Section 3

Question 1

Which hormones are involved in the complex monthly cycling in females, and what is their role?

Answer 1

The female sex hormones, estrogen and progesterone, are involved in the complex monthly cycling. They influence the maturation and release of an egg (ova) and prepare the uterine lining for potential implantation of a fertilized egg.

Question 2

What happens if the released egg is not fertilized in females?

Answer 2

If the released egg (ova) is not fertilized, it decays, and the uterine lining is shed during the menstrual phase.

Question 3

What is the first step in oogenesis, and what is the outcome during fetal life?

Answer 3

Undifferentiated primordial germ cells in the ovaries undergo mitotic division during fetal life. By around the fifth month of gestation, this results in 6 to 7 million primary oocytes. The process ceases with the primary oocytes arrested just before their first meiotic division. Each primary oocyte is surrounded by a single layer of granulosa cells, forming a primordial follicle. By birth, only 2 million primordial follicles remain, representing the entire complement of potential ova a woman will have throughout her life.

Question 4

What happens to the number of primary oocytes from birth until menopause?

Answer 4

The number of primary oocytes starts to decay immediately after birth, and by menopause, the pool of primary follicles is exhausted, marking the end of a woman’s reproductive capacity.

Question 5

When do primary follicles develop into secondary follicles, and what happens just prior to ovulation?

Answer 5

From puberty until menopause, a small fraction of primary follicles develops into secondary follicles on a cyclic basis. Just prior to ovulation, the primary oocyte undergoes its first meiotic division, producing two daughter cells: the secondary oocyte and the first polar body.

Question 6

What happens to the secondary oocyte during ovulation, and what occurs if it is fertilized by a sperm?

Answer 6

The secondary oocyte is released during ovulation. If fertilized by a sperm, it undergoes the second meiotic division, forming the second polar body and combining its remaining chromosomes with those of the sperm.

Question 7

What are granulosa cells?

Answer 7

The layer of cells immediately surrounding a developing oocyte within an ovarian follicle

Question 8

What are the two cycles in female reproductive physiology, and what do they prepare for?

Answer 8

The two cycles in female reproductive physiology are the ovarian cycle (preparing an ova for release in the ovaries) and the uterine cycle (preparing the uterus for implantation).

Question 9

Describe the phases of the ovarian cycle at the onset of puberty.

Answer 9

At the onset of puberty, the ovarian cycle alternates between two phases:

1. Follicular Phase: Prepares a mature egg.
2. Luteal Phase: Prepares the reproductive tract for potential implantation.

Question 10

How long, on average, does the ovarian cycle last?

Answer 10

The ovarian cycle, on average, lasts 28 days.

Question 11

What is the duration of the follicular phase in the ovarian cycle?

Answer 11

The follicular phase lasts for the first 14 days of the ovarian cycle.

Question 12

What are the six stages of the follicular phase, and what happens during each stage?

Answer 12

1. Proliferation of Granulosa Cells: Begins with the proliferation of granulosa cells in a primary follicle. Granulosa cells divide to form layers around the oocyte.
2. Zona Pellucida Formation: Granulosa cells secrete glycoproteins, forming the zona pellucida membrane that surrounds the oocyte. Thecal cells surround the granulosa cells, collectively known as follicular cells. FSH and estrogen influence the development of the primary follicle.
3. Formation of Secondary Follicle: The follicle enlarges to become a secondary follicle capable of secreting estrogens, primarily estradiol, influenced by FSH and estrogen.
4. Antrum Formation: A fluid-filled cavity (antrum) forms within the granulosa cells, increasing the follicle’s size. Estrogen secretion increases.
5. Maturation of the Follicle: One follicle develops faster, becoming a mature follicle by around day 14. The oocyte undergoes its first meiotic division, becoming a secondary oocyte.
6. Ovulation: Under the influence of LH and FSH, ovulation occurs around day 14. The mature follicle ruptures, releasing the ovum into the abdominal cavity. The ovum is pushed into the oviduct by leaking antral fluid, marking the end of the follicular phase.

Question 13

What is the role of FSH, LH, and estrogen in the development of the follicular phase?

Answer 13

FSH and estrogen influence the development of the primary and secondary follicles. LH and FSH, under their influence, lead to ovulation around day 14, marking the end of the follicular phase.

Question 14

How long does the luteal phase last in the ovarian cycle?

Answer 14

The luteal phase occurs during the last 14 days of the ovarian cycle.

Question 15

What are the two stages of the luteal phase, and what happens during each stage?

Answer 15

1. Formation of Corpus Luteum: Once the ovum is released, the remaining follicular cells undergo luteinization to form the corpus luteum. The corpus luteum becomes highly vascularized and actively secretes hormones, mainly progesterone with some estrogens.
2. Degeneration into Corpus Albicans: If the ovum is not fertilized and implanted within approximately 14 days, the corpus luteum rapidly degenerates to form the corpus albicans, a fibrous scar tissue. This marks the end of one ovarian cycle, and the follicular phase begins again.

Question 16

What hormones are mainly secreted by the corpus luteum, and what signifies the end of the luteal phase?

