AGR 506 Early Embryogenesis and MRP

What is Syngamy?

fusion of male and female pronuclei

What is an Embryo?

Organism in early stages of development

Is an Embryo recognizable in appearance as a member of the specific species?

No

What is a Fetus?

Potential offspring still within the uterus

T/F:

A Fetus is recognizable as a member of a given species.

True

What is the product of conception defined as?

Conceptus

What does the preattachment embryo of the Extraembryonic membreane consist of?

-Yolk sac

-Chorio

-Amnion

-Allantois

What 4 components does the Extraembryonic membranes originate from?

-Trophoblast

-Endoderm

-Mesoderm

-Embryo

Where does the Yolk sac originate from?

Endoderm

Where does the chorion originate from?

-Trophoblast

-Endoderm

-Mesoderm

What will chorion attach to?

Uterus

Where does Amnion originate from?

-Trophoblast

-Endoderm

-Mesoderm

How does the Amnion contribute to the fetus?

Provides fluid filled protective sac for the fetus to develop in

What are the functions of the Allantois?

-collects waste from embro

-press on chorion and fuse becoming the allantochorion once large enough

What is the 4-step process that must be achieved before embryo can attach to the uterus?

-Development within confines of zona pellucida

-Hatching of blastocyst from zona pellucida

-Maternal recognition of pregnancy

-Formation of extraembryonic membrane

When a male and female pronuclei can be observed, what is it called?

ootid

T/F:

An ootid is not the largest single cells in the body.

False

How are ootid characterized?

Enormous cytoplasmic volume relative to nuclear volume that plays a big role in subsequent cell division.

Following fusion of male and female pronuclei, the single celled embryo is called what?

Zygote

What is the cleavage division?

Zygote undergoing a series of mitotic division

The first mitotic division generates two celled embryo, cells of that embryo are called what?

Blastomeres

Blastomeres from the 2-,4-,8-, and 16- celled embryos are called what?

Totipotent

How may daughter cells do blastomere undergoing further cleavage division yield?

-4

-8

-16

A solid ball of cells where individual blastomeres can no longer be counted acuatly are called?

Morula

When water diffuses through zona pellucida into embryo, a fluid filled cavity is formed called?

Blastocoele

When a distinct cavity is recognized, the embryo is then called what?

blastocyst

During the development of Extraembryonic Membranes, mammalian embryos are subdivided into what two groups?

-Long Preattchment Period

-Short Preattachment Period

How does Long Preattachment Period differ from Short Preattachment Period?

-Occurs in most domestic animals

-Last several weeks

-Extensive extraembryonic membranes forms folding process that generates amnion, chorion, and allantochorion

How does Short Preattachment Period differ from Long Preattachment Period?

-Implants soon after entering uterus

-Occurs in Primates

-Extraembryonic membranes form after implantatin or attachment

What must be prevented and maintained in order to establish pregnancy?

-Luteolysis needs to be prevented

-Progesterone must be maintained

A critical series of events by which conceptus initially signals its presence to the dam and enables pregnancy to continue is known as?

Maternal recognition of pregnancy

Explain Ewe and Cow Maternal recognition process

Free-floating blastocyst produces proteins called Interferons that provide signal for prevention of luteolysis

Explain Sow Maternal recognition process

-Conceptus produces estradiol, serves as signal for maternal recognition

-PGF2a produced and rerouted into uterine lumen

-MUST HAVE ATLEAST 2 CONCEPTUSES IN EACH HORN FOR PREGNANCY TO BE MAINTAINED

Explain Equine Maternal recognition process

-Conceptus is moved from one uterine horn to other by uterine contractions

---Must happen 12-14 times daily during days 12, 13, and 14 of pregnancy

---Distributes Prego recognition factors to endometrial cells

T/F:

in Dogs and Cats, maternal recognition of pregnancy does require signal from conceptus.

False

T/F:

CL of pregnancy and CL of cycle have similar life spans in a Bitch.

True

T/F:

CL duration is the same as gestation in Queens.

True

T/F:

In Queens, if mating does not occur, CL forms anyways.

False, Queens are induced ovulaters and need mating to occur for CL to be formed.

A successful pregnancy requires maintanance of high blood _________ concentration.

Progesterone

T/F:

Embryo transfer provides avenues fro reproductive and gentetic enhancments.

True

Embryo Transfer requires a set of procedures to do what?

-Removal of pre-attachment embryos from reproductive tract of donor female and transfers them into repro tract of recipient female

What are the advantages of embryo transfer?

-Circumvention of seasonal reproduction

-Enhanced offspring in monotoccus species

-Assisted repro for infertility in humans

-Enhanced repro potential of endangered species

-Enhanced genetic diversity across wide regions (shipping embryos)

Successful Embryo Transfer involves what?

-Synchronization cycles of donor and recipient

-Superovulation of donor

-AI of donor female

-Recovery of embryos from donor

-Maintenance of viable embryos in vitro

-Transfer of embryos to recipient females

What is given to a donor to make them superovulate?

Gonadotropins, typically FSH

When a donor of a monotocous species superovulates, how much more do they produce in comparison to normal ovulation?

5-10 times more

When a donor of a Polytocous species superovulates, how much more do they produce in comparison to normal ovulation?

2-3 time more

What are ways to recover embryo from the ovaries?

-Surgically exposing ovary and aspirating follicles

-Non-surgically aspirating follicles utilizing ultrasonography (vitro fertilization)

-Aspirating follicles postmortem in an abattoir

What are ways to recover embryo from uterus?

-Surgecally in small animlas

-Transrectal palpation, induced catheter for removal of embryos by flushing with various culture media in horses and cattle

What ways can viable embryos in vitro be maintained?

- Environment specific made for embryo storage

-Can be frozen for long term

What two ways can the embryo be transferred to recipient?

-Non-surgically

-Surgically