32 Male reproduction Flashcards
State all the male accessory sex glands.
- Prostate gland
- Bulbourethral gland
- Seminal vesicles
State the functions of seminal vesicles.
- Supply fructose to nourish the ejaculated sperm
- Secrete prostaglandins that stimulate the motility to help transport the sperm within the male and female
- Provide bulk of the semen
- Provide precursors for the clotting of the semen
State the functions of the prostate gland.
pH!
- Secretes alkaline fluid that neutralizes the acidic vaginal secretions
- Triggers clotting of the semen to keep sperm in vagina during penis withdrawal
State the function of the bulbourethral gland.
Secrete mucus for lubrication
The major cell type in interstitial tissue and seminiferous tubule is _________________ and _________________ respectively.
Leydig cells; Sertoli cells (spermatogenic cells)
Sertoli cells is for (3 functions), and has feedback control on _______.
Structural support, spermatogenesis, tubule fluid excretion (exocrine);
FSH
What is the function of Leydig cells?
Steroidogenesis (endocrine) = production of male sex hormones
State the anterior pituitary trophic hormones of Leydig cells and Sertoli cells respectively.
Leydig cells: LH
Sertoli cells: FSH
State the gonadal hormones of Leydig cells and Sertoli cells respectively.
Leydig cells: testosterone (+dihydrotestosterone and estradiol) ;
Sertoli cells: inhibin (+dihydrotestosterone and estradiol)
State the organization of hypothalamic-pituitary testicular axis in men.
Trophic stimulation
- hypothalamus: gonadotrophin releasing hormone (GnRH)
-anterior pituitary:
LH: acts on Leydig cells to stimulate androgen (testosterone production)
FSH: acts on Sertoli cells (spermatogenesis)
- paracrine control:
Androgens (testosterone and dihydrotestosterone) produced by Leydig cells act synergistically with FSH on Sertoli cells to support spermatogenesis
Describe the feedback control by gonadal hormones in men.
- Sex steroids (testosterone), mainly from Leydig cells are involved in the feedback control of GnRH, LH and FSH.
- inhibin (mainly inhibin B in men) produced by Sertoli cells is selectively involved in the feedback control of FSH only.
Briefly state the main components invovled in the action by LH.
stAR protein, side chain cleavage and other steroidogenic enzymes,
cholesterol esterase,
LDL receptor
Which enzyme is important in FSH action?
Aromatase enzyme
State the 2 ways of testicular steroid hormone production.
- By testis
- By peripheral conversion
- LH act on Leydig cells to stimulate testosterone production
- Estradiol is formed from aromatization of androgen by aromatase in Leydig cells and Sertoli cells
- In testis, target cells and peripheral tissues, testosterone is converted by 5-alpha-reductase into a more potent dihydrotestosterone and by aromatase to estradiol.
What is the definitions of spermatogenesis and spermiogeneis?
Spermatogenesis: spermatogonia give rise to spermatozoa through meiotic cell division and cell differentiation
Spermiogenesis: cell differentiation
What is spermiation?
process by which mature spermatids are released from Sertoli cells
What is/are the hormone(s) required for normal spermatogenesis in Sertoli cells? Describe.
both FSH and LH! + testosterone
- LH: effect is indirect and mediated through testosterone produced by Leydig cell (as there is no LH receptors in Sertoli cells)
- high intratesticular level of testosterone (paracrine control) is needed to support spermatogenesis
- FSH: testosterone and dihydrotestosterone synergize with FSH to support spermatogenesis
State the 3 ways of achieving high intratesticular testosterone level.
- Proximity of Leydig cells: testosterone is released from them to Sertoli cells > bound to androgen binding protein > cary it to lumen
- FSH + testosterone stimulation: Sertoli cells secretes androgen binding protein to concentrate testosterone into the seminiferous tubule
- High testosterone in testicular venous blood is re-circulated back to testis via aterio-venous exchange at the level of pampiniform plexus by counter-current mechanism (testosterone is recycled to arteries)
Giving exogenous androgen will result in?
- suppression of LH and FSH secretion
(feedback inhibited hypothalamus to secrete GnRH and pituitary to secrete LH and FSH) - intratesticular level of androgen falls and sperm production decreases
- although sex drive and sexual potency increases, fertility is reduced
How is the optimal temperature required for normal spermatogenesis obtained in males?
- Scrotal testis, testicular descent
- Arteriovenous heat exchange through a counter-current mechanism at the level of pampiniform plexus
- Dartos muscles (lining scrotal wall) - contraction increases skin folding and reduces surface area for heat loss
- Cremaster muscle - relaxation > descend further away from body core
- Darker colour (pigmentation) of scrotal skin - black body radiation
- Sweat glands of scrotal skin: evaporate heat loss
What is cryptochidism?
Failure to descend testis during fetal developement
What are the endocrine functions of Sertoli cells?
- Endocrine
- produce inhibin
- produce steroid hormones through conversion
What are the exocrine functions
- Exocrine
- Mediate FSH and androgen effects in supporting spermatogenesis
- produce androgen binding protein to concentrate testosterone in seminiferous tubules
- provide physical, nutritional and trophic support to germ cells
- move spermatogenic cells from basal to luminal side of seminiferous epithelium and control the release of mature spermatids
- secrete seminiferous tubule fluid
Which of the following is/are true about the function of Sertoli cells?
A. They phagocytose damaged spermatogenic cells
B. They form blood testis barrier to isolate halpoid germ cells from body’s immune cells
All true
