Human Reproduction And Development. (Test 1, Bio 2)

Front 1

Describe the cervix?

Back 1

The cervix is an extra thick bond of muscle, with a little opening that widens during menstrual period so wall of uterine lining can be shed.

Front 2

What are the three sections of the uterus that we should know?

Back 2

The layer against the lumen is the endometrium. (It changes during monthly cycle—builds up and breaks down.) The myometrium is a thick muscle layer. The parametrium is the surrounding connective tissue.

Front 3

What is endometriosis?

Back 3

A condition that can result from endometrium growing up into tubes or abdomen. It can cause pain and damage.

Front 4

What happens if the egg released from the ovary doesn’t make it to the Fallopian tube?

Back 4

The egg can fall and it can lead to an ectopic pregnancy, where the implantation occurs in the abdomen wall or Fallopian tube wall, neither of which are prepared to handle pregnancy.

Front 5

How would one describe the uteri (plural uterus) of animals that have litters compared to animals like humans?

Back 5

Bifurcated-2 uteruses.

Front 6

How many primary follicles are we born with?

Back 6

500,000.

Front 7

With menstruation, what happens with follicles?

Back 7

During any given cycle, 10-20 follicles begin to mature, which involves the oocyte frozen at prophase I and surrounding follicle cells that start multiplying. The one that goes out into the lead will eventually have a very large follicle and will develop a space called the antrum.

Front 8

What hormone do follicle cells produce and how do the hormone levels shift during cycle?

Back 8

Follicle cells produce estrogen and during cycle, estrogen rises and falls as follicle grows and falls back.

Front 9

What is the name of the fully mature follicle?

Back 9

Mature vesicular follicles or Graafian follicles.

Front 10

What happens on day 12 of the 28 day cycle?

Back 10

The mature vesicular follicle/Graafian follicle positions itself right beneath the wall of the ovary and creates a physical bulge.

Front 11

When does ovulation occur? What does it involve?

Back 11

Ovulation occurs in the middle of the cycle. It involves ripe Graafian follicles rupturing and releasing the secondary oocyte, which travels down the Fallopian tube.

Front 12

What happens to the follicle cells that remain from follicle that went through ovulation?

Back 12

They reorganize into corpus luteum in second half of cycle, and they hang around for about a week and become an endocrine organ that secretes estrogen and progesterone.

Front 13

What happens to the corpus luteum if no pregnancy occurs?

Back 13

If no pregnancy occurs, no signal arrives to preserve corpus luteum and it will disintegrate, shrink, and turn white. The white bodies remain in ovary (white spots in adults are remaining corpus albicans). The corpus luteum, then, possesses self-timing mechanism to disintegrate.

Front 14

Where is the pituitary gland?

Back 14

It’s at the base of the brain.

Front 15

What hormones are controlled by the pituitary?

Back 15

FSH (Follicle Stimulating Hormone) and LH (Leutinizing Hormone)

Front 16

What is the first half of menstrual cycle called?

Back 16

Follicular stage.

Front 17

What is the second half of menstrual cycle called?

Back 17

Luteal phase.

Front 18

What happens in the first days of menstrual period?

Back 18

The wall sloughs off which signals start of next cycle.

Front 19

What does FSH stimulate?

Back 19

It stimulates 10-20 follicles to start maturing.

Front 20

What secretes estrogen during menstrual cycle—and what do rising estrogen levels cause?

Back 20

Maturing follicle cells secrete estrogen—and the rising level of estrogen stimulates a thickening of walls of uterus in preparation for possible pregnancy.

Front 21

When do luteinizing hormone levels rise—and what does that rise cause?

Back 21

They increase in center (peak around Day 13), and the surge causes ovulation to occur (egg breaks out and travels down tube and the remaining follicles reorganize into the corpus luteum).

Front 22

What hormone surges to cause ovulation? What is its source?

Back 22

Luteinizing Hormone, which comes from the pituitary gland.

Front 23

What are the two hormones that the corpus luteum secretes? What do they do?

Back 23

Estrogen and progesterone. Estrogen prepares for pregnancy by thickening the wall of the uterus and making it highly vascularized. Progesterone maintains that condition and keeps everything ready for pregnancy.

Front 24

What does an increase in progesterone signal? What does a decrease in progesterone signal?

Back 24

An increase signals maintenance of the uterine wall to prepare for implantation. A decrease in progesterone signals onset of menstrual period.

Front 25

What does the presence of a small quantity of estrogen stimulate? What does the presence of a larger quantity of estrogen stimulate?

Back 25

A little estrogen causes more estrogen to be generated. A larger amount of estrogen feeds back and inhibits FSH (Follicle Stimulating Hormone) and LH (Luteinizing Hormone) preventing additional follicle growth.

Front 26

What is the hormonal mix in modern birth control and what does it accomplish?

Back 26

Estrogen and progesterone—and it works to stop follicles from being stimulated, and thus stops ovulation.

Front 27

Where in the female body would fertilization occur?

Back 27

It would occur in the Fallopian tube/oviduct.

Front 28

What is hCG and what role does it play?

Back 28

hCG is Human Chorionic Gonadotropin. It maintains corpus luteum (so that it doesn’t degenerate), allowing it to continue to produce estrogen and progesterone, which maintain the endometrial wall of the uterus where the embryo is implanted. hCG also inhibits the contractility of uterine muscle and firms & closes the cervix.

Front 29

What produces hcG?

Back 29

Chorion produces hcG.

Front 30

Where does chorion come from?

Back 30

The outer cells of the fertilized egg form the chorion, which contributesto the placenta, surrounds the outside, and produces hCG.

Front 31

Compare the gestation and lactation periods of marsupials and primates (placental mammals)?

