Early Embryogenesis and Maternal Recognition of Pregnancy

Ootid

Female and male pronuclei are present and distinguishable

Largest single cell in the body

Syngamy

Fusion of two gametes (male and female pronuclei) to produce a zygote

Zygote

Single-cell embryo that eventually divides

Blastomere

Individual, totipotent cell of an embryo

Embryo

Organism in the early stages of development

Morula (16 cell stage)

Solid ball of cells in which cells in the center compact more than those on the edges

Blastocyst (32 cell stage)

Cells begin to migrate to border of zona pellucida, interior of embryo becomes fluid filled

Blastocoele

Fluid filling cavity of blastocyst

Conceptus

Embryo proper + Placental membranes

Cleavage

Cellular divisions without gaining specificity (Mitotic division)

Totipotency

Capable of giving rise to any cell type

2 to 16 cells

Preattachment

Conceptus stage, making contact with uterine epithelium

Attachment

Implantation into the uterine wall

Fetus

Offspring still within the uterus, recognizable as a particular species

Inner cells of Morula develop _____ junctions and groups of cells form

Gap

Outer morula forms cell to cell adhesions called ________ junctions.

Tight

inner Cell Mass →

Embryo Proper

Trophoblast →

Placental Membranes

Blastoceole -

Fluid filled cavity

Maternal Recognition of Pregnancy

Biochemical signal from conceptus that prevents luteolysis , results in maintenance of pregnancy and progesterone levels

When does MRP happen in cows?

15-16 days post ovulation

When does MRP happen in sheep?

13-14 days post ovulation

What signal is the pregnancy recognition factor for cows and sheep?

bIFN-T = Cows

oINF-T = sheep

What cells produce bINF-T and oINF-T?

Trophoblast cells

How does bINF-T and oINF-T work?

Blastocyst binds to the endometrium → Blocks oxytocin receptor → decrease in PGF2a

When does MRP happen in sows?

11-12 days post ovulation

What signal makes MRP happen in sows?

Multiple concepti produce estrogen

How many concepti must be present for MRP to occur in sows?

12 concepti

If concepti are not present in one horn of the sow → PGF2a cannot be blocked → ________

Luteolysis

When does MRP happen in mares?

14-16 days post ovulation

T/F: The mare conceptus has a filamentous stage.

False: The conceptus must migrate 12-14x/day on days 12-14 to inhibit PGF2a

What does MRP in the mare rely on?

Proteins and estrogen

What causes the hatching of the blastocyst?

Blastocyst growth and fluid accumulation: Increased pressure

Enzyme production by trophoblastic cells: weakens zona