Y2S2 P1 Male Reproductive Physiology
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Questions and Answers

What is the primary function of the Sertoli cells in the testes?

  • Inhibin B secretion
  • Spermatogenesis (correct)
  • Hormone production
  • Testosterone conversion

    • Which hormone is responsible for stimulating Leydig cells to produce testosterone?

  • LH (correct)
  • FSH
  • GnRH
  • Inhibin B

    • What is the consequence of primary testicular failure?

  • Decreased FSH, increased inhibin
  • Normal hormone levels
  • Increased FSH and LH, decreased testosterone (correct)
  • Increased testosterone, decreased FSH

    • What happens during the amplification pathway of androgen production?

    <p>Conversion to dihydrotestosterone</p> Signup and view all the answers

    Which hormone has a feedback mechanism to inhibit LH production?

    <p>Testosterone</p> Signup and view all the answers

    During male puberty, which of the following is a direct result of testosterone action?

    <p>Muscle growth</p> Signup and view all the answers

    Which of the following is NOT a characteristic of the male androgen production pathway?

    <p>Increased levels of estrogen</p> Signup and view all the answers

    What is the most significant factor contributing to the decline of testosterone levels in men from ages 30 to 70?

    <p>Obesity and chronic disease</p> Signup and view all the answers

    What is the primary hormonal stimulus for testosterone production in the testes?

    <p>LH</p> Signup and view all the answers

    During male puberty, which process is driven by rising testosterone levels?

    <p>Development of secondary sexual characteristics</p> Signup and view all the answers

    What is the role of Sertoli cells in testicular function?

    <p>Support and nourishment of developing sperm</p> Signup and view all the answers

    What is the end product when testosterone undergoes the diversification pathway?

    <p>Estradiol</p> Signup and view all the answers

    Which statement best describes 1˚ testicular failure?

    <p>Increased levels of FSH and LH with decreased testosterone</p> Signup and view all the answers

    Which hormone is primarily responsible for the negative feedback to inhibit FSH production?

    <p>Inhibin B</p> Signup and view all the answers

    What effect does chronic disease have on testosterone levels in men as they age?

    <p>It contributes to a gradual decline</p> Signup and view all the answers

    What is the main outcome of the hepatic oxidation/conjugation of testosterone?

    <p>Renal excretion</p> Signup and view all the answers

    What is one of the roles of Testosterone besides spermatogenesis?

    <p>Promotes virilisation</p> Signup and view all the answers

    Which statement accurately describes spermatogenesis's hormonal dependence?

    <p>Testosterone is necessary for FSH to promote spermatogenesis.</p> Signup and view all the answers

    What is the consequence of decreased testosterone production due to chronic disease?

    <p>Reduced spermatogenesis</p> Signup and view all the answers

    At what age range is a typical decline in serum testosterone observed?

    <p>30 to 70 years</p> Signup and view all the answers

    Which pathway involves the conversion of testosterone into estradiol?

    <p>Diversification pathway</p> Signup and view all the answers

    What condition is characterized by decreased levels of all hormones involved in testicular function?

    <p>2˚ testicular failure</p> Signup and view all the answers

    What is a key factor that contributes to testosterone's negative feedback on LH?

    <p>Leydig cell testosterone production</p> Signup and view all the answers

    What role does 5-alpha reductase play in testosterone metabolism?

    <p>Converts testosterone into DHT</p> Signup and view all the answers

    What role does inhibin B have in hormonal control of testicular function?

    <p>Provides negative feedback on FSH production</p> Signup and view all the answers

    Which statement best describes the function of the 5-alpha reductase enzyme in androgen metabolism?

    <p>Converts testosterone to dihydrotestosterone for virilisation</p> Signup and view all the answers

    Which factor is least associated with the decline of testosterone in men between the ages of 30 and 70?

    <p>Increased FSH levels</p> Signup and view all the answers

    What effect does the amplification pathway have on testosterone when it interacts with the prostate?