Answer 16

The corpus luteum mainly secretes progesterone with some estrogens. The end of the luteal phase is marked by the rapid degeneration of the corpus luteum into the corpus albicans if the ovum is not fertilized and implanted within approximately 14 days.

Question 17

What hormones control the ovarian cycle, and what are their roles during the follicular phase?

Answer 17

The ovarian cycle is controlled by FSH, LH, and estrogen. FSH and estrogen stimulate early follicular development and the formation of the secondary follicle. LH is crucial for the production of estrogen, secreted in increasing quantities by the secondary follicle.

Question 18

What inhibitory role does circulating estrogen play during the follicular phase, and how does this change as estrogen levels rise?

Answer 18

During the follicular phase, circulating estrogen inhibits the actions of GnRH on FSH-secreting cells of the anterior pituitary. However, as estrogen levels continue to rise, it exerts a positive feedback action on the anterior pituitary, causing a surge in LH secretion.

Question 19

What is the significance of the LH surge?

Answer 19

The LH surge, triggered by rising estrogen levels, has several actions during the ovarian cycle.

Question 20

What are the several actions of the LH surge during the ovarian cycle? (4)

Answer 20

1. Inhibition of Estrogen Synthesis: The LH surge stops estrogen synthesis by follicular cells.
2. Reinitiation of Meiosis: LH reinitiates meiosis in the oocyte.
3. Triggering Release of Local Factors: The LH surge triggers the release of local factors that increase the swelling of the follicle and weaken the wall.
4. Differentiation of Follicular Cells: LH differentiates the follicular cells into luteal cells.

Question 21

What is the role of LH during the luteal phase, and what hormone does the corpus luteum primarily secrete during this phase?

Answer 21

During the luteal phase, LH continues to maintain the corpus luteum. The corpus luteum primarily secretes large amounts of progesterone in preparation for a potential pregnancy.

Question 22

What does progesterone, secreted by the corpus luteum, cause in the uterine lining during the luteal phase?

Answer 22

Progesterone causes changes in the uterine lining, preparing it for potential implantation of an embryo to establish a pregnancy.

Question 23

What happens if no implantation occurs during the luteal phase, and what is the consequence for circulating progesterone levels?

Answer 23

If no implantation occurs, the rapid degradation of the corpus luteum results in a rapid drop in circulating progesterone.

Question 24

______________: Causes changes in the uterine lining to prepare for potential implantation of an
embryo to establish a pregnancy

Answer 24

Progesterone

Question 25

______________: Important in the production of estrogen which is secreted in increasing quantities
by the secondary follicles

Answer 25

LH

Question 26

______________: Exerts a positive feedback action to cause a surge in LH secretion

Answer 26

Estrogen

Question 27

______________: Important for stimulating early follicular development and formation of the secondary follicle

Answer 27

FSH

Question 28

______________: Inhibit the production of LH and FSH by the pituitary gland

Answer 28

Inhibin

Question 29

What is the duration of the uterine or menstrual cycle, and what is its purpose in relation to the possible implantation of a fertilized ovum?

Answer 29

The uterine or menstrual cycle lasts around 28 days and prepares the uterus for the possible implantation of a fertilized ovum. If implantation doesn’t occur, the uterus is stripped clean to prepare for the next cycle.

Question 30

What are the two layers of the uterus, and how does estrogen influence their growth?

Answer 30

The two layers of the uterus are the myometrium (outer layer of smooth muscle) and the endometrium (inner lining with many glands). Estrogen stimulates the growth of both the endometrium and the myometrium.

Question 31

How does estrogen influence the responsiveness of the endometrium to progesterone, and what is the role of progesterone in the uterus?

Answer 31

Estrogen causes the expression of progesterone receptors in the endometrium, allowing progesterone to act on it. Progesterone transforms the endometrium into a lining suitable for the implantation of a fertilized ovum and reduces uterine contractility to enhance implantation and embryo development.

Question 32

What are the three phases of the uterine cycle, and what characterizes each phase?

Answer 32

The three phases of the uterine cycle are:

1. Menstrual Phase: Decreased estrogen at the end of the luteal phase leads to the sloughing off of the endometrial lining through vaginal expulsion. Prostaglandins cause blood supply constriction and myometrial contractions. Menstruation lasts around five to seven days.
2. Proliferative Phase: Initiated after the menstrual flow ceases, coincides with the later stages of the ovarian follicular phase. Under the influence of estrogen, endometrial cells proliferate, and glands and blood vessels grow, resulting in an endometrial thickness of 3 to 5 mm. Ovulation occurs during this phase.
3. Secretory Phase: Starts with the formation of the corpus luteum and the beginning of the ovarian luteal phase. Progesterone and estrogen from the corpus luteum convert the endometrium into a richly vascularized and glycogen-filled tissue to support an early embryo. If no implantation occurs, the corpus luteum degrades, triggering the next menstrual phase.

Question 33

Which parts of the ovarian and uterine cycles align, and how do they align?

Answer 33

The menstrual phase coincides with the end of the luteal phase and the beginning of a new follicular phase, marking the simultaneous start of both ovarian and uterine cycles.

