Embryo: Placenta

Question 0

What are the tertiary villi?

Answer 0

Develop blood vessels in mesoderm (3rd week)

Question 1

What forms the secondary villi?

Answer 1

Core of mesoderm develops at day 16

• the extraembryonic mesoderm as it fills in the core of the villis
• happens early in 3rd week

Question 2

What is the chorion frondosum?

Answer 2

Elaboration of villi at embryonic pole

Question 3

What is chorion laeve?

Answer 3

Smooth portion (no villi) at abembryonic pole

Question 4

What is deciduous basalis?

Answer 4

(Decidual plate) adjacent to chorion frondosum

- the villi on the maternal side of the placenta or embryo; unites with the chorion to form the placenta

Question 5

What is decidua capsularis?

Answer 5

At abembryonic pole

- the part of the decidua surrounding the chorionic sac

Question 6

What is Decidua parietalis?

Answer 6

Uterine wall away from implantation site

• not part of placenta
• uterine endometrium opposite to the sides if implantation

Question 7

What does a mature placenta consist of?

Answer 7

Chorion frondosum and decidua basalis

Question 8

Does maternal and fetal blood exchange?

Answer 8

No

Question 9

How many initial layers separate fetal and maternal blood?

Answer 9

Four

Question 10

What are the names of the 4 initial layers that separate fetal and maternal blood?

Answer 10

1. Endothelium
2. Connective tissue
3. Cytotrophoblast
4. Syncytiotrophoblast

Question 11

After four months, how many layers are left and what are they?

Answer 11

1. Endothelium

2. Syncytium

Question 12

What is the endothelium and syncytium called?

Answer 12

Placental membrane

Question 13

What are the 5 functions of the placenta?

Answer 13

1. Exchange of gaseous products
2. Exchange if metabolic products
3. Transmission of maternal antibodies
4. Hormone production
5. Passage of deleterious substances

Question 14

How does the exchange of gaseous products occur?

Answer 14

Oxygen and carbon dioxide diffuse across placental membrane

Question 15

What metabolic products are exchanged across the placental membrane?

Answer 15

1. Carbohydrates
2. Amino acids
3. Fatty acids
4. Electrolytes
5. Vitamins

Question 16

What does the passage of antibodies provide for the fetus?

Answer 16

1. Confers passive immunity for period prior to maturation of fetal immune system
2. Some antibiotics can’t pass

Question 17

What hormones are produced in the placenta?

Answer 17

1. Progesterone - to maintain pregnancy (4 mo replaces corpus luteum)
2. Estrogen - stimulate uterine growth and mammary gland development
3. hCG (human chorionic gonadotropin) - similar to LH; early appearance in urine of mother provides basis for pregnancy tests
4. Sommatomammotropin - similar to GH; gives fetus priority to maternal glucose

Question 18

What deleterious substances pass through the placental membrane?

Answer 18

1. Viruses - rubella, measles, poliomyelitis

2. Most drugs - can be harmful to fetus