    <p>Stimulates the production of dihydrotestosterone for hair growth</p> Signup and view all the answers

    Which of the following pathways does not directly lead to a physiological action of testosterone?

    <p>Inactivation pathway</p> Signup and view all the answers

    In primary testicular failure, which hormonal levels are expected?

    <p>Low testosterone, high FSH and LH</p> Signup and view all the answers

    Which hormone plays a role similar to testosterone in stimulating spermatogenesis?

    <p>FSH</p> Signup and view all the answers

    During male puberty, which sequence correctly represents the initiation of testosterone production?

    <p>Pulsatile GnRH, leading to LH secretion</p> Signup and view all the answers

    What is the first step in the onset of male puberty?

    <p>Pulsatile GnRH from the hypothalamus</p> Signup and view all the answers

    Which metabolite of testosterone is primarily associated with bone growth?

    <p>Estradiol</p> Signup and view all the answers

    Which of the following directly results from the action of dihydrotestosterone during puberty?

    <p>Development of body hair</p> Signup and view all the answers

    What physiological change is primarily driven by rising LH levels during male puberty?

    <p>Leydig cell stimulation to secrete testosterone</p> Signup and view all the answers

    What characteristic is NOT typically associated with normal testicular volume during puberty?

    <p>Stabilization of estradiol levels</p> Signup and view all the answers

    What is the primary process that transforms spermatids into spermatozoa during spermiogenesis?

    <p>Nuclear compaction and cytoplasm discarding</p> Signup and view all the answers

    Which of the following structures primarily contributes to the alkaline fluid found in semen?

    <p>Seminal vesicles</p> Signup and view all the answers

    What mechanism initiates an erection in the male reproductive system?

    <p>Relaxation of cavernosal smooth muscle</p> Signup and view all the answers

    Which part of the male reproductive system is responsible for the storage and maturation of sperm?

    <p>Epididymis</p> Signup and view all the answers

    How do Leydig cells contribute to male reproductive physiology?

    <p>They secrete testosterone</p> Signup and view all the answers

    What role does phosphodiesterase type 5 (PDE5) play in the physiology of erection?

    <p>It breaks down cGMP, limiting relaxation of smooth muscle</p> Signup and view all the answers

    Which of the following components is NOT typically produced by the prostate gland?

    <p>Fructose</p> Signup and view all the answers

    What triggers the ejaculation process in the male reproductive system?

    <p>Sympathetic nervous system stimulation</p> Signup and view all the answers

    Study Notes

    Testes Function

    • Two main functions:
      • Androgen (testosterone) production: Primarily by Leydig cells.
      • Spermatogenesis: Production of sperm, facilitated by Sertoli cells.

    Hormonal Control of Testicular Function

    • Hypothalamus: Secretes GnRH (gonadotropin-releasing hormone) which stimulates the anterior pituitary.
    • Anterior Pituitary:
      • FSH (follicle-stimulating hormone): Acts on Sertoli cells, promoting spermatogenesis (in the presence of testosterone) and producing inhibin B. Inhibin B provides negative feedback on FSH production.
      • LH (luteinizing hormone): Stimulates Leydig cells to produce testosterone which provides negative feedback on LH production.

    Androgen Production

    • Occurs in Leydig cells in the interstitium of the testes.
    • Triggered by LH.
    • Leads to:
      • Male puberty and virilisation (development of male characteristics).
      • Spermatogenesis (indirectly, through stimulation of Sertoli cells).

    Androgen Pathways

    • Direct pathway: Testosterone directly exerts its effects on muscle and contributes to virilisation.
    • Amplification pathway: Testosterone converted to dihydrotestosterone (DHT) by 5-alpha reductase. DHT is active in the prostate, skin, and contributes to pubic hair growth and sebum production.
    • Diversification pathway: Testosterone converted to estradiol by aromatase. Estradiol plays a role in bone maturation and epiphyseal closure.
    • Inactivation pathway: Testosterone is metabolized and eliminated through hepatic oxidation/conjugation and renal excretion.

