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Endocrine Exam 1 > 2 - Principles of Reproduction > Flashcards

2 - Principles of Reproduction Flashcards

1
Q

What are the primary functions of the testes?

A
  • Hormone production (testosterone)

- Sperm production

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2
Q

What makes up 80% of the testicular mass?

A

Seminiferous tubules

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3
Q

What are the key cell types for testicular function?

A
  • Leydig cells

- Sertoli cells

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4
Q

Describe Leydig cells

A

Cells which lie between the seminiferous tubules and produce testosterone

They produce testosterone in the presence of luteinizing hormone (LH).

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5
Q

Describe Sertoli cells

A

Cells which are part of the wall of the tubules and divide the tubules into two compartments

They help in the process of spermatogenesis; that is, the production of sperm.

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6
Q

What is the function of Leydig cells?

A
  • Testosterone synthesis
  • Testosterone secretion into the blood

THINK TESTOSTERONE

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7
Q

Describe the structure and orientation of Sertoli cells

A
  • There are tight junctions between adjacent Sertoli cells in order to form a blood-testis barrier
  • Just below the tight jucntions, speratogonia develop into primary spermatocytes
  • Tight junctions will then “open” and allow spermatocytes to access adluminal compartments
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8
Q

What are the key functions of Sertoli cells?

A
  • Supports germ cells
  • Signal spermatogenesis
  • Regulates pituitary function
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9
Q

What do Sertoli cells produce?

A

Androgen binding protein

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10
Q

What are gonadotropins?

A

Gonadotropins are glycoprotein polypeptide hormones secreted by gonadotrope cells of the anterior pituitary of vertebrates

They regulate testicular function

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11
Q

What are the two gonadotropins in males?

A

LH and FSH

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12
Q

Describe LH

A

LH is the key regulator of testosterone production in Leydig cells

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13
Q

Describe FSH

A

FSH is a key regulator of Sertoli cell proliferation and seminiferous tube growth

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14
Q

What regulates the release of gonadotropins (LH, FSH)?

A
  • GnRH
  • Testosterone
  • Inhibin B
  • Activin
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15
Q

How does GnRH regulate gonadotropins?

A

GnRH regulates pulsatile release which is impacted by multiple factors.

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16
Q

How does testosterone regulate gonadotropins?

A

Testosterone from Leydig cells inhibits release through negative feedback loop

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17
Q

How does inhibin B regulate gonadotropins?

A

Inhibin B produced by Sertoli cells in response to FSH inhibits release through negative feedback

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18
Q

How does Activin regulate gonadotropins?

A

Activin from multiple tissues (i.e. pituitary) blocks effects of inhibin B

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19
Q

What does LH promote?

A
  • Cholesterol movement from outer to inner mitochondrial membrane by steroidogenic acute regulatory protein (StAR)
  • LH also controls the conversion of cholesterol to pregnenolone (P450 scc)
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20
Q

What does 17 beta hydroxysteroid dehydrogenase do?

A

17-beta-HSD

  • Specific to the gonads
  • An enzyme that converts androstenedione into the final product, testosterone
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21
Q

What else is expressed by the Leydig cells?

A

Aromatase

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22
Q

What does aromatase do?

A

Converts testosterone into 17-beta estradiol

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23
Q

How is testosterone secreted into circulation?

A

Primarily bound to proteins

  • Albumin
  • Sex hormone binding globulin (SHBG)
  • Androgen binding protein (from Sertoli cells)
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24
Q

How does testosterone mediate its effects?

A
  • Binding and activating androgen receptors
  • Conversion to DHT and binding to androgen receptors (prolonged androgen action) - Can think of DHT as a long-acting androgen
  • Conversion to estradiol and binding to estrogen receptors
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25
Q

What is the physiological effect of testosterone?

A

Testosterone:

  • sexual development
  • sexual maturation, sexual function
  • spermatogenesis
  • libido
  • secondary sex characteristics
  • anabolic effects in muscle/bone
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26
Q

What is the physiological effect of DHT?

