Embryology - First week of Development

Question 1

What are the three consequences of the fusion of the plasma membranes of the sperm cell and the oocyte?

Answer 1

1. The cortical and the zona reactions
2. The Metabolic activation of the oocyte to get ready for embryogenesis
3. The completion of meiosis 2 and the formation of the second polar body and female pronucleus.

Question 2

What happens when the male and female pronuclei meet?

Answer 2

1. The nuclear membrane breaks down
2. DNA synthesis - the replication of DNA
3. The 23 maternal and paternal chromosomes move to the opposite ends of the cell.

Question 3

What are the main results of fertilization?

Answer 3

1. Restoration of the diploid number of the chromosomes
2. Determination of the sex of the new individual
3. Initiation of cleveage.

Question 4

Describe the formation of the Blastocyst

Answer 4

1. Blastocele formation - fluid moves into the intercellular space and formed a cavity
2. Flattening of the outer trophoblastic cells.
3. Dissapearence of the zona pellucida

Question 5

Explain how the implantation of the blastocyst into the uterine mucosa happens.

Answer 5

• The Trophoblast cells have L selectin
• The uterine mucosa has carbohydrate receptors.

1. The selection first binds
2. Laminin and Fibronectin bind to the Integrin receptors for further attachment.

Question 6

What are the three layers of the uterus?

Answer 6

1. Endometrium
2. Myometrium
3. Perimetrium

Question 7

What are the three phases that the endometrium goes through?

Answer 7

1. Follicular/ Proliferative phase
2. Secretory/ Progestational phase
3. Menstrual Phase.

Question 8

Describe the timings of the three phases of the menstrual cycle.

Answer 8

1. Follicular/ Proliferative phase - begins at the end of the menstrual phase
2. Secretory/ Progestational phase - 2-3 days after ovulation
3. Menstrual Phase - during the shedding of the endometrium.

Question 9

What happens during the secretory phase of the menstrual cycle?

Answer 9

1. The uterine glands and arteries become coiled
2. Tissue becomes succulent

Question 10

The three distinct stages of the endometrium during the secretory phase?

Answer 10

1. Superficial compact layer
2. Intermediate spongy layer
3. Basal layer

Question 11

Describe the menstrual phase.

Answer 11

1. venules and sinusoidal spaces become packed with blood cells
2. Extensive diapedesis of the blood is seen.
3. Blood escapes from the superficial arteries
4. Small pieces of stroma and glands break away.
5. Compact and spongy layers are expelled
6. Basal arteries function as a regenerative layer in the rebuilding glands.