Pregnancy - PTQs

Question 1

Why is it important for spermatozoa to have 23 chromosomes?

Answer 1

• sperm and ova combine to create new individual during fertilisation
• must avoid doubling of chromosomes and retain original chromosome number (n vs 2n)

Question 2

Age of an individual when oogenesis occurs

Answer 2

Foetal development/before birth.

Question 3

Important of producing meiosis variation in new cells

Answer 3

• variations provide an advantage to the individual

- cope better with environmental changes and increase variation, enabling survival, of the species

Question 4

List the steps by which the placenta develops

Answer 4

1) as the blastocyst implants, microvilli develop on its outer wall
2) micro villi contain blood vessels
3) villi form blood pools in endo
4) foetal and maternal blood remain separated by placental membranes

Question 5

What does not result in increased variation?

Answer 5

Replication of chromosomes in the nucleus

Question 6

Name the location from which embryonic and adult stem cells are obtained.

Answer 6

Embryonic - ICM

Adult stem cells - bone marrow, brain, cord blood

Question 7

Which 4 embryonic membranes form outside the embryo

Answer 7

Amnion --> amniotic fluid
Chorion --> main part of foetal portion of placenta
Yolk sac 
Allantois
(^^ umbilical cord)

Question 8

Why is there an increase in progesterone after day 14?

Answer 8

There is a rise in progesterone for maintenance of endometrium and a possible pregnancy.

Question 9

The human chorionic gonadotropin is secreted by which structure and what effect does it have on its target organ?

Answer 9

It is secreted by the placenta and maintains the CL during the early stages of pregnancy

Question 10

Luetinising hormone (LH) targets what organs, and what effect does it have?

Answer 10

LH targets the interstitial cells of the testes and cells of the ovaries to stimulate the secretion of testosterone and oestrogen/progesterone

Question 11

What are the 2 gonadotrophic hormones of the pituitary gland

Answer 11

FSH and LH

Question 12

What does the ovarian cycle include? MRDF

Answer 12

• maturation of an egg
• release of egg into uterine tube
• development of follicles in ovary
• formation of CL

Question 13

How does the mature egg travel towards the uterus

Answer 13

Beating cilia within the uterine tube create a current which sweeps the egg into the uterine tube and towards the uterus

Question 14

What stimulates the secondary oocyte to complete the second meiotic division

Answer 14

The entrance of the sperm stimulates the egg just before fertilisation

Question 15

In what ways do stem cells differ from ordinary body cells?

Answer 15

• SCs have the ability to either divide for indefinite periods in culture to create more stem cells
• give a rise to specialised cells

Question 16

What is the function of the chorion membrane

Answer 16

It become the main part of the foetal portion of the placenta, as it surrounds the other 3 embryonic membranes.

Question 17

What is the function of the amnion

Answer 17

The amnion membrane is an enclosed membrane that secretes amniotic fluid which serves to protect embryo.

Question 18

Distinguish between proliferation and differentiation

Answer 18

Proliferation - when cells replicate themselves many times over

Differentiation - the process by which unspecialised cells develop the characteristics and the functions of particular types of cells (eg. Blood, muscle, nerve, bone cells)

Question 19

List the changes of the mother during pregnancy

Answer 19

• growing abdomen
• enlargement of breasts
• increase in size of heart and blood volume
• increased blood flow to kidneys
• changes in mood

Question 20

How long after reaching the uterus does the blastocyst implant into the endometrium

Answer 20

2-3 days

Question 21

What causes menstruation to cease during pregnancy

Answer 21

The continued development of the blastocyst depends on the endometrium being maintained. High levels of hormones in the blood stop the endometrium breaking down, and so the menstrual cycle ceases.

Question 22

What does the ICM of a blastocyst develop into

Answer 22

The ICM will develop into the embryo, and the cells that compose it are termed stem cells.