TBL7 Male Sexual Repro Flashcards
The ______ in the testes is where all the seminiferous tubules are collected.
rete testis
Spermatozoa mature in the __________ of the testis. (numerous coiled tubules)
epididymis
Why is spermatozoa produced continually throughout a male’s reproductive life?
Not all the spermatogonia are activated together - there is always a pool of spermatogonia which remains available for subsequent spermatogenic cycles throughout life.
The initial germ cells are (haploid/diploid).
_________ then undergo the first meiotic division to produce haploid _______, which then undergo the second meiotic division to transform into spermatids.
diploid
First meiotic division: Primary spermatocytes (diploid) –> Secondary spermatocytes (haploid)
Second meiotic division: Secondary spermatocytes –> Spermatids
______ cells lie within the seminiferous tubules. It synthesises FSH and androgen receptors, and responds to FSH to produce molecules like inhibin.
Sertoli cells
- within the seminiferous tubules
- synthesise FSH and androgen receptors
- responds to FSH
- associated with spermatogenesis
_______ cells in the testis lie outside the seminiferous tubules in the interstitial spaces.
Leydig cells
- lie outside seminiferous tubules
- synthesise LH receptors
- produce testosterone in response to LH
The tubular lumen of a seminiferous tubule is full of _________.
inactive mature spermatozoa (matures towards the lumen)
Sertoli cells are surrounded by spermatogonia-containing fluid along with primary and secondary spermatocytes.
Sertoli cells are linked together by _________, in which secondary spermatocytes will push their way through.
Sertoli cells linked together by tight junctions
- secondary spermatocytes squeeze their way through to become enclosed by the Sertoli cells and undergo transformation under the influence of molecules produced by the Sertoli cells to form spermatozoa
Androgens are _____ hormones produced by 2 organs:
1.
2.
Androgens are steroid hormones.
Produced by:
1. Adrenal cortex
2. Gonads (Testis)
Precursor of androgen is
cholesterol –> pregnenolene –> progesterone —> Androstenedione
In the gonads, androstenedione is converted to testosterone, and both are converted to ________ via in males and females, which is then converted to the biologically active ________.
In males, some of the testosterone is converted to ________.
Androstenedione –> testosterone –> oestrogen –> 17B-oestradiol
testosterone –> dihydrotestosterone (more potent androgen)
Testosterone can be converted to either DHT or oestrogens like 17B-oestradiol.
What type of reaction and what enzyme?
Testosterone to DHT:
- Reduction
- By 5a-reductase
Testosterone to oestrogen:
- Aromatisation
- by enzyme aromatase
Testosterone and DHT are transported in the BLOOD via ________ protein.
Sex hormone-binding globulin (SHBG)
Albumin
Androgens in the SEMINIFEROUS fluid is bound by _______.
Androgen-binding globulin (ABG)
Importance of androgens in foetal development
- Development of male genitalia
- Stimulates foetal growth
- Male behaviour in CNSS
Importance of androgens in adults
- Spermatogenesis
- Growth and development of male genitalia
- Sexual characteristics
- PROTEIN ANABOLISM
- Behavioural CNS effects
Note: Some androgenic effects are mediated by the conversion of testosterone to oestrogen!
-
Androgens bind to (intracellular/membrane) receptors.
intracellular receptors
- forming androgen-receptor complex
- stimulates synthesis of new proteins
Hypothalamo-pituitary-gonadal axis:
Hypothalamus secretes _______.
________ pituitary gland secretes ____.
Hypothalamus: Gonadotrophin-releasing hormone (GnRH)
Anterior pituitary gland: LH and FSH
LH acts on ________ cells to produce testosterone.
FSH acts on _______ cells to initiate spermatogenesis
LH –> Leydig cells –> testosterone
FSH –> Sertoli cells to initiate spermatogenesis (produce inhibin)
The main stimulus for the penis is ______.
tactile
- due to stretch receptors along the penis which can be stimulated
Main control over penile erection is via the __________.
limbic system in the brain
- thoughts, visual stimuli can activate pathway down the spinal cord to cause penile erection
- send efferent signals down
There are 3 efferent pathways involved in penile erection.
