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Biomedical physiology > Week 7: The reproducive system > Flashcards

Week 7: The reproducive system Flashcards

1
Q

What is the reproductive system made of?

A
  • The gonads
  • The external and internal genitalia/reproductive tracts
    • Ducts that transport and/or house gametes (germ cells)
      Mullerian duct (female) and Wollfian duct (male) derivatives
  • Accessory sex glands
    • Supportive secretions for gametes - secreted into reproductive tract
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2
Q

What makes up the accessory reproductive organs?

A
  • Organs of the reproductive tract: transport of gametes
  • Glands: secrete fluids into reproductive tract
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3
Q

What are the functions of the gonads?

A
  1. Produce haploid gametes (germ cells)= gametogenesis
    - Spermatogenesis in the testis and oogenesis in the ovaries
  2. Produce and secrete gonadal hormones; either peptide or steroid hormones (steroidogenesis)
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4
Q

What are the 3 major hormone types secreted by the reproductive system?

A
  • Steroid hormones (testosterone, progesterone and oestrogens)
    • These are produced from cholesterol
  • Gonadotropins - peptide/protein hormones
    • FSH (pituitary gland)
    • LH (pituitary gland)
    • hCG (chorionic gonadotropin) - produced by placenta
  • Oxytocin - a peptide/protein hormone
    • Produced in the hypothalamus, excreted by the pituitary gland
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5
Q

Where does progestogen orginate from?

A

Cholesterol (C27)

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6
Q

Where does androgen originate from?

A

Progestogen

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7
Q

How many carbons does progestogen and androgens have?

A

Progestogen - C21 , androgen - C19

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8
Q

Where does oestrogen originate from?

A

Androgen

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9
Q

How many carbons does oestrogen have?

A

C18

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10
Q

Name a type of oestrogen and progestogen

A

Oestradiol and progesterone

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11
Q

How does sex determination occur after the genetic sex is determined by XX or XY?

A

during fertilisation the SRY gene (sex-determining region of Y-chromosome) codes for the production of TDF (testis-determining factor)

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12
Q

Without the TDF and SRY region what is the default?

A

To differentiate into ovaries

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13
Q

Apart from testosterone what else do the testes secrete?

A

Mullerian-inhibiting factor

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14
Q

What is the effect of the absence of testosterone?

A

Degeneration of Wolffian ducts + development of undifferentiated external genitalia to female reproductive lines

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15
Q

What are the effects of testosterone?

A

Secondary sexual characteristics
Libido at puberty
Growth & maturation of genitalia
Protein anabolic effect
Spermatogenesis
Bone growth at puberty

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16
Q

When is testosterone secreted?

A
  • Secreted before birth (masculinize developing reproductive system)
  • Ceases until puberty, continues throughout life
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17
Q

Describe the progression of a ovary

A

primordial → primary → secondary → pre-antral → antral →ovulatory / Graafian follicle)

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18
Q

What gonadal hormones are synthesized by the follicles?

A

androstenedione & oestradiol

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19
Q

What gonadal hormones are synthesized by the corpus luteum?

A

progesterone & oestradiol

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20
Q

What are the target cells of oestrogen and FSH?

A

Granulosa cells- they secrete chemical messengers in response

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21
Q

What other hormones do Granulosa cells secrete in response to oestrogen and FSH?

A
  • secrete inhibin - provides negative feedback to FSH secretion,
  • transport nutrients to oocytes through gap junctions
  • Secrete oestrogens
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22
Q

What is the effect of oestradiol?

A
  • ova maturation & release (ovulation)
  • development of female sex characteristics
  • transport of sperm within the female
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23
Q

What is the function of progesterone?

A
  • prepares suitable environment to nourish
  • developing embryo/foetus
  • breasts ability to produce milk
  • breast differentiation (development of lobuloalveolar tissue- ability to produce milk)
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24
Q

What hormones trigger the menstrual cycle?

A

decreased oestrogens and progesterone.

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25
Q

What hormone triggers ovulation?

A

Surge in LH, the surge is caused by high levels of estradiol secreted by the mature follicle

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26
Q

What does the corpus luteum produce?

