W8L1 Male Reproductive 2 Flashcards
What two hormones are required for initiation of male puberty? After puberty, which of these hormones may be sufficient on its own to supplement if hormone levels are too low?
LH and FSH (coming from adenohypophysis) initiate puberty
LH alone may be enough to supplement after full sexual development during puberty
What temperature should the testis be for normal function?
30-32 degrees C
Locally in the properly-functioning testis, there are high concentrations of:
(6 things, just be familiar…)
Growth factors
Inhibins
Vitamins A, B, E, D ("a bed")
E2
ICAMs
Testosterone
(acronym = “give it”)
About how many days have passed by the time spermatozoa have reached the head of the epididymis?
At what point are spermatozoa mature?
74 days, but still not mature until 2-3 weeks later (85 - 100 days total) when they arrive at the tail of the epididymis
Sperm are stored at what part of the epididymis where they wait to be released during emission/ ejaculation?
In the tail of the epididymis
What percentage of sperm is composed of sperm cells? What percentage is the product of accessory male sex gland secretions?
10% sperm cells, 90% accessory product secretions
The seminal vesicles are responsible for what percentage of semen volume? What 3 important things are produced here?
65-70% of semen volume
Produce:
- Fibrinogen (responsible for semen coagulation)
- Prostaglandins
- Fructose (fuel for sperm)
What are 2 known functions of prostaglandins in semen?
- Some immunomodulatory roles to prevent female immune system from attacking them
- induce rhythmic contractions of uterus to support uptake of semen
The prostate gland depends on what enzyme for its proliferation? What is the clinical relevance of this?
Dependent on 5 alpha reductase, which converts T to DHT
Prostate tumors can be attacked by inhibiting 5 alpha reductase
The prostate produces what percent of semen volume?
What are 2 important proteases that it contributes to semen + 2 other products mentioned in lecture?
-> 25-30% semen volume
2 proteases: PSA and Fibrinolysin
2 other products: Zinc and Acid Phosphatase
What does PSA stand for? What is the clinical relevance of PSA?
Prostate Specific Antigen.
Prostate cancer cells usually produce this enzyme and secrete it into the blood. Concentration is proportional to tumor size
What is the role of zinc in semen?
Inhibits full-blown activation of sperm cells so they are not completely activate until they meet the egg
What is the clinical significance of acid phosphatase in semen?
Physio importance not fully know, but as with PSA it is used to monitor prostate tumor growth (some prostate cancers produce this acid phosphatase more than PSA)
What percentage of semen is produced by the Bulbourethral (Cowper’s) glands?
When is this secreted?
3-5% of total seminal volume
Appears before ejaculation (pre-ejaculate), which lubricates the normal ejaculate.
May or may not contain sperm.
Normal semen, per the WHO, is more than __ mL per ejaculate, has a pH in ___ range, and consists of ____ (number) spermatozoa per mL.
> 2 mL
pH 7.2 - 8 (slightly basic)
40 million spermatozoa / mL
What percentage of normal spermatozoa after 1 hour must be motile?
> 50%
For normal semen, what percentage of spermatozoa must have a normal morphology?
> 30% (human spermatozoa are relatively poor quality and are prone to not develop correctly, have 2 heads or some other problems)
Where does the complete activation of sperm take place?
In the genital tract of females
What 3 phases describe the entire act of sex for males?
Erection
Emission (semen enters and mixes in proximal urethra)
Ejaculation
The cavernous arterioles of the penis have what two types of innervation? What are their key neurotransmitters here?
Sympathetic (NE)
Parasympathetic (NO, VIP)
In a flaccid penis, the parasympathetic tone is ____, and the sympathetic tone is ____, so the arteriovenous shunts are _____
Parasymp tone is low, sympathetic tone is high, so arteriovenous shunts are open and there is little blood flow through the penile capillaries
In an erect penis, the parasympathetic tone is ____, and the sympathetic tone is ____, so the arteriovenous shunts are _____
Parasymp tone is high, sympathetic tone is low, so arteriovenous shunts are closed and blood flows through the penile (helicine) arterioles and capillaries
Blood flowing through penile capillaries cannot create a full erection on its own, so what other mechanism is necessary?
The venules from which penile blood is drained has to be occluded so blood can be stored in the penis for longer.
This is achieved when enough blood fills the cavernous bodies that they compress the venules between them and the tunica albuginea
What is the main drive to start an erection? (in the nervous system)
What is the dominant neurotransmitter in an erection?
Locally increased parasympathetic tone that increases parasymp neurotransmitters (NO, VIP) in the cavernous bodies
NO is dominant, VIP less important (and Ach may play a role in stimulating NO too)
What are the effects of NO that lead to erection?
Diffuses easily across membrane, then stimulates cGMP, leading to PKG.
Then, calcium pump activity increases and calcium channels decrease activity. There is lower calcium concentration, causing the smooth muscle to relax and arterioles to widen.
What is the mechanism for how Viagra (Sildinafil) promotes erection?
These are phosphodiesterase inhibitors (specifically of PDE 5) which prevent breakdown of cGMP, thus allowing PKG to accumulate if the upstream mechanisms (NO, sacral parasympathetic, etc.) all functioned correctly
What are the effects of VIP that lead to an erection?