- Parasympathetic pathway
- Somatic pathway
- Sympathetic pathway
- Parasympathetic pathway via the pelvic nerve (main) to promote erection
- Somatic pathway via the pudendal nerve to promote erection
- Sympathetic pathway via the hypogastric nerve to depress erection
Penile erection is the (relaxation/contraction) of vascular smooth muscles.
Penile erection:
- Relaxation of vascular smooth muscles
- To dilate cavernous arteries in the corpus cavernosa (to increase blood flow)
__________ is the main penile tissue surrounding the urethra and prevents it from collapsing during increased arterial pressure from penile erection.
Corpus spongiosum
__________ lies outside the corpus spongiosum and contains the blood flow to the penis.
Blood enters via the _____ artery and leaves via the ____ vein.
Corpus cavernosa
Blood enters via pudendal artery and leaves via dorsal vein.
________ is a phosphodiesterase inhibitor, preventing cGMP from being broken down.
=> maintains vasodilatation and hence penile erection
Viagra
The bulk of seminal fluid comes from the accessory sex glands -
Seminal vesicles, prostate gland, bulbourethral glands
Ejaculation is under the control of _________ nervous system, which causes the (relaxation/contraction) of smooth muscle of the vas deferens.
Ejaculation:
- Sympathetic control
- Contraction of smooth muscle of vas deferens
On ejaculation, the efferent ductules contract and the spermatozoa contained in the ejaculate is passed into the _________.
prostatic urethra
Testosterone is clinically used as a (anabolic/catabolic) steroid to increase lean body mass and muscle size and strength.
anabolic steroid (stimulates protein synthesis and bone formation)
If pituitary testicular function is absent, will administering testosterone alone restore fertility?
No. Treatment requires LH and FSH replacement to stimulate both the Leydig cells to produce testosterone and the Sertoli cells that are also involved in spermatogenesis.
Kallmann syndrome is associated with _________ and _______.
Kallmann syndrome:
- low GnRH levels
- anosmia (unable to smell)
=> Olfactory bulb cannot develop normally, so GnRH cannot migrate to the hypothalamus
In Kallmann syndrome, patients are usually (taller/shorter) than usual.
taller than normal (lack of androgens prevents epiphysis of long bones from fusing)
___________ (XXY) is a congenital primary gonadal disease that is due to an extra X chromosome, causing the testes to fail to produce androgens.
Klinefelter syndrome
In patients with __________ deficiency, testosterone cannot be converted to the more potent DHT androgen, so there are no effects on Sertoli cells to cause spermatogenesis.
5a-reductase deficiency
congenital primary gonadal disease
Testicular torsion refers to the rotating of the testis which twists the __________ that brings blood to the scrotum, resulting in reduced blood flow.
Testicular torsion: Rotating of the testis which twists the spermatic cord
=> reduced blood flow
High _______ levels are associated with the inhibition of the hypothalamo-pituitary-gonadal axis, causing low LH and FSH.
Prolactin (inhibits GnRH release from the hypothalamus)
Clinical features of hypogonadism:
- Loss of libido
- Impotence
- Small testes (lack of stimulation)
- Decreased muscle bulk
- Osteoporosis
For patients with hyperprolactinaemia which causes hypogonadism, ________ can be used to block the production of prolactin from the tumour.
dopamine agonists like bromocriptine or cabergoline
=> dopamine inhibits prolactin secretion
When men age, they develop an enlarged prostate that can give rise to lower urinary tract symptoms (LUTS) and bladder outflow obstruction. This condition is known as __________.
Benign Prostatic Hyperplasia (BPH)
- Due to the increase in the number of cells, not the size of cells
How does an enlarged prostate (in BPH) lead to LUTS and bladder outflow obstruction?
When the prostate enlarges, it compresses the urethra => Bladder needs to work harder to pump urine out => Detrusor muscle hypertrophy
BPH most commonly occurs in ________ zone of the prostate.
transition zone
- surrounds part of the urethra
LUTS may be divided into ______ and ______ symptoms.
LUTS:
- Voiding symptoms (Obstruction to urine flow)
- Slow urinary flow
- Straining
- Terminal dribbling
- Incomplete emptying - Storage symptoms (Abnormal bladder function)
- Urinary urgency
- Nocturia
- Incontinence
PSA is a _______ protein secreted by ________ cells of the prostate into the lumen of the duct, used to find prostate cancer and BPH.
