L8. Physiology Male Reproductive System
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Questions and Answers

What distinguishes the β subunits of LH and FSH?

  • They influence the secretion of inhibin.
  • They determine the overall structure of the proteins.
  • They determine receptor-binding specificity. (correct)
  • They regulate testosterone production.

How does hCG function in men with hypogonadotropic hypogonadism?

  • It blocks the secretion of GnRH.
  • It directly causes sperm maturation.
  • It acts like LH to upregulate testosterone production. (correct)
  • It inhibits testosterone production.

What is the primary function of Sertoli cells in the male reproductive system?

  • They transport sperm through the ducts.
  • They produce inhibin, inhibiting FSH secretion. (correct)
  • They produce fructose in semen.
  • They mature sperm within the epididymis.

What is the approximate contribution of the prostate gland to the total volume of semen?

<p>20% (C)</p> Signup and view all the answers

What is the average sperm concentration in semen?

<p>100 million/ml (D)</p> Signup and view all the answers

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

<p>Support and nurture developing sperm cells (A)</p> Signup and view all the answers

Which of the following structures is primarily responsible for sperm maturation?

<p>Epididymis (A)</p> Signup and view all the answers

What is the primary purpose of the accessory glands in the male reproductive system?

<p>Contribute nutrients and buffers to semen (B)</p> Signup and view all the answers

What role do Leydig cells play in the testes?

<p>Producing testosterone (B)</p> Signup and view all the answers

The process of spermatogenesis results in the formation of what type of cells?

<p>Haploid sperm cells (A)</p> Signup and view all the answers

Which hormone is primarily synthesized in the testes and plays a vital role in male characteristics?

<p>Testosterone (C)</p> Signup and view all the answers

Which structure carries sperm from the epididymis to the ejaculatory duct?

<p>Ductus deferens (D)</p> Signup and view all the answers

What is the primary regulatory mechanism controlling male reproductive hormones?

<p>Hypothalamic-Pituitary-Gonadal Axis (C)</p> Signup and view all the answers

What is the first step in the synthesis of testosterone?

<p>Conversion of cholesterol to pregnenolone (C)</p> Signup and view all the answers

Which enzyme is responsible for converting testosterone to dihydrotestosterone?

<p>5-alpha reductase (D)</p> Signup and view all the answers

What is the primary location of aromatase in the body?

<p>Brain and adipose tissue (C)</p> Signup and view all the answers

How is most of the circulating testosterone in a young adult male transported in the blood?

<p>Bound to sex hormone binding globulin and albumin (D)</p> Signup and view all the answers

Which statement accurately describes the action of androgens in the male body?

<p>They interact with specific intracellular receptors. (B)</p> Signup and view all the answers

What role does LH play in the function of Leydig cells?

<p>Maintaining the Leydig cells themselves (B)</p> Signup and view all the answers

Which of the following hormones is a more potent androgen than testosterone?

<p>Dihydrotestosterone (A)</p> Signup and view all the answers

What is the daily secretion level of testosterone in a young adult male?

<p>7 mg (B)</p> Signup and view all the answers

What is the primary location of the testes?

<p>In the scrotal sac outside the body cavity (D)</p> Signup and view all the answers

What type of cells line the seminiferous tubules and nurture developing sperm?

<p>Sertoli cells (B)</p> Signup and view all the answers

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

<p>Synthesize and secrete testosterone (B)</p> Signup and view all the answers

Which hormone is necessary for maintaining spermatogenesis in Sertoli cells?

<p>Follicle stimulating hormone (FSH) (D)</p> Signup and view all the answers

What crucial role does the blood/testis barrier serve?

<p>Protects developing gametes from harmful substances (C)</p> Signup and view all the answers

What is the role of androgen-binding protein (ABP) secreted by Sertoli cells?

<p>Maintaining high concentrations of androgens in the tubules (A)</p> Signup and view all the answers

Why are the testes maintained at a temperature 2°C below basal body temperature?

<p>To ensure proper spermatogenesis (C)</p> Signup and view all the answers

Which hormone stimulates the production of testosterone by Leydig cells?