A

Progesterone and oestrogen

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27
Q

Where are LH and FSH secreted from?

A

The anterior pituitary gland

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28
Q

Oestradiol and progesterone are secreted by what?

A

Oestradiol - follicles and CL
Progesterone is only secreted by the CL

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29
Q

Where does spermatogenesis occur?

A

In the seminiferous tubules

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30
Q

What is the function of a Sertoli cell?

A

To support spermatogenesis and secrete inhibin (which inhibits FSH)

31
Q

Where are Leydig cells located and what is their function?

A
  • Leydig cells are located between the seminiferous tubules (interstitial cells)

Function: To synthesise/secrete testosterone.

→ Secretion of testosterone is stimulated by LH

The release of hormones is regulated by a negative feedback loop

32
Q

Where is GnRH (gonadotropin releasing hormone) secreted from and what does it do?

A

-Hypothalamus
-Activates the release of FSH and LH from the anterior pituitary (activating mechanism)

33
Q

What is the effect of FSH in males?

A

acts on Sertoli cells and stimulates the production of gametes in the seminiferous tubules

34
Q

What is the effect of LH in males?

A

acts on the interstitial space (between the seminiferous tubules) activates release of testosterone which further activates the production of sperm

35
Q

Explain how the male hormones can act as a negative feedback loop

A
  • High levels of testosterone inhibit the activation of the anterior pituitary and the hypothalamus
  • So decrease in LH and FSH and GnRH
  • Less testosterone
36
Q

What are spermatogonia?

A

Undifferentiated haploid spermatids

37
Q

What is the difference between spermatogenesis and spermiogenesis

A

Spermatogenesis = the whole process (stimulated by testosterone)
spermiogenesis = subset of spermatogenesis (stimulates by FSH)

38
Q

How does a spermatogonium develop to a matuer spermatozoa?

A

Spermatogonium -> primary spermatocyte -> secondary spermatocyte -> spermatid -> mature spermatozoa

39
Q

What hormone is more important in the early stages of meiosis and which one is more important in the later stages?

A

FSH- early stages
Androgens - later

40
Q

Where do sperm complete their spermiogenesis

A

In the caput epididymis

41
Q

Where are the sperm stored?

A

In the cauda epididymis

42
Q

What fuels the spermatozoa for movement?

A

Epididymal secretions (e.g. glyceryl phosphorylcholine and inositol)

43
Q

What makes up the accessory sexual organs/glands in the male reproductive system?

A

Seminal vesicles and prostate gland

44
Q

What is the function of the seminal vesicles?

A

fructose production (anaerobic fructolysis)

45
Q

What is the function of the prostate gland?

A
  • release citrate (anticoagulant- chelates Ca2+ and prevents coagulation of the seminal fluid)
  • Releases acid phosphatase (which cleaves choline from glyceryl phosphorylcholine)
46
Q

What hormones does the placenta secrete?

A
  1. Human chorionic gonadotropin (hCG)
  2. Oestrogens (estrone, oestradiol and estriol)
  3. Progesterone
47
Q

What are the functions of hCG?

A
  • maintains the CL during pregnancy (because it produces other hormones)
  • Stimulates testosterone synthesis in the developing testes of the male (XY) embryo
48
Q

What is the function of oestrogens on the placenta?

A
  • Stimulate the endometrial growth
  • Stimulates proliferation of mammary tissue (for lactation)
49
Q

What is the effect of progesterone on the placenta?

A
  • Promotes the formation of cervical mucus plug - which protects the embryo
  • Supress the uterine contractions - to prevent early childbirth
  • Stimulates the differentiation of lobuloalveolar system of the mammary glands (for lactation)
  • Prevents subsequent follicular development and ovulation
    • Negative feedback on LH and FSH; it suppresses the ovulatory LH surge
50
Q

What is the effect of human chorionic somatomammotropin?

A
  • Similar to growth hormone and Prolactin
  • It increases the availability of glucose and NEFA (foetus)
51
Q

What is the function of relaxin?