PSA:
- Kallikrein protein
- Secreted by epithelial cells of the prostate
- Into the lumen of the duct (Discharged into the urethra)
Under normal circumstances, PSA (will/will not) be detected by the blood as it is prevented by the ________ of the prostate from leaving the cells by any other route.
PSA:
- will not be detected in the blood under normal circumstances
- protected by the basal lamina from leaving
=> Prostate damage can result in PSA leakage into the bloodstream measured by serum immunoassay
The pharmacotherapy for bladder obstruction (2 types of drugs):
- 5a-reductase inhibitors
- prevent conversion of testosterone to DHT
=> size reduction of prostate gland - a1-adrenoreceptor antagonists
- leads to smooth muscle relaxation at the bladder neck and prostate
=> symptomatic relief (not treating cause)
The surgical relief of bladder obstruction is _______.
Transurethral resection of the prostate (TURP)
- Hot wire loop allows for resection of enlarged prostate tissue, creating a cavity
Any bleeding in TURP is stopped with _______.
diathermy
Men tend to be ________ after TURP, so it is usually carried out for older men who have finished with family planning.
infertile (Cut out prostate)
Most malignant neoplasms of the prostate gland are _________, arising in the _______ zones.
Most malignant neoplasms of the prostate gland are adenocarcinomas (glandular in origin), arising in the peripheral zones.
Histological diagnosis for prostate cancer is made with a _________.
transrectal ultrasound-guided prostate biopsy (TRUS)
The tumour (prostate cancer) can be graded using 2 systems.
TNM system
Gleason grading system (histological system based on gland architecture and degree of differentiation)
Advanced prostatic cancer shows features of __________ or __________.
Advanced prostatic cancer:
- Extraprostatic extension
- Seminal vesicle invasion
- Lymph node involvement
- Metastatic prostate cancers
Since prostate growth is androgen-dependent, the principle of management for advanced prostate cancer is to treat palliatively with ____________ therapy.
androgen deprivation therapy
Androgen deprivation therapy involves the use of _______ analogues.
LHRH analogues
(e. g. goserelin)
- causes overstimulation of pituitary gland and overproduction of testosterone, which reduces LHRH via negative feedback
Kidneys arise from the ____________.
intermediate mesoderm
Development of the kidneys passes through 3 phases
- Pronephros (cervical region)
- Mesonephros (thoracolumbar region)
- Metanephros (sacral region)
The mesonephros (during kidney development) gives rise to the _______ duct.
Mesonephric duct/Wolffian duct
- gives rise to reproductive tract and ureters in males
- ureters in females
The caudal tip of the mesonephric duct gives rise to the __________.
ureteric bud
The Y chromosome contains the ____ gene. Protein product of this gene is the _______, which is a transcription factor initiating a cascade of downstream genes to determine the fate of rudimentary sexual organs.
SRY gene
Protein product: testis-determining factor
(presence of TDF - male development; absence of TDF - female development)
Early in development, the embryo has the full complement of tissues and tubes to develop as a male or female.
The ______ duct gives rise to male reproductive tract.
The ______ duct gives rise to female reproductive tract.
Wolffian duct/mesonephric duct - male reproductive tract
Mullerian/paramesonephric duct - female reproductive tract
Set of tubes that remain depends on whether the gonads turn into testes or ovaries
The __________ is the precursor to gonads and is triggered to differentiate into testis or ovary on the signal __________ from the yolk sac.
genital ridge (precursor to gonads)
triggered to differentiate on signal from germ cell migration from yolk sac
In males, the SRY gene activates the _____ transcription factor, which upregulates the expression of MIS, FGF9 and SF1 to stimulate the differentiation of ______ and ______ cells.
SRY gene => SOX9 transcription factor
=> Sertoli and Leydig cells
________ produced by Sertoli cells causes the regression of the Mullerian ducts.
MIS (AMH)
________ produced by the Leydig cells mediate virilisation of mesonephric ducts to form male genital ducts.
Testosterone
Except for the __________ and _________, the Wolffian ducts persist to form the main genital ducts.
utriculus prostaticus and appendix epididymus
- arise from the remnant of the regressed Mullerian ducts
The __________ attaches the testis and mesonephros to the posterior abdominal wall.
urogenital mesentery