<p>Luteinizing hormone (LH) (D)</p> Signup and view all the answers

What is the primary role of androgens in male reproductive function?

<p>They promote growth and differentiation of reproductive accessory organs. (B)</p> Signup and view all the answers

Which hormone is crucial for the regulation of testosterone production by Leydig cells?

<p>LH (D)</p> Signup and view all the answers

What happens to the secretory epithelia of the seminal vesicles and prostate in the absence of androgens?

<p>They atrophy. (A)</p> Signup and view all the answers

What physiological changes do androgens stimulate during puberty?

<p>Increased secretion of sebaceous glands and vocal cord thickening. (C)</p> Signup and view all the answers

What is the effect of androgens on hair growth?

<p>They stimulate growth of body hair and cause hair recession at the temples. (B)</p> Signup and view all the answers

How often is Gonadotropin Releasing Hormone (GnRH) released into the portal circulation?

<p>Once an hour to once every 3 hours. (B)</p> Signup and view all the answers

Which hormone works in concert with testosterone to stimulate Sertoli cells?

<p>FSH (B)</p> Signup and view all the answers

What is one consequence of athletes using androgens to improve performance?

<p>Hypothalamic feedback leading to reduced testicular size. (C)</p> Signup and view all the answers

Flashcards

Testes

The primary male reproductive organ responsible for producing sperm and testosterone.

Spermatogenesis

The process of developing sperm cells from diploid germ cells into haploid sperm cells, each with 23 chromosomes.

Sertoli Cells

Specialized cells in the testes that nurture developing sperm cells and produce proteins necessary for their maturation.

Leydig Cells

Cells in the testes responsible for producing testosterone.

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Testosterone

The primary male sex hormone responsible for development and maintenance of male sexual characteristics.

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Epididymis

A coiled tube located on the posterior surface of each testis, where sperm cells mature and are stored.

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Ductus deferens

A muscular tube that connects the epididymis to the ejaculatory duct and is involved in sperm transport.

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Accessory Glands

Glands that contribute fluids to semen, including the seminal vesicles, prostate gland, and bulbourethral (Cowper's) glands.

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Blood-Testis Barrier

A barrier formed by tight junctions between Sertoli cells in the seminiferous tubules, preventing harmful substances from reaching developing sperm cells.

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Androgen-Binding Protein (ABP)

A protein secreted by Sertoli cells that binds to testosterone, keeping its concentration high within the seminiferous tubules and ducts.

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Luteinizing Hormone (LH)

A hormone produced by the pituitary gland, essential for stimulating Leydig cells to produce testosterone.

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Follicle-Stimulating Hormone (FSH)

A hormone produced by the pituitary gland, essential for initiating and maintaining spermatogenesis.

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Sperm Transport

The movement of sperm cells through the seminiferous tubules and epididymis, facilitated by fluid secretion and muscle contractions.

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What are the two key steps in testosterone synthesis?

Conversion of cholesterol to pregnenolone and side chain cleavage at C-17 are crucial steps in its synthesis.

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How is dihydrotestosterone (DHT) produced?

A potent androgen, dihydrotestosterone (DHT) is formed from testosterone through the action of 5-alpha reductase enzyme.

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What enzyme converts testosterone into estrogen?

The aromatase enzyme converts testosterone into 17-beta estradiol (E2), a type of estrogen, in tissues like the brain, adipose tissue, and breast.

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Where is testosterone primarily synthesized?

Leydig cells, located within the testes, are responsible for testosterone synthesis.

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What is the role of LH in testosterone production?

LH (Luteinizing Hormone) is vital for both testosterone secretion and the maintenance of Leydig cells themselves.

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How does testosterone exert its effects?

Testosterone acts by binding to a specific androgen receptor, leading to changes in transcription and protein production.

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Why is DHT considered more potent than testosterone?

DHT binds more tightly to the androgen receptor than testosterone, explaining why DHT is more potent.

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What are some of the actions of testosterone in the male body?

Testosterone's action on the male reproductive system includes promoting sperm production, maintaining secondary sexual characteristics, and contributing to muscle growth.

