The Menstrual Cycle

Question 1

What is the main affect on the periodontal tissue during puberty?

Answer 1

Increased gingival inflammation

Question 2

In females, when does reproductive potential start and end?

Answer 2

Puberty

Menopause

Question 3

Where does reproductive control start?

Answer 3

Pre-optic part of the hypothalamus

Question 4

Explain the mechanism behind the release of LH and FSH

Answer 4

Gonadotrophin-releasing hormone (GnRH) neurones.
GnRH released from nerve terminals into blood vessels.
Hormone travels down portal vessels.
GnRH stimulates release of LH and FSH from gonadotroph cells in the anterior pituitary into the circulation.

Question 5

What is the function of LH and FSH?F

Answer 5

FSH = stimulates growth of the ovarian follicles 
LH = stimulates production of steroid hormones and ovulation

Question 6

What are the two main roles of the ovaries?

Answer 6

1. Production of oocytes (egg cells)

2. Production and release of steroid hormones

Question 7

What are all steroid hormones generated from?

Answer 7

Cholesterol

Question 8

What are the two key points about steroid hormones?

Answer 8

• They pass through cell membranes (lipophilic) to act on intracellular receptors
• Receptor activation leads to changes in gene transcription

Question 9

What are oestrogens?
What is the naturally occurring one in pregnant women?
What are they synthesised and released from?

Answer 9

• They are steroid hormones that function as the primary female reproductive hormone.
• Oestradiol
• From androgens and released from ovaries

Question 10

What are progestagens?

What are they involved in?

Answer 10

They are steroid hormones derived from the same precursor as testosterone and oestrogen.
They are involved in the menstrual cycle and pregnancy.

Question 11

Explain how the oocytes are stimulated

Answer 11

GnRH is released and goes to anterior pituitary to stimulate it to produce LH and FHS. These stimulate the ovaries to stimulate oocytes. They also cause the ovaries to release hormones into wider circulation.
LH and FSH have a negative feedback affect.

Question 12

How do men and women differ in reproduction?

Answer 12

• Men have continuous reproduction but women stops
• Steroid hormones in males can be affected by the environment but womens can’t
• Mens hormone levels are relatively stable but females change over the cycle

Question 13

Give the number of eggs:

1. Before birth
2. At birth
3. Puberty
4. Menopause

Answer 13

1. 7 million eggs
2. 2 million eggs
3. 0.4million eggs
4. <1000 eggs

Question 14

What is found scattered throughout ovaries?

What form are they in?

Answer 14

Ovarian follicles

Inactive

Question 15

What are the 3 phases of the ovarian cycle?

What days are each of these?

Answer 15

Follicular phase: Days 1-10
A follicle grows in preparation for ovulation
The growing follicle releases oestradiol
Ovulatory phase: Days 11-14
High oestradiol causes the LH surge
Ovulation
Luteal phase: Days 14-28
• Remains of the follicle release progesterone – Corpus Luteum
This phase prepares for possible fertilisation.

Question 16

Give details on the follicular phase

Answer 16

FSH causes follicles to grow.
(Not known as to when individual follicles are known when to be stimulated and growth. A few primordial follicles respond to FSH in each cycle).

Primordial follicle = immature dormant oocytes, surrounded by flat granulosa cells.
Changes to a mature follicle = dependant on FSH to grow, competition for limited FSH means that only one follicle is left by day 10. As the follicle grows, the theca cell and granulosa cells release oestradiol in response to LH.

Question 17

What is the antrum?

Answer 17

Fluid filled sac around the outside of the follicle.

Question 18

What are the two layers which surround each oocyte?

Answer 18

Each oocyte is surrounded by many layers of granulosa cells. These granulosa cells are surrounded by a well vascularised thecal cell layer.

Granulosa cells secrete the fluid that accumulates in the extracellular space. The spaces coalesce (come together) to form the antrum.

In the mature Graafian follicle, a cluster of granulosa cells called the cumulus oophorus surround the accentrically-located oocyte.

Question 19

What does LH and FSH do to the follicle?

Answer 19

LH = stimulates the theca cells to produce androgens

FSH = stimulates growth of granulosa cells

Question 20

What happens to androgens in the follicle?

Answer 20

Androgens are main male reproductive hormone.
LH stimulates theca cells to produce androgens but we do not want a lot of this in females. The androgens are absorbed by the granulose cells in centre of the follicle and converted into oestrogen.
Oestrogen is then released into wider circulation.

Question 21

What happens during the follicular phase?

Answer 21

FSH causes follicles to grow.
LH stimulates hormone production from the growing follicles.
As the follicles grow, oestradiol levels increase.

Question 22

What happens during ovulatory phase?

Answer 22

Normally oestradiol have a negative feedback effect on LH release.
But during ovulation, oestradiol stimulates LH causing the LH surge.
The LH surge triggers ovulation.

Oestrogen normally has a negative feedback affects and inhibits LH and FSH.
Oestrogen can have a positive feedback affect when levels are high enough (changes from - to + feedback affect).
Oestrogen is high stimulates LH which then the Lh stimulates osteogen. The two cause each other to keep increasing. Spike in LH release is the trigger for ovulation.

Question 23

What happens after the release of the oocyte?

Answer 23

The follicle then collapses and the remaining granulosa and theca cells differentiate to become luteal cells, gaining the ability to secrete large quantities of progesterone.
The reputed follicles becomes the corpus leteum.

