Post-Fertilization Events

Question 1

Keys to embryonic development

Answer 1

1. Cell division
2. Migration

Question 2

Early/embryonic development

Answer 2

• Refers to the 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
• From cells to tissues to organs = 2D to 3D transformation

Question 3

Development 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

The collective duration of embryo/fetal growth periods, that ends in birth

Question 8

Embryology

Answer 8

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

Question 9

Gestational length in domestic animals

Answer 9

Varies with different species
- Dogs 63 days
- Cats 62 days
- Cattle 9months
- Horse 11 months
- Swine 3.5 months
- Sheep/goats 5 months

Question 10

Why is normal early development so important?

Answer 10

• If the tissues and organs won’t form properly, it affects body functions and leads to diseases
• Proper form needed for normal function

Question 11

Examples of diseases with developmental origin

Answer 11

• Polydactyly in cats
• Cleft palate
• Dentigerous cysts of impacted teeth
• Microphthalmos- smaller eyes
• Cryptorchidism
• Ectopic ureters- ureters are misplaced and draining poorly

Question 12

Formation of zygote

Answer 12

Single cell with combination of both the female and male genetic material.

Zygote surrounded by zona pellicida

Question 13

Zona Pellicida

Answer 13

• surrounding layer of the zygote
• made up of glycoproteins; no cells

Question 14

Zygote division

Answer 14

1. cleavage
2. morulation
3. blastulation

Question 15

How is the mitotic division different in cleavage compared to mitosis?

Answer 15

1. During mitosis, cell division results in cells of the same size. In cleavage, cells divide into smaller and smaller cells
2. Another difference is that cleavage division is synchronous whereas mitosis is not.

Question 16

Cleavage

Answer 16

Division of zygote into blastomeres (cells from result of cleavage)

• cells getting smaller and smaller
• synchronous
• eventually becomes morula at end of cleavage event

Question 17

Morulation

Answer 17

formation of morula from zygote

Question 18

Blastulation

Answer 18

The whole process from zygote to cleavage to morula to blastocyst

Question 19

How is Morula formed?

Answer 19

Forms at the end of cleavage. Morula contains many blastomeres (multi-blastomere stage). Blastomeres undergo compaction to form the morula

Question 20

Blastocyst components

Answer 20

• The start of apical, basal, and lateral sides

1. Intracellular contents that are beginning to fuse together. Will lead to cavity called blastocyst cavity
2. Layer surrounding cavity called trophoblast layer
3. A bunch of cells will form at the surface called inner cell layer
4. Layer of cells lining top of the inner cell mass is called a Rauber’s layer.

Question 21

What will the inner cell mass of the blastocyst form?

Answer 21

Will eventually form the germ layers

Question 22

Other names for blastocyst

Answer 22

• blastula
• blastodisc

** all mean the same thing but different for different species**

Question 23

Blastocyst elongation

Answer 23

Blastocyst emerges from soma pellucida (disintegrates in rodents and horses; other species like cracked egg)

Growth and expansion: invades endometrium in primates, Guinea pigs, rodents. Round expansion in dogs, cats, horses, rabbits. Thread-like in cattle, sheep, pigs.

Inner cell mass and degenerated Reuber’s layer form the embryonic disc