A

DHT

  • sexual development
  • pubic and underarm hair development
  • activity of sebaceous glands
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27
Q

What is the physiological effect of estradiol?

A

Estradiol

  • epiphyseal closure
  • suppress osteoporosis
  • feedback regulation at hypothalamus
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28
Q

What are the four steps of spermatogenesis?

A

1 - Spermatogonia proliferation (mitosis)
2 - Spermatid formation (meiosis)
3 - Maturation of spermatids (spermiogenesis)
4 - Release from Sertoli cells

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29
Q

Describe spermatogonia proliferation (mitosis)

A

a. near basal lamina

b. rounds of mitotic division yielding a pool of spermatogonia and primary spermatocyte

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30
Q

Describe spermatid formation (meiosis)

A

a. Meiotic division produces 2 secondary spermatocytes
b. Division of secondary spermatocytes produces spermatids
c. Process occurs in luminal compartment

31
Q

Describe maturation of spermatids (spermiogenesis)

A

a. nuclear condensing
b. formation of acrosome
c. positioning for tail formation

32
Q

What is the final step of spermatogenesis?

A

Release from Sertoli cells (spermiation)

33
Q

What is an important difference between males and females?

A

a mitotic process is going to yield 4 haploid mature sperm – compare this to female when you don’t produce 4 viable haploid cells, you yield 4 cells, but 3 of them are non-viable polar cells

34
Q

How do males and females differ in the production of germ cells?

A

Male – continue to produce germ cells throughout life

Females – stop producing germ cells during gestation

35
Q

Summary of spermatogenesis

A

THIS IS WHAT YOU NEED TO KNOW
1 - LH stimulates testosterone production by Leydig cells.
2 - Testosterone promotes initiation and maintenance of spermatogenesis by stimulating Sertoli cells.
3 - FSH stimulates Sertoli cell proliferation.
4 - FSH and testosterone stimulate ABP synthesis/secretion by Sertoli cells.
5 - FSH and testosterone are needed for complete maturation of the spermatozoa.

36
Q

What is the role of GnRH?

A

Gonadotropin releasing hormone

  • Released from the hypothalamus to act on the pituitary
  • Causes the pituitary to release both LH and FSH
  • LH works on Leydig cells to release testosterone
  • FSH works on the Sertoli cells to synthesize and secrete ABP
  • Testosterone and ABP lead to spermatogenesis
37
Q

What are the four female reproductive organs?

A
  • Ovaries
  • Uterus
  • Fallopian tubes
  • Mammary glands
38
Q

Describe the ovaries

A

Ovaries: Principal reproductive organ responsible for estrogen and progesterone production as well as the storage and release of the ovum.

39
Q

Describe the uterus

A

Uterus: 3 tissue layers which consists of the serous, muscular and mucous. The majority of the uterus is smooth muscle. The mucous layer (or endometrium) is ciliated secretory endothelium that undergoes cycle of proliferation, differentiation and shedding every 28 days.

40
Q

Describe the fallopian tubes

A

Fallopian tubes: secretory and ciliated cells for sperm movement, fertilization, and zygote transport to uterus.

41
Q

Describe the mammry glands

A

Mammary glands: network of lobes for milk production and storage.

42
Q

Describe oogenesis

A
  • During development oogonia undergo rounds of mitotic proliferation.
  • Total number of oogonia reached during gestation (6-7 million).
  • By the time of birth this number has been reduced to 2 million.
  • At puberty this number has been further reduced to 400,000 with less than 500 that will actually ovulate.
  • Diploid oocyte remains arrested until signaled to undergo apoptosis or develop to haploid secondary oocyte.
  • Oocytes associate with follicular cells to form the follicle.
  • Follicle consists of “internal” granulosa cells and “external” thecal cells.
43
Q

Describe the difference between males and females in haploid production during meiosis

A
  • In females, polar bodies develop after rounds of division, but only ONE will fully mature and differentiate
  • Polar bodies are going to regress, be absorbed and never leave the ovary (chromosonal “wastage”)
  • Males will actually have the four viable haploid sperm cells
44
Q

What occurs in each ovarian cycle?

