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GI GU Repro > Male Physiology > Flashcards

Male Physiology Flashcards

1
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A
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2
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3
Q

Where does spermatogenesis occur?

A

Intratubular compartment of seminiferous tubules

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4
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5
Q

Which of these cells are the sertoli cells?

A

St –> longer cells

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6
Q

Seminiferous tubules are contained by […]

A

Perytubular myoid cells

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7
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8
Q

Leydig Cells

  • What do they do?
  • What activates them?
  • When do we see peak amounts of them?
A
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9
Q

Sertoli Cells

  • What are the many functions of these cells?
  • What signals do they respond to to execute functions?
A
  • Functions:
    • Support spermatogenesis
    • Maintain blood-testis barrier through tight junctions, adherens junctions, and gap junctions
    • Secrete testicular fluid that is rich in hormones, enzymes and nutrients
    • Secrete androgen binding protein and inhibin
    • Phagocytosis to clean up remnants of spermatogenesis
  • Testosterone from Leydig cells and FSH from AntPit
    *
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10
Q
  • What is the blood-testis barrier and why is it important?
  • What can damage this barrier?
A
  • It is the barrier created by sertoli cells in the seminiferous tubules of the testis that controls the content of the tubule and prevents passage of cytotoxic agents into the tubule. It also prevents immune cells/cytokines from entering to prevent an autoimmune response to the testis. Serves as barrier protecting sperm.
  • Trauma and vasectomy
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11
Q

What is residual body?

A

Mature spermatozoa shed their cytoplasm as residual bodies

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12
Q

What external factors are important for sperm development?

A

Temperature (2 deg C beow body temp)

Time (takes 74 days)

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13
Q

Describe the importance of temperature on spermatogenesis, including:

  • the temperature that must be maintained in the testis
  • the mechansisms that help maintain that temp
  • Causes of increased temp
A
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14
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15
Q

Describe the general steps of spermiogenesis (note: not spermatogenesis).

A
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16
Q

Where does the acrosome arise from?

A

Proacrosomal granules of hyaluronidases nad proteolytic enzymes in the golgi

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17
Q

The sperm flagellum grows out from a […]

A

Centriole

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18
Q

How is DNA packing in a sperm different than DNA packing in any other cell?

A

Sperm coil DNA around protamines, which makes the DNA form a toroid structure instead of solenoid structure. In this image, the DNA is wrapped around the protamine like a donut and then the protamines are stacked on top of one another. This increases the packing efficiency of the DNA superstructure (bottom image). There are histone solenoids interspersed thoughout for easier transcription.

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19
Q

[…] mL of sperm per ejaculate

[…] sperm per mL

A

3.5

120 million

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20
Q

What factors determine infertility in men?

A

Sperm count less than 20 million

Motility less than 50%

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21
Q

After production in the seminiferous tubules, sperm travel next to the […]

A

Epididymis

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22
Q

Epididymis

  • Function of structure?
  • How long does it take sperm to traverse this structure?
  • Are sperm able to fertilize when in epididymis?
  • How long do they remain viable once in epididymis?
A
  • Store sperm
  • Several days, structure is 6m long
  • Sperm are non-motile and thus cannot fertilize. This is because they are under the influence of inhibiting proteins. They gain motility capabilities upon ejaculation.
  • Viable for up to month
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23
Q

What are the implications of pH on sperm function?

A
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24
Q

Seminial Vesicles

  • What are these?
  • What do they produce?
  • When / Where do they empty their contents?
  • What is the function of their secretions?
A
  • Tortuous tube lined with secretory epithelium, just prior to prostate gland
  • Mucoid material rich in fructose, citric acid, nutrients, prostaglandins, fibrinogen
  • Empty into vas deferens when the vas deferens contracts during ejaculation
  • React with female cervical mucosa and make it more receptive to sperm and reverse peristaltic actions of uterus
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25
Q

Prostate gland

  • What does this secrete?
  • When does this contract?
  • What is the pH?
A
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26
Q

Describe the fluid composition of semen from:

  • Vas deferens
  • Seminal vesicle
  • Prostate gland
  • Mucus glands / bulbourethral glands
A
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27
Q

Fluid from the […] is the last to be ejaculated and it washes out the vas deferens / urethra.

