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Repro Final > Male Reproductive Physiology _ PV > Flashcards

Male Reproductive Physiology _ PV Flashcards

1
Q

Gonads at first 5 weeks of gestational life

A

gonads are bipotential ( neither male or female)

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2
Q

Gestational week 6-7

A

testes begin to develop in genetic males

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3
Q

gestational week 9

A

ovaries begin to develop in genetic females

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4
Q

Gonadotropin secretion over lifetime

  • childhood
  • adult reproductive period
  • senescence
A
  • childhood: FSH>LH
  • adult reproductive period: LH> FSH
  • senescence: FSH>LH ( menopause= lack of negative feedback of LH/FSH secretion)
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5
Q

Secretion of GnRH

  • how is it secreted
  • if it doesn’t follow patter
A

PULSATILE secretion of GnRH=> PULSATILE secretion of FSH and LH => steroid, testosterone, estradiol => puberty is administered

if long-acting, chronic GnRH is administered=> puberty is not initiated

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6
Q

What can alter onset of puberty? (3)

A
  1. caloric deprivation
  2. extreme stress
  3. MELATONIN
    - highest in childhood and declines in adults
    - removal of pineal gland causes early puberty
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7
Q

List the anatomy of male reproductive tract (8)

A
  1. Testes
  2. Epididymis
  3. Scrotum
  4. Vas Deferens
  5. Seminal Vesicles
  6. Prostate Gland
  7. Seminiferous tubules
  8. Leydig Cells
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8
Q

Testes

- functions (2)

A
  1. secretion of testosterone

2. develop sperm (spermatogenesis)

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9
Q

Scrotum

- function

A

its lower temperature is essential for spermatogenesis

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10
Q

Epididymis

- function (2)

A

1) primary location for sperm maturation

2) storage of sperm

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11
Q

Vas Deferens

- function (2)

A
  1. provide another storage area for sperm (ampulla)

2. secretes fluid rich in citrate and fructose

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12
Q

Seminal vesicles

- function

A

secretes fluid rich in citrate, prostaglandins, and fibrinogen

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13
Q

Prostate gland

- function

A

secretes milky aqueous solution rich in citrate, calcium, and enzymes

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14
Q

seminiferous tubules

- describe components

A

epithelium formed by Sertoli cells

  • spermatogonia: most immature germ cells, located near the periphery of tubules
  • spermatozoa: mature germ cells, located near the lumen of the tubules
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15
Q

Leydig cells

A

interstitial cells that lie between tubules

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16
Q

What is the adult testis made up of

A
  • 80% seminiferous tubules

- 20% CT interdispersed with leydig cells

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17
Q

Leydig cells

- function

A

synthesis and secretion of testosterone

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18
Q

Sertoli cells

- function (3)

A
  1. provide nutrients to differentiating sperm
  2. form tight junctions with each other, creating a barrier between testes and bloodstream
  3. secrete an aqueous fluid into lumen of seminiferous tubules
    - helps to transport sperm through the tubules into epididymis
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19
Q

What does testes secrete? (3)

what is most abundant

A
  1. testosterone (MOST abundant)
  2. dihydrotestosterone
  3. androstenedione
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20
Q

What happens to testosterone in target tissues

A

T converts to DHT via 5 a reductase**

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21
Q

Testosterone

  • describe (A LOT)
  • where is it made
  • what does is lack
  • what does it have
A

major androgenic hormone

made in LEYDIG cells

In testes

  • lack 21b hydroxylase & 11B hydroxylase => no glucocorticoid or minercorticoid
  • HAVE 17B hydroxysteroid dehydrogenase
    • converts androstenedione to testosterone
    • end product of steroid synthesis => testosterone (NOT DHEA and androstenedione)
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22
Q

Testosterone

  • binding proteins
  • tissues ( think DHT)
A

in lumen of seminiferous tubules => bind to androgen-binding protein

in circulating testosterone=> bound to plasma protein and albumin ( Sex hormone-binding globulin)