A
  • To soften the cervix and loosen the connective tissue
  • Parturition - cervical dilation
  • Pelvic bones
52
Q

What is the function of placental PTHRP?

A

To increase the maternal calcium

53
Q

What hormones are seen in the first trimester of pregnancy?

A

The placenta secretes high levels of hCG

  • This activates LH -Chorionic gonadotropin receptors in the CL to stimulate progesterone and oestradiol synthesis/secretion
54
Q

What hormones does the placenta secrete in the 2nd and 3rd trimester?

A
  • Secretes progesterone and oestradiol
  • Produces oestriol from the foetal adrenal androgen substrate
55
Q

How is the actual lactation suppressed during pregnancy and how is it stimulated?

A

Oestrogen and progesterone suppress
Prolactin and oxytocin stimulate

56
Q

What are the theories for the initiation of birth (parturition)?

A
  1. high levels of oestrogen
  2. High levels of oxytocin
  3. CRH (corticotropin releasing hormone) - placenta
  4. Inflammation
57
Q

How are high levels of oestrogen supposed to initiate parturition?

A
  • Oestrogen upregulates connexins - increased gap junctions
  • Upregulate myometrial receptors for oxytocin
  • Stimulate the local prostaglandin synthesis
58
Q

How are high levels of oxytocin supposed to initiate parturition?

A
  • Myometrial responsiveness exceeds critical thresholds
  • Increased Ca2+ which activates myosin light chain kinase (MLCK) which triggers contraction of the uterine muscles
59
Q

How are high levels of CRH supposed to initiate parturition?

A
  • May increase oestrogen synthesis (from foetal androgens)
  • Increased cortisol (increases local prostaglandin synthesis and promotes lung maturation)
60
Q

How is inflammation supposed to initiate parturition?

A

Increased nuclear factor k-B upregulates the inflammatory cytokines and increases local prostaglandin synthesis

61
Q

What is the Fergusson reflex?

A

The positive spiral feedback for uterine contractions

62
Q

Describe the steps that lead to uterine contractions

A
  1. High levels of oestrogen increase uterine responsiveness to OT (1st high oestrogen promotes synthesis of connexins within uterine smooth-muscle cells.)
  2. These are inserted into myometrial plasma membranes to form gap junctions so smooth muscle cells contract as co-ordinated unit.
  3. 2nd high of oestrogen increases concentration of myometrial receptors for OT)
  4. Foetal pressure stimulates receptors in cervix > neural signal to spinal cord to hypothalamus > triggers OT release from PP
  • Positive-feedback cycle continues throughout labour until delivery when pressure on cervix (stimulus for oxytocin release) is removed
63
Q

What is another myometrial stimulant apart from OT?

A

PGF2α is a powerful myometrial stimulant > further enhances uterine contractions

64
Q

When do oestrogen and progesterone levels fall?

A

During labour

65
Q

What are the two main groups of reproductive hormones?

A

steroid hormones and gonadotropins

66
Q

Which chain is common between LH and FSH?

A

The alpha chain

67
Q

What is testosterone converted to in target tissue cells in males?

A

Oestradiol

68
Q

What is the effect of oestradiol in males?

A

Ligand for oestrogen receptors (ER) in testes, prostate, bone & brain
Affects spermatogenesis, bone homeostasis / epiphyseal fusion

69
Q

What are the non-reproductive actions of oestradiol and progesterone in females?

A

Increased adipogenesis
Increased bone mineral denisty

70
Q

What phase are unmature oocytes stuck in?

A

In prophase 1

71
Q

What is the effect of anabolic steroids on males?

A

More testosterone inside the blood (not the testes)-> negative feedback loop, suppresses the anterior pituitary gland -> less FSH and LH + GnRH -> decreased activity of Sertoli cells and suppressed spermatogenesis

72
Q

Where is oxytocin produced and released from?

A

produced - hypothalamus
released - pituitary gland

73
Q

What are the secondary effects of oxytocin in females?

A

Neuromodulator in communication between neurons (e.g. recognition and trsut)

Biomedical physiology (3 decks)

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