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Hypothalamic-Pituitary-Gonadal Axis

A group of hormones that regulate the production and release of testosterone, FSH, and LH.

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Gonadotropin Releasing Hormone (GnRH)

A hormone released by the hypothalamus that stimulates the pituitary gland to release LH and FSH.

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Testosterone and FSH Interaction

Testosterone and FSH work together to stimulate Sertoli cells.

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Pulsatile Release of LH and FSH

The release of LH and FSH from the pituitary gland occurs in bursts, not a steady stream.

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What is the HPG axis?

The Hypothalamic-Pituitary-Gonadal (HPG) axis is a complex feedback loop that regulates male reproductive function. It involves the hypothalamus, pituitary gland, and testes, with hormones like GnRH, LH, and FSH playing key roles in the process.

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What is testosterone's role?

Testosterone, the primary male sex hormone, is produced by Leydig cells in the testes. It plays a crucial role in male development, maintaining secondary sexual characteristics, and promoting sperm production.

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What does inhibin do?

Inhibin is a hormone produced by Sertoli cells within the testes. Its primary function is to inhibit the release of FSH (follicle-stimulating hormone) from the pituitary gland, thereby regulating sperm production.

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What happens in the epididymis?

The epididymis is a coiled tube located on the posterior surface of each testis. It plays a crucial role in sperm maturation. During their passage through the epididymis, sperm acquire the ability to move and fertilize an egg.

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What is semen composed of?

Semen is the fluid that is ejaculated during sexual intercourse. It contains sperm cells along with secretions from the accessory glands. The seminal vesicles, prostate gland, and bulbourethral glands each contribute fluids that nourish and protect sperm.

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Study Notes

Male Reproductive System Physiology

  • Learning Objectives: Summarize functions related to gamete production and sperm transport, describe testis physiology (Sertoli and Leydig cells, hormone synthesis and action), explain duct and accessory gland function, and discuss clinical problems.

Overview of Male Reproductive System

  • The male reproductive system's purpose is sexual reproduction. This includes sperm production and delivery to the female reproductive tract.

Physiology of the Testes

  • Sertoli Cells: Nourish and support developing sperm. They also form the blood-testis barrier maintaining a specialized environment.
  • Leydig Cells: Produce testosterone (T), the main male sex hormone.
  • Endocrine Role: Testes play a crucial endocrine role, producing hormones that regulate development and function.
  • Testosterone Synthesis: Cholesterol is converted to pregnenolone, then to testosterone. This process is a key step.
  • Actions of Androgens: Testosterone affects various bodily functions, including development of male characteristics (muscle mass, bone density, secondary sex characteristics), libido, and spermatogenesis.
  • Hypothalamic-Pituitary-Gonadal (HPG) Axis: This axis regulates testosterone production and is a critical feedback loop. LH, FSH, and testosterone interact in this complex process.

Functions of Ducts & Accessory Glands

  • Ducts: Epididymis for sperm maturation, ductus deferens for sperm transport and storage, ejaculatory ducts, and urethra, which are involved in overall transport of sperm and fluids.
  • Accessory Glands: Seminal vesicles, prostate, and bulbourethral glands produce fluids that nourish and protect sperm, forming semen. These secretions are crucial for sperm viability and motility, and the volume of semen.

Male Reproductive Pathophysiology

  • Androgen insensitivity syndrome (AIS): Genetic condition where the body does not respond to androgens, often presenting as female phenotype.
  • Hypogonadism: Impaired testicular function, which can be primary or secondary. This may cause low testosterone levels.
  • Aromatase deficiency: A condition where the conversion of testosterone to estrogen is compromised, affecting bone development, fertility and other metabolic processes.
  • Other mutations and diseases: Mutations of genes associated with the male reproductive system can lead to various conditions. Other diseases like pituitary tumors can also impact hormone production.

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Description

Explore the fascinating functions of the male reproductive system, focusing on gamete production and sperm transport. Learn about the roles of Sertoli and Leydig cells in the testes, hormone synthesis, and the physiological processes involved. The quiz also covers the functions of various ducts and accessory glands, alongside clinical issues related to male reproductive health.

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