Back 31

Primates have very long gestation and mid-length lactation. Marsupials have very short gestation and long lactation.

Front 32

How do fraternal twins come about on a fertilization level?

Back 32

If there is a tie in the developing follicle, two eggs may travel down the tube and become fertilized, allowing 2 ovulations to occur at the same time, become fertilized, and implant at the same time.

Front 33

How do identical twins come about on a fertilization level?

Back 33

A single is fertilized, but when it divides into 2 cell stage, it separates cells—and it displays indeterminate cleavage so each cell has all of the components that it needs to develop. Two embryos implant separately. The cellular split can happen at different points—and therefore you can have either 1-2 placentas, amnions etc.

Front 34

What happens with the Zona pellucida after fertilization?

Back 34

Although the first cell division happens around 30 hours after fertilization, it’s important that the zona pellucida remains because it and the embryo have receptors that match with the uterine wall to allow for implantation.

Front 35

When is the blastocyst stage of cleavage and when does it occur?

Back 35

It occurs at around 4-6 days after fertilization, when embryo ‘hatches’ from zona pellucida that has fallen off, yielding the blastocyst. At this stage, we see rapid divisions without growth at the lumen of the uterus.

Front 36

When is the implantation stage of cleavage and when does it occur?

Back 36

It occurs at one week. The uterine wall is now ready and the embryo contacts the uterine wall via receptors. Trophoblast cells rapidly divide on one side and form synctiotropoblasts, which digest way into wall of uterus.

Front 37

How soon does neurulation begin in humans?

Back 37

It begins at week 3, with the formation of the CNS and the neurula.

Front 38

What positive role does folic acid have with regards to fertilization & development?

Back 38

Taking folic acid can reduce incidence of neural tube defects, helping in DNA replication and blood cell formation.

Front 39

Where are the different sites for blood cell formation?

Back 39

Early blood cells are made in the yolk sac, which switches to the liver as the liver begins to develop, and ultimately bone marrow takes over.

Front 40

When do we begin to see sexual differentiation in humans?

Back 40

At 10 weeks.

Front 41

Where do germ line cells come from?

Back 41

Gonads

Front 42

If there is no Y chromosome present, what happens to the junction?

Back 42

It develops into a uterus.

Front 43

If there is a Y chromosome present, what happens to the junction?

Back 43

The Wolfian duct develops. The Malurian ducts fade and the W duct becomes vas deferens (which will become sperm-conducting tubes).

Front 44

In development, when do we begin to see sexual differentiation?

Back 44

10 weeks.

Front 45

What is the cellular origin of the placenta?

Back 45

Trophoblasts multiply and become synctiotophoblasts The uterus and trophoblasts organize cells to structure that comprises placenta.

Front 46

Characterize the placenta with four details?

Back 46

It is a life support system. It has both maternal and embryonic contributions. It weighs about 1 lb. It is disc-shaped. The chorion side is ‘messy’; it is smooth on the side that faces baby.

Front 47

Do we see continuous blood between mom and baby in placenta?

Back 47

No—there can be no mixing because of potential immune system compatability issues.

Front 48

Thinking about the cycle, when does the hCG peak occur?

Back 48

hCG peak is early—to preserve corpus luteum, allowing estrogen and progesterone to be maintained.

Front 49

What hormones does the placenta end up generating? And what implication does this have for placenta?

Back 49

Placenta begins producing estrogen and progesterone—which implies that placenta is an endocrine organ secreting hormones itself.

Front 50

What is the role of placental progesterone (3 roles)?

Back 50

It maintains the wall of the uterus, instead of the corpus luteum which degrades. It inhibits prolactin (stimulating of milk production) and placental lactogen stimulates production of milk ducts in breasts.

Front 51

What is one of the main placental hormone side effects?

Back 51

It inhibits ADH (antidiuretic hormone) with the net result that mom feels the need to pee more often.

Front 52

When do we see that the fetus begins to kick?

Back 52

4th month.

Front 53

In what trimester do we see large amount of growth in both the whole fetus and the brain in particular?

Back 53

Third trimester.

Front 54

Describe the hormonal & nerve sequence that occurs at birth?

Back 54

The head pushes against the stretch receptors in the uterus base, which signals through nerves to the hypothalamus, which releases oxytocin to posterior pituitary, which enters bloodstream and causes major contractions in smooth muscle of uterus. The net result is that the more you contract, the more you signal to contract harder again until birth.

Front 55

What is CRH, where is it produced, and how might it be involved?

Back 55

CRH is corticotrophin releasing hormone. It comes from the pituitary and it may be part of a signal for timing about when to start labor, but it is still mysterious.

Front 56

What is the initial substance that is secreted by the breasts?

Back 56

Colostrum—a yellowish substance with maternal antibodies and other healthy substances. It gives babies immune protection .

Front 57

Why does milk begin to secrete?

Back 57

Milk begins to secrete when the nerves detect suckling and signal the hypothalamus to synthesize oxytocin.

Front 58

Where is oxytocin released from and what does it do?

Back 58

While synthesized by the hypothalamus, oxytocin is released by the pituitary—and it causes contraction of muscles around the milk glands which stimulates the milk to be let down.

Front 59

What role does prolactin have on follicles?

Back 59

It inhibits formation of new follicle.

Front 60

What is relaxin? What generates it and what role is it thought to play?

Back 60

Relaxin is produced by the corpus luteum—it is thought to play a role in loosening of fibrous cartilage tissue in large, non-human mammals. Some women have reported feeling ‘loose jointed’ during pregnancy.

Front 61

What is cervical effacement?

Back 61

It refers to the thinning of the cervix. This occurs near the time of birth in pregnancy.