Ch. 46/47 Warm-Up1. (Ch. 46) How do oogenesis and spermatogenesis

differ?

2. (Ch. 46) How do these hormones affect the menstrual cycle?

a) LHb) FSHc) Estrogend) Progesterone

3. (Ch. 47) Describe the process of fertilization.

Chapter 47Animal 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 Fertilization1. 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 Fuse4. Cortical reaction: sperm + egg fusion triggers release of Ca2+

1. 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 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.

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 Early human embryonic embryonic

developmentdevelopment

Embryo

Amnioticcavitywithamnioticfluid

AllantoisAmnion

Albumen

Yolk(nutrients)

Yolk sacChorion

Shell

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

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 typesall cells of mammalian embryos are totipotent until

the 16-cell stage