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Steps in animal development
•Fertilization - fusion of the nuclei of sperm and egg
•Cleavage- rapid cell division. transforms zygote into multicellular blastula , or blastblastocytes in mammals
•Gastrulation-cells on outside of young embryo move to the interior of embryo (results in mesoderm, endoderm, ectoderm
•Organogenesis- occurs after gastrulation in vertebrates where major organs develop from the 3 tissue types
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•Fertilization
•Cleavage
•Gastrulation
•Organogenesis
Steps in animal Development
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3 main structures in sperm
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Head midpiece and tail
3 main structures in sperm
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Head of sperm
–contains nucleus and acrosome (enzyme filled structure)
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–contains nucleus and acrosome (enzyme filled structure)
Head of sperm
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midpiece in sperm
packed with mitochondria for energy
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packed with mitochondria for energy
Midpiece in sperm
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Tail in sperm
flagellum for motility (flagellum, microtubules)
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flagellum for motility
Tail in sperm
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Egg structure and function
- Has:
- Nucleus
- Yolk
- Cortical Granules
- Vitelline envelope
- Jelly Layer
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Yolk
nutrition source for egg-laying species
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nutrition source for egg-laying species
Yolk
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Cortical granules
•small vesicles filled with enzymes activated during fertilization (these enzymes are what prevent polyspermy)
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Small vesicles filled with enzymes activated during fertilization (These enzymes are what prevent polyspermy)
Cortical Granules
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Vitelline envelope
- sheet of glycoproteins surrounding egg
- (called zona pellucida in humans)
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sheet of glycoproteins surrounding egg(called zona pellucida in humans) passes oxygen to chick embryo
Vitelline envelope
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Acrosomal reaction
- Part of fertilization used to digest jelly layer of egg so the sperm can get through.
- "needed to get through jelly layer or glycoproteins release of enzymes that digest jelly layer
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Part of fertilization used to digest jelly layer of egg so the sperm can get through. "needed to get through jelly layer or glycoproteins release of enzymes that digest jelly layer
Acrosomal reaction
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What happens during fertilization
- Sperm digests jelly layer.
- sperm binds to vitelline envelope and cuts a hole in it
- Sperm enters egg and the nucleus of the egg and sperm will bind
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Polyspermy
fertilization of egg by more than one sperm
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fertilization of egg by more than one sperm
polyspermy
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What happens to prevent polyspermy in aquatic animals?
–vitelline envelope swells and forms fertilization envelope (creates physical barrier)
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Fertilization envelope
- physical barrier created to prevent polyspermy in aquatic animals.
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physical barrier created to prevent polyspermy in aquatic animals.
Fertilization envelope
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Cleavage
- •rapid cell divisions after fertilization
- –creates many small cells (blastomeres)
- without overall growth.
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•rapid cell divisions after fertilization–creates many small cells (blastomeres)without overall growth.
Cleavage
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Blastomeres
the small cells created during cleavage / cell division
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the small cells created during cleavage / cell division
Blastomeres
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Morula
- solid ball of cells
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Solid ball of cells
Morula
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Blastula
- •hollow ball of cells with blastocoel
- (fluid-filled center)
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•hollow ball of cells with blastocoel (fluid-filled center)
Blastula
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blastocoel
It's the fluid filled center in blastula
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It's the fluid filled center in blastula
Blastocoel
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CYTOPLASMIC
DETERMINANTS
- Signals in the egg cytoplasm that determine the
- fate (what type of cell they'll be) of specific blastomeres.
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Signals in the egg cytoplasm that determine the fate (what type of cell they'll be) of specific blastomeres
Cytoplasmic determinants
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Gastrulation
- •Movements that rearrange cells into a gastrula
- •Forms embryonic tissue layers
- –ectoderm,mesoderm, endoderm
- •Forms gut
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•Movements that rearrange cells into a gastrula•Forms embryonic tissue layers–ectoderm,mesoderm, endoderm
forms gut
Gastrulation
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Gastrula
An embryo at the stage following the blastula, consisting of a hollow, two-layered sac of ectoderm and endoderm
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An embryo at the stage following the blastula, consisting of a hollow, two-layered sac of ectoderm and endoderm
Gastrula
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Ectoderm
- –outer layer of skin
- nervous system (brain and such)
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–outer layer of skin nervous system (brain and such
Ectoderm
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Mesoderm
- –muscle
- –most internal organs
- –connective tissues
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–muscle–most internal organs–connective tissues
Mesoderm
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Endoderm
- –most epithelial lining
- –some organs
- lines the inside of shit and is the liver
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Organogenesis
•Tissue and organ formation after gastrulation
- Cells become differentiated
- (specialized)
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Notochord
•forms from dorsal mesoderm
–rod-like structure along length of body
–present in chordates
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•forms from dorsal mesoderm–rod-like structure along length of body–present in chordates
Notochord
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Neural tube
•forms from fold of ectoderm
–signals come from notochord
–will become brain and spinal cord
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•forms from fold of ectoderm–signals come from notochord–will become brain and spinal cord
Neural tube
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Somites
–blocks of tissue formed from mesoderm
–both sides of the neural tube along length of body.
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–blocks of tissue formed from mesoderm–both sides of the neural tube along length of body.
somites
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Somite cells become several different tissues
based on location within somite.
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Somite determination
•Somite cells differentiate in response to signals from nearby tissues•Signals diffuse from notochord, neural tube, nearby ectoderm and mesoderm
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