A

Seminal vesicle

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28
Q

Why is there clotting enzyme and fibrinogen in semen?

A

Clotting enzyme causes fibrinogen to form a coagulum in deeper regions of the vagina. This helps protect the sperm as it reaches deep into the female uterus. The coagulum is degraded in 15-30 minutes by fibrinolysin in the semen from the prostate gland and this releases highly motile sperm into the vagina/uterus.

29
Q

What is sperm half life in:

  • Epididymis
  • Post ejaculation
  • At low temp
  • At - 100 deg C
A
30
Q

What is sperm capacitation?

A

Sperm is mature but inactive when in epidiymis. It is activated by coming in contact with female vaginal secretions due to several factors (see image).

31
Q

Describe the process of fertilization.

A
  • Acrosome binds to either:
    • ZP3 receptors on zona pellucida –> Acrosome degranulates releasing hyaluronidase and protelytic enzymes that degrade the zona pellucida and granulosa cells to reach the egg
    • ZP2 receptors on zona pellucida –> sperm head invades zona pellucida and then releases enzymes into ZP to degrade it and the granulosa cells to reach egg
  • Once sperm is able to pass through to egg, Ca++ enters (membrane made more permeable to Ca++ by vaginal environment) and causes sperm to initate PLC signaling cascade that results in changes to remaining zona pellucida that prevents additional sperm from binding
  • Membrane of sperm nucleus and egg nucleus occurs rapdily after penetration to nucleus (~ 30mins)
32
Q

What determines sex in humans?

A

Genetics (on Y chromosome) and hormones

  • SRY gene –> produces TDF protein –> expressed in sertoli cells
  • SRY gene products induce genital ridge cells to become leydig cells —> testosterone –> male sex determination
  • SRY gene –> sertoli cells –> produce antimullerian hormone
  • Eif2s3y gene –> helps spermatogonia develop into spermatids
33
Q

Leydig cells produce testosterone, which in the developing embryo stimulates maturation of the wolffian ducts. What structures arise from the wolffian duct?

A

Epidiymis

Vas deferens

Ejaculatory duct

Seminal vesicle

34
Q

Where do the external male genetalia develop from?

  • Prostate
  • Penis
  • Scrotum
A
  • Urethral epithelium (leydig cells –> Testosterone –> circulate –> UE converts to DHT with 5alpha reductase –> stimulate differentiation into prostate)
  • Primoridial cells (leydig cells –> Testosterone –> circulate –> primordial genital ridge cells convert to DHT with 5alpha reductase –> stimulate differentiation into penis and scrotum)
35
Q

The induction of differentiation from bipotential gonad to testes (or ovaries) occurs between weeks […] and […]

A

6 and 7

36
Q

Retention of wolffian ducts and regression of mullerian ducts (or opposite in females) occurs on week […]

A

8

37
Q

External genetalia develop weeks […] to […]

A

9 to 12

38
Q
A
39
Q

Testosterone

  • Produced by…
  • Decreases after age …
  • How does it circulate
  • How is it removed from body
  • Basics of receptor interaction and signaling cascade
  • What is the significance of androgen binding protein in the testes?
A
  • Leydig cells (~95%) and adrenal gland (only ~5%)
  • 50 y/o
  • Bound to sex hormone binding globulin (Most), albumin (~38%), and 2-3% free
  • Eliminated by liver, excreted via bile and urine
  • Diffuse through membrane, bind to cytosolic androgen receptor, go to nucleus, dimerize, activate transcription
  • ABP allows for highly concentrated binding of testosterone in the seminiferous tubules so it can influence spermiogenesis
40
Q

True/False: GnRH is released constantly and induces constant release of FSH and LH.

A

False

  • GnRH is released in pulsatile manner for a few mins duration every 1-3 hours
  • LH is release is pulsatile, follows GnRH
  • FSH is constant, but follows GnRH long term
41
Q

What 2 male hormones feedback and inhibit the HPT axis?

A

Testosterone

Inhibin

42
Q
A
43
Q

Describe the process of penile erection.

