Chapter 17.4-17.5 Homework

Ovulation usually occurs on or about day _____ of a 28-day ovarian cycle.

14 - Ovulation usually occurs about halfway through the 28-day ovarian cycle.

The researchers studied the patient's cloned estrogen receptors to determine whether they were responsible for her delayed onset of puberty. Having eliminated two of the hypotheses considered in Part A, they hoped to determine whether any of the three remaining hypotheses explained the patient's condition. Hypothesis 1: The patient's estrogen receptors cannot bind estrogen. Hypothesis 2: The patient has too few estrogen receptors. Hypothesis 3: The patient's estrogen receptors cannot enter the target cell nucleus. To test these hypotheses, the researchers ran three separate experiments: Experiment A: They used a fluorescent dye to trace whether mutant and normal estrogen receptors could be found in the nucleus. Experiment B: They compared how well mutant and normal estrogen receptors bind to estrogen. To examine binding, they measured the amount of estrogen signal needed to produce a particular response. (If high levels of estrogen are needed to produce a response, it means binding is weak.) Experiment C: They measured expression levels of mutant and normal estrogen receptors.The results of the three experiments are shown in the data table below. Review each experiment and identify which of the three hypotheses under consideration it tested. Then decide whether the data support or refute (fail to support) that hypothesis. Drag the appropriate labels under each column in the data table.

Because estrogen therapy was ineffective, researchers were able to eliminate two hypotheses -- that the patient's estrogen levels were too low and that there was a defect in the patient's estrogen molecule. This suggested that the patient's issue most likely involved her estrogen receptors. DNA sequencing revealed a mutation in the patient's estrogen receptor gene. The researchers then carried out three experiments to test three different hypotheses regarding the estrogen receptor. Through these experiments, they eliminated two hypotheses -- that expression levels of the receptor were too low and that the receptor was unable to enter the nucleus. The data did support the final hypothesis -- that the mutant estrogen receptor was not effective at binding estrogen. This hypothesis is also supported by the observation that the mutation in the patient's estrogen receptor gene affects the region of the receptor protein where estrogen normally binds. Although the researchers note that the patient's clinical symptoms suggest she may be completely insensitive to estrogen, they also state that some residual estrogen sensitivity may be present in certain tissues.

The patient's doctor decided to put the patient on estrogen therapy for five months. Supplemental estrogen would be expected to correct some of the potential problems in estrogen signaling identified in Part A. This would allow estrogen signaling to go forward. Unfortunately, after five months, the patient still showed no signs of puberty. Based on this result, which of the hypotheses from Part A can you now eliminate? Select all that apply. Estrogen level too low Estrogen molecule is structurally defective Estrogen receptor cannot bind estrogen Too few estrogen receptors Estrogen receptor cannot enter nucleus

Estrogen level too low Estrogen molecule is structurally defective If the patient's estrogen levels had been too low, then giving her supplemental estrogen should have corrected her condition. Similarly, if her estrogen molecule had been defective, supplemental estrogen should have helped. This suggests that the issue is not with estrogen but with the patient's estrogen receptor. Researchers sequenced the patient's estrogen receptor gene and found that it contained a genetic mutation. The next step was for the researchers to determine the effect of this mutation.

Fertilization of an egg normally occurs within the uterus.

False

Menstrual cramps are caused by progesterone produced by the endometrium.

False

The anterior pituitary gland produces follicle-stimulating hormone (FSH), which triggers ovulation.

False

Which of the following statements is false?

Females enter menopause when their follicles become overly responsive to LH and FSH.

Choose the INCORRECT statement about the endometrium.

It is where fertilization usually takes place.

Which of the following statements about the endometrium is TRUE?

It thickens to prepare for implantation of the fertilized egg. - The endometrium is the lining of the uterus that thickens in response to estrogen and progesterone in preparation for implantation of the fertilized egg.

Which hormone spikes midway through the menstrual cycle and triggers ovulation?

Luteinizing hormone (LH) - Luteinizing hormone (LH) secreted by the pituitary gland causes the mature ovarian follicle to rupture during the process called ovulation.

A pregnant woman (first trimester) is concerned that she has been exposed to a chemical that blocks estrogen and progesterone receptors so that the body does not recognize these hormones. What is the most important reason she should be worried about this?

Menstruation may occur, thus causing the embryo or early fetus to be lost.

If a woman were exposed to a chemical that caused the cilia in her reproductive system to stop moving, what specifically is likely to happen?

Ova could no longer pass through oviducts.

Where does fertilization of an egg cell occur?

Oviduct

Which of these can be described as the release of the oocyte from an ovary?

