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Reg Phys and Pharm > Reproductive Endocrinology I > Flashcards

Reproductive Endocrinology I Flashcards

1
Q

Development of male reproductive tract

A
  • progression of Wolffian ducts
  • degeneration of Mullerian ducts
  • testosterone stimulated by hCG, secreted from the placenta
  • mullarian inhibiting factor (MIF) needs to be present
  • without stimulus of male testicular homeones, Wolffian ducts regress, Mullerian ducts devevlop and foetus develops female characteristics
  • begins in early development and seizes until puberty
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2
Q

Development of female reproductive tract

A
  • wolffian ducts degenerate
  • progression of mullerian ducts
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3
Q

SRY gene

A
  • encodes for production of testes determining factor
  • direct differentiation of gonads to testes
  • not present in females
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4
Q

Gonadal sex is determined by

A

presence or absence of SRY gene

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5
Q

Role of testosterone

A
  • converted to dihydrotestosterone to promote development of external male genitalia
  • transports wolffian ducts into male reproductive tract (e.g. epididymis, ductus deferens, ejaculatory duct, seminal vesicles)
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6
Q

Phenotypic sex is determined by

A

presence or absene of masculinising hormones

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7
Q

When does genitalia differentiation begin

A

10 weeks

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8
Q

Seminiferous tubules

A
  • where sperm is formed
  • stored within epididymis and ductus deferens
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9
Q

Role of prostate and bulbourethral glands

A

provide ejaculate fluid

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10
Q

Function of testes

A
  • produce sperm and secrete testosterone
  • Leydig cells lie in the connective tissue of the seminiferous tubules
  • in utero, develop in abdominal cavity of foetus
  • drop into scrotal sac before birth
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11
Q

Testosterone effects on events before birth

A
  • masculinises the reproductive tract and external genitalia
  • promotes decent of the testes into the scrotum
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12
Q

Testosterone effects on sex-specific tissues

A
  • Leydig cells secrete testosterone again at puberty
  • promotes growth and maturation of repro system at puberty
  • causes tests to enlarge and become capable of spermatogenesis
  • maintains repro tract throughout adulthood
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13
Q

Other reproductive effects of testosterone

A
  • develops libido at puberty and can maintain it for life
  • controls gonadotrophin hormone secretion (negative feedback - controls spermatogenesis)
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14
Q

Testosterone effects on secondary sexual characteristics

A
  • inducers characteristic male patterns of hair growth
  • enlarges larynx and thickens vocal chords
  • thickens skin
  • causes male body shape
  • eunuch -> male castrated before puberty
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15
Q

Nonreproductive effects of testosterone

A
  • anabolic - promotes protein and bone growth / development
  • induces oil secretion by sebaceous glands
  • aggressive behavior
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16
Q

Why is it important that testes descend

A
  • lower temp outside body to facilitate spermatogenesis
  • nervous reflexes trigger muscle movement in scrotal sac to lower or raise testes according to external temp
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17
Q

What is cryptorchidism

A

individual has reached adulthood and testes have not descended

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18
Q

Effects of androgen secretion from the adre- nal cortex in males

A
  • testicular enlargement and public hair growth
  • trigger for not certain - programmed within adrenal cortex independent of ACTH
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19
Q

What triggers testes maturation and androgen/sperm production

A

FSH and LH due to GnRH release from hypothalamus

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20
Q

What sexual characteristics of males appear during puberty

A
  • growth of larynx
  • deepening of voice
  • increased bone mass
  • increased mass and strength of skeletal muscle
  • thickened skin
  • increased and thickened hair on trunk, arms, legs, face
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21
Q

What induces somatic growth

A

gonadal sex steroids, growth hormone, and insulin-like growth factor

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22
Q

What is spermatogenesis

A
  • conversion of germ cells into motile sperm
  • supported by sertoli cells
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23
Q

Development of male gamete

A
  • differentiation takes 64 days
  • multiply by mitosis and generates more spermatogonia
  • give rise to primary spermatocytes
  • Sertoli cells support sperm development and prevent infections
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24
Q