The proliferative phase aligns with the later stages of the ovarian follicular phase.

The secretory phase aligns with the beginning of the luteal phase and the formation of the corpus luteum.

Question 34

What is endometriosis?

Answer 34

Endometriosis is a disorder where the endometrium, the tissue lining the uterus, grows outside of the uterus. It can affect various pelvic structures, such as the ovaries, fallopian tubes, and connective tissues, and, less commonly, it may spread to tissues beyond the pelvic region, including the large and small bowel or the abdomen. This condition can be debilitating and affects over 176 million women worldwide.

Question 35

What does ectopic mean?

Answer 35

In an abnormal location or position

Question 36

During endometriosis, just as the endometrial tissue in the uterus thickens, breaks down and bleeds with each menstrual cycle, so does the endometrial tissue outside of the uterus.

What do you think would be the result of this ectopic tissue?

Can you predict any long term consequences of this disease?

Answer 36

The tissue has no way to exit the body and it becomes trapped. Due to this entrapment, the surrounding tissue may become irritated, eventually developing into scar tissue and adhesions. When endometriosis specifically involves the ovaries, this tissue can lead to the formation of cysts, known as endometriomas.

Endometriosis increases the risk of developing ovarian cancer. Endometriosis can also lead to fertility problems, as the lesions that form from the outer uterine tissue can prevent the sperm from penetrating and fertilizing the egg.

Question 37

What is the order of the ovarian cycle?

Answer 37

The follicular phase, and then the luteal phase

Question 38

What is the order of the uterine cycle?

Answer 38

The menstrual phase, then the proliferative phase, then the secretory phase

Question 39

What is the ovarian cycle?

Answer 39

The ovarian cycle is a cyclical process that occurs in the ovaries and involves the preparation of an egg (ova) for release. It consists of two phases: the follicular phase, which prepares a mature egg, and the luteal phase, which prepares the reproductive tract for potential implantation.

Question 40

What are the two phases of the ovarian cycle, and how long does the entire ovarian cycle typically last?

Answer 40

The two phases of the ovarian cycle are the follicular phase (first 14 days) and the luteal phase (last 14 days). The entire ovarian cycle lasts around 28 days on average.

Question 41

Describe the stages of the follicular phase in the ovarian cycle.

Answer 41

1. Proliferation of granulosa cells in a primary follicle.
2. Formation of the zona pellucida, a membrane around the oocyte.
3. Development of secondary follicles capable of secreting estrogen.
4. Formation of antrum, a fluid-filled cavity within granulosa cells.
5. Maturation of one follicle into a mature follicle, releasing the ovum around day 14.

Question 42

What happens during the luteal phase of the ovarian cycle?

Answer 42

After ovulation, the remaining follicular cells undergo luteinization to form the corpus luteum. The corpus luteum secretes hormones, mainly progesterone, and some estrogens. If fertilization does not occur within approximately 14 days, the corpus luteum degenerates into the corpus albicans, marking the end of the ovarian cycle.

Question 43

What triggers the release of the ovum during ovulation?

Answer 43

The release of the ovum during ovulation is triggered by a surge in luteinizing hormone (LH) and follicle-stimulating hormone (FSH), with LH playing a crucial role. This surge is influenced by positive feedback from increasing estrogen levels.

Question 44

What are the three phases of the uterine cycle, and how long does the entire uterine cycle last?

Answer 44

The three phases of the uterine cycle are the menstrual phase, proliferative phase, and secretory phase. The entire uterine cycle also lasts around 28 days, aligning with the ovarian cycle.

Question 45

What is menopause, and when does it typically occur?

Answer 45

Menopause is a significant event in the female reproductive system, signifying the end of reproductive capacity. It usually occurs sometime between the ages of 45 and 55

Question 46

How many primary follicles do women have in their ovaries at birth, and what happens to them before puberty?

Answer 46

At birth, women have around 2 million primary follicles in their ovaries. Before puberty, there is continual decay or atresia of these follicles.

Question 47

Describe the changes in primary follicles and the ovarian cycle during and after puberty.

Answer 47

After puberty, several primary follicles begin to develop each month, but typically only one releases an ovum. This monthly cycle continues until, around the age of 45 to 55, no more viable primary follicles are present, leading to the cessation of ovarian and uterine cycles.

Question 48

What is a notable consequence of menopause, and how does it impact estrogen secretion?

Answer 48

A notable consequence of menopause is a dramatic decrease in estrogen secretion due to the absence of monthly follicular development. This decrease affects various body systems, including the skeletal and cardiovascular systems.

Question 49

How does estrogen contribute to bone health, and what is the consequence of reduced estrogen after menopause?

Answer 49

Estrogen helps promote strong bones by inhibiting osteoclast activity. After menopause, the increase in osteoclast activity can lead to osteoporosis, characterized by low bone mass and increased risk of fractures.

Question 50

Define osteoclast and osteoporosis.

Answer 50

Osteoclast is a type of bone cell that breaks down bone tissue. Osteoporosis is a disease characterized by low bone mass and deterioration of bone tissue, leading to an increased risk of fracture.