Chapter 3 Part 2

Question 1

What happens when the morula enters the uterine cavity?

Answer 1

Fluid starts penetrating through the zona pellucida into the intercellular spaces of the inner cell mass.

Question 2

What is formed as the intercellular spaces become confluent in the inner cell mass?

Answer 2

A single cavity known as the blastocyst.

Question 3

What are the two parts of the blastocyst, and where are they located?

Answer 3

The embryoblast (inner cell mass) is at one pole, and the trophoblast (outer cell mass) forms the epithelial wall of the blastocyst

Question 4

When does the zona pellucida disappear?

Answer 4

The zona pellucida disappears to allow implantation to begin.

Question 5

How do trophoblastic cells initiate attachment during implantation?

Answer 5

Trophoblastic cells express L-selectin, which binds to carbohydrate receptors on uterine epithelium.

Question 6

What is the role of selectins in implantation?

Answer 6

Selectins mediate the initial attachment of the blastocyst to the uterine epithelium.

Question 7

What molecules are involved in further attachment and invasion after initial attachment?

Answer 7

Integrins on the trophoblast interact with extracellular matrix molecules like laminin and fibronectin.

Question 8

What is the role of integrins in attachment and invasion?

Answer 8

Integrins expressed by the trophoblast interact with extracellular matrix molecules to promote attachment and migration.

Question 9

How do integrin receptors for laminin and fibronectin differ in function?

Answer 9

Integrin receptors for laminin promote attachment, while those for fibronectin stimulate migration.

Question 10

How do trophoblast and endometrial actions contribute to implantation?

Answer 10

Trophoblast and endometrial actions interact along signal transduction pathways to regulate trophoblast differentiation, resulting in implantation.

Question 11

When does the human zygote begin implantation?

Answer 11

By the end of the first week of development, after passing through the morula and blastocyst stages.

Question 12

What is the embryonic structure at one pole of the blastocyst called?

Answer 12

The embryoblast, which was previously known as the inner cell mass.

Question 13

What is the function of trophoblastic cells during implantation?

Answer 13

Trophoblastic cells initiate attachment and invasion, facilitating the implantation process.

Question 14

What is the initial attachment process of the blastocyst called?

Answer 14

The initial attachment process is mediated by the interaction between L-selectin on trophoblast cells and carbohydrate receptors on the uterine epithelium.

Question 15

What molecules are involved in the attachment and migration of the trophoblast?

Answer 15

Integrins, laminin, and fibronectin play roles in trophoblast attachment and migration during implantation.

Question 16

What influences embryoblast cell differentiation at the early blastocyst stage?

Answer 16

Fibroblast growth factors (FGFs) influence embryoblast cell differentiation.

Question 17

What are the two types of cells that embryoblast differentiates into under FGF influence?

Answer 17

Epiblast and hypoblast cells

Question 18

How do epiblast and hypoblast cells initially appear in the embryoblast?

Answer 18

They are scattered throughout the embryoblast

Question 19

What happens to epiblast and hypoblast cells near the time of implantation?

Answer 19

They segregate based on their specification, forming a dorsal layer of epiblast cells and a ventral layer of hypoblast cells adjacent to the blastocyst cavity

Question 20

How is dorsal-ventral polarity established in the embryo?

Answer 20

Dorsal-ventral polarity is established by the segregation of epiblast and hypoblast cells into distinct layers.

Question 21

What is the role of some hypoblast cells in the embryo?

Answer 21

Some hypoblast cells are specified to form the anterior Visceral endoderm (AVE).

Question 22

Where do AVE cells migrate, and what is their function?

Answer 22

AVE cells migrate to the cranial end of the embryo and secrete nodal antagonists, including cerberus and lefty, to specify the cranial end of the embryo

Question 23

How is the cranial-caudal embryonic axis established, and when does it occur?

Answer 23

The cranial-caudal embryonic axis is established near the time of implantation (days 5.5 to 6) through the interaction of AVE cells secreting nodal antagonists to specify the cranial end, while nodal promotes the primitive streak formation at the caudal end.

Question 24

Three layers of the uterine wall

Answer 24

Endometrium
Myometrium
Perimetrium

Question 25

mucosa lining the inside
wall

Answer 25

Endometrium

Question 26

a thick layer of smooth muscle

Answer 26

Myometrium

Question 27

the peritoneal covering lining
the outside wall

Answer 27

Perimetrium

Question 28

begins at the end of the menstrual phase and is under the influence of estrogen, and parallels growth of the ovarian follicles.

Answer 28

Follicular or Proliferative phase

Question 29

3 stages uterine endometrium passes through

Answer 29

1. Follicular or proliferative phase
2. Secretory or progestational phase
3. Menstrual phase

Question 30

Shedding of the endometrium marks the beginning of this phase if fertilization does not occur

Answer 30

Menstrual phase

Question 30

begins approximately
2 to 3 days after ovulation in response
to progesterone produced by the corpus luteum

Answer 30

Secretory or Progestational phase

Question 31

What happens if the oocyte is not fertilized?

Answer 31

Venules and sinusoidal spaces fill with blood cells, leading to diapedesis of blood into the tissue.

Question 32

Describe the events during the menstrual phase

Answer 32

Blood escapes from superficial arteries, and fragments of stroma and glands are shed. The compact and spongy layers of the endometrium are expelled, leaving only the basal layer.

Question 33

What remains in the uterus after the menstrual phase?

Answer 33

After the expulsion of the compact and spongy layers, the basal layer of the endometrium remains.

Question 34

How does the basal layer of the endometrium function?

Answer 34

The basal layer, supplied by its own arteries (basal arteries), serves as the regenerative layer responsible for rebuilding glands and arteries during the proliferative phase.

Question 35

What role does diapedesis play during the non-fertilization process?

Answer 35

Diapedesis leads to the infiltration of blood into the tissue when the oocyte is not fertilized.