Female Reproduction 2

Question 1

Define the following:
Post-conceptional age
Ovulation age
Gestational age
Menstrual age

Answer 1

Post-conceptual age starts right at fertilization.

Ovulation age starts at the time the oocyte was ovulated.

Gestational age is the age since the prior menses. Roughtly 2 weks longer than ovulation age. Menstrual age is the same thing as gestational age.

Question 2

How long does it take for the zygote to get to the uterus after fertilization? How does it get there?

Answer 2

Takes three days. Facilitated by gentle fluid flow and cliliary movement in the fallopian tube.

Question 3

In what cellular stage is the zygote when it reaches the uterus? What are the subsequent cellular differentiation steps?

Answer 3

It is in blastocyst stage when it gets to the uterus. The 52 cell blastocyst forms the trophoectoderm (an outer cell layer) and further development produces the synciciotrophoblast (outer, multinucleated cell) and the cytotrophoblast (inner cells).

Question 4

Where does implantation normally occur in the uterus?

Answer 4

Posterior wall

Question 5

How long after fertilization does implantation usually occur?

Answer 5

1 week

Question 6

Which cell layer of the blastocyst is responsible for invading the decidua?

Answer 6

The outer synciciotrophoblast layer

Question 7

Name two GFs that are released at the time of implantation that cause an increase in protease production by the trophoblast.

Answer 7

Leukemia inhibitory factor and colony stimulating factor-1

Question 8

Which important substance is secreted by the blastocyst that sustains the corpeus luteum despite the falling levels of maternal LH?

Answer 8

hCG

Question 9

Aside from sustaining the corpus luteum, what two other functions does hCG have?

Answer 9

1. Immunosuppressive agent

2. Autocrine growth factor activity

Question 10

Name the four implantation events.

Answer 10

1. Hatching
2. Apposition
3. Adhesion
4. Invasion

Question 11

What happens during the hatching stage of implantation?

Answer 11

Breakdown of the zona pellucida by lytic factors such as plasmin

Question 12

What happens during the apposition stage of implantation? What is an important factor in this process?

Answer 12

Loose connection is made between the blastocyst wall and the endometrial epithelium. Orientation is important - the inner cell mass must be nearest to the endometrial epithelium.

Question 13

What happens during the adhesion stage of implantation?

Answer 13

Integrin receptors on the trophoblast bind initially to laminin on the endometrium. Once invasion happens into the endometrium, the trophoblast integrins will bind to fibronectin on the decidual basement membrane.

Question 14

What happens during the invasion stage of implantation?

Answer 14

Trophoblast (outer cells) of the blastocyst differentiate into two layers: the inner cytotrophoblast and the outer syncitiotrophoblast. The outer syncitiotrophoblast spits out projections into the myometrium with the help of factors like TNF-alpha to degade the ECM, etc.

Question 15

Describe how the placenta forms following implantation.

Answer 15

8 days following fertilization the projections of the outer syncitiotrophoblast develop lacunae. By 12-15 days these lacunae envelop uterine blood vessels. By 20 days the blood vessels are broken down and the lacunae fill with maternal blood, forming an early placental structure.

Question 16

High levels of the hormones _________ and __________ are required for pregnancy, which are supplied by the corpus luteum for the first 8 weeks of pregnancy. After those 8 weeks, the ________ becomes the major source of these hormones.

Answer 16

High levels of estrogen, progesterone needed. Placenta takes over production of these hormones at 8 weeks

Question 17

What specific structure in the breasts are estrogens responsible for stimulating during pregnancy? Name two other things estrogen does.

Answer 17

Ducts. Also aids in deposition of fatty tissue and prolactin production by the anterior pituitary.

Question 18

What specific structure in the breasts are progestins responsible for stimulating during pregnancy? Name one other thing that progestins do.

Answer 18

Glandular tissue (acini). Progestins also suppress uterine contractions so the developing fetus isn’t birthed prematurely.

Question 19

At what point in pregnancy do weak and irregular contractions usually start?

Answer 19

In the last month of pregnancy

Question 20

What are the three key endocrine mediators of parturition? What does each one do?

Answer 20

1. Prostaglandins initiate labor, stimulate smooth muscle contraction, promote gap junction formation b/t smooth muscle cells, and soften, dilate, and thin the cervix.
2. Oxytocin stimulates contractions.
3. Relaxin dilates the cervix and softens ligaments of the pubic symphysis.

Question 21

What are prostaglandins used for clinically?

Answer 21

To induce labor

Question 22

What is oxytocin used for clinically?

Answer 22

To augment labor - help induce contractions.

Question 23

What happens to the frequency of oxytocin release as labor ensues?

Answer 23

It increases

Question 24

What is the Ferguson reflex?

Answer 24

Distension of the cervix causes oxytocin release

Question 25

What is oxytocin’s role immediately after partuition?

Answer 25

It helps constrict uterine blood vessels to aid in coagulation.

Question 26

Describe the partuition positive feedback loop.

Answer 26

As the fetus drops lower into the uterus, the cervix stretches.

Cervical stretch stimulates oxytocin release from the posterior pituitary, and stimulates uterine contractions.

Oxytocin stimulates prostaglandin release from the uterine wall and also stimulates uterine contractions.

Prostaglandin release stimulates uterine contractions.

The uterine contractions drop the fetus lower into the uterus, promoting more cervical stretch.

Question 27

What is the major cause of uterine involution following partuition?

Answer 27

Loss of estrogens and progestins

Question 28

How much breast volume is gained during pregnancy? What happens to breast blood supply?

Answer 28

Up to 1/3 kg of fluid (333 cc). Blood supply doubles.

Question 29

When does colostrum production begin?

Answer 29

3rd trimester

Question 30

What hormone is responsible for inhibiting lactation before birth? What happens when it is gone (as a result of partiution)?

Answer 30

Progesterone. Removal of progesterone allows cortisol and prolactin to act on acinar epithelium to make milk.

Question 31

What are the two neural pathways of lactation stimulation?

Answer 31

1. Breast –> hypothalamus, blocks dopamine release –> increase in prolactin from the anterior pituitary.
2. Breast –> mesencephalon –> increase in oxytocin release from the posterior pituitary.

Both neural pathways enter at T4, 5, 6 levels

Question 32

What is Sheehan syndrome?

Answer 32

When severe hypotension following birth results in ischemic necrosis of the posterior pituitary and therefore no oxytocin from that point onwards.

Question 33

What type of protein is breast milk high in?

Answer 33

High whey content (low caesin content)

Question 34

What is Bifidus factor?

Answer 34

A probiotic found in colostrum and breast milk.

Question 35

Does colostrum have enough calories to sustain a baby?

Answer 35

Yeah but the baby won’t really grow at all. Need milk, too.

Question 36

What are the three mechanisms of galactopoiesis?

Answer 36

Regular and frequent milk removal stimulates these things:

1. Stimulation of prolactin and oxytocin release.
2. Promotion of blood supply to deliver nutrients to breast tissue.
3. Matches output to demands.

Question 37

Are low stress levels and adequate dietary intake required for galactopoiesis?

Answer 37

Yeah

Question 38

Which of the two pituitary gonadotropins is analogous to hCG?

Answer 38

LH