Has a Gs G-coupled protein receptor that creates cAMP, PKA, etc. that leads to intracellular calcium concentration decreased
What happens to local sympathetic tone that is necessary for erection?
Alpha1 receptor vasomotor tone is decreased, which allows for vasodilation / erection
What are 4 “contractile elements” that contribute to ejaculation? What type of innervation do they have?
Vas deferens, prostate, seminal vesicles, and inner urethral sphincter
All have smooth muscle elements with sympathetic (NE) innervation
What are the accessory glands that contribute to semen? What type of innervation do they have?
Prostate, seminal vesicles, bulbourethral glands
Have parasympathetic innervation for secretion + sympathetic for contraction during ejaculation
What are 4 muscles that have somatic motor innervation that contribute to ejaculation?
What neurotransmitter is responsible for this?
Pelvic musculature, bulbospongiosus, ischiocavernosus, and outer urinary sphincter
Acetylcholine for neurotransmission
What is the difference between the “unconditional” and “conditional” reflex, when talking about the erection - emission - ejaculation reflex?
The unconditional reflex occurs without any cortical stimuli and only stimulation of the sex organ, whereas the conditional reflex (more normal in humans) occurs as a result of integration with visual/tactile information, mood, erotic stimuli, etc.
When parasympathetic tone is active during erection, is it local or general throughout the body?
What about sympathetic stimulation during ejaculation?
Parasympathetic effect is local, don’t see bradycardia or other parasympathetic effects
The sympathetic system, however, has general effects throughout the body during ejaculation / orgasm (tachycardia, etc.). May be a problem for patients with heart conditions.
How does the body prevent ejaculate from entering the bladder during ejaculation?
Sympathetic tone causes a contraction of the inner urinary sphincter to prevent retrograde ejaculation
What muscle must relax while bulbospongiosus and ischocavernosus contract during ejaculation?
Outer urinary sphincter relaxes
At 6 weeks of human development, in place of genitalia there is the _______ that is not committed to either gender
“bipotential genital ridge”
At 6 weeks, if there is no Y chromosome, then what extracellular protein will rise in concentration? What transcription factor does that lead to, and what does it do?
No Y chromosome -> Wnt4 protein -> β-catenin (transcription factor) which inhibits Sox9 and leads to development of ovary
At 6 weeks, if there is a Y chromosome (specifically the ____ gene), then what two key male transcription factors rise in concentration? What protein do they induce?
SRY gene -> TDF (testis determining factor, aka SRY protein) and Sf1 (steroidogenic factor 1)
They induce Sox9
What are the effects of Sox9?
Inhibits β-Catenin transcription (stops female pathway)
Helps Sertoli cells differentiate, which then produce Anti-Mullerian Hormone (AMH)
Helps Leydig cells differentiate, which leads to the first peak in plasma testosterone in male life
How much more AMH do fetal males have than females?
2 orders of magnitude more (there is almost no anti-mullerian hormone in females)
AMH is produced by ______ cells and is responsible for regression and atrophy of ______ ducts, which otherwise become what structures?
Produced by Sertoli cells
Atrophies the Mullerian ducts
Otherwise would become fallopian tubes, uterus, upper vagina
Production of testosterone in fetal males is supported by what organ? What is the hormone this organ produces that supports testosterone production?
The placenta produces hCG, which supports the fetal Leydig cells to produce testosterone
Testosterone directly activates and supports the _____ ducts, so that they differentiate into which structures?
Wolffian Ducts
-> epididymis, vas deferens, and seminal vesicles
Without testosterone, the Wolffian duct regresses in females
What hormone is responsible for external male genitalia development? Where is this largely produced?
DHT; produced by prostate gland via 5 alpha reductase converting testosterone.
When is the second testosterone peak in males? What is the major effect of this peak?
Occurs in “perinatal” period, just after birth
Important effects on male development of CNS
(a nucleus in the hypothalamus, lumbosacral organization that allows for erection/ejaculation reflexes, and possibly some epigenetic programming)
What is the first hormonal change of puberty?
The zona reticularis begins to produce more DHEA at around age 10-11 (in both males and females) aka “adrenarche”
Occurs before the GnRH secretion starts!
What is “gonadarche?”
Following the start of GnRH production at puberty, LH and FSH production begins, leading to full development/activation of the gonads, secondary sex characteristics, and anabolic / growth promoting effects
What is the effect of melatonin on GnRH?
Inhibits it
What changes about GHRH (growth hormone releasing hormone) during puberty?
Its secretion is much higher than it is either before or after puberty
Secretion is highest at night, during early part of the sleep cycle
What are 4 factors that must also be “normal” in order for puberty to continue normally, because they play a permissive role?
- nutritional status
- leptin homeostasis
- T3/ T4 level
- Glucocorticoid levels
What changes about insulin secretion during puberty?
Secretion is higher in response to normal food intake, and because insulin activates IGF1 and has general anabolic effects, it helps increase growth rate.
Note: was told that erectile dysfunction and anabolic steroids would not be on quiz
Yes I’ve had enough, please stop making cards about penises