    Male Puberty

    • Onset: Triggered by pulsatile GnRH release from the hypothalamus.
    • Progression:
      • Rising LH levels lead to testosterone production by Leydig cells, causing virilisation.
      • Testosterone is converted into metabolites: estradiol (for bone development) and dihydrotestosterone (for hair growth and acne).

    Testicular Volume

    • Normal testicular volume is not specified in the text.

    Additional Notes

    • There is no equivalent of menopause in men, although there is a gradual decline in serum testosterone (approximately 30% between 30-70 years old).
    • This decline is often associated with obesity and chronic diseases.

    Testes Function

    • Two main functions:
      • Androgen (testosterone) production
      • Spermatogenesis

    Hormonal Control of Testicular Function

    • Hypothalamus secretes GnRH
    • Anterior pituitary:
      • FSH → Sertoli cells:
        • Stimulates spermatogenesis (only when testosterone is present)
        • Inhibin B - negative feedback on FSH
      • LH → Leydig cells:
      • Stimulates testosterone production, which has negative feedback on LH
    • Testosterone plays a key role in spermatogenesis and somatic effects
    • TSH, LH, FSH, and HCG are structurally similar, resulting in similar effects

    Testicular Failure

    • Characterized by primary (1°) or secondary (2°) testicular failure
    • Primary: Failure at the testes, resulting in:
      • Increased FSH and LH
      • Decreased testosterone and inhibin
    • Secondary: Failure at the pituitary or hypothalamus, leading to:
      • Decreased levels of all hormones

    Androgen Production

    • Produced by Leydig cells in the interstitium in response to LH
    • Leads to:
      • Male puberty and virilisation (development of male characteristics)
      • Spermatogenesis (stimulated by Sertoli cells)

    Androgen Pathways

    • Direct Pathway: Testosterone acts directly, targeting muscles and causing virilisation
    • Amplification Pathway (5-10%): Testosterone converted to DHT via 5-alpha reductase, targeting the prostate and skin (androgen receptor)
      • Leads to pubic hair growth, sebum secretion
    • Diversification Pathway (0.1%): Testosterone converted to estradiol via aromatase, targeting the brain and bone (estrogen receptor)
      • Leads to bone maturation and epiphyseal closure
    • Inactivation Pathway: Testosterone is inactivated by hepatic oxidation/conjugation and renal excretion

    Male Puberty

    • Onset:
      • Pulsatile GnRH release from the hypothalamus
      • Rising LH levels stimulate Leydig cells to secrete testosterone, causing virilisation
    • Tanner Staging: Used to assess puberty progression
    • Testosterone metabolites:
      • Estradiol impacts bone development
      • Dihydrotestosterone influences hair growth and acne

    Testicular Volume

    • Normal volume should be [insert volume]
    • No Male Menopause: Serum testosterone naturally declines ~30% between ages 30-70
      • Often influenced by obesity and chronic diseases

    Testes Function

    • Two main functions: androgen (testosterone) production and spermatogenesis
    • Androgen production occurs in Leydig cells, stimulated by luteinizing hormone (LH)
    • Spermatogenesis occurs in Sertoli cells, stimulated by follicle-stimulating hormone (FSH) and testosterone

    Hormonal Control of Testicular Function

    • Hypothalamus: secretes gonadotropin-releasing hormone (GnRH)
    • Anterior pituitary: releases FSH and LH
      • FSH stimulates Sertoli cells, which are vital for spermatogenesis and also produce inhibin B, which inhibits FSH
      • LH stimulates Leydig cells to produce testosterone, which inhibits LH
    • Testosterone: responsible for both spermatogenesis and somatic effects (e.g., male secondary sexual characteristics)
    • TSH, LH, FSH and HCG: these hormones share structural similarities and have similar effects

    Diseases of the Testicular System

    • Characterized by primary or secondary testicular failure:
      • Primary: dysfunction at the testes level
        • Increased FSH and LH
        • Decreased testosterone and inhibin
      • Secondary: dysfunction at pituitary or hypothalamus level
        • Decreased levels of all hormones