Question 24

What happens during luteal phase?

Answer 24

The follicle becomes the corpus luteum and released oestriadiol and progesterone to prepare for pregnancy.
If the cell is not fertilised the corpus luteum degenerates.

The cycle then starts again.

Question 25

What phase is the only one where oestrogen can have a positive effect?

Answer 25

The ovulatory phase.

Question 26

Explain what the hypothalamic-pituitary gonadal axis does in 1)follicular phase 2)ovulatory phase 3)luteal phase

Answer 26

1) FSH causes follicle growth, increased oestradiol release as follicle grows
2) High oestradiol switches to a positive feedback effect. LH surge in response to positive feedback causes ovulation
3) The follicle collapses forming the corpus luteum and releasing oestradiol and progesterone.

Question 27

Give some information on the uterus during the menstrual cycle

Answer 27

The uterus also changes across the ovarian cycle.
Series of changes in the endometrium in response to changes in hormone levels.
The uterus lining thickens through the cycle in preparation for pregnancy. During the luteal phase the endometrium becomes dependent on progesterone. (thickest during luteal phase).
End of luteal phase, progesterone levels fall, uterus lining then breaks down during a period (menstruation).

Question 28

What actually causes the uterus to degenerate?

Answer 28

Corpus Leutum degenerates, progesterone secretion stops, uterus lining shed (menstruation).

Question 29

What happens if the egg does get fertilised?

Answer 29

Progesterone secretion continues, uterus lining and implants embryo survives.
Implantation causes hCG (human Chorionic gonadotrophin) secretion which stimulus the corpus leteum to survive.

Question 30

What are the 6 functions of the placenta?

Answer 30

1. Gas exchange
2. Nutrient transfer
3. Excretion
4. Immune protection
5. Drug transfer and metabolism
6. Hormone synthesis

Question 31

What hormones does the placenta secrete?

Give the examples and the pattern of growth of it

Answer 31

Both steroid and protein hormones.

Human Chorionic Gonadotrophin (hCG) - increases and then decreases to flatten out at a lower level

Progesterone - increases throughout

Oestrogens - increases but lower than progesterone

Question 32

What tooth effects can pregnancy cause?

What symptoms of pregnancy cause this?

Answer 32

Pregnancy gingivitis, pregnancy granuloma, increased tooth mobility.

Salivary changes (flow, minerals, buffer).
Acid increase (due to morning sickness, dietary changes, oesophageal reflux)

Question 33

Explain hormone secretion at parturition

Answer 33

• During pregnancy: high levels of placental oestrogen sensitise the uterus to oxytocin.
• Just before birth: the maternal hypothalamus stimulates the posterior pituitary to secrete oxytocin, which increases uterine contractions.
The uterine endometrium also secretes prostaglandins, which aid in uterine contractions.
• After birth: Oestrogen and progesterone decrease when placenta expelled.

Question 34

What are advantages of breast feeding?

Answer 34

• Rapid establishment of infant-mother bond
• Protects against malnutrition and environmental factors
• Low cost food with minimal danger of contamination
• Maternal immunoglobulin to infant
• Ovulation is delayed by frequent suckling, spacing births (prevents a pregnancy from occurring too early)

Question 35

Explain hormone secretion and lactation during:

• pregnancy
• after birth
• suckling

Answer 35

• During pregnancy: oestrogen and progesterone increase fat and connective tissue in mammary glands, but not milk production.
• After birth: hypothalamus stimulates the anterior pituitary to secrete prolactin, which stimulates milk production (but not milk ejection).
• Suckling: stimulates the nerves in nipples → hypothalamus → posterior pituitary secretes oxytocin, which stimulates the milk ejection reflex

Question 36

How does suckling stimulate milk production?

Answer 36

Inhibiting dopamine secretion.
This increases the release of prolactin in the anterior pituitary.
Sucking communicates back to hypothalamus but to the oxytocin neurones. This causes the release of oxytocin into the blood from the posterior pituitary to decrease LH and FSH release.

Question 37

What happens after the menopause to the reproductive system?

Answer 37

No follicles, no oocytes, no oestradiol, oestrogen-deficency state

Question 38

Give 6 symptoms of the menopause

Answer 38

1. Atrophic conditions (reproductive organs, skin)
2. Osteoporosis
3. Vasomotor symptoms (hot flushes, unstable blood pressure)
4. Atherosclerosis and cardiovascular disease
5. Emotional changes (nervousness, insomnia, depression, impairment of memory, tiredness, frigidity)
6. Weight Gain

Question 39

What are clinical changes in the periodontal tissues during menopause and postmenopause?

Answer 39

• Reduction in epithlial keratinisation
• A reduction in salivary gland flow
• Drying of oral tissues
• Redness and abnormal paleness of gingival tissues
• Bleeding on probing and brushing

Question 40

What are the take home messages from this lecture?

Answer 40

• Female reproductive hormones and ovulation are cyclical.
• The reproductive cycle is controlled by interactions between the ovarian follicles and the hypothalamus and pituitary.
• During pregnancy the placenta secretes high levels of many hormones into the body of the mother.
• Lactation is regulated by changing hormone levels.
• The menopause marks the end of female reproductive function, with corresponding loss of steroid hormones.
• The changing hormone levels involved in all of these female reproductive states can have major effects on the body – including the teeth and periodontal tissues.