Physiological Changes During Pregnancy

Question 1

Explain the sperm journey to the ovum

Answer 1

1. 300 to 400 million sperms are introduced to the vagina,
2. About 2 million reach the cervix, only motile sperms can pass through this barrier,
3. Uterine contractions due to high estrogen, oxytocin (orgasm) and prostaglandins,
4. Sperms undergo capacitation,
5. About 200 sperms reach the secondary oocyte in the uterine tube

Question 2

What are the two things that happen to the sperms during capacitation?

Answer 2

Cell membrane becomes weaker due to cholesterol removal, less seminal fluid,
Increase of cell membrane permeability to Ca2+

Question 3

What facilitates the acrosome reaction?

Answer 3

The increased cell membrane permeability to Ca2+

Question 4

What helps the transport of the cumulus-oocyte complex (pre-zygote)?

Answer 4

1. Progesterone: stimulates fluid secretion from oviduct epithelium,
2. Estrogen: stimulates cilia to beat towards the uterine cavity, contraction of the oviduct.

Question 5

Which part of the fallopian tube helps capture the cumulus-oocyte complex?

Answer 5

The fimbriated end

Question 6

What triggers the acrosome reaction?

Answer 6

Sperm binding to the ZP3 receptors

Question 7

What is the zone pellucida made of?

Answer 7

4 glycoproteins: ZP1, ZP2, ZP3, ZP4.

Question 8

Which glycoproteins does the sperm cell have receptors for?

Answer 8

ZP2 and ZP3

Question 9

Explain the process of fertilisation?

Answer 9

PH-20 breaks down the hyaluronic acid,
Sperm has receptors to ZP3, so it binds to ZP3,
Acrosome reaction occurs,
Loss of ZP3 receptors, Secondary binding to ZP2.

Question 10

What happens during the acrosome reaction?

Answer 10

Sperm head continents are released, PLCζ converts PIP2 to DAG & IP3.

Question 11

What is the function of IP3?

Answer 11

IP3 sends a message to increase intracellular calcium, which causes exocytosis of small granules (cortical) and meiosis II.

Question 12

What is the function of cortical granules?

Answer 12

They cause cortical reaction and remove/digest ZP2 so no polyspermy.

Question 13

What is the rapid mitotic division of the zygote called?

Answer 13

Cleavage

Question 14

Where are the inner mass cells in relation to the endometrium during implantation?

Answer 14

They are facing the endometrium

Question 15

What is the endometrium known as after implantation?

Answer 15

Decidua

Question 16

What passes using passive diffusion through the placenta?

Answer 16

Water, electrolytes, free fatty acids, steroids, fat soluble vitamins, alcohol, oxygen and CO2

Question 17

What passes using facilitated diffusion through the placenta?

Answer 17

Glucose

Question 18

What passes using active transport through the placenta?

Answer 18

Amino acids, water soluble vitamins, calcium, iron, iodine

Question 19

What passes using endocytosis through the placenta?

Answer 19

Phospholipids, globulins, lipoproteins

Question 20

Which haemoglobin has higher affinity?

Answer 20

The fetal because there is a high RBC count in the fetus.

Question 21

What is the Bohr effect?

Answer 21

CO2 diffuses from fetal blood to maternal because there is low PCO2 in fetal blood.

Question 22

Why does BMR increase during pregnancy?

Answer 22

Due to thyroxine, cortisol and androgens increase

Question 23

What is the primary energy source for the mother during pregnancy?

Answer 23

Fatty acids, achieves that by adapting a catabolic state, so maternal insulin resistance increases.

Question 24

What happens to the mean atrial pressure during pregnancy?

Answer 24

It decreases towards mid-pregnancy and increases to equilibrium towards the end.

Question 25

What affects Mean Arterial
Pressure?

Answer 25

There is an increase in cardiac output but a decrease in total peripheral resistance

Question 26

What causes the decrease in total peripheral resistance?

Answer 26

Progesterone relaxes smooth muscles.

Question 27

What causes increase in cardiac output?

Answer 27

Increase in heart rate and stroke volume

Question 28

What happens to the minute ventilation during pregnancy? Why?

Answer 28

Increases 40 to 50%
Increase in respiratory rate and tidal volume due to progesterone

Question 29

What happens to GFR during pregnancy? Why?

Answer 29

Increases 40 to 50% due to renal vasodilation (relaxin and nitric oxide)

Question 30

What happens to Na+, Cl- and H2O reabsorption? Why?

Answer 30

50% increase due to aldosterone and oestrogen

Question 31

What happens to urine formation during pregnancy?

Answer 31

Increase due to H2O intake increase

Question 32

What are some skin changes pregnant women endure?

Answer 32

Chloasma, caused by an increase in melanin-stimulating hormone,
Linda nigra, due to increase in melanin stimulating hormone,
Striae gravidarum: stretch marks due to damage of elastic fibers in the dermis,
Acne,
Hair growth, cortisol and androgens