    Androgen Production

    • Leydig cells: located in the interstitium of the testes
    • LH stimulation: triggers androgen production
    • Testosterone: key androgen responsible for:
      • Male puberty and virilisation
      • Supporting spermatogenesis (through Sertoli cells)

    Testosterone Pathways

    • Direct pathway: testosterone acting directly as a hormone (targets muscles, virilisation)
    • Amplification pathway: testosterone converted to dihydrotestosterone (DHT) via 5-alpha reductase (targets prostate, skin, responsible for pubic hair, sebum secretion)
    • Diversification pathway: testosterone converted to estradiol via aromatase (targets brain, bone, responsible for bone maturation, epiphyseal closure)
    • Inactivation pathway: testosterone is metabolized and excreted via hepatic oxidation/conjugation and renal excretion

    Male Puberty

    • Onset:
      • Pulsatile GnRH secretion from hypothalamus
      • Rising LH levels stimulate Leydig cells to secrete testosterone, leading to virilisation
      • Testosterone metabolites:
        • Estradiol: responsible for bone growth
        • Dihydrotestosterone: responsible for hair growth and acne
    • Tanner Staging: used to assess the progression of puberty

    Testicular Volume

    • Normal testicular volume: is important for assessing testicular function and overall male health

    Notes

    • No male menopause, but there's a decrease in serum testosterone levels (around 30%) between ages 30-70
      • This is due to factors like obesity and chronic diseases

    Testes Function

    • The testes serve two main functions: androgen production (primarily testosterone) and spermatogenesis (sperm production).

    Hormonal Control of Testicular Function

    • Hypothalamus: Releases gonadotropin-releasing hormone (GnRH).
    • Anterior Pituitary:
      • Follicle-stimulating hormone (FSH): Targets Sertoli cells, promoting spermatogenesis in the presence of testosterone. Sertoli cells also produce inhibin B, which provides negative feedback on FSH production.
      • Luteinizing hormone (LH): Targets Leydig cells, stimulating testosterone production. Testosterone provides negative feedback on LH production.
    • Testosterone: Plays a crucial role in both spermatogenesis and the development of male secondary sexual characteristics.
    • TSH, LH, FSH, and HCG: Share structural similarities and therefore have similar effects.

    Testicular Failure

    • Primary testicular failure: Occurs at the level of the testes. Characterized by increased FSH and LH, but decreased testosterone and inhibin.
    • Secondary testicular failure: Occurs at the level of the pituitary or hypothalamus. Characterized by decreased levels of all hormones.

    Androgen Production

    • Androgens, primarily testosterone, are produced by Leydig cells within the testicular interstitium in response to LH.
    • Testosterone plays a crucial role in:
      • Male puberty and virilisation (development of male secondary sexual characteristics).
      • Spermatogenesis (through its interaction with Sertoli cells).

    Testosterone Pathways

    • Direct pathway: Testosterone acts directly on its target tissues, such as muscle, to promote virilisation.
    • Amplification pathway: About 5-10% of testosterone is converted into dihydrotestosterone (DHT) by 5-alpha reductase. DHT is responsible for the development of the prostate, skin characteristics like pubic hair, and sebum secretion.
    • Diversification pathway: A small percentage (0.1%) of testosterone is converted into estradiol by aromatase. Estradiol is involved in brain development and bone maturation, as well as the closure of the epiphyseal plates.
    • Inactivation pathway: Testosterone is inactivated through hepatic oxidation and conjugation, followed by renal excretion.

    Male Puberty

    • Onset of puberty: Marked by pulsatile GnRH release from the hypothalamus, leading to rising LH levels. This, in turn, stimulates Leydig cells to produce testosterone, initiating virilisation.
    • Tanner Stages: Stages that describe the typical progression of male puberty.
    • Testosterone Metabolites:
      • Estradiol: Influences bone development.
      • Dihydrotestosterone (DHT): Plays a role in hair growth and the development of acne.

    Testicular Volume

    • Normal testicular volume: Should be assessed and compared to appropriate reference ranges.
    • Hypoplasia: Small testes may indicate insufficient testosterone production.

