Male Reproductive System Flashcards
Spermatogenesis takes about……
74 days
Describe the role of the following hormones in spermatogenesis:
1. Testosterone
2. LH
3. FSH
4. Estrogen
5. GH
- Stimulates maintenance & development of germinal epithelium, needed for mitotic & meiotic divisions
- Acts on Leudig cells to produce testosterone
- Acts on Sertoli cells to activate their role in spermatogenesis by facilitating spermatid maturation to spermatozoa & promoting production of ABG
- Formed from testosterone by Sertoli cells, essential for spermiogenesis
- Promotes early division of spermatogonia. Its absence can lead to infertility
What is effect of high PRL level on males?
Inhibits testosterone synthesis via inhibition of GnRH, LH & may produce infertility in adult males
The suitable tempertaure for spermatogenesis is…….
32-35degC
Normally testes descend into scrotum at…….under effect of……
7th month of pregnancy
Fetal testosterone
Testes are kept cool by:
- Circulating air around scrotum
- Heat exchange in a countercurrent fashion between the spermatic arteries & veins
- Absence of subcutaneous fat in the scrotum
List functions of Sertoli cells
- Form blood testis barrier
- Provide nutrition for developing sperms by their glycogen content
- Have phagocytic function (engulf cytoplasm extruded from spermatids & destroy defective germ cells)
- Secretion of fluid into lumen of seminiferous tubules that pushed sperms into epididymid
- Secretion of ABG
- Site of action of testosterone & FSH
- Secretion of hormone inhibin that inhibits FSH
- Secrete Mullerian-inhibiting factor that cause regression of Mullerian duct
- Formation of estrogen by aromatase
What is the function of epididymis?
- Most sperms are stored in epididymis
- Epididymis concentrate sperm 100-fold by absorbing most fluid that enters seminiferous tubules
- Sperm leaveing the testes are not fully motile, they continue their maturation & acquire motility during passage in epididymis
How does sperms acquire motility?
The Catsper (alkaline-sensitive Ca++) channels are sperm-specific, Ca++ permeable, pH dependent, present in the membrane of sperm tail. They become more active as the sperm pass from acidic vaginal secretion to alkaline cervical mucus causing Ca++ entry into sperm cells which is crucial for fertility. Ca entry is necessary for capacitation, hyperactivated motility & the acrosome reaction.
Describe func of seminal vesicles
Secretes fluid that:
1. Dilutes the thick mass of sperm that make them immobile
2. Provides more than half of semen thus helps push seprm into urethra
3. Contains fructose & citric acid used as nutrient for the ejaculated sperm
4. Contain fibrinogen that helps clot semen in vagina immediately after ejaculation
5. Contains prostaglandins which help fertilization by reacting with female cervical mucus to help rapid passage of the sperm into uterus, induce reverse peristaltic contraction in the uterus & fallopian tubes to move sperm toward the ovaries.
Describe functions of prostate gland
Secretes a thin milky fluid:
1. Is slightly alkaline helps to neutralize the acidity of the fluid of vas deferens and of vaginal secretion & thus inc motility & fertility of sperm
2. Contains calcium, citrate & phosphate ions
3. Contains clotting enzymes (act on fibribogen from seminal vesicles to clot the semen in female reproductive tract during withdrawal of penis) & fibrinolysin (dissolve clot after few minutes to release sperms)
The normal volume of semen is……
Percentages is…..(sperm), ………(seminal vesicle fluid),……..(prostate)
2-4 ml per ejaculation
10%, 30%, 60%
Normal sperm count is……., while……is considered sterile.
60-100 million/ml
20 million/ml
Sperm normally live ……in female genital tract but can live for several yrs at temp…..
72 hrs
-100degC
Normally 60% of sperm are motile after …….
6 hrs
What are risks of untreated undescended testis
- Potent risk of irreversible damage of spermatogenic epithelium by high body temp
- Higher incidence of malignant tumors in undescended testes
What is the treatment of undescended tesis?
- Administer testosterone or gonadotrophic hormone which usually causes testis to desced if inguinal canal is wide enough
- Defect is corrected surgically
What are tests of male fertility?
