Physiology - Endocrine - Male

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  1. Testes have two main functions:
    • Synthesis of androgens
    • Gametogenesis
  2. Androgens (testosterone) are C__ compounds,
    Estrogens (estradiol) are C__ compounds
    • 19
    • 18
  3. _____ cells and _____ cells are the major components of the seminiferous tubules. ____ cells, aka ______, lie between the tubules.
    • Sertoli
    • germinal
    • Leydig
    • interstitial cells
  4. _____ cells secrete 4-10 mg testosterone daily (~95% of the circulating testosterone)
    Leydig
  5. Leydig and Sertoli cells are engaged in a cross-talk:
    • Leydig synthesize testosterone which diffuses into seminiferous tubules to maintain spermatogenesis
    • Sertoli cells synthesize
    • 1. P-450 aromatase that converts testosterone to estradiol.
    • 2. Androgen binding protein (ABP) that binds to testosterone.
  6. Circulation and mechanism of action of testosterone
    • ~2% circulates freely
    • 45-65% bound to sex hormone-binding globulin (SHBG)
    • The rest bound to serum albumin

    can be converted to dihydro-testosterone (DHT) by the 5α-reductase enzyme in target cells, similar to glucocorticoids and mineralocorticoids: both bind to cytoplasmic androgen receptor, release HSP, dimerization, activate transcription of genes by binding to an estrogen-like hormone response element (ERE)
  7. Which androgen has the higher potency, DHT or testosterone?
    DHT
  8. Testosterone induces transcription of genes that encode for proteins involved in:
    • Growth/development
    • Sexual differentiation
    • Gametogenesis
  9. Functions of androgens
    • On growth and development on somatic tissues: anabolic
    • On development and growth of the male reproductive tract and of secondary sexual characteristics: androgenic
    • So far, no synthetic steroids have discriminating effects
  10. Sexual Differentiation of the testes
    • formation of sex cords that incorporate the primitive germ cells; ~7th week
    • secretion of AMH and involution of Müllerian ducts
    • Leydig cells appear and secrete antrogens, essential to the masculinization of the fetus
    • the Wolffian ducts develop into the epididymis, the vas deferens and the seminal vesicles
  11. The initial steps of sex differentiation of testes are driven by __________, the gene of which is located on ___________.
    • Testis determining factor (TDF)
    • Y chromosome
  12. sex cords is the future ______
    Sertoli cells
  13. By the 8th fetal week, Leydig cells appear in the differentiating testis and begin to secrete androgens, the actions of which are essential to the ________ of the fetus.
    masculinization
  14. With the regression of the ________ and under the influence of _________, the Wolffian ducts develop into the _______, the _______ and the _______.
    • Müllerian ducts
    • testosterone

    • epididymis
    • vas deferens
    • seminal vesicles
  15. DHT is responsible for ______.
    the urogenital sinus and external genitalia development
  16. Gametogenesis:
    •Spermatogenesis is under the control of ______ secreted by ________ and greatly affected by ______
    •________ provide the support
    •3 processes occur concurrently in the tubules:
    • testosterone
    • Leydig cells
    • temperature
    • Sertoli cells
    • • Mitosis (increase in number of cells)
    • • Meiosis (reduction in number of chromosomes)
    • • Spermiogenesis (production of mature sperm)
  17. Secretion of steroid by testes is under the control of the ______. ______ produces the ________, which stimulates _______.
    • hypothalamopituitary axis
    • Hypothalamus
    • gonadotropin-releasing hormone (GnRH)
    • in the anterior pituitary gland the secretion of luteinizing hormone (LH) and follicle stimulating hormone (FSH)
  18. LH and FSH are the primary ______ that stimulate testicular function:
    LH acts on _____ cells, just like ____ on ____, to synthesize _____ and increase:
    • gonadotropins
    • Leydig
    • ACTH
    • adrenal cortical cells
    • Enzymes involved in testosterone biosynthesis and sterol-carrier protein (SCP-2) involved in cholesterol transport across mitochondrial membrane
    • • intracellular concentrations of free cholesterol,
    • • its transport to the mitochondria
    • • Conversion of cholesterol to pregnenolone by P450scc
  19. FSH: acts on _____ cells to stimulate _____ synthesis, mobilization of ______, production of ______, and the output of proteins such as ________.
    • Sertoli
    • protein
    • energy resources
    • testicular fluid
    • inhibin, ABP, P450 aromatase, AMH and 5α-reductase
  20. Functions of following Sertoli cells products
    Aromatase:
    Inhibin:
    • converts testosterone into estradiol
    • exerts a negative feed-back on FSH secretion
  21. ______ stimulates _______ LH and FSH
    _______ of the proteins occurs in ______
    LH and FSH act on ____ cells via _____
    • GnRH
    • transcription of the genes coding for
    • Glycosylation
    • the pituitary gland
    • gonadal
    • GsPCR and GqPCR, and GsPCR
  22. •One testis can produce ____ sperm/day
    •Sperm maturation occurs in ______
    •Sperm can be stored up to ____ in _________.
    • 200 million
    • the epididymis
    • 5 weeks
    • the tail of the epididymis and vas deferens
  23. •Sensory stimulation induced _____
    •________ and ______ engorged with blood which results in erection.
    • At ejaculation the semen (_______) is expelled from the ______
    • vasodilatation of arterioles
    • Corpus spongiosum
    • cavernosum
    • sperm +seminal fluid
    • posterior urethra
  24. (Erection-inducing) vasodilatation is under the control of the ______ pathway:
    • NO-cGMP
    • NOS (nitric oxide synthase) -> NO -> soluble GC -> cGMP -> vasodilation
    • cGMP -phosphodiesterase-> GMP
    • Viagra (sildenafil) inhibits phosphodiesterase
  25. 5α‐reductase deficiency (___________)
    • hermaphrodism
    • ambiguous genitalia at birth due to impaired external genital development
  26. AR deficiency ‐ Due to mutation(s) in the androgen receptor
    Various degrees of androgen insensitivity syndrome (AIS) ‐ In 46XY with complete AIS, ________ (phenotypically _____).
    • no proper development of external and internal genitalia
    • female

Card Set Information

Author:
akhan
ID:
316873
Filename:
Physiology - Endocrine - Male
Updated:
2016-03-06 16:25:59
Tags:
physiology endocrine
Folders:
physiology
Description:
Physiology - Endocrine - Male
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