Mitotic proliferation stage of spermatogenesis

A

spermatogonia (46 chromosomes) divide - one daughter cell remains undifferentiated, the other divides twice more to form primary spermatocytes

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25
Q

Meiotic division stage of spermatogenesis

A
  • 1st meiotic division - each primary spermatocyte divides into 2 haploid secondary spermatocytes
  • 2nd meiotic division - secondary spermatocytes divide to form 2 single-stranded spermatids
  • testosterone is required for mitosis and meiosis stages
26
Q

Spermiogenesis (3rd stage of spermatogenesis)

A
  • packaging - spermatids converted to spermatozoa, removal of unnecessary cellular components and rebuilding into specialised, motile spermatozoa
  • FSH required
27
Q

Structure of sperm

A
  • head = acrosome (contains enzymes for penetration of ovum)
  • nucleus contains genetic material
  • centriole
  • tail provides motility; packed with microtubules and energised by mitochondria
28
Q

Sertoli cells role in blood-testes barrier

A
  • tight junctions protect sperm from antibody attack
  • provides a regulated fluid composition which allows for later stages development of sperm
29
Q

Sertoli cells role in phagocytosis

A

remove surplus cytoplasm from packaging and destory defective cells

30
Q

Seminiferous tubule fluid secreted from Sertoli cells

A

used to carry cells to epididymis along pressure gradient

31
Q

Androgen binding protein secreted from Sertoli cells

A
  • binds to testosterone so that concentration remains high in lumen - essential for sperm production
32
Q

Inhibin

A
  • secreted from Sertoli cells
  • hormone that regulates FSH secretion via negative feedback and controls spermatogenesis
33
Q

Hormones that control the testes

A
  • 2 gonadotropic hormones secreted by anterior pituitary
  • Lutenizing hormone (LH); acts on Leydig cells to promote testosterone secretion
  • Follicle-stimulating hormone (FSH); acts on Sertoli cells to enhance spermatogenesis - essential for spermatid remodeling
  • GnRH stimulates release of LH and FSH
34
Q

Control of testicular function

A
  • GnRH secreted from anterior pituitary to stimulate gonadotrope secretion of LH and FSH
  • LH acts on Leydig cells to stimulate secretion of testosterone
  • testosterone produces masculinising effects, selectively inhibits LH secretion, and acts on hypothalamus to secrete GnRH
  • FSH acts on Sertoli cells to stimulate spermatogenesis and secretion of inhibin
  • inhibin selectively inhibits FSH secretion from gonadotrope
35
Q

Importance of female reproduction system

A
  • production of ova
  • reception of sperm
  • transport of sperm and ova to site of fertilisation
  • gestation
  • parturition
  • nourishment of the infant by lactation
36
Q

Oogenesis

A
  • identical mitotic and meiotic divisions to male
  • takes many years to complete
  • begins in utero
  • suspended for many years
  • begins again at puberty
  • completed at fertilisation
  • oogenesis ceases at menopause
37
Q

Stages of oogenesis

A
  • mitotic proliferation occurs prior to birth
  • primary oocytes are formed at birth and are suspended at the end of the first meiotic division, which is completed prior to ovulation
  • ovulation commences the secondary oocyte, which has not completed the second meiotic division
  • mature ovum contains haploid chromosomes and half the genetic content
  • second meiotic division completed only at fertilisation
38
Q

What is adrenarche

A
  • 6-8 years of age
  • adrenal gland secretes androgens
  • growth spurt
  • pubic hair growth starts as consequence of androgen secretion
39
Q

What is thelarce

A

the start of breast development

40
Q

What is menarche

A
  • onset of menstrual cycle at 10-16 years old
  • increase FSH and LH from pituitary
  • ovaries produce steroids
  • establishment of oestrogen inducing ovulation by positive feedback
  • onset related to critical level of body fat which triggers GnRH release
41
Q

In females, secondary sexual characteristics are induced by

A
  • ovarian oestrogens
  • causes pubic hair, growth and maturation of repro tract and external genitalia, fat deposition - breasts, butt, thighs, closure of epiphyseal plates
42
Q

