Transcript 2010: Embryology

Embryology
Embryology:
- study of the development of an
embryo
Fertilization:
male and female gametes fuse to form a zygote
• Fertilization usually
occurs in the funnel
shaped end of a
Fallopian Tube
– A sperm must penetrate
the egg
• ZYGOTE
– Tiny cilia line the tube to
propel the fertilized egg
toward the uterus
Cleavage
(Process by which a zygote divides by mitosis to form 2 new cells)
• Cell # doubles with
each division
– each cell smaller than
zygote
– 2 cell stage
– 4 cell stage
8 Cell Stage
• PROTOSTOMES
• DEUTEROSTOMES
• Spiral Cleavage:
• Radial Cleavage:
when cells divide they
Results in 8 cells sitting
do not sit on top of
directly on top of each
each other, they spiral
other
• Clams, worms,
• Starfish and vertebrates
insects
MORULA:
– A zygote consisting of about 12-32 cells in a
solid ball
– Reaches the uterus in about 3-4 days after
fertilization
BLASTULA formation
BLASTULA
• a hollow ball of cells that forms 58 days after fertilization
• Cells start to compact and move
to the edge, leaving a fluid-filled
space in the centerBLASTOCOEL
•
Blastula will attach to the lining of
the uterus
Gastrulation
• Gastrula: structure made up of 2 layers of cells
with an opening at one end
– Cells that are folding inward form a cavity lined with a
2nd layer of cells - Blastospore
– In deuterostomes the blastospore will eventually
develop into the anus
– Gastrulation - sorts all the cells into distinct cell
layers (ectoderm, endoderm, and mesoderm)
ECTODERM
• Layer on the outer surface of
the gastrula is called the
ECTODERM
– SKIN and NERVOUS
tissue
ENDODERM
• Layer on the INNER
SURFACE of the gastrula
is called the ENDODERM
– ENDODERM: lining of the
digestive tract and organs
associated with digestion
MESODERM
• Mesoderm is the 3rd cell
layer found in the
developing embryo
between the ECTO and
ENDODERM (“meso”
means middle)
– MESODERM: muscle
cells, circulatory, and
excretory cells, bone cells
and respiratory system
Terms to Know!
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Embryology
Egg
Sperm
Ovary
Uterus
Fallopian Tube
Zygote
Fertilization
Cilia
Flagella
2 cell stage
4 cell stage
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8 cell stage
Protostome
Deuterostome
Spiral Cleavage
Radial Cleavage
Morula
Blastula
Blastocoel
Gastrula
Blastospore
Endoderm
Ectoderm
Mesoderm