- Analysis of semen: sperm (count, morphology, motility), fluid (volume & viscosity)
- Estimation of hormones (testosterone, FSH, LH, PRL)
Mention are the two fates of testosterone produced by cells of Leydig
- Part is secreted into blood and carroed by plasma proteins to be delivered to target organs where it has numerous effects
- Another part goes to seminiferous tubules where it is bound to ABG, important for spermatogenesis
Describe effects of testosterone during intra-uterine life
Fetal testes are stimulated by hCG to secrete testosterone imp for:
1. Musculizing reproductive tract and external genitalia
2. Promoting descent of testes into scrotum during late months of pregnancy
Describe effects of testosterone at puberty
On reproductive system:
1. Promotes growth, maturation and maintenance of male reproductive system
2. Is essential for vitality of germinal epithelium
3. Needed for maturation of spermatozoa
4. Has -ve feedback on LH and FSH
On 2ry sex chct:
1. Induced male pattern of hair growth (pubic hair is triangle with apex up)
2. Deep voice by enlargement of larynx and thickening vocal cords
3. Male body shape
4. Skin acne
5. Develops libido by direct effect on certain neuron in hypothalamus
6. Aggressive behaviour
Describe non-reproductive effects of testosterone
- Exerts a protein anabolic effect
- Enhances bone growth and closes epiphyseal plate after its conversion to estorgen
- Enhances erythropoiesis
- Inc BMR
- Causes retention of Na, Ca, H2O
Hypothalamus releases GnRH once every…….
1 to 3 hrs
In -ve feedback regulation of testosterone, Testosterone inhibits……., while inhibin inhibits…..
GnRH, LH
FSH
Describe role of testosterone in spermatogenesis
- Essential for meiosis and mitosis of germ cells
- FSH and testosterone are imp for spermiogenesis
1ry hypogonadism is also called….., while 2ry hypogonadism is also called…….
Hypergonadotrophic hypogonadism
Hypogonadotrophic hypogonadism
Describe features of a person whose testes were destroyed before age 20
- Sexual organs remain infantile
- No development of male sexual chct (female fat and pubic hair distribution, base up)
- Inc in average bone length bec epiphysis remain open
Describe features of a person whose testes were destroyed aftet age 20
- Gradual atrophy of reproductive organs
- 2ry sexual chct regress slowly but deep voice remains and pubic and axillary hair remain due to adrenocortical hormones.
- Sex drivw still present but at reduced level
- Psychological changes: irritability and depression
Mention stimuli for erection
- Physical tactule stimulation by highly sensitive touch receptors in glans penis
- Psychologic stimuliay be stimulatory or inhibitory
Erection is a….reflex its center is in….via…….
Spinal
Lumbar segments
Parasympathetic and nonadrenergic noncholinergic
Parasympathetic fibers that stimualte erection release…..
Ach and vasoactive intestinal peptide
Describe mechanism of action of nonadrenergic noncholinergic fibers
They contain NO synthase that catalyzes formation of NO that activates guanylyl cyclase reaulting in production of cGMP which is potent VD of penile arterioles. It is broken down by PDE-5
Erection is terminated by……..
Sympathetic VC impulses in penile arterioles
Describe cause and treatment of impotence
It is failure to achieve or maintain erection cause may be organic or psychic. Treated by inc NO or prevent breakdown of cGMP. Sildenafil inhibit phosphodieterase-5 prolonging erection time.
But they also inhibit PDE-6 causing loss of blue/green discrimination
Explain steps of emission
Touch receptors in glans penis stimulate center in upper lumbar segments of spinal cord send sympathetic impulses that cause contraction of smooth muscles of vas deferens, prostate and seminal vesicles resulting in movement of semen into urethta.
Explain steps of ejaculation proper
Filling of urethra with semen stimulates center in upper sacral and lowest lumbar segments sending rhythmic contractions of skeletal muscles at base penis thus inc pressure within penis and cause forceful expulsion of semen through urethra to exterior
…….is closed during male sexual act to prevent urine outflow
Internal urethral sphincter
