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Endo-Repro Final > Physiology > Flashcards

Physiology Flashcards

1
Q

What hormones initiate puberty and how does this lead to the development of secondary sex characteristics

A

pulsatile secretion of GnRH -> pulsatile secretion of FSH and LH -> stimulates testosterone & estrogen (causes secondary sex characteristics)

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2
Q

Name 2 things that could delay the onset of puberty?

A

extreme stress or caloric deprivation

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3
Q

What is melatonin a natural inhibitor of? What would occur if the pineal gland was removed?

A
  • melatonin inhibits GnRH

- if pineal gland was removed, early puberty would occur in children

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4
Q

What is most testosterone converted to when it reaches target tissues?

A

dihydrotestosterone (DHT)

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5
Q

What cells make the majority of testosterone and in what organ are they located?

A

Leydig cells of the testes

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6
Q

What does 17B-hydroxysteroid dehydrogenase do in the testes?

A

coverts androstenedione to testosterone

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7
Q

Name some tissues where DHT is the active androgen (4)

A

prostate gland, external genitalia of male fetus, skin, liver

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8
Q

What enzyme converts testosterone to DHT in the peripheral tissues?

A

5a-reductase

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9
Q

What is the majority of circulating testosterone bound to?

A

sex hormone-binding globulin (SHBG) and albumin

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10
Q

What binds to testoserone as it is concentrated in the lumen of seminiferous tubules?

A

antigen binding protein (ABP)

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11
Q

Where does estrogen come from in males?

A
  • some produced by sertoli cells
  • aromatase converts testosterone to estrogen
  • liver (accounts for 80% of male estrogen)
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12
Q

What is the RLS of testosterone synthesis? What stimulates this step?

A
  • cholesterol -> pregnenolone by cholesterol desomolase (P450scc)
  • stimulated by LH (acts on Leydig cells)
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13
Q

What type of receptor are androgen receptors (AR)?

A

nuclear receptors

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14
Q

Which has a higher affinity for the AR - testosterone or DHT?

A

DHT

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15
Q

What is the biologically active form of testosterone in the body?

A

free unbound testosterone (2%)

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16
Q

What actions do testosterone have during fetal development?

A
  • fetal differentiation into internal and external genital organs
  • cause descent of testes into scrotum towards last few months of pregnancy
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17
Q

Name 7 actions of testosterone during puberty?

A
  • increased muscle mass
  • growth spurt
  • closure of epiphyseal plates
  • penile growth
  • deepening of voice
  • spermatogenesis
  • libido
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18
Q

Name 4 specific actions of DHT

A
  • fetal differentiation of male external genitalia
  • male hair distribution and baldness
  • sebaceous gland activity
  • prostatic growth
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19
Q

What can be used as a tx for BPH and male patter baldness in males?

A

5a- reductase inhibitors (inhibits DHT production)

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20
Q

Name some anabolic actions of androgens

A
  • stimulates EPO
  • nitrogen retention
  • stimulates linear body growth
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21
Q

What are the intracellular mechanisms of LH on Leydig cells?

A

Bind to LH receptor -> Gs pathway -> protein synthesis (produces enzymes involved in testosterone synthesis)

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22
Q

What hormones do the Leydig cells and Sertoli cells respond to?

A
  • Leydig: LH

- Sertoli: testosterone and FSH

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23
Q

What are the intracellular mechanisms of FSH and testosterone on Sertoli cells

A
  • FSH: binds to FHS receptor -> Gs pathway -> protein synthesis (ABP, inhibin, and aromatase)
  • Testosterone: converted into estradiol by aromatase or enters lumen w/ developing spermatogonia
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24
Q

What is the function of inhibin in both males and females?

A

inhibits FSH release

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25
Q

Name 3 supporting functions of Sertoli cells

A
  • blood-testis barrier
  • phagocytosis
  • supply nutrients to sperm from blood
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26
Q

Name 3 exocrine functions of Sertoli cells

A
  • production of fluid
  • production of ABP
  • determination of sperm release from seminiferous tubules
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27
Q

Name 4 endocrine functions of Sertoli cells

A
  • expression of ABP, testosterone, and FSH receptor
  • production of AMH
  • aromatization of testosterone to estradiol
  • production of inhibin
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28
Q

How long does the process of spermatogenesis take?

A

between 64-72 days

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29
Q

What is spermatocytogenesis and when does it begin? End result?

A
  • mitotic division phase - begins at puberty

- results in primary spermatocytes

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30
Q

What does the meiosis phase of spermatogenesis result in?

