Transcript Ch. 47 Animal Development 9e

Ch. 46/47 Warm-Up
1. (Ch. 46) How do oogenesis and spermatogenesis
differ?
2. (Ch. 46) How do these hormones affect the menstrual
cycle?
a) LH
b) FSH
c) Estrogen
d) Progesterone
3. (Ch. 47) Describe the process of fertilization.
Chapter 47
Animal Development
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
Mammalian Fertilization
1. Sperm binds to receptors in zona pellucida (extracellular
matrix of egg)
2. Acrosomal reaction: sperm releases hydrolytic enzymes to
digest z.p.
(Sea Urchins) Depolarization of membrane: prevent other
sperm from binding = fast block to polyspermy
3. Sperm + Egg Fuse
4. 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
5. Ca2+ release also triggers activation of the egg
Fertilization in mammals
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)
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
• Epithelial linings of
systems
digestive, respiratory,
excretory tracts
• Notochord
• Excretory, circulatory • Liver, pancreas
• Reproductive system
• Blood, bone, muscle
* For AP Test, you should know at least 2 derivatives of each germ layer.
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
Early human
embryonic
development
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
Amnion
Allantois
Embryo
Amniotic
cavity
with
amniotic
fluid
Albumen
Shell
Yolk
(nutrients)
Chorion
Yolk sac
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