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Endocrine > Reproduction: Physiology and Biochemistry > Flashcards

Reproduction: Physiology and Biochemistry Flashcards

1
Q

Key Reproductive hormones (6)

A 
GnRH (gonadotrophin releasing hormone) 
LH (luteinizing hormone)
FSH (follicle stimulating hormone) 
Oestrogen 
Progesterone
Testosterone
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2
Q

Gonadotropic Hormones (2) released by pituitary gland

A

Follicle Stimulating Hormone

Luteinizing Hormone

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3
Q

Follicle Stimulating Hormone role

A

male: causes testes to produce sperm (spermatogenesis)

Female: causes growth of ovarian follicles (oogenesis) and causes ovary to secrete oestrogen

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4
Q

Luteinizing Hormone role

A

male: causes testes to release testosterone

Female: causes ovulation and it causes progesterone production by the corpus luteum (progesterone produced from cholesterol)

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5
Q

Gonadotrophin Releasing Hormone (GnRH) role

A

Responsible for the release of LH and FSH from the anterior pituitary

Its a neuropeptide hormone synthesised and released from GnRH neurons within hypothalamus

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6
Q

GnRH release

A

Released in a pulsatile manner

Males: secreted in pulses at constant frequency

Females: frequency of pulses varies during menstrual cycle

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7
Q

High frequency GnRH pulses

A

Stimulates LH release

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8
Q

Low frequency GnRh pulses

A

FSH release

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9
Q

Effect of oestrogen on GnRH pulsatility

A

Oestrogen concentration above a certain threshold will increase pulsatility
- drive release of LH

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10
Q

Effect of progesterone on GnRH pulsatility

A

Progesterone increase reduces pulsatility

- drive release of FSH

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11
Q

Pubertal maturation on GnRH pulsatility

A

Onset of pubertal maturation results in a steady acceleration in GnRH pulsatility

Activation of GnRH pulse frequency in central mechanism associated with delayed puberty

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12
Q

GnRH regulation

A

Regulated by kisspeptin

GnRh neurons do not contain a receptor for oestrogen or progesterone

Oestrogen and progesterone influence kisspeptin neurons that then subsequently release GnRH neurons.

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13
Q

menstrual cycle phases

A

Follicular Phase

  • proliferative phase
  • variable
  • typically 14 days +/- 7 days
  • Characterised by follicular growth

Ovulation

Luteal Phase

  • secretory phase
  • Constant at 14 days
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14
Q

Menstrual Cycle - stages

A

FSH stimulates growth of ovarian follicles (associated with increased oestrogen)

Rising oestrogen levels exert a negative feedback regulation to lower FSH levels.

Once oestrogen reaches a certain concentration it exerts a positive feedback regulation

  • Increase FSH levels
  • Increase LH (LH surge)

LH surge eventually leads to ovulation and regulates formation of corpus luteum and progesterone production and secretion

Increasing progesterone decrease LH secretion by influencing GnRH pulsatility

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15
Q

Follicle

A

Consists of an oocyte surrounded by follicular cells (granuloma and theca)

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16
Q

Follicle Growth

A

Increase in number of follicular cells
Accumulation of follicular fluid

–> Increase in diameter and overall size of follicle
(Oocyte remains dormant)

17
Q

Oestrogen impact on endometrium

A

Endometrium thickens

18
Q

Progesterone impact on endometrium

A

Endometrium becomes a secretory tissue

19
Q

Follicluogenesis

A

Early stages of growth occur independently of gonadotrophin

Once follicle reaches certain size (2-5mm in diameter) it becomes gonadotrophin dependent

Number of follicles will continue to grow under influence of FSh but only 1 will be selected for ovulation

Totally dependent on FSH levels (if removed follicles are lost)

20
Q

Theca cell

A

LH hormones cause theca cells to convert cholesterol to androgens

21
Q

Granuloma cell

A

FSH hormones cause granuloma cells to convert androgen to oestrogen (requires aromatase)

22
Q

LH surge

A

LH surge precedes ovulation by 34-36 hours

23
Q

LH surge requirements

A

Threshold of oestrogen (200pg/ml) us required for an increase in GnRH pulsatility and therefore LH surge

24
Q

LH surge and progesterone

A

Increase LH levels leads to increase in progesterone levels

Crucial for ovulation as progesterone stimulates expression of enzymes that help breakdown follicular wall to release oocyte.

25
Q

Formation of corpus luteum

A

Occurs under influence of LH

Granulosa and theca cells transform to luteal cells

Increase in progesterone production

  • LH stimulates angiogenesis
  • LH stimulates enzymes involves in conversion of cholesterol –> progesterone
26
Q

Oestrogen functions (4)

A

Increase thickness of vaginal walls

Regulate LH surge

Reduce vaginal pH through increase in lactic acid production

Decrease viscosity of cervical mucus to facilitate sperm production

27
Q

Progesterone functions (4)

A

Pro-gestration: maintain pregnancy

Maintains thickness of endometrium

Responsible for. infertile thick mucus (prevent sperm transport and help prevent infection)

Relaxes myometrium ( smooth muscle), Finctional progesterone withdrawal through to regulate parturition (birth)

28
Q

Sperm Production

A

Spermatogenesis

Occurs within the testes

29
Q

Spermatogenesis: hormones

A

LH
FSH
Testosterone

30
Q

Spermatogenesis process duration

A

Takes 70 days

31
Q

Testicular Organisation

A

Extratubular Compartment

  • interstitial
  • intravascular

Intratubular compartment

  • basal
  • adluminal
  • Sertoli cells
  • Germ Cells
32
Q

Hormone Action: Male reproductive tract

A

Endocrine Factors
- LH and FSH

Paracrine Factors

  • Testosterone
  • Inhibin
33
Q

Testosterone release

A

Testosterone is also released into the circulation

- Taken up by Sertoli cells (90%)

34
Q

Testosterone during spermatogenesis

A

Maintains integrity of blood-testes barrier

Release of mature spermatozoa from Sertoli cells by influencing peritubular myeloid cells

35
Q

LH and testosterone

A

LH stimulates testosterone secretion

Testosterone decreases release of GnRH and LH

36
Q

FSH and testosterone

A

FSH stimulates spermatogenesis together with testosterone

Inhibit decreases secretion of FSH

37
Q

Sertoli cells

A

Sertoli cell in seminiferous tubule secretes androgen binding globulin (ABG) and inhibit

38
Q

Dihydrotestosterone

A

Enlargement of male sex organs
Secondary sexual characteristics
Anabolism

Endocrine (25 decks)

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