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Colin Endo/Repro Final > PHYS - Male Reproduction > Flashcards

PHYS - Male Reproduction Flashcards

1
Q

What is phenotypic sex?

A

Physical characteristics of external and external genitalia

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2
Q

During the first 5 weeks of development, what are the state of the gonads?

A

Gonads are BIPOTENTIAL

This means that they are neither male nor female

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3
Q

At which week of development do the testes and ovaries develop?

A

Weeks 6-7 the testes develop

Week 9 the ovaries develop

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4
Q

When are gonadotropin secretions at their lowest, and which of the two is more prominent?

A

During fetal development, gonadotropin secretion is lowest

FSH > LH

Gonadotropin secretion exhibits a gradual spike through fetal development

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5
Q

What happens to Gonadotropin secreiton during childhood?

A

Stays low and stagnant

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6
Q

What happens to Gonadotropin secretion during puberty?

A

Gradually rises throughout puberty until adult reproductive period is reached (when girls start having menses and boys can ejaculate)

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7
Q

What happens to Gonadotropin secretion during adult Reproductive Period?

A

Adult reproductive period is achieved once girls have menses and boys can ejaculate.

Girls have regular oscillating spikes of FSH and LH secretions throoughout menstrual cycle

Boys maintain a steady level of gonadotropin secretion through this period

LH > FSH

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8
Q

What happens to Gonadotropin secreitons during senescence?

A

Senescence occurs when women reach menopause

Men and women have gradual increase in gonadotropin secretions (women more sharply than men)

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9
Q

What causes puberty to be initiated?

A

Pulsatile GnRH secretion from the hypothalamus, causing pulsatile LH and FSH secretions from the Anterior Pituitary gland

LH and FSH stimulate increased circulating elvels of sex steroids (testosterone and estradiol)

Increased testosterone and estradiol levels cause secondary sexual characteristics to develop

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10
Q

What happens is a long acting GnRH analogue is administered instead of a pulsatile GnRH analogue?

A

Puberty is not initiated if a long acting GnRH analogue is secreted

MUST BE A PULSATILE administration

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11
Q

What effect does melatonin have on puberty?

A

Melatonin levels are greatest during childhood and decline through adulthood

Melatonin inhibits GnRH secretion, preventing the onset of puberty

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12
Q

What do the testes do?

A

Spermatogenesis

Testosterone secretion

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13
Q

What does the epididymis do?

A

The epididymis is the primary location for maturation and storage of sperm

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14
Q

What secretion does the vas deferens produce?

A

Vas Deferens produces a secretion of serous fluid containing citrate and fructose

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15
Q

What do the seminal vesicles do?

A

Seminal vesicles secrete a fluid rich in citrate, fructose, prostaglandins, and fibrinogen into the ductus deferens

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16
Q

What does the prostate gland do?

A

Produces a milky, aqueous solution rich in citrate, calcium, and enzymes

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17
Q

What are sertoli cells?

A

Cells found in the testicle that make up the epithelium of the seminiferous tubule

They provide nutrients to the differentiating sperm cells

They have tight junctions between them, forming a barrier between the testes and the blood stream

They secrete aqueous fluid in the seminiferous tubules to help mature sperm move through the epididymis

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18
Q

What are the Leydig Cells?

A

Interstitial cells found between the seminiferous tubules

They produce and secrete testosterone from cholesterol

Leydig cells either synthesize their own cholesterol or they absorb it from the blood in LDLs or HDLs

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19
Q

What are broad stages of sperm cell development?

A

Spermatogonia (most immature germ cell, located at the the perifery of the seminiferous tubule)

Primary Spermatocyte

Secondary Spermatocyte

Spermatozoa (mature sperm at the center of the seminiferous tubule)

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20
Q

What are the three hormones that are produced and secreted from the testes?

A

Testosterone

Dihydrotestosterone (DHT)

Androstenedione

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21
Q

What steroid hormone producing enzymes are testes lacking and why?