A

primary spermatocytes -> secondary spermatocytes -> spermatids

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31
Q

What is spermiogenesis?

A

maturation of spermatids into mature spermatozoa

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32
Q

What affect does GH have on spermatogenesis?

A
  • controls background metabolic function of testes

- promotes early division of sperm themselves

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33
Q

What is the effect of exogenous testosterone in peripheral tissues and testes?

A
  • peripherally more free testosterone (anabolic effects)

- increased negative feedback on LH -> less testosterone produced in testes -> decrease in spermatogenesis

34
Q

What is decapacitation?

A

addition of molecules to the membranes of sperm to prevent acrosomal reaction before contact w/ egg

35
Q

What is the purpose of fructose in semen? What produces it?

A
  • main energy source for sperm

- seminal vesicles

36
Q

What is the purpose of prostaglandins in semen (2)? what produces it?

A
  • react w/ cervical mucus and makes it thinner to be more receptive to sperm
  • causes backward contraction of uterus/fallopian tubes to move sperm towards ovaries
  • seminal vesicles
37
Q

What is the final pH of semen?

A

7.5 - alkaline

38
Q

What is the maximal life span of sperm after ejaculation?

A

24-48 hours

39
Q

What number of sperm is considered to be infertile?

A

< 20 million

40
Q

In what way does the nervous system initiate an erection?

A

parasympathetic nerves innervating vascular smooth muscle release NO

41
Q

How does NO cause vasodilation?

A

stimulates guanylyl cyclase -> GTP to cGMP -> decreased intracellular Ca -> relaxation of smooth muscle -> blood flow increases

42
Q

What converts cGMP -> GMP in the penis at the end of an erection?

A

Type 5 phosphodiesterase

43
Q

What is the MOA of viagra?

A

Type 5 PDE inhibitor (helps maintain erection)

44
Q

Under what type of control is emission?

A

sympathetic control

45
Q

What effect does smooth muscle contractions of the vas deferens have (2)? Why is this important?

A
  • movement of sperm to the ejaculatory duct

- closure of the internal urethral sphincter (prevents back flow semen into the bladder)

46
Q

What muscles contract during ejaculation? What are they innervated by?

A
  • bulbospongiosus M. and ischiovacernous M.

- innervated by somatic motor nerves

47
Q

What changes occur in the female tract that allow for capacitation of sperm?

A
  • wash away inhibitory factors
  • loss of cholesterol built up on head of sperm
  • membrane more permeable to Ca -> increased motility
48
Q

Explain the effects of testosterone deficiency at each of the following time periods: 2-3 months gestation, 3rd trimester of pregnancy, puberty, post-puberty

A
  • 2-3 months gestation: ambiguity of male genitalia
  • 3rd trimester: cryptorchidism and micropenis
  • puberty: poor secondary sex characteristics and eunuchoid features
  • post-puberty: erectile dysfunction, decreased libido, and infertility
49
Q

What is eunuchoidism?

A

persistence of prepubertal characteristics and often presence of characteristics typical of opposite sex

50
Q

What is Kallmann’s syndrome? Sxs?

A
  • genetic disorder where GnRH neurons fail to migrate to hypothalamus during development (tertiary hypogonadism)
  • delayed/absence of puberty and impaired sense of smell
51
Q

What is Klinefelter syndrome and what is seen with it?

A
  • 47, XXY
  • appear male at birth
  • failure to induce testicular growth/spermatogenesis at puberty
  • androgen production usually low but gonadotropins are high (primary hypogonadism)
  • seminiferous tubules are destroyed -> infertility
52
Q

Give an example of primary, secondary, and tertiary male hypogonadism

A
  • primary: klinefelter syndrome (decreased testosterone production)
  • secondary: pituitary dysfunction (decreased LH/FSH secretion)
  • tertiary: Kallmann’s syndrome (decreased GnRH secretion)
53
Q

What occurs as a result of decreased gonadal sensitivity to LH in males around the age of 40?

A
  • increased serum levels of LH and FSH (FSH > LH)
  • decreased testosterone production
  • decreased bone formation, muscle mass, facial hair, appetite, and libido
54
Q

What 3 layers of the oocyte does the sperm have to penetrate?

A
  • cumulus cell matrix (corona radiata)
  • zona pellucinda
  • plasma membrane of oocyte
55
Q

Around what day of the menstrual cycle does fertilization usually occur?

A

day 15-16

56
Q

Which part of the uterine tube does fertilization generally occur? Which part of the uterus does implantation generally occur?