Ovulation

In young women, the hormone estrogen is essential for normal development. At puberty, estrogen triggers the development of female features such as a higher-pitched voice, smaller body size, breasts, and wider hips.Estrogen is a lipid-soluble, steroid hormone. The diagram below shows the estrogen signaling process that normally functions in the body. Next to the diagram is a list of some possible causes for this young woman's delayed puberty. Evaluate each possible cause based on what you know about the woman's symptoms and the estrogen signaling pathway. Drag a check mark next to those causes that are consistent with what you know so far. Drag an "X" next to those causes that are not likely because they are inconsistent with what's known.

The estrogen signaling pathway involves many critical steps. This patient's delayed puberty could have resulted from issues that arose at any step in the pathway. At this point, the only hypothesis on the list that can be ruled out is that the patient's estrogen level was too high. Since estrogen triggers puberty, high estrogen levels would not likely be associated with delayed puberty. To further narrow down the list of possible causes, the patient's doctor will need to run some tests on the patient.

Which of the following statements describes endometriosis?

Tissue from the lining of the uterus is found on surfaces outside the uterus.

True or false. The corpus luteum develops from the ruptured follicle during the luteal phase after ovulation and produces hormones that can aid in pregnancy.

True

A structure covered by the anterior labia minora that contains many nerve endings and functions in sexual arousal in females is called the ________.

clitoris

In the female, the ________ secretes both estrogen and progesterone, and if fertilization does not occur, this structure degenerates.

corpus luteum

What do the cells that form the outer sphere of the mature Graafian follicle become once luteinizing hormone transforms the cells?

corpus luteum

Which of the following is related to an increase in the chance of breast cancer?

early first menstruation

If there is no fertilization, degeneration of the corpus luteum results in a drop in _____, which results in the sloughing off of the uterus's endometrium.

estrogen and progesterone - Estrogen and progesterone are responsible for maintaining the endometrium in the event that the egg has been fertilized.

After ovulation, high levels of _____ inhibit _____ secretion.

estrogen and progesterone ... FSH and LH - By secreting estrogen and progesterone, the corpus luteum maintains the endometrium and inhibits FSH and LH secretion.

Developing ovarian follicles primarily secrete _____.

estrogens - Developing ovarian follicles secrete estrogen.

The uterine lining is prepared for implantation by ________.

hormones produced by the ovaries - The ovarian hormones estrogen and progesterone prepare the lining of the uterus for implantation.

If there is fertilization, secretion of _____ by the early embryo maintains the corpus luteum.

human chorionic gonadotropin - HCG, secreted by the early embryo, maintains the corpus luteum. The corpus luteum secretes estrogen and progesterone, which maintain the endometrium for implantation.

What is the most proximate cause of menstrual flow?

lack of fertilization

A rapid increase in the _____ level stimulates ovulation.

luteinizing hormone - A surge in LH levels is responsible for triggering ovulation.

Which of the following signals the end of the reproductive period in females?

menopause

Prostaglandins are thought to cause ________.

menstrual cramps

What is the usual site of the fertilization of an egg cell?

oviduct - The oviducts are the usual sites of fertilization.

The ________ are the tubular structures that occur between the ovaries and the uterus.

oviducts

The tubes that extend from the uterus and function to transport the immature egg from the ovary to the uterus are known as ________.

oviducts

The functions of the corpus luteum include all of the following except ________.

secretion of follicle-stimulating hormone (FSH)

When a female has low levels of estrogen and progesterone, ________.

she is menstruating

When discussing the events that immediately follow ovulation, we can say that ________.

the burst follicle develops into the corpus luteum - After ovulation, development of the corpus luteum will produce progesterone needed for implantation of a fertilized egg into the endometrium.

After a fertilized egg implants ________.

the corpus luteum will continue to produce progesterone until the placenta forms - The placenta will take over production of hormones after it forms, but the corpus luteum must provide progesterone until then to prevent menstruation.

Select the most correct answer. Menstruation is the process by which ________.

the endometrium is expelled from the body - Menstruation is the process by which the uterine lining (the endometrium) is shed, or expelled, from the body.

A fertilized egg usually implants itself and develops in the _____.

uterus - The uterus is the usual site of the implantation and development of the fertilized egg.

During sexual intercourse, sperm are deposited into the __________.

vagina

After sperm are released in the female reproductive system, they can move to the egg and fertilize it. Which is the correct order of structures through which the sperm will pass?

vagina, cervix, body of uterus, oviduct

The external genitalia of a woman refer to the reproductive structures that lie outside the opening to the vagina. They are also known as the ________.

vulva

When does development of the oogonia first begin?

while the female is still in the womb