DHT
- active androgen in prostate gland, external genitalia,skin, liver

23
Q

Leydig Cells

- cholesterol production

A

makes cholesterol de novo - from the circulation through LDL and HDL

  • stores cholesterol as cholesterol ester
    (made by cholesterol HSL)
    cholesterol ester -> free cholesterol via HSL

cholesterol transferred within mitochondrial membranes via steroidogenic acute regulatory protein ( StAR)

cholesterol converted to pregnenolone

24
Q

Estrogen

  • location
  • function
A

in seminiferous tubules (SERTOLI CELLS)

T-> estradiol via aromatase

important role in spermatogenesis

much larger amounts of estrogen are formed from testosterone andandrostenediol in other tissues like liver

25
Q

Mitochondrial pathway for testosterone synthesis

- RLS

A

Cytochrone P450 cleavage enzyme removes side chain from carbon at position cholesterol

RLS= desmolase

26
Q

What stimulates the conversion of cholesterol to pregnenolone?
- how (2)

A

LH
- regulates overall rate of testosterone synthesis by Leydig cells

  1. increases affinity of P450cc enzyme for cholesterol
  2. stimulates synthesis of P450scc enzyme (LT action)
27
Q

Testosterone production

  • when does it begin
  • what does it bind to
  • target tissues
A

7-8 weeks of gestation
- bind to androgen receptor (AR)=> nuclear receptor

location in male:
- prostate, testis ( sertoli, leydig, and myoid cell), epididymis, seminal vesicles

non-reproductive tissue: neurons in CNS, anterior pituitary, thyroid skin, adrenal cortex, liver, kidney, bladder

location in female:
- ovary, mammary glands, uterus

28
Q

DHT production

  • bind
  • enzyme
A

bind to androgen receptors, with greater affinity

plays important role in causing changes at puberty

29
Q

deficiency of 5a reductase

A

results: ambiguos external genitalia

30
Q

Testosterone

  • binding protein proportions
  • where is it excreted and how
A

60% circulating T bound to SHBG

38% circulating T bound to albumin

2% free T

Excreted via urine as urinary 17 ketosteroid (50%) or conjugated androgens/diol

31
Q

Tissues that produce androgen

A

Adrenal gland

  • cholesterol
  • androstenedione

Peripheral tissues

  • testosterone
  • DHT
  • estradiol
32
Q

Fetal development

  • with testosterone
  • without testosterone
  • disease
A

with testosterone= penis and scrotum

without testosterone= clitoris and vagina

fetal differentiation of internal male genital tract (epididymis, vas deferens, seminal vesicle)
- causes descent of testes into scrotum

Cryptorchidism: lack of descent

33
Q

Testosterone at puberty

- characteristics (7)

A
  1. increased muscle mass
  2. pubertal growth spurt
  3. closure of epiphyseal plates
  4. growth of penis and seminal vesicles
  5. deepening of voice
  6. spermatogenesis
  7. libido
34
Q

Specific actions of DHT (4)

- clinical correlation

A
  1. external male genetilia
  2. male hair distribution and male pattern baldness
  3. sebaceous gland activity
  4. growth of prostate

Baldness=> 5a reductase inhibitor for treatment

35
Q

Andrgenic actions (4)

A
  1. regulation of differentiation of male internal and external genetilia in fetus
  2. stimulation of growth, development of 2 secual characteristics at puberty
  3. maintenance of reproductive tract and production of semen
  4. initiation and maintenance of spermatogenesis
36
Q

anabolic actions of androgens (7)

A
  1. stimulation of erythropoietin synthesis (RBC)
  2. stimulation of sebaceous gland secretion
  3. control of protein anabolic effects ( nitrogen retention )
  4. stimulation of linear body growth , bone growth and closure of epiphyses
  5. stimulation of ABP synthesis
  6. maintenance of secretion of sex glands
  7. regulation of behavioral effects, libido
37
Q

