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IC1&3 Physiology of Endocrine > Reproductive System > Flashcards

Reproductive System Flashcards

1
Q

What hormones does the gonads (testis, ovary) release?

A

Testis: Testosterone (LH -> Leydig cells), Inhibin (FSH -> Sertoli cells)

Ovaries: Estrogen (follicular granulosa cells + CL), Inhibin (follicular granulosa cells), Progesterone (CL)

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2
Q

What makes up the male external and internal genitalia?

A

External genitalia: penis, scrotum

Internal genitalia: seminal vesicle, ejaculatory duct, vas deferens, epididymis

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3
Q

What are the 3 functions of male reproductive system?

A
  1. Produce, maintain, transport, and nourish sperm and protective fluid
  2. Discharge sperm within female reprod tract
  3. Produce and secrete male sex hormones (e.g., testosterone)
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4
Q

What is testosterone role in descent of testes?

A

Testosterone (from fetal testes) enables testes to descend into 2 sides of the scrotum, shortening of the gubernaculum (cord of muscle)

Descent completed by 7th month of gestation

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5
Q

Undescended testes is known as ____

A

Cryptorchidism

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6
Q

What is testosterone role in sexual development?
Why undescended testes unable to achieve this role?

A

Spermatogenesis (sperm cell production)
*temp sensitive process, occurs in scrotum where temp is 35dc

Thus, if undescended testes, unable to produce viable sperm (temp is not high)

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7
Q

Hormonal changes occur during puberty.
GnRH is released from the hypothalamus in a pulsatile manner (1-3h). Give 2 reasons for this pulsatile secretion.

A
  1. Regulate secretion of FSH and LH from anterior pituitary which are also released in a pulsatile fashion
  2. Continuous exposure of GnRH receptor on anterior pituitary to GnRH causes desensitization of GnRH receptors, leading to decrease LH and FSH release. Hence, pulsatile secretion prevents desensitization of GnRH receptors in pituitary.
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8
Q

What happens in male puberty?

A
  1. Onset of spermatogenesis
  2. Enlargement of testes
  3. Development of secondary characteristics
  • Testosterone effects:
    Internal male genitalia differentiation
    Pubertal growth spurt
    Penis growth
    Deepening of voice
    Spermatogenesis
    Libido
    Muscle mass (anabolic steroid)
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9
Q

Spermatogenesis occurs throughout the seminiferous tubules in the testes. What are the cells present in the tubules, and what are their functions?

A
  1. Leydig cells
    - Convert cholesterol to testosterone
  2. Sertoli cells
    - Nurse cell, provide support and nourishment for spermatogenesis
    - Convert testosterone to DHT via 5a-reductase
    - Produce inhibin which selectively inhibits FSH secretion from anterior pituitary
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10
Q

What is the function of Luteinizing Hormone (LH) in testicular function?

A

LH stimulates leydig cells to produce testosterone

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11
Q

What is the function of Follicle Stimulating Hormone (FSH) in testicular function?

A

FSH stimulates Sertoli cells to induce spermatogenesis.

Testosterone also stimulates Sertoli cells to induce spermatogenesis.

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12
Q

What are the 3 negative feedback loops present in control of testicular function?

A
  1. Testosterone decreases GnRH release by acting on hypothalamus, thus indirectly decreases LH and FSH release from anterior pituitary
  2. Testosterone selectively inhibits LH secretion by acting on anterior pituitary
  3. Inhibin (produced by Sertoli cells) selectively inhibits FSH secretion by acting on anterior pituitary
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13
Q

What happens to the testes after administration of exogenous androgens (testosterone, DHT)?

A

Testosterone secretion decreases due to negative feedback, this causes decrease in FSH and LH release from the anterior pituitary which in turn decreases sperm production (dcr spermatogenesis) ==> testes shrink

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14
Q

What are the effects of dihydrotestosterone (DHT)?

A
  • External male genitalia (differentiation)
  • Sebaceous glands => cause pimples
  • Prostate (growth, enlargement)
  • Male hair pattern baldness (DHT is a body and facial hair growth promoter, but adversely affects hair growth on the head as it shrinks hair follicles)
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15
Q

Describe male pattern baldness due to DHT.
How can it be treated?

