Pregnancy1

Question 1

Embryo

Answer 1

Early stages of development

Question 2

Fetus

Answer 2

Unborn young still within uterus

Question 3

Conceptus

Answer 3

Products of conception embryo+membrane+fetus+placenta

Question 4

What happens during implantation?

Answer 4

• development within ZP
• hatching of blastocysts
• extrameabryonic membrane formation
• maternal recognition of pregnancy

Question 5

What happens during pre implantation development?

Answer 5

Syngamy: fusion of male and female pronuclei
-zygote forms—> mitotic division—> daughter cells
Cleavage= division without growth

Question 6

Blastocysts in pre-implantation
Consists of:
Why is this stage important?

Answer 6

Inner cell mass
Blastocoele
Trophoblast layer
—-> hatches from ZP and becomes free floating in uterus

Important= EMBRYONIC STEM CELLS

Question 7

Blastocysts Hatching

Answer 7

• fluid fill up
• Trophoblas cells begin to producing enzymes»ZP weakens
• Blastocyst contracts/relaxes
• ZP ruptures embryo free into UT lumen

Question 8

POST HATCHING

Membranes necessary for attachment are:

Answer 8

Chorion
Amnion
Yolk sac
Allan this
—-> endoderm forms below ICM/embryo lining trophoblast
—->Mesoderm development

Question 9

Yolk sac

Answer 9

CAVITY FORMED BY ENDODERM
-used for energy until placenta is formed
-regresses as embryo develops
—> contributes to primitive germ cells which migrate to genital ridge

Question 10

Chorion

Answer 10

• fusion of mesoderm

- forms fetal site of placenta attachment

Question 11

Allantois

Answer 11

Develops from the embryonic gut and collects liquid waste

Question 12

Amnion

Answer 12

Fluid filled sac formed from the trophectoderm and mesoderm

-surrounds and protects embryo

Question 13

Allantochorion

Answer 13

• fusion of the membranes

- fetal contribution to the placenta

Question 14

Maternal recognition

Answer 14

EMBRYO MUST SIGNAL MOM OR PREGNANCY ENDS

Question 15

Signals of maternal recongition

Answer 15

• usually biochemical
• mechanical
• species specific

Question 16

Net effect of maternal recongition

Answer 16

Prevents luteolysis

Maintain levels of P4

Question 17

P4 in pregnancy

Answer 17

• promote mammary gland development
• endometrial growth and gland secretions into uterine lumen
• inhibit myometrial contractions

Question 18

No conceptus present

Answer 18

• lute always OT binds to OTr
• stimulates pulsatile release of PGF2a
• induces luteolysis and P4 decline

Question 19

Early pregnancy hormones

Answer 19

Conceptus signal prevents PGF2a
Blocks luteolysis
Maintains P4

Question 20

Maternal recognition: COW/SHEEP

Answer 20

IFN-tau:

• decrease in OTr so OT cannot increase PGF2a
• protein synthesis is increased—>promotes implantation

Question 21

Maternal recognition: PIGS

Answer 21

ESTRADIOL-pig fetus secretes 11-12d

• promotes exocrine/endocrine secretion of PGF2a
• PGF2a into uterine lumen
• PGF2a doesn’t reach circulation= no luteolysis
• CL SURVIVES

Question 22

Mechanical signals:PIGS

Answer 22

• 2 concept uses are needed per horn

- if only 1 PGF2a will be secreted and pregnancy ends

Question 23

Maternal recognition: HORSE

Answer 23

-Conceptus migrates/uterine contact
-multiple contacts with UT endometrium
Low PGF2a
Low luteolysis

Question 24

maternal recognition: humans

Answer 24

HCG

• 8-10d post concept by blastocysts trophectoderm
• chorion cells produces hCG

Question 25

ATTACHMENT

Answer 25

- conceptus forms close relationship with endometrium | - conceptus elongation is required(not in rodents)

Question 26

IMPLANTATION

Answer 26

-conceptus embeds in the UT wall in contact with vascular/connective tissue on all sides

Question 27

Differences in pre-implantation development: MOUSE/HUMAN/PIG

Answer 27

DELAYED IMPLANTATION - Blastocysts floats in UT lumen until attachment/implantation - ensures young are born at right time