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Semester 3: Reproductive > Session 3 > Flashcards

Session 3 Flashcards

1
Q

What is the general overview of puberty?

A
  • Accelerated somatic
  • Maturation of primary sexual characteristics
  • Appearance of secondary sexual characteristics
  • Menstruation and spermatogenesis
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2
Q

What are environmental inferences on puberty?

A
  • Triggered by changes in day length
  • Involvement of pineal gland
  • Secretion of melatonin
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3
Q

What is the critical weight for girls to begin puberty?

A

47kg

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4
Q

What is the effect of significant weight loss in women?

A

The reproductive cycle ceases

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5
Q

What are the sequence of changes girls follow in puberty?

A

9-13

  • Breast bud appears
  • Pubic hair growth
  • Growth spurt
  • Onset of menstrual
  • Pubic hair becomes adult like
  • Breast become adult like
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6
Q

Why does pubic hair grow?

A

It is a response to oestrogen and testosterone levels

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7
Q

What are the sequence of changes boys follow in puberty?

A

10-14 years of age

  • Genital develpment
  • Pubic hair growth
  • Spermatogenesis
  • Growth spurt
  • Genitalia becomes adult like
  • Pubic hair becomes adult like
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8
Q

What does genital development in boys depend on?

A

Testosterone

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9
Q

What is accelerated somatic growth?

A

Period of growth that pepends on growth hormone and sex steroids in both sexes

  • It is earlier and shorter in girls
  • It is longer and faster in men so larger growth spurt
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10
Q

How does accelerated osmotic growth stop?

A

Epiphyseal fusion in response to oestrogen

-Ended earlier in girls

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11
Q

What triggers the onset of puberty?

A

Switching on the HPG axis. Done by:

  • Increased stimulation of hypothalamus-pituitary-gonadal axis
  • Gradual activation of GnRH
  • Increases frequency and amplitude of LH pulses
  • Gonadotropins stimulate secretion of sexual steroids
  • Extragonadal hormonal changes
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12
Q

What is the GnRH-1 gene?

A
  • Repsosnible for mammalian GnRh

- Exclusive expressed in a discrete population of neutrons in the hypothalamus

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13
Q

What is the effect of treating prepubertal primates with pulsatile GnRH alone?

A

Induces puberty

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14
Q

What happens if GnRH secretion is blocked?

A

Lack of gonadotrophin synthesis and secretion and reproductive development

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15
Q

What hormone plays a critical role in reproductive maturation?

A

GnRH

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16
Q

What are the characteristics of hypothermic releasing hormones?

A
  • Secretion in pulse tied to the internal biological clock
  • Act on specific membrane receptors
  • Transduce signals via secondary messengers
  • Stimulate release of stored pituitary hormones
  • Stimulate synthesis of pituitary hormones
  • Stimulates hyperplasia and hypertrophy of target cells
  • Regulates it own receptor
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17
Q

What does the GnRH stimulate in the anterior pituitary gonadotrophs?

A

Stimulates production of

  • Luteinizing hormone
  • Follicle Stimulating hormone

from

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18
Q

What is leptin?

A

Adipocyte derived protein hormone that signal information about energy stores to the CNS and plays an important role in regulating neuroendocrine function.

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19
Q

How can leptin affect the reproductive cycle?

A
  • If deficient, associated with reproductive dysfunction

- Leptin can accelerate the onset of reproductive function

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20
Q

How is leptin released?

A

Pulsatile release pattern significantly associated with the variations in LH

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21
Q

What the effects of growth hormone secretion fro the pituitary?

A
  • Increases TSH
  • Increased metabolic rate
  • Promote tissue growth
  • Increases androgens so retention of minerals in body to support bone and muscle growth

Growth spurt

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22
Q

How is the anterior pituitary connected to the hypothalamus?

A

Superior hypophyseal artery

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23
Q

What are the 6 hormones produced in the anterior pituitary?

A
  • Growth hormone
  • Thyroid stimulation hormone
  • Adrenocorticotropic hormone
  • Follicle stimulating hormone
  • Lutenizing hormone
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24
Q

How does the hypothalamus exert control on release of FSH and LH?

A

GnRH

-Released every 1.3 hours

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25
Q

Describe the sleep dependant nocturnal rise in LH

A
  • Increase in sleep related LH
  • Stimulates a nocturnal rise in Testosterone
  • Could account of early pubertal changes seen in males
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26
Q

Describe the hormonal control of puberty in an overview.

A

Brain > Hypothalamus > Pituitary > Increase in LH and FSH levels > Gonadal development > Androgens and oestrogen

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27
Q

Describe the HPG axis in a male

A
  • LH stimulates Leydig cells in testis
  • Production of steroid hormone testosterone (mostly testes)
  • Testosterone levels remain constant in the medium long term
  • Circadian rhythm and environmental stimuli have an effect
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28
Q

Where is the location of spermatogenesis?

