Lecture 25: Male Reproductive Physiology Flashcards
The pulsatile secretion of what hormone initiates puberty?
GnRH
GnRH drives the pulsatile secretion of what hormones?
What are these hormones responsible for?
FSH and LH
-secondary sex characteristics
During the adult reproductive period, is LH or FSH secreted more?
LH
What is the function of the testes?
1) Spermatogenesis
2) Testosterone secretion
What is the function of the epididymis?
Primary location for maturation and storage of sperm
What is the function of the vas deferens?
- Storage for sperm
- Secrete rich fluid
What is the function of the sminal vesicle?
Secretes fluid that aids in the motility of sperm and penetration –> becomes semen
- prostaglandins helps semen react with female cervix
- helps ejaculated sperm into fallopian tube and uterus
What is the function of the prostate gland?
Secrete solution that gives the semen an alkaline pH to survive in the acidity in female vagina
What two type of cells are found in the seminiferous tubules?
What are their functions?
Sertoli cells: produce sperm and forms barrier between testes and bloodstream
Leydig cells: produce testosterone
Where are spermatogonia and spermatozoa found?
Spermatogonia (immature sperm): periphery
Spermatozoa (mature sperm): lumen of tubule
In the lumen of the seminiferous tubules, how is testosterone concentrated?
Testosterone is bound to androgen-binding protein (ABP)
-ABP secreted by sertoli cells
What converts androstenedione to testosterone?
17β-hydroxysteroid dehydrogenase
What converts testosterone to dihydrotestosterone?
5α-reductase
In circulation, what is testosterone bound to?
Sex hormone binding globulin (SHBG)
What is the first step in testosterone production?
Cholesterol –> Pregnenolone
-RATE LIMITING STEP
Where is estrogen produced in the males?
1) Sertoli Cells:
Testosterone –> Estradiol via aromatase
2) Liver
What stimulates the conversion of cholesterol into pregnenolone?
LH
- Leydig cells has receptor for LH
- increased affinity of P450scc enzyme
The androgen receptor complex is a ____ receptor.
Nuclear receptor
What might happen if there is a deficiency of 5α-reductase?
Lack of dihydrotestosterone (DHT)
-ambiguous external genitalia
What is cryptorchidism?
Lack of descent of testes
What is testosterone responsible for?
- Increased muscle mass
- Pubertal growth spurt
- Closure of the epiphyseal plates
- Growth of the penis & seminal vesicles
- Deepening of the voice
- Spermatogenesis
- Libido
What is DHT responsible for?
- External male genitalia
- Male hair distribution
- Sebaceous gland activity
- Growth of prostate
What is benign prostatic hyperplasia?
Prostate gland enlargement
-more DHT receptors
What stimulates Sertoli cells?
Testosterone and FSH
-secretes ABP into seminiferous tubules (increase testosterone concentration)
What inhibits Sertoli cells?
Inhibin which inhibits FSH
Describe the process of spermatogenesis.
Phase 1: Mitotic divisions
-results in primary spermatocytes (diploid 4N)
Phase 2: Meiotic divisions
- Secondary spermatocytes (haploid 2N)
- Spermatids (haploid 1N)
Phase 3: Spermiogenesis
-spermatids mature into spermatozoa
What hormones stimulate spermatogenesis?
LH: stimulate secondary spermatocyte FSH: stimulate primary spermatocyte GH Testosterone Estrogen
In the epididymis, how does the sperm mature?
- Becomes more motile
- Decapacitation to prevent acrosomal reaction before contact egg
- Will spend a month
What is the function of the bulbourethral gland?
Located beneath the prostate gland at the beginning of the internal portion of the penis;
- add fluids to semen during the process of ejaculation
- alkaline fluid to neutralize any mild acidity
What three erectile bodies make up the penis?
2 corpus cavernosa
1 corpus spongiosum
During an erection, what do the parasympathetic nerves stimulate?
Innervate vascular smooth muscle of helicine arteries
- NO released –> relaxation of smooth muscle
- penis is engorged and erect
- somatic stimulation increases contraction of muscle
During an erection, what does the sympathetic control do?
Movement of semen from epididymis to ejaculatory duct
-closing internal sphincter of bladder
What causes ejaculation?
Rhythmic contraction of bulbospongiosus and ischiocavernosus muscles at base of penis
-innervated by somatic motor nerves
When sperm enters the female tract, what happens to the sperm?
Capacitation of sperm
- loss of inhibitory factors
- more permeable to calcium, increasing motility
What is Kallman’s syndrome?
GnRh neurons fail to migrate
-delayed of absent puberty
What is Klinefelter’s syndrome?
XXY genotype
- puberty: failure to induce normal testicular growth
- infertile