    Male Menopause

    • Unlike female menopause, there is no defined "male menopause." However, serum testosterone levels gradually decline by approximately 30% between the ages of 30 and 70.
    • This decline is often associated with factors like obesity and chronic disease.

    Male Puberty Onset

    • Male puberty begins with the hypothalamus releasing GnRH (gonadotropin-releasing hormone) in a pulsatile pattern.
    • The increase in GnRH leads to a surge in LH (luteinizing hormone), which stimulates Leydig cells in the testes to produce testosterone.
    • Rising testosterone levels trigger virilization, the development of male secondary sex characteristics.
    • Testosterone is converted into two important metabolites:
      • Estradiol, which plays a role in bone growth and development.
      • Dihydrotestosterone, which influences hair growth and contributes to acne development.

    Testicular Volume

    • Testicular volume is a key indicator of pubertal development.
    • Normal testicular volume varies depending on age and stage of puberty.

    Spermatogenesis

    • Final step of spermatogenesis is spermiogenesis
    • Spermiogenesis involves:
      • Nuclear compaction
      • Cytoplasm largely discarded
      • Tail develops from a pair of centrioles near the nucleus
      • Acrosome develops from the Golgi apparatus
    • Spermatogenesis occurs in a helical pattern within seminiferous tubules
    • Cross sections of seminiferous tubules will show different stages of spermatogenesis

    Spermatogenesis Histology

    • Spermatogonium: found between the basal lamina and Sertoli cells
    • Primary spermatocytes: found between Sertoli cells and the lumen
    • Spermatids: have a round shape
    • Leydig cells are located outside the seminiferous tubule
    • Sertoli cells have a triangular nucleus

    Ejaculation

    • Typical semen volume: 2 mL with pH 8
    • Semen pathway:
      • Seminiferous tubules
      • Rete testes
      • Efferent tubules
      • Epididymis (head, body, tail)
      • Vas deferens
      • Ejaculatory duct
      • Prostatic urethra
    • Semen composition:
      • 5% sperm
      • 60% seminal vesicle fluid
      • 30% prostatic fluid
      • 5% bulbourethral gland fluid

    Semen Composition

    • Epididymis: storage, sperm gain motility and ability to fertilise
    • Seminal Vesicles:
      • contribute 60% of semen volume
      • secrete alkaline fluid, fructose, prostaglandins, and clotting factors
    • Prostate:
      • contributes 30% of semen volume
      • secretes citric acid, seminal plasmin (to combat UTIs), prostate-specific antigen (liquifies semen), proteolytic enzymes (break down clotting factors)
    • Bulbourethral glands:
      • contribute 5% of semen volume
      • secrete mucus for lubrication and alkalinity

    Erection

    • Erection is driven by various brain regions:
      • Visual: occipital lobe
      • Tactile: thalamus
      • Olfactory: rhiencephalon
      • Imaginative: limbic system
    • Erection pathway:
      • Relaxation of cavernosal smooth muscle due to:
        • Release of nitric oxide (NO) via cavernous nerves (autonomic)
        • Guanylyl cyclase activity
        • Increased cyclic guanosine monophosphate (cGMP) levels, leading to a decrease in intracellular calcium and potassium efflux
      • Increased blood inflow into lacunar space due to:
        • Dilated cavernosal artery by pelvic splanchnic nerve activation
        • Restricted outflow: elongation of subtunical vein
      • Expansion of lacunar space and compression of the subtunical space as blood pressure increases inside the tissue
    • Viagra is a phosphodiesterase type 5 (PDE5) inhibitor, which prevents the breakdown of cGMP, allowing for sustained smooth muscle relaxation

    Innervation of Erection and Ejaculation

    • Point and Shoot
      • Parasympathetic nervous system (PNS) = erection
        • S2-4 via pelvic splanchnic nerves
      • Sympathetic nervous system (SNS) = ejaculation
        • Sacral splanchnic nerves from T12-L2
    • Sensation
      • Dorsal penile nerve to S2-4

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