A

Seminiferous tubules

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29
Q

Which cells can be found in the interstitial tissue?

A

Leydig cells which produce testosterone. They function independently of the seminiferous tubules

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30
Q

What do the seminefrous tubules require?

A

Testosterone (functioning leydig cells)

31
Q

What is the structure of seminiferous tubules?

A

Lined by complex epithelium made up of 2 cells types

  • Support cells which are the sertoli cells
  • Spermatogenic cells
32
Q

What is the function and control of the Sertoli cells?

A
  • Provide nutrition and hormonal support to the germ cells allowing sperm formation
  • Sensitive to FSH
  • Inhibin negatively feeds back on the anterior pituitary to decrease FSH
33
Q

Which cells reduce a tight unction in the seminiferous tubules and why?

A

Sertoli cells

-Prevent blood and sperm mixing to prevent an immune reaction

34
Q

What is the primary target cells of FSH and LH in the female and the effect?

A
  • Ovarian granulose cells
  • Theca interna

Stimulate sex hormone synthesis and control gamete production

35
Q

What is the effect of moderate and high levels of oestrogen on GnRH secretion?

A
  • Moderate amounts of oestrogen reduce GnRH secretion by negative feedback
  • High amounts of oestrogen alone promotes GnRH secretion by positive feedback causing an LH surge
36
Q

What is the effect of progesterone on oestrogen?

A
  • Increases the inhibitory effects of moderate oestrogen

- Prevents positive feedback of high oestrogen so no LH surge

37
Q

Where is inhibin realised from?

A

Granulosa cells of corpus luteum

38
Q

What is the function of inhibin?

A
  • Inhibits the secretion of FSH

- Has a small inhibitory effect on LH

39
Q

What do germ cells do after colonising the gonad?

A
  • Proliferate by mitosis
  • Reshuffle genetically and reduce haploid by meiosis
  • Cytodifferentiate into mature gametes
40
Q

What are the features of oogenesis?

A
  • Usually 1 ovum per 28 day menstrual cycle
  • One ovum with unequal division of cytoplasm and 3 polar bodies formed
  • Starts in the foetus
  • Ends at menopause
  • Non motile gametes
  • Last stage of meiosis 2 occurs in the oviduct
41
Q

What are the features of spermatogenesis?

A
  • Huge number of sperm reduced (200 million)
  • 4 spermatids formed with no polar body formation and equal division of cytoplasm
  • Starts at puberty
  • Continuous production from puberty throughout adult life
  • Motile gametes
  • All stages are completed in the testes
42
Q

What are the main functions of meiosis?

A
  • Reduction of chromosome number to 23
  • Ensures gametes is genetically unique
  • Used only in production of sperm and eggs
  • 2 successive cell divisions
  • Production of 4 daughter cells
43
Q

How many mature oocytes are formed in the female?

A

1

The rest are polar bodies

44
Q

What does genetic variation arise from?

A
  • Crossing over (exchange of DNA between 2 homologous chromosomes)
  • Independent assortment (random orientation of each bivalent along the metaphase plate with respect to other bivalents)
  • Random segregation (random distribution o alleles among four gametes)
45
Q

Where do the seminiferous tubules concentrate the sperm?

A

Ductile differentes

46
Q

Describe spermatogenesis

A
  • Spermatogonia fide by mitosis to give Ad spermatogonium(resting) and Ap spermatogonium(active)
  • Ap spermatogonium maintain stock and from puberty onwards produce type B spermatogonia which give rise to primary spermatocyte
  • Primary spermatocyte divide by meiosis giving rise to secondary spermatocytes then spermatids
  • Each primary spermatocyte divides to form 4 haploid spermatids which differentiate into spermatozoa
47
Q

What is the definition of the spermatogenic cycle?

A

The time it take for the appearance of the same stage within a segment of the tubule

48
Q

What is the definition of the spermatogenic wave?

A

Distance between the same stag is called the spermatogenic wave

49
Q

Describe the process that results in the differentiation of the spermatids to spermatozoa.

A
  • Spermatids are related into the lumen of seminiferous tubules
  • They remodel as the pass down seminiferous tubules. through the rete testis and ductile efferentes and into epididymis to finally form spermatozoa
50
Q

Where do the spermatids become motile?

A

When they reach the epididymis

51
Q

Where are secretions for semen released from?

A
  • Seminal vesicle secretions (about 70%)
  • Secretion of prostate (about 25%)
  • Sperm (about 2-5%)
  • Bulbourethral gland (less than 1%)
52
Q

What is secreted form seminal vesicle?