A

21(beta)-hydroxylase and 11(beta)-hydroxylase

These two hormones are required for glucocorticoid and mineralocorticoid synthesis

Neither of which do the testes produce

22
Q

What negative feedback mechanisms exist in the male sex hormone signaling axis?

A

Inhibin

  • Secreted from Sertoli Cells
  • Inhibits FSH secretion from the Anterior Pituitary

Testosterone

  • Secreted from the Leydig Cells
  • Inhibits GnRH secretion from the Hypothalamus
  • Inhibits LH secretion from the Anterior Pituitary
23
Q

FSH signals what in the testes?

A

FSH signals the Sertoli cells to promote spermatogenesis

24
Q

LH signals what in the testes?

A

LH signals Leydig cells to produce and secrete testosterone

25
Q

What is 5(alpha)-reductase?

A

It is an enzyme found in some tissues that are not responsive to Testosterone, instead they are responsive to dihydroxytestosterone

5 alpha reductase is an enzyme that converts Testosterone into dihydroxytestosterone (DHT)

Tissues with 5 alpha reductase:

  • Prostate
  • Liver
  • Skin
  • External male genitalia
26
Q

What important steroid synthesis enzyme do the testes have and what does it do?

A

17(beta) hydroxysteroid dehydrogenase

Converts Adrostenedione to Testosterone

27
Q

Is testosterone able to be present in free form in the seminiferous tubules?

A

No

It is a steroid hormone, seminiferous tubules contain aqueous fluid

Testosterone is found bound to ABP (androgen binding protein)

28
Q

What is the synthesis pathway of dihydroxytestosterone from cholesterol?

A

Cholesterol –> Pregnenolone ( CYP 450SCC; promoted by LH)
RATE LIMITING STEP

Pregnenolone –> 17 hydroxypregnenolone

17-hydroxypregnenolone –> DHEA

DHEA –> Androstenedione

Androstenedione –> Testosterone (17[beta] hydroxysteroid dehydrogenase)

Testosterone –> dihydroxytestosterone (5 alpha reductase)

29
Q

Where in the males in the testes is there a high concentration of estrogens, and where are they coming from?

A

Estrogens are in highest concentrations in the male seminiferous tubules

Estradiol is produced by the sertoli cells

They convert testosterone to Estradiol via Aromatase enzyme

30
Q

What is the rate limiting step of Testosterone synthesis?

A

Cholesterol –> Pregnenolone

31
Q

How does testosterone enter the blood stream?

A

Testosterone is produced in Leydig cells (tissue outside of the seminiferous tubules)

Testosterone secreted from leydig cells diffuses into the seminiferous tubules, where it then diffuses into the peritubular circulation

32
Q

What binding proteins are used in testosterone transport?

A

ABP (androgen binding protein) is used in the seminiferous tubule

SHBG (steroid hormone binding globulin) and Albumin carry testosterone in the blood stream

33
Q

What are the actions of testosterone in fetal development vs puberty?

A

Fetal development:

  • Promotes development of internal male genitalia (epididymis, ductus deferens, seminal vesicles)
  • Promotes degredation of internal female genitalia (uterus, uterine tubes)
  • Promotes development of external male genitalia (scrotum and penis)
  • Promotes the descent of the testicles

Puberty:

  • Secondary Sexual characteristics
  • Libido
34
Q

What are some actions of DHT?

A

Fetal differentiation of external male genitalia (penis, scrotum, prostate)

Male hair distribution

Male pattern baldness

Prostate growth

35
Q

What can a 5 alpha reducatse inhibitor be used for?

A

5 alpha reductase promotes the conversion of Testosterone to dihydroxytestosterone

Inhibitor prevents conversion

Used to treat male pattern baldness and benign Prostatic Hyperplasia (BPH)

36
Q

What is BHP?

A

Benign Prostatic Hyperplasia

DHT promotes prostate growth

Concentration of DHT is NOT HIGHER in prostates of BPH patients

Rather, prostate has more DHT receptors, thus more sensitive to DHT

37
Q

What are spermatogonia?

