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16 Cards in this Set

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refers to the haploid male gametid that results from division of secondary spermatocytes. As a result of meiosis, each spermatid contains only half of the genetic material present in the original primary spermatocyte.
Seminiferous tubules
location of meiosis, location of gamete production. contain sertoli cells.
after the egg is fertilized it is a zygote and it undergoes cleavage. The egg entire egg undergoes cleavage (total or holoblastic). The first cleavage splits the zygote into two blastomeres.
after the first cleavage, the zygote is split into blastomeres. The cleavage passes through the animal-vegetal axis. The two blastomeres are equivalent. The divisions continue and the cells are called blastomeres until the fourth cleavage is complete and the 16 cell stage, we get mesomeres, micromeres, and maromeres.
16 cell stage. Tier nearest animal pole, 8 blastomeres
tier nearest the vegetal pole, consisting of four blastomeres are called micromeres.
between, four larger blastomeres is the macromeres.
In sea urchin embryos between 32 and 64 cell stage, the embryo is called a morula or ball of blastomeres.
Blastomeres become arranged around a central cavity called the blastocoel
developing embryo at the blastocoel stage is known as the blastula. With formation of the blastocoel and blastula, the process of blastulation occurs
Invagination of the blastopore continues to form the archenteron (=primitive gut) until it reaches the other pole and forms a tube. Formation of the primitive gut is called gastrulation. Vegetla plate initiates invagination into the blastocoel to form the beginnings of the Archenteron.
sea urchines are deuterostomes because their second opening forms the mouth. The first opening or blastopore forms the anus
Blastopore forms the anus, the first opening.
begin to form a larval skeleton at the end of the gastrula stage
Pluteus larvae
the larva at the stage with two anal arms and one oraal lobe is known as the pluteus larva. The Pluteus larvae enentually get two oral arms that grow out of the oral lobe.
each of the arms (oral and anal arms) contains a well formed spicule
in the pluteus larvae is subdividing into the esophagus, stomach, and intestine