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Kofi: Pure Clinical Sem 3 > Repro: Puberty > Flashcards

Repro: Puberty Flashcards

1
Q

What are environmental influences on puberty?

A
  • Triggered by changes in day length

- Involvement of pineal gland which secretes melatonin

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2
Q

What is the critical weight for girls to begin puberty?

A

47kg

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3
Q

What is the effect of significant weight loss in women?

A

The reproductive cycle ceases

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4
Q

What are the sequence of changes girls follow in puberty?

A

9-13

  1. Breast bud appears
  2. Pubic hair growth
  3. Growth spurt
  4. Onset of menstrual
  5. Pubic hair becomes adult like
  6. Breast become adult like
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5
Q

Why does pubic hair grow?

A

It is a response to oestrogen and testosterone levels

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6
Q

What are the sequence of changes boys follow in puberty?

A

10-14 years of age

  1. Genital develpment (Testosterone)
  2. Pubic hair growth
  3. Spermatogenesis
  4. Growth spurt
  5. Genitalia becomes adult like
  6. Pubic hair becomes adult like
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7
Q

How does accelerated somatic growth stop?

A

Epiphyseal fusion in response to oestrogen

-Ended earlier in girls

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8
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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9
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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10
Q

What happens if GnRH secretion is blocked?

A

-Lack of gonadotrophin synthesis and secretion and reproductive development. GnRH plays a critical role in reproductive maturation

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11
Q

What are the characteristics of hypothalamic 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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12
Q

What does the GnRH stimulate in the anterior pituitary gonadotrophs?

A

Stimulates production of

  • Luteinizing hormone
  • Follicle Stimulating hormone

GnRH Released Every 1.3 hours

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13
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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14
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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15
Q

How is leptin released?

A

Pulsatile release pattern significantly associated with the variations in LH

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16
Q

What are the effects of growth hormone secretion from 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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17
Q

How is the anterior pituitary connected to the hypothalamus?

A

Superior hypophyseal artery

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18
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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19
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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20
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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21
Q

What do the seminiferous tubules require?

A

Testosterone (functioning leydig cells)

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22
Q

What is the control of Sertoli cells?

A
  • Sensitive to FSH

- Inhibin negatively feeds back on the anterior pituitary to decrease FSH

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23
Q

Which cells produce a tight junction in the seminiferous tubules and why?

A

Sertoli cells

-Prevent blood and sperm mixing to prevent an immune reaction

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24
Q

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

A
  • Ovarian granulosa cells
  • Theca interna

Stimulate sex hormone synthesis and control gamete production

25
Q

Where is inhibin realised from?

A

Granulosa cells of Corpus luteum

26
Q

What is the function of inhibin?

A
  • Inhibits the secretion of FSH

- Has a small inhibitory effect on LH

27
Q

What do germ cells do after colonising the gonad?

A
  • Proliferate by mitosis
  • Reshuffle genetically and reduce to haploid by meiosis
  • Cytodifferentiate into mature gametes
28
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
29
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
30
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
31
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)
32
Q

Where do the seminiferous tubules concentrate the sperm?

A

Vas Deferens (ductus deferentes)

33
Q

Describe spermatogenesis

A
  • Spermatogonia divide 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
34
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

35
Q

What is the definition of the spermatogenic wave?

A

Distance between the same stage is called the spermatogenic wave

36
Q

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

A
  • Spermatids are released into the lumen of seminiferous tubules
  • They remodel as the pass down seminiferous tubules through the rete testis and vas deferens and into epididymis to finally form spermatozoa
37
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%)
38
Q

What is released from the prostate?

A
  • Proteolytic enzymes
  • Milky slightly acidic fluid
  • Citric acid, acid phosphatase
39
Q

What is secreted form seminal vesicle?

A
  • Amino acids
  • Citrate (better than glucose as less completion from bacteria)
  • Fructose
  • Prostagladins
40
Q

What is released for the bulbourethral gland?

A
  • Mucoproteins which help lubricates

- Alkaline fluid to neutralise acidic urine in distal urethra

41
Q

What is sperm capacitation?

A

Conditions in the female genital tract stimulate:

  • Removal of glycoproteins and cholesterol from sperm membrane
  • Tail movement changes from beat to whip like action
  • Activation of sperm signalling pathways
  • Allow sperm to bind to the zona pellucida of oocyte and initiate acrosome reaction
42
Q

When does maturation of oocytes begin?

A

Before birth

43
Q

Describe the maturation of germ cells before birth

A
  • Germ cells differentiate to oogonia
  • Oogonia proliferate by mitosis
  • By end of the 3rd month oogonia are arranged in clusters surrounded by flat epithelial cells
  • Some enter meiosis and arrest in prophase of meiosis 1 and become primary oocytes. Other continue with mitosis
  • Cell death begins and by 7th month 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
44
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
45
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
46
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
47
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
48
Q

What stimulates growth of the follicle during ovulation?

A

FSH and LH

49
Q

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

A

Graafin follicle

50
Q

What stimulate collagenase activity?

A

LH surge

Collagenase helps in ovulation

51
Q

What is the function of prostaglandins in relation to LH?

A

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

52
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
53
Q

How is the corpus luteum formed?

A

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

54
Q

What is the function of the corpus luteum?

A

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

55
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
56
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.

57
Q

Why does menstrual bleeding occur?

A

Progesterone production decreases

58
Q

Where is the fertilisation site?

A

Ampulla of uterine tube

Kofi: Pure Clinical Sem 3 (44 decks)

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