A

Least mature sperm cells.

They have 2N DNA (diploid; 46 chromosomes)

They enter meiosis to become Primary Spermatocytes

38
Q

What is a primary Spermatocyte?

A

It is a germ cell Half Way through Meisosis I

It has 4N DNA (92 chromosomes)

It will split in the second half of Meiosis I to form 2N (haploid; 46 chromosomes) Secondary Spermatocytes

39
Q

What are Secondary Spermatocytes?

A

Germ cell in the second half of Meisosis I that has 2N DNA (diploid, 46 chromosomes)

It will split into two haploid Spermatids (N DNA; 23 chromosomes)

40
Q

What is a spermatid?

A

Immature, haploid sperm cell (N DNA; 23 chromosomes)

No tail, head, etc.

Will mature into a Spermatozoa

41
Q

What is a spermatozoa?

A

Mature, haploid (23 chromosomes) sperm cell with a head and tail

42
Q

What is the order of sperm cell development?

A

Spermatogonia (2N - 46 chromosomes)

MEIOSIS I:

Primary Spermatocyte (4N - 92 Chromosomes)
Secondary Spermatocyte)

Secondary Spermatocyte (2N (diploid) - 46 Chromosomes)

MEISOSIS II:

Spermatid (N (haploid) - 23 Chromosomes)

SPERMIOGENESIS (maturation):

Spermatozoa (N (haploid) - 23 chromosomes)

43
Q

What happens you take exogenous testosterone/androgens (steroids)?

A

Increase circulating levels of testosterone inhibit LH secretion from the anterior Pituitary

Causes decrease in intratesticular testosterone

Decreased intratesticualr testosterone results in insufficient spermatogenesis

causes hypotrophy of testicles (shrinking tesitcles)

44
Q

Where are prostoglandins produced in the male genitalia and what are its functions?

A

Prostaglandins are synthesized and secreted from the Seminal Vesicles

They react with female cervical muscous to make it less viscous (easier for sperm to move through

Prostaglandins also induce reverse peristaltic movement in the uterus and uterine tubes (propelling sperm toward the ovum)

45
Q

How is pH adjusted in the seminal fluid?

A

The seminal vesicles and epididymis add acidic secretions to seminal fluid

Prostate gland secretes alkaline fluid into semen promoting some neutralization of the fluid, promoting motility and fertility of the sperm

46
Q

What is capacitation?

A

Capacitation of the sperm occurs when they enter the female genital tract

Epididymis makes chemical adjustments to sperm while in storage, preserving their activity to break through the egg.

Fluids in the uterus and uterine tubes was away these chemical adjustments, weakening the acrosome and making the sperm more permeable to Ca2+ (promoting sperm motility)

47
Q

What are the effects of testosterone deficiency in 2nd-3rd month of gestation?

A

Male pseudohermaphrodism

48
Q

What are the effects of testosterone deficiency in 3rd trimester of pregnancy?

A

Problems with tesituclar descent and micropenis

49
Q

What are the effects of testosterone deficiency in puberty?

A

Poor development of secondary sexual characteristics

Eunuchoid features (persistance of pre-pubertal characteristics

50
Q

What are the effects of testosterone deficiency in post puberty?

A

Decreaed libido

Erectile dysfunction

decrease facial hair and body hair growth

Infertility

Low energy

51
Q

What is Kallman’s syndrome?

A

Form of Male Hypogonadism (SECONDARY HYPOGONADISM)

Genetic disorder where GnRH neurons fail to migrate in the hypothalamus during development (thus decreased GnRH secretion)

Hypogonadotropic Hyogonadism

Delayed or absent onset of puberty

Loss of sense of smell

52
Q

What is Kleinfelter’s syndrome?

A

Male with an extra X chromosome (XXY)

PRIMARY HYPOGONADISM

Phenotypically male

At puberty, increased gonadotropins fail to stimualte sufficient testosterone secretion

Results in destruction of seminiferous tubules, causing infertility

Colin Endo/Repro Final (12 decks)

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