesoderm arranged along notochord; sign of segmentation

10. Early human embryonic development

11. Amniotic embryos (reptiles, birds, mammals)
Develop in fluid-filled sac w/in a shell or uterus
Amnion: fluid protects embryo – prevent dehydration, cushions mechanical shock
Yolk : nutrients in egg
Mammalian eggs: little stored food
Embryo
Amniotic
cavity
with
amniotic
fluid
Allantois
Amnion
Albumen
Yolk
(nutrients)
Yolk sac
Chorion
Shell

12. Patterns of development
Cytoplasmic determinants: chemical signals such as mRNAs and transcription factors, influence pattern of cleavage
Induction: interaction among cells that influences their fate, cause changes in gene expression
Totipotent cells: capable of developing into all the different cell types
all cells of mammalian embryos are totipotent until the 16-cell stage