A
  • Amino acids
  • Citrate (better than glucose as less completion from bacteria)
  • Fructose
  • Prostagladins
53
Q

What is released from the prostate?

A

Proteolytic enzymes

54
Q

What is released for the bulbourethral gland?

A

Mucoproteins which help lubricates and neutralised acidic urine in distal urethra

55
Q

What is sperm capacitation?

A

Conditions in the female genital tract stimulate:

  • Removal of glycoproteins and cholesterol from sperm membrane
  • Activation of sperm signalling pathways
  • Allow sperm to bind to the bona pellucida of oocyte and initiate acrosome reaction
56
Q

When does maturate of oocytes begin?

A

Before birth

57
Q

Describe the maturation of germ cells before birth

A
  • Germ cells colonise the gonadal codex and differentiate oogonia
  • Oogonia then proliferate rapidly by mitosis
  • By end of the 3rd month oogonia are arranged inc clusters surrounded by flat epithelial cells
  • Majority then continue to divide by mitosis but some enter meiosis and these arrest in prophase of meiosis 1 and are called primary oocytes
  • Max number f germ cells reached mid gestation
  • Cell death then begins and oogonia and primary oocytes begin to degenerate. by 7th moth most oogonia degenerated
  • All surviving primary ones have now entered meiosis 1 and are individually surrounded by layer of flat epithelial cells called follicular cells.
  • Follicular cells are now called primordial follicle cells
58
Q

Describe maturation of oocytes at puberty

A

15-20 oocytes start to mature each month passing through 3 stages

  1. Preantral
  2. Antral
  3. Preovulatory
59
Q

What is the preantral stage?

A

As Primordial follicles begin to grow

  • Surrounding follicular cells change from flat to cuboidal and proliferate to produce a stratified epithelium of granulosa cells
  • Granulosa cells secrete layer of glycoprotein on oocyte forming the bona pellucida
60
Q

What is the antral stage?

A

As development continues

  • Fluid filled spaces appear between the granulosa cells and these come together to form the antrum
  • Several follicles begin to develop with each ovarian cycle and usually one will reach maturity
61
Q

Describe the features of the preovulatory phase

A
  • Surge in LH induces this stage
  • Meiosis 1 is complete resulting in 2 haploid daughter cells of unequal size due to one cells revving most of the cytoplasm and the other (1st polar body) receiving none.
  • Each daughter cells now has 23 chromosomes and 46 chromatids
  • Cell enters meiosis 2 but arrest in metaphase 2
  • Meiosis 2 is only completed if the oocyte is fertilised otherwise the cell degenerates
62
Q

What stimulates growth of the follicle during ovulation

A

FSH and LH

63
Q

What is the mature follicle called when it is 2.5cm in diameter

A

Graafin follicle

64
Q

What stimulate collagenase activity

A

LH surge

65
Q

What is the function of prostaglandins in relation to LH.

A

Increase response to LH and cause local muscular contractions in ovarian wall

66
Q

Give an overview of ovulation

A
  • Rapid growth of follicle several hours before ovulation occurs
  • Graffin follicle formation
  • Local muscular contractions in ovarian wall and increase in collagenase activity
  • Oocyte is extruded and breaks free from ovary
67
Q

How is the corpus leteum formed.

A

-Remaining granulosa and theca internal cells become vascularised and develop yellowish pigment and change into lutein cells which form the corpus luteum

68
Q

What does the corpus luteum secrete?

A

Oestrogens and progesterone

69
Q

What is the function of the corpus luteum?

A

-Stimulates the uterine mucos to enter secondary stage in preparation for the embryo implantation

70
Q

What happens to the corpus luteum if fertilisation doesn’t occur?

A

Dies

71
Q

How is the oocyte transported?

A
  • Fimbriae sweep over surface of ovary shortly before ovulation
  • Uterine tube begins to contract rhythmically
  • Oocyte carried into tube by sweeping movement s of fimbriae and by motion of cilia on epithelial lining
  • Oocyte is then propelled by peristaltic muscular contractions of the tube and by cilia in the mucosa
  • If fertilised, oocyte reaches uterine lumen in 3 to 4 days
72
Q

What forms the corpus albicans?

A

-If fertilisation does not occur corpus luteum degenerates and forms mass of fibrotic scar tissue which is the corpus albicans.

73
Q

Why does menstrual bleeding occur?

A

Progesterone production decreases

74
Q

What happens in the event of fertilization?

A
  • HCG secreted boy the embryo prevent corpus luteum from degenerating
  • Corpus luteum continues to grom ad form the corpus luteum of pregnancy
  • Cells contine to secrete progesterone until the 4th month when the secretion from the placenta is adequate

Semester 3: Reproductive (5 decks)

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