A

Horseshoe-shaped ring of hair around the back of the head
Gradual hair loss (recedes along temples, thins in a circular pattern)

Can treat using DHT inhibitors (target 5a reductase in sertoli cells), prevent conversion of testosterone to DHT

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16
Q

What genetic factor may cause male pattern baldness?

A

Increase expression of androgen receptor gene can cause more DHT to bind to receptors, result in hormonal processes such as male pattern baldness.

Polymorphism of androgen receptor gene may also be associated with male pattern baldness.

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17
Q

What makes up the female external and internal genitalia?

A

External:
- Clitoris
- Labium minus
- Labium majus
- Vagina (lower 2/3)

Internal:
- Vagina (upper 1/3)
- Uterus
- Uterine duct

18
Q

What are the 2 functions of the ovaries?

A
  1. Produce ova (oogenesis - starts in fetus)
  2. Secrete sex hormones (estrogen, progesterone)
19
Q

What are the 2 functions of female sex hormones (estrogen, progesterone)?

A
  1. Fertilization of ovum (ovarian cycle)
  2. Prepare female reprod tract for pregnancy (uterine cycle)
20
Q

What is the major female hormone-responsive reproductive organ?

What is its function?

A

Uterus
(Uterine cycle reflects cyclic changes of female sex hormones during the ovarian cycle)

Function: prepare endometrium for implantation and maintenance of pregnancy

21
Q

Name and describe the characteristics of the 2 phases in the ovarian cycle.

A
  1. Follicular phase (14days) - presence of maturing follicles
    *primary follicles = primary oocyte + surrounding granulosa cells (nurse) + theca cells
  2. Luteal phase (14days) - presence of corpus luteum formed from follicles after release of ovum
22
Q

What characterizes the start of the follicular phase?

A

Start of puberty/start of every cycle, rising levels of GnRH released in pulses by the hypothalamus to induce FSH and LH secretion from the anterior pituitary.

23
Q

How does LH and FSH cause release estrogen from follicular cells?

A

Both LH and FSH are required to release estrogen from the developing follicle

LH binds to receptor on theca cells, while FSH binds to receptor on granulosa cells in developing follicles.

*Aromatase enzyme found in granulosa cells converts testosterone to estradiol

24
Q

What are 2 roles of FSH acting on developing follicles?

A
  1. Aid in follicle growth and maturation
  2. Induce antrum formation in ovarian follicles for storage (estrogen storage site)
25
Q

Follicular (granulosa) cells secrete inhibin which selectively inhibits FSH secretion from the anterior pituitary.

Describe the negative feedbacks by rising moderate levels of estrogen.

A

Rising moderate levels of estrogen:

  1. Act on hypothalamus to decrease secretion of GnRH, indirectly dcr FSH and LH secretion from anterior pituitary
  2. Act on anterior pituitary to selective inhibit FSH secretion

==> As a result, LH secretion continues to rise slowly during follicular phase

26
Q

Follicular (granulosa) cells secrete inhibin which selectively inhibits FSH secretion from the anterior pituitary.

Describe the negative feedbacks by rising moderate levels of estrogen. What happens as a result of this?

A

Rising moderate levels of estrogen:

  1. Act on hypothalamus to decrease secretion of GnRH, indirectly dcr FSH and LH secretion from anterior pituitary
  2. Act on anterior pituitary to selective inhibit FSH secretion

==> As a result, LH secretion continues to rise slowly during follicular phase
Tonic LH secretion causes developing follicles to mature

27
Q

As follicles mature, high levels of estrogen is secreted.
Describe the positive feedback associated with high levels of estrogen. What happens as a result of this?

A

Rising high levels of estrogen:

  1. Act on hypothalamus to increase GnRH secretion, indirectly incr FSH and LH secretion from anterior pituitary
  2. Act on anterior pituitary to selectively increase LH secretion

*No more negative feedback by estrogen, the onle negative feedback present is inhibin selectively inhibiting FSH secretion from anterior pituitary.

