Placenta

Question 1

What is an ectopic pregnancy?

Answer 1

Implantation of blastocyst outside the uterine body - e.g. Abdomen, caesarean scar, cervix, ampulla, fimbria, ampulla.

Question 2

What are dizygotic twins?

Answer 2

Twins formed from two independently released oocytes and two separate sperm.

Question 3

What are monozygotic twins?

Answer 3

Twins produced from one fertilised egg, with the same genetic make up. Arise from splitting of zygote at 2 cell stage or splitting of inner cell mass.

Question 4

How are conjoined twins formed?

Answer 4

When inner cell mass tries to divides into two, but fails to do so completely.

Question 5

How is the placenta a unique organ?

Answer 5

It is a dual origin organ - from both maternal and feral tissue. It has a limited life span. Allows exposure of maternal blood to fetal tissue.

Question 6

What are the functions of the placenta?

Answer 6

Respiration, nutrition and storage, excretion, protection and hormone synthesis.

Question 7

What is the decidual reaction?

Answer 7

Progesterone causes endometrial cells to convert into secretory decidual cells, that provide nourishment.

Question 8

How does the decidual reaction occur?

Answer 8

1) Vascular permeability of tissue underlying fetus increases.
2) Edema collects in the intracellular matrix.
3) Stromal cells swell as glycogen granules accumulate.
4) Progressive sprouting and ingrowth of capillaries occurs.