A

One mature oocyte produced monthly

45
Q

What are the two phases of the ovarian cycle?

A
  • Follicular phase

- Luteal phase

46
Q

Describe the follicular phase

A

Follicular Phase (day 1)

  • follicle development
  • follicular phase is followed by ovulation
  • endocrine function (estradiol***)
47
Q

Describe the luteal phase

A

Luteal Phase (after ovulation)

  • corpus luteum forms
  • followed by menses
  • endocrine function (estradiol & progesterone***)
48
Q

Describe the role of the theca and granulosa cells during the ovarian cycle

A

During ovarian cycle theca and granulosa cells synthesize and secrete progesterone, androgens, and estrogens

49
Q

What is imporatnt to remember about the follicular and luteal phases?

A

Follicular phase –> think ESTRADIOL –> primary hormone

Luteal phase –> Think ESTRODIOL AND PROGESTERONE) –> two primary hormones

50
Q

What happens in the follicular phase (just read through it - don’t worry about specifics)

A
  • Follicle production of estradiol and inhibins (particularly inhibin B in early follicular phase). Estradiol production is under the control of LH and FSH.
  • Rise in estradiol produces a low-amplitude, high-frequency LH secretion needed for follicle development.
  • Estradiol positive feedback produces LH and FSH surge at mid-cycle which induces ovulation.
  • Inhibins A & B regulate LH and FSH secretion
  • Corresponds to proliferative phase of the endometrial cycle. Estrogen promotes proliferation of the endometrial lining.
51
Q

What is a major difference between the luteal and follicular phases?

A

Estrogen in the follicular phase is controlled by both LH and FSH – this is different in the luteal phase

52
Q

Describe the role of theca cells and granulosa cells in the production of estradiol during the follicular phase

TEST QUESTION*

A

Estradiol production during follicular phase

  1. Theca cells synthesize androstenedione in response to LH.
  2. Androstenedione is converted to estradiol in granulosa cells which is controlled by FSH.
53
Q

What phase does the “two cell theory” apply to?

A

Follicular phase

54
Q 
Describe ovulation
(just read through it, don't worry too much about it)
A
  • Day 14, ovulation is stimulated by a surge in LH.
  • LH stimulates rupture of the follicle by promoting a remodeling of the follicle through changes in gene expression patterns and cell signaling events.
  • Corpus luteum forms (thecal, granulosa, fibroblast, endothelial, and immune cells).
    - temporary endocrine gland
    - estradiol and progesterone
55
Q

How can you predict ovulation?

A
  • Basal body temperature (BBT) is the body temperature at rest. This is typically take after waking from 6 hours or more of sleep.
  • Pregesterone is thermogenic and produces a 0.5-0.8 degree increase in BBT.
  • Monitoring BBT can be used as an indicator of ovulation.
56
Q

Describe the follicular phase leading to ovulation

A
  • Gonadotropin induced steroidogenesis that is balanced by negative feedback regulation of estrogen.
  • Inhibin B feedback regulation of gonadotropin release.
  • Mid-cycle surge in LH induced by positive feedback of high estrogen levels.
57
Q

Describe the luteal phase (just read through it)

A
  • Rise in progesterone mediates a suppression of LH release through negative feedback. Resulting in decreased frequency in LH release.
  • Rise in progesterone and estradiol is under the control of LH.
  • Spike in inhibin B secretion following ovulation.
  • Rise in inhibin A secretion during luteal phase.
  • Corresponds to secretory phase of endometrial cycle. Progesterone promotes differentiation of endometrial cells into secretory cells.
58
Q

Describe estradiol and progesterone production during the luteal phase

A
  1. Luteinized theca cells synthesize androstenedione in response to LH.
  2. Androstenedione is converted to estradiol in the luteinized granulosa cells which is controlled by LH. Additionally, there is an upregulation of genes required for progesterone synthesis also under the control of LH.
59
Q

Describe the points of regulation during the luteal phase

A
  • LH induced steroidogenesis.
  • Rise in steroids (particularly progesterone) exerts negative feedback on gonadotropin production. This will result in a decline in steroid production.
  • Inhibins negatively regulate gonadotropin release.
60
Q