Somatic growth in females

A
  • begins two years earlier in girls
  • induced by gonadal sex steroids, growth hormone, and insulin-like growth factor
43
Q

Menopause

A
  • 5th decade of life as ovaries atrophy
  • decrease in fertility, shortening of menstrual cycle
  • FSH levels rise, causing ovarian oestrogen, progesterone and inhibin to fall
  • cessation of ovulation and menstruation
  • hot flushes
  • vaginal and uterine atrophy, decreased breast size
  • longer-term susceptibility to osteoporosis and cardiovascular disease
44
Q

The 1st half of the ovarian cycle

A
  • follicular phase
  • maturation of egg, ready for ovulation at midcycle - ovulation signals end of follicular phase
45
Q

The 2nd half of the ovarian cycle

A
  • luteal phase
  • development of corpus luteum
  • induces preparation of reproductive tract for pregnancy
46
Q

The primary follicle of the follicular phase

A
  • primary oocyte is surrounded by single layer of granulosa cells before birth (primary follicle)
  • each is capable of producing single ovum
  • until puberty, all primary follicles degenerate to scar tissue
  • after puberty, secondary follicles develop cyclically
47
Q

The secondary follicle of the follicular phase

A
  • oocyte grows and follicle expands and becomes differentiated under hormonal influence
  • after puberty, about 400 will be ovulated, the rest will undergo atresia
  • follicular phase ends with ovulation
48
Q

The luteal phase

A
  • follicluar cells left behind after ovulation undergo lutenisation and transform the corpus luteum
  • CL secretes progesterone and oestrogen
  • oestrogen secreted is essential for preparation of uterine lining for implantation
49
Q

Corpus luteum

A
  • after ovulation, CL grows for 8-9 days
  • if no fertilisation has occurred, it will survive for no longer than 14 days after ovulation
  • corpus albicans is formed (white body, fibrous tissue)
  • degeneration of corpus luteum signals start a new follicular phase
  • if fertilisation, CL persists and produces increasing quantities of progesterone and oestrogen until after pregnancy
50
Q

Hormonal control of uterine and ovarian cycles

A
  • oestrogen inhibits LH and FSH release
  • oestrogen stimulates LH and FSH release at approx day 14 of cycle
51
Q

What marks the beginning of both uterine and ovarian cycles

A

mensturation

52
Q

The anterior pituitary secretes

A

FSH and LH a few days before menstruation

53
Q

Follicle maturation

A

increases production of oestrogen

54
Q

The one remaining follicle

A

secretes increasing amounts of oestrogen and stimulates uterus to grow

55
Q

The first 12 days of the ovarian cycle

A

oestrogen exerts negative feedback on gonadotropin release

56
Q

Days 12-14 of ovarian cycle

A

oestrogen exerts positive feedback on the pituitary

57
Q

What triggers ovulation

A
  • LH surge
  • stimulates follicle cells to develop into the corpus luteum and secretes progesterone and oestrogen
58
Q

Role of oestrogen and progesterone

A
  • maintenance of uterine lineing
  • send negative feedback to anterior pituitary to inhibit gonadotropin release
59
Q

What happens to corpus luteum if fertilisation does not occur

A

degenerates on day 26

60
Q

What happens to uterine lining in absence of progesterone

A

sloughs off and menstruation occurs

61
Q

Negative feedback on anterior pituitary

A

decrease in oestrogen and progesterone relieves the negative feedback on anterior pituitary, causing an increase in GnRH, FSH, and LH

62
Q

Feedback control of FSH and LH secretion during follicular phase

A
  • Hypothalamus sends signal to stimulate GnRH in anterior pituitary
  • GnRH acts on gonadotrope to secrete LH and FSH
  • LH and FSH act on developing follicle to increase and moderate levels of oestrogen
  • Rising levels of oestrogen act on hypothalamus and gonadotrope to selectively inhibit FSH secretion
  • inhibin is secreted from the developing follicle and acts on gonadotrope to selectively inhibit FSH

Reg Phys and Pharm (16 decks)

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