The Reproductive System Quiz
232 Questions
0 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the primary function of the reproductive system?

  • To filter waste from the blood
  • To transport oxygen throughout the body
  • To regulate body temperature
  • To pass genetic information from one generation to the next (correct)

    • Why is the reproductive system not essential for individual survival?

  • It functions only in childhood and becomes irrelevant after puberty
  • It is only needed for reproduction and not for day-to-day bodily functions (correct)
  • The reproductive system doesn't contribute to the production of energy
  • It is involved in waste elimination rather than survival

    • Which cells are involved in reproduction?

  • Nerve cells
  • Germ cells (gametes) (correct)
  • Epithelial cells
  • Red blood cells

    • What are gonads responsible for producing?

    <p>Gametes and reproductive hormones</p> Signup and view all the answers

    What are the gonads in females