Describe the menstrual phase

A
  • Progesterone exhibits negative feedback and decreases LH.
  • The decrease in LH leads to regression of the corpus luteum.
  • As a result, steroidogenesis by the corpus luteum declines.
  • Decline in estrogen and progesterone production results in:
    a. the release of proteolytic enzymes that cause lysis of tissue.
    b. increase of prostaglandin production that increases myometrial contractions
61
Q

Describe the process of fertilization and implantation

A

Millions of sperm deposited in the vagina, however only a very small fraction (100 sperm) reach the ovum at ampulla of the fallopian tube.

Sperm binds to zona pellucida. Acrosomal reaction that allows penetration of the zona pellucida by proteolytic degradation.

Membrane fusion of sperm and ovum that result in release of sperm nucleus into ovum cytoplasm as well ovum membrane changes that prevent penetration by additional sperm.

Fertilized egg or zygote undergoes mitosis to yield a multicellular blastocyst.

Blastocyst uses expresses multiple enzymes that allow invasion into the endometrium.

62
Q

What happens if implantation occurs?

A

If implantation occurs, the corpus luteum does not regress. Instead placental derived human chorionic gonadotropin (hCG) stimulates ovarian steroidogenesis.

When implantation occurs, P and E will be on the downward trend b/c negative feedback, but need to maintain those during pregnancy, so in order to supplement the LH that will be going down, the body makes hCG which is the hormone we test for in pregnancy tests

63
Q

What else happens following implantation?

A

In addition, corpus luteum secretes relaxin to inhibit myometrial contractions.

64
Q

What happens after 8 weeks of pregnancy?

A

After week 8, maintenance of pregnancy is not dependent on corpus luteum since the placenta can synthesize steroids.

  • Progesterone: suppress uterine contractions, inhibit prostaglandin production, impact immune response
  • Estrogen: stimulate uterine growth, thicken vaginal epithelium, growth and development of mammary epithelium
65
Q

During implantation and formation of the placenta, what is “hatching?”

A

Break down of the zona pellucida

66
Q

During implantation and formation of the placenta, what is apposition?

A

Trophoblastic cells of the blastocyst makes contact with endometrium

67
Q

During implantation and formation of the placenta, what is adhesion?

A

Integrin mediated attachment between the trophoblast and stromal cells (decidual cells) of the endometrium.

68
Q

During implantation and formation of the placenta, what is invasion?

A

a. Trophoblast differentiates into cytotrophoblast and syncytiotrophoblast
b. Syncytiotrophoblasts send out finger-like protrusions and invade endometrium

69
Q

What do you need to know about the invasion process?

A

What you need to know here about the invasion process, is that maternal and fetal blood does NOT mix or come in contact at this point

  • Invading syncytiotrophoblast breaks through maternal veins and arteries.
  • Allows for pools of maternal blood to interface with syncytiotrophoblasts
  • Primary chorionic villi forms
  • Within villi, capillaris form
70
Q

There are three parts of the placenta, what are they?

A

1 - Fetal component
2 - Intervillous space
3 - Maternal component

71
Q

Describe the fetal component of the placenta

A

The mature chorionic villlus

Contains

a. Syncytiotrophoblasts
b. Cytotrophoblasts
c. Mesenchyme
d. Fetal blood vessels

72
Q

Describe the intervillous space

A

Blood trapped between fetal villous and maternal endometrium

73
Q

Describe the maternal component of the placenta

A
  • Decidual cells

- Maternal arteries and veins

74
Q

There is a diagram that what EMPHASIZED… What is the take-away point?

A

Emphasized this diagram

  • The villi structure here
  • Realize that the oxygen from blood from mom needs to diffuse across the villus capillary then into the villi then into the fetal blood stream
  • The oxygen has to cross many membranes in order to go from mom to baby
  • Invasive process, tap into the blood, form a space between mom and villi, allow blood to pool, then let nutrients can fuse across the structure (placenta)

Endocrine Exam 1 (18 decks)

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