Lecture 22

Question 1

What are the three germ layers formed by gastrulation?

Answer 1

Ectoderm, mesoderm, endoderm

Question 2

What are the functions of the placenta?

Answer 2

• nutrient and oxygen exchange between foetal and maternal blood streams
• removal of CO2 and other wastes from foetal blood
• secretes hormones into both bloodstreams

Question 3

What is the difference between the placenta and the umbilical cord?

Answer 3

The placenta is the interface between the foetus and pregnant person, and the umbilical cord is the connection between the placenta and the foetus

Question 4

What are the three hormones secreted by placental tissues? When are their secretions elevated?

Answer 4

Estrogen (estriol) , progesterone

- the end of the first trimester

Question 5

What is the definition of organogenesis?

Answer 5

When the embryo forms organs

Question 6

What is the definition of teratogen?

Answer 6

Molecules/other biological factors that can adversely affect development, especially organogenesis
- roaccutane, thalidomide

Question 7

When does fertilization happen?

Answer 7

Fusion between two haploid gametes to produce a zygote

Question 8

What prevents sperm from entering the ovum?

Answer 8

Biochemical reactions in the zona pellucida

Question 9

How does sperm break through the oocyte’s membrane?

Answer 9

Enzymes in the acrosome of the sperm break down the layers of the follicular cells in the corona radiata

Question 10

How many sperm are needed to break through the membrane, and how many penetrate the oocyte?

Answer 10

Many, one

Question 11

What happens after the sperm enters the ovum?

Answer 11

Two haploid pronuclei develop and mingle chromosomes, forming a zygote

Question 12

What is a blastomere?

Answer 12

Daughter cells produced during cleavage

Question 13

What is a morula?

Answer 13

Solid ball of cells

Question 14

What does the morula create once it enters the uterus?

Answer 14

Sheds the zona pellucida and creates a blastocyst

Question 15

How does implantation happen?

Answer 15

The blastocyst fuses to the endometrium

- trophoblast erodes the endometrial epithelium and lodges the blastocyst within the endometrium

Question 16

What is the difference between cytotrophoblast and syncytiotrophoblast?

Answer 16

Cyto: individual cells with plasma membranes
Syncytio: many nuclei sharing one cytoplasm

Question 17

What are the four extra-embryonic membranes?

Answer 17

1. Amnion (cavity for embryo to develop in)
2. Yolk sac (pouch for distributing nutrients)
3. Chorion (separates blastocoele from the trophoblast)
4. Allantois (forms the umbilical cord)

Question 18

What is the function o the trophoblast?

Answer 18

Surround each villus and is responsible for hormone secretion of the placenta

Question 19

What is the function of hCG and what releases it?

Answer 19

• Human chorionic gonadotropin, maintains production of progesterone, supports the function of the corpus luteum
• the embryo