Male Reproductive System Flashcards
State the 2 main functions of the male reproductive system.
- steroidogenesis - produce sex hormones
- spermatogenesis - produce, maintain and transport viable spermatozoa
State the parts of the male genitalia involved in the production, maintenance and transport of viable spermatozoa
- testes - spermatogenesis
- epididymis + vas deferens - storage
- prostate, seminal vesicles, bulbourethral glands - transport
Recap: Regarding the control of production of TESTOSTERONE/OESTROGEN/PROGESTORONE, state the
- hormones involved
- level of production of each hormone
hypothalamus - GnRH (gonadotropin releasing hormone)
anterior pituitary/adenohypophysis - FSH, LH
testes - testosterone; ovaries - progesterone, oestrogen
Explain the pathway from hypothalamic stimulus to production of testosterone. (use HPA axis)
- hypothalamus produces GnRH
- GnRH is transported to anterior pituitary gland via vascular link to stimulate anteiror pituitary to produce FSH and LH
- LH stimulates LEYDIG CELLS to produce TESTOSTERONE
- TESTOSTERONE binds to ABP (androgen-binding protein)
- TESTOSTERONE induces NEGATIVE FEEDBACK by inhibiting GnRH production by hypothalamus + FSH/LH production by anterior pituitary gland
Explain the pathway from hypothalamic stimulus to production of spermatozoa. (use HPA axis)
- hypothalamus produces GnRH
- GnRH is transported to anterior pituitary gland via vascular link to stimulate anteiror pituitary to produce FSH and LH
- FSH binds to receptor on SERTOLI CELLS and stimulates SECOND MESSENGER which stimulates SPERMATOGENESIS and secretes INHIBIN and ABP (androgen-binding protein)
- INHIBIN induces NEGATIVE FEEDBACK by inhibiting GnRH production by hypothalamus + FSH/LH production by anterior pituitary
Draw out the coordination of action by leydig cells and sertoli cells
State the actions of the 3 proteins formed by testosterone.
INHIBIN, ACTIVIN, FOLLISTATIN
- inhibin + follistatin - suppresses FSH by targeting anterior pituitary gland
- activin - potentiates FSH by targeting anterior pituitary gland
State the main functions of testosterone (6)
- controls development of internal male genitalia
- supports spermatogenesis in sertoli cells
- supports puberty
- supports development of secondary sex characteristics
- promotes sex drive/libido
- promotes protein synthesis and muscular growth
State the 4 products of testosterone. (state any enzymes involved in conversion)
- estradiol (catalysed by AROMATASE)
- dihydrotestosterone (catalysed by 5a-REDUCTASE)
- conjugates
- 17-ketosteroids (catalysed by 17b-DEHYDROGENASE)
DIHYDROTESTOSTERONE (DHT)
- More potent/less potent than testosterone
- Enzyme catalysing conversion of testosterone to DHT:
- Production localised to ____, ____, ____, ____, ____
- 3 functions:
DIHYDROTESTOSTERONE (DHT)
- More potent than testosterone
- Enzyme catalysing conversion of testosterone to DHT: 5A-REDUCTASE
- Production localised to PROSTATE, PENIS, TESTES, SKIN, SCALP
- 3 functions:
- development of male external genitalia
- development and growth of prostate gland
- growth of male sexual hair
Describe the mechanism of action for testosterone/DHT.
- testosterone is a steroid and has a lipophilic cholesterol backbone which allows it to cross the cellular membrane easily
- testosterone enters cytoplasm and is converted to DHT by 5a-reductase to combine with AR (androgen receptors) –> dimerisation and phosphorylation –> activation of testosterone
- Activated T-AR passes through nuclear membrane and act on androgen response elements in DNA –> recruits coactivator –> targets gene activation –> biological response
List the following from least mature to most mature:
- spermatocyte
- spermatozoon
- spermatid
- spermatogonium
- spermatogonium
- spermatocyte
- spermatid
- spermatozoon
Regarding the 3 stages of spermatogenesis, state…
- duration of each stage
- cell types
- number of chromosomes
(1) PROLIFERATION
- 3-4 weeks
- cell types: spermatogonium
- 2x chromosomes, 2x genetic material (mitosis)
(2) GROWTH
- 3-4 weeks
- cell types: primary spermatocyte, secondary spermatocyte
- 2x chromosomes, 2x genetic material (meiosis I and II)
(3) MATURATION/DEVELOPMENT
- 3-4 weeks
- cell types: spermatids, mature spermatozoa
- x chromosomes
Describe the processes involved in spermatogenesis.
- proliferation - primordial germ cells of sperm enter adluminal portion of seminiferous tubules to become spermatogonium
- proliferation - diploid spermatogonium undergo mitosis to form primary spermatocyte
- growth - primary spermatocyte undergoes meiosis I to form secondary spermatocyte
- growth - secondary spermatocyte undergoes meiosis II to form spermatids
- maturation - spermatids in intracellular space mature and differentiate in epididymis to from mature spermatozoa
State the differences between mitosis and meiosis.