Benign prostatic
hyperplasia
- symptoms

A

symptoms

  • urinary frequency
  • nocturia
  • difficulty initiating and maintaing a urinary strem

DHT concentration equal but MORE DHT receptors on prostate compared to normal

38
Q

intracellular mechanism of testosterone

  • Leydig cells
  • sertoli cells
A

Leydig cells: LH receptor (cAMP-PKA pathway)

  • results in steroidogenesis and testosterone production
  • testosterone diffuses into seminiferous tubules and peripheral circulation

Sertoli cell: stimulated by testosterone and FSH (cAMP-PKA pathway_
- results in protein synthesis and production of inhibin (inhibits FSH release), ABP, aromatase, and other products

39
Q

Sertoli cell and testosterone relationship

A

FSH stimulates the sertoli cells to secrete ABP into lumen of seminiferous tubules
- binding of testosterone in lumen provides a local testosterone supply for teh developing spermatogonia

aromatization of testosterone to estradiol 17B

40
Q

Supportive function of sertoli cells (4)

A
  1. maintaining blood-testis barrier
  2. phagocytosis
  3. transfer of nutrients from blood to sperm ( transferrin, Fe, lactate)
  4. receptors for hormones and paracrine
41
Q

exocrine functions of sertoli cells (3)

A
  1. production of fluid
  2. production of ABP
  3. determination of release of sperm from seminiferous tubules
42
Q

Endocrine function of sertoli cells

A
  1. expression of ABP, T and FSH receptors
  2. production of AMH
  3. aromatization of testosterone to estradiol 17B
  4. production of inhibin to regulate FSH levels
43
Q

Spermatogenesis

  • occurs where?
  • timeline
  • cell type
  • cells
A

occurs in seminiferous tubules

lined by stratified epithelium

Spermatogenic and Sertili cells

64 days

for supportive and nutrient function

44
Q

Phases of spermatogenesis (3)

A
  1. mitotic division
  2. meiotic division
  3. spermogenesis
45
Q

Mitotic division of spermatogenesis

A
  • proliferative phase
  • puberty=> mitotic cycles increase
  • stem cell divide to produce daughter spermatogonia
  • primary spermatocytes
46
Q

Meiosis division of spermatogenesis

A

production of haploid gamete

  • primary spermatocytes undergo two meiotic divisions
  • two secondary spermatocytes each with haploid # of duplication crhomosomes
  • then 2nd meiotic division=> producing two spermatids, each with a haploid number of unduplicated chromosomes
47
Q

spermiogenesis (maturation)

A

spermatids undergo spermiogenesis and mature into spermatozoa

  • nuclear and cytoplasmic changes to produce mature spermatozoa
  • ends in testis with release of spermatozoa from sertoli cells
48
Q

Hormones that stimulate spermatogenesis ( 5)

A
  1. luteinizing hormone
  2. follicle- stimulating hormone
  3. growth hormone
  4. testosterone
  5. estradiol
49
Q

Luteinizing hormone

  • secreted by
  • function
A

secreted by anterior pituitary

stimulates leydig cells to secrete testosterone

50
Q

Follicle- stimulating hormone

  • secreted by
  • function
A

secreted by anterior pituitary

stimulates sertoli cells to nurse and form sperm

w/o FSH= no spermiogenesis

51
Q

Growth hormone

A

necessary for controlling background metabolic functions of the testes

promotes early division of sperm themselves

w/o it= pituitary dwarfs
(spermatogenesis is severely deficient)

52
Q

Testosterone

  • secreted by
  • function
A

secreted by leydig cells

essential for growth and division of testicular germinal cells, which is beginning of sperm formation

53
Q

estrogen

  • location
  • function
A

formed from the testosterone by the sertoli cells when they are stimulated by FSH

essential for spermatogenesis

54
Q

Feedback regulation of spermatogenesis

  1. normal
  2. with exogenous testosterone
A
  1. negative feedback loop

2. increasing circulating T=> more negative feedback on LH/FSH=> decrease in spermatogenesis

Repro Final (9 decks)

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