Gastrulation- Mammals & Fish

Question 1

How are mammals unique from the other animals we have been studying?

Answer 1

-Internal development and is supported with nutrients by the placenta

Question 2

With respect to the amount of yolk present, what type of egg is the egg cell?

Answer 2

-Isolecithal
-Little to no yolk

Question 3

How do the early cells cleave?

Answer 3

-Holoblastic
-Equal
-Rotational

Question 4

Why is compaction able to occur at the 8-cell stage

Answer 4

-The cells flatten
-Expression of adhesion molecules on cell surface
-Cavitation to create a blastocoel

Question 5

What occurs during the blastocyst stage

Answer 5

-The inner cells get displaced to one side of the blastocoel

Question 6

Characteristics of the blastocyst

Answer 6

-Blastocoel
-External cells
-trophoblast/ trophectoderm
-becomes the chorion
-Internal cells
-Inner cell mass
-becomes the embryo, yolk sac, allantois, and amnion

Question 7

How does the blastocyst hatch in the uterus?

Answer 7

-Hatches from the zona pellucida via protease

Question 8

How does implantation work in the human uterus?

Answer 8

-Inner cell mass delaminates to form 2 cell layers
-Trophoblast separates
-cytotrophoblast
-syncytiotrophoblast
-Epiblast delaminates to form the amnion and amniotic cavity
-Hypoblast forms the yolk sac

Question 9

What is the conceptus?

Answer 9

-Everything that is derived from the zygote

Question 10

What are the features of the conceptus?

Answer 10

-Cytotrophoblast: chorion of placenta
-Syncytiotrophoblast: secretes enzymes to digest the endometrium
-Amnion and amniotic cavity
-Yolk sac
-this is residual from reptiles

Question 11

What happens in mammalian gastrulation?

Answer 11

-This is identical to what occurs in the chick