A
  • PSNS –> cavernous nerve –> produce NO –> (+) guanylyl cyclase –> (+) cGMP –> (+) relaxation –> increase blood flow to cavernous artery and helicine arteries –> increased blood entry into sinusoidal spaces –> erection
  • Sexual stimulation –> contraction of muscles around penis base –> decreased venous return to cavernous spaces –> increased blood in cavernous spaces –> erection

NOTE: Production of NO is cyclic. Increased relaxation produced by NO allows more NO to be produced.

44
Q

Describe process of penile emission and ejaculation.

A
45
Q

What is male circumcision?

A

Removal of the foreskin/prepuce from the penis

46
Q

What are the current recomendations regarding circumcision?

A

Health benefits of newborn male circumcision outweigh the risks, but the benefits are not so much greater than the risks that it warrants recommendation of universal newborn circumcision, so the decision is left to the parents.

47
Q

What is one reason why circumcision rates are so much higher in all of Africa?

A

Prevalence of HIV and fact that circumcision reduces likelihood of contracting HIV from infected female partner

48
Q

What are the benefits of circumcision for males and any female partners they may have?

A
49
Q

Why is it not recommended to wait to circumcise until the child is old enough to decide for themselves?

A
50
Q

What is the difference bewteen puberty and adolescence?

A
51
Q

What is minipuberty?

A

Important for maturation of male sex organs and descent of testes into scrotum

52
Q

What is hypospadias?

A
53
Q

Prenatal peak of T and minipuberty are necessary for what?

A

Decent of testicles into scrotum

54
Q

After minipuberty within the 1st year of life, GnRH neurons are essentially quiescent until puberty. What is regulating these neurons so that this is the case?

A

KNDy Neurons which secrete dynorphin and kisspeptins regulate GnRH neuron function. Dynorphin is inhibitor and is released until puberty and kisspeptins are stimulatory. During puberty, these neurons heavily stimulate GnRH neurons resulting in GnRH secretion profile throughout remainder of life of individual.

55
Q

What factors inhibit KNDy neurons?

What factors stimulate them?

A

Inhibit

  • Stress
  • Inflammation
  • Sex-steroids
  • Drugs
  • Metabolism

Stimulate –> Nerurokinin B

56
Q

What factors inhibit and stimulate GnRH neurons?

A

Inhibit

  • Dynorphin from KNDy neurons
  • GnIH

Stimulate

  • Kisspeptins from KNDy neurons
  • Neurokinin B from KNDy neurons
57
Q

What is the role of leptin in puberty?

A
58
Q

What does testosterone do?

A
59
Q

What does testosterone NOT do?

A
60
Q

What is the normal sequence of development in males?

A
61
Q

True/false: normal puberty can start at a range of ages but follows the same sequence.

A

True

62
Q

Review this slide on the tanner stages. Not for memorization, just appreciation / general understanding of trends. (Flip card)

A
63
Q

Male Growth Spurts

  • Generally occurs at age […]
  • Does it occur ahead of or behind females?
  • Avg. height gained during puberty
  • When does it stop and why?
  • Why males tend to be taller than females?
A
  • 13.5
  • Behind females by 18 - 24 months
  • 10.3 cm
  • Stops ~ 15.8 y/o due to closure of epiphyseal plates from estradiol influence
  • Males taller b/c have typical childhood rates of growth prior to puberty, so their “base” height prior to puberty is greater than females
64
Q

Pubertal weight gain accounts for […] of ideal adult body weight

A

50%

65
Q

When does weight gain happen in males and females?

A

Males - coincides w/ puberty

Females - lags 6-9 months behind

66
Q
  • What is the mean age for males entering stage 2 of puberty?
  • Range for males entering stage 2?
  • When do males typically complete puberty? What is the range?
A
  • 10 y/o
  • 9 - 14
  • 3 years after onset, can be as much as 2 - 5 years
67
Q

True/False: Boys and girls who develop earlier will be shorter than those who are late because of baseline growth prior to onset of growth spurt.

A

True

68
Q

True/False: Early maturing boys are more likely to have substance abuse and/or tobacco issues.

A

False - late maturing boys are more likely for these things

69
Q

What are some of the perils of puberty?

A

GI GU Repro (58 decks)

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