Lab 7 embryology
description
Transcript of Lab 7 embryology
Summary
• Here is the bottom line:– Every animal starts out as one cell (zygote).– This cell divides (Cleavage) into two cells, then
those 2 cells divide and become 4 cells, then 8, and so forth
– Cleavage starts at the animal pole and proceeds towards the vegetal pole.
– This continues until you get a hollow ball of cells• It is at this stage that the embryo is called a blastula
Summary
• Next, invagination of the cells on one side of the blastula develops a hollow center within the embryo that becomes the gut, or archenteron.
• It is at this stage that the embryo is called a gastrula.
• The hole that formed on the side as a result of the invagination is called a blastopore.
Starfish (Asterias) early embryology
Blastopore Archenteron (early gut)
Ectoderm
Endoderm
Nucleolus
Nucleus
Single cell(haploid gamete)
Nucleusnot visible
Single diploid cell
(Early cleavage =10 or fewer cells)
OR
-ovum, an unfertilized egg; nucleus and nucleolus are visible-zygote, a fertilized egg (diploid); the nucleus is not visible
-2 cells, the product of mitosis of the zygote, cell size is halved, then again to 4 cells, etc., to blastula
-gastrula forms as a result of the infolding of cells to form a gut
Archenteron
FROG EMBRYOLOGY
Ovary
Early cleavage
Gastrula
EggsEarly cleavage
Blastula
Neurula
Micromeres
Macromeres
Animal pole
Vegetal pole
Vegetal pole
Micromeres
Macromeres
Animal poleBlastocoel
Blastocoel(the smaller cavity)
Archenteron
EctodermMesoderm
EndodermBlastopore
Yolk plug
Neural groove(forming neural
tube)
Gut
Somites
Notochord
(Early cleavage =16 or fewer cells)
Notes
• Neural tube becomes the dorsal nerve cord
• Notochord becomes the backbone (vertebral column)
CHICK EMBRYO Eye
Brain
Ear (hard to see)
Heart
Neuraltube
Somites
Misc follows
Starfish
• Egg Zygote
Archenteron