A
  • fertilization in the ampulla of the uterine tube

- implantation in the posterior wall of the fundus of the uterus

57
Q

Explain the purpose of decapacitation in the male?

A

cholesterol hardens the acrosome to prevent it from releasing its proteolytic enzymes in the male genitalia

58
Q

What causes capacitation of sperm?

A

uterine/fallopian fluid washes away the inhibitor factors on the sperm (ex. cholesterol)

59
Q

What changes occur in the sperm after capacitation occurs?

A
  • membrane becomes permeable to extracellular Ca (increased tail movement and activation - preparation to release enzymes)
  • gains ZP3 receptors
60
Q

What is the cumulus cell matrix made of?

A

mainly hyaluronic acid

61
Q

Describe the 3 glycoproteins that make up the zona pellucida

A
  • ZP1: structural (crosslinks ZP2 and ZP3)
  • ZP2: blocks polyspermy
  • ZP3: initiates acrosome reaction
62
Q

What specific proteolytic enzyme does the acrosome of sperm contain? Which layer does this break through?

A

hyaluronidase - breaks through cumulus cell matrix

63
Q

Explain how ZP3 initiates acrosome reaction?

A

sperm w/ ZP3 receptor (from capacitation) bind to ZP3 in zona pellucida and release proteolytic enzymes to break apart structural components of zona pellucida

64
Q

What occurs after the sperm break through the ZP3 layer of zona pellucida?

A

ZP3 receptor falls off and sperm can bind to ZP2 (prevents any more sperm from breaking through)

65
Q

What is the sperm reservoir?

A

place in the isthmus of the uterine tube where sperm bind to epithelium to wait for oocyte to be released

66
Q

What is the cortical reaction (3 steps)?

A
  • initiated during fertilization
  • release of granules to prevent polyspermy (ZP2 -> ZPf); hardens zona pellucida
  • Ca stimulates completion of meiosis II
  • egg activation (fusion of male and female pronuclei
67
Q

Describe compaction and blastocele development in embryonic development

A

occurs w/ the morula (16 cell mass) around day 3 -> cells compact tightly to create outer trophoblast and inner cell mass (embryoblast) with blastocele space in between (due to Na)

68
Q

What is blastocyst hatching?

A

blastocyst breaks free from hardened zona pellucida to continue growing (day 5)

69
Q

What occurs if blastocyst hatching occurs too early?

A

blastocyst can attach early in the uterine tube (ectopic pregnancy)

70
Q

What are the functions of hCG (3)?

A
  • prevents involution of the corpus luteum which is producing progesterone and estrogen (prevents menstruation and maintains early pregnancy up to 10 weeks)
  • stimulates trophoblast growth (via progesterone)
  • stimulates placental growth
71
Q

What 2 types of cells do trophoblasts develop into?

A
  • cytotrophoblasts (supporting cells)

- synchitiotrophoblasts

72
Q

Name 4 functions of synchitiotrophoblasts

A
  • increased invasion of endometrium
  • secrete hCG (high levels after week 10)
  • secretes progesterone (week 10)
  • phagocytosis and bidirectional placental transfer
73
Q

What are the 3 steps of implantation?

A

apposition; attachement; invasion

74
Q

What occurs in apposition during implantation?

A

contact between endometrium and trophoblasts; inner cell mass rotates to face endometrium

75
Q

What occurs in attachment during implantation?

A
  • trophoblasts adhere and surface proteins interact w/ epithelial cells
  • initiates changes of endometrial stroma (decidualization - maternal reaction to implantation)
76
Q

What occurs in invasion during implantation?

A
  • degradation of endometrial epithelial cells

- trophoblast fusion and formation of syncytiotrophoblasts

77
Q

What is added to endometrial stroma after decidualization? What hormone is involved in this process?

A

filled and glycogen filled decidual cells (endometrium -> decidua); through progesterone

78
Q

What is the function of the decidua?

A
  • involved in nutrient exchange w/ embryo
  • protects embryo from maternal immune system
  • controlled invasion of trophoblast (sticks to proper layer of uterus)
79
Q

What develops in synchitiotrophoblasts around day 9?

A

lacunae (spaces filled w/ endometrial secretion and blood for nutrient transfer)

80
Q

Describe the primary placental villi

A

proliferation of syncytiotrophblasts and cytotrophoblasts into lacunae

81
Q

Describe the secondary placental villi

A

mesenchyme cells from extra embryonic mesoderm invade villi

82
Q

Describe the secondary placental villi

A

mesenchymal cells from fetal blood vessels de novo

Endo-Repro Final (7 decks)

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