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