==> As a result, surge in LH (LH burst) causes differentiation of follicular cells into luteal cells + ovulation (rupture of ovarian follicle, release of mature egg)

28
Q

What is Corpus Luteum (CL) made up of?

A

Follicular remnants (luteinized thera + granulosa cell)

29
Q

Under the influence of LH, what is secreted by CL during luteal phase?

A

CL secretes progesterone and estrogen (more P than E)

30
Q

During the Luteal Phase, high levels of estrogen continue to exert positive feedback. However, high levels of progesterone exert negative feedback instead.

Describe the negative feedback associated with high levels of progesterone.
What happens as a result of this?

A
  1. Act on hypothalamus to decrease GnRH secretion
  2. Act on anterior pituitary to decrease both FSH and LH secretion

==> As a result, decrease FSH and LH causes dampening of new development of egg, and prepares the body for implantation and pregnancy

31
Q

What happens to the CL if no fertilization occurs?

A

CL degenerates, no more Estrogen and Progesterone produced
[inhibition of negative feedback whereby high levels of P decrease GnRH, LH, FSH]

Low levels of estrogen signals start of new follicular phase, whereby GnRH secretion increases

32
Q

What are the 3 phases of the endometrium in the uterine cycle, and how do they correlate with the 2 phases of the ovarian cycle?

A
  1. Menstruation phase “destruction” [follicular phase]
  2. Proliferative phase “repair and regeneration” [follicular phase]
  3. Secretory phase “secretion of endometrial glands” [luteal phase]
33
Q

How does estrogen and progesterone affect the endometrium?

A

Estrogen causes thickening of the endometrium, growth of endometrial glands and emergence of spiral arteries [PROLIFERATIVE PHASE]

After release of ovum,

Progesterone increases the number of blood vessels and secretory glands in the endometrium [SECRETORY PHASE]
*Secretory glands secrete nutrients to nourish baby in the uterus/womb

34
Q

What causes shedding of the endometrium (menstrual phase)?

A

Low hormone (E + P) levels after CL degenerates (when there is no fertilization). Hence insufficient hormonal support and nutrients to nourish the endometrium.
Low P levels also cause collapse of spiral arteries.

35
Q

What happens to basal body temperature during the secretory phase?

A

During secretory phase of uterine cycle (luteal phase of ovarian cycle), CL formation causes secretion of Progesterone and Estrogen.

Increase in Progesterone causes 0.5dc incr in body temperature.

FYI: rising estrogen levels also changes consistency of cervical mucus, thin watery mucus during ovulation period (more viable for sperm survival)

36
Q

What might explain younger onset of puberty in females?

A

Exposure to external estrogen (e.g., BPA, paraben) - mother intake, plastic bottle products

37
Q

What are the signs of female puberty in succession?

A
  1. Thelarche (breast)
  2. Pubarche (pubic and axillary hair)
  3. Menarche (first period)

Others:
- growth of secondary sex organs
- fat deposition (esp around hip in prep for pregnancy)
- rapid incr in height (growth hormone)

38
Q

Menopause is characterized by low levels of circulating estrogen (decrease in hormone secretion). Explain how this occurs.

A

Ovaries have fewer remaining follicles, hence they have reduced sensitivity/responsiveness to circulating gonadotropins (FSH and LH)
Hence, this causes less secretion of estrogen and progesterone

Eventually, with very low levels of E, negative feedback on hypothalamus and pituitary gland to be removed, no more GnRH -> FH, LSH -> E, P
Thus, hypothalamus is less responsive to negative feedback

39
Q

What are some signs of menopause (change in hormonal balance)?

A
  • Cessation of menstrual period (12m after last period)
  • Gradual atrophy genital organs
  • Vasomotor changes (vasodilation/constriction => hot flushes)
  • Skin changes
  • Psychological, emotional
  • Increase cholesterol levels => CVD risk
  • Increase risk of osteoporosis (because estrogen regulates bone metabolism, hence dcr estrogen causes dcr bone mass/density)
40
Q

What are the two risks that increase with menopause?

A
  1. CVD risk
  2. Osteoporosis risk - supplement with calcium

IC1&3 Physiology of Endocrine (3 decks)

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