FORM & FUNCTION (Post-fertilization Events)

Question 1

Early/embryonic development:

Answer 1

-continuous chain of post-fertilization events that leads to the formation of an embryo and the different embryonic germ layers that form tissues/organs to enable proper function/physiology
*cells to tissues to organs = 2D to 3D transformation

Question 2

Key pieces for embryology:

Answer 2

1. Cell division
2. Migration of cells

Question 3

Developmental periods:

Answer 3

1. Embryonic period
2. Fetal period

Question 4

Embryonic period:

Answer 4

-transition of zygote into an embryo that develops organs

Question 5

Fetal period:

Answer 5

-further development of the embryo until birth
-tissues/organs grow and prepare for/gain functions that continue post-birth

Question 6

Fetus:

Answer 6

-developing embryo/progeny

Question 7

Gestation:

Answer 7

-collective duration of embryo/fetal growth periods, that end in birth

Question 8

Embryology:

Answer 8

-field of study that deals with pre- and post-fertilization events that leads to development of embryo and fetus

Question 9

Why is normal early development so important?

Answer 9

-if the tissues and organs wont form properly, it affects body functions and leads to disease
*proper form is essential for normal function

Question 10

Examples of diseases with developmental origins:

Answer 10

-polydactyly in cats
-cleft palate
-etc.

Question 11

Zygote:

Answer 11

-formed by fusion of the male and female nuclei
-single cell
-surrounded by zona pellucida (no cells, just secreted material)

Question 12

Clevage and blastocyst formation

Answer 12

1. Clevage
2. Morula
3. Blastocyst

Question 13

Clevage:

Answer 13

-zygote starts dividing
-forms blastomeres
-becomes morula at 16- or 32-cell stage

Question 14

Difference between clevage and mitosis:

Answer 14

-progressive decrease in cells (blastomeres)
-synchronized: divide at the same time

Question 15

Morula:

Answer 15

-still surrounded my zona pellucida
-under goes compaction: mediated by junctional complexes

Question 16

Blastocyst:

Answer 16

-intracellular spaces start to fuse together and eventually leads to a cavity (blastocyst cavity)
-trophoblast: outer layer of cells
-inner cell mass
-Rauber’s layer

Question 17

Rauber’s layer:

Answer 17

-layer of cells just above the inner cell mass

Question 18

Inner cell mass:

Answer 18

-what will eventually become the germ layers

Question 19

Blastulation:

Answer 19

-zygote to blastocyst

Question 20

Morulation:

Answer 20

-formation of morula from zygote

Question 21

Blastocyst elongation:

Answer 21

-inner cell mass starts dividing and get some endoderm
-Rauber’s layer degenerates
-formation of embryonic disc
-zona pellucida is now gone

Question 22

Emergence of blastocyst from zona pellucida:

Answer 22

-key aspect that determines blastocyst development
*species differences
>further growth and expansion also different

Question 23

Zona pellucida, species differences general:

Answer 23

-rodents and horses: completely disintegrates
-cattle, sheep, pigs: blastocyst ‘hatches’ from a cracked zona

Question 24

Further growth and expansion species differences:

Answer 24

Primates, rodents, guinea pigs: blastocyst invades the endometrium and little expansion could occur
-horses, dogs, cats and rabbits: due to nature of attachment they have round or oval expansion of blastocyst
-cattle, sheep, pigs (with porcine blastocyst): thread-like expansion (10mm diameter sphere at 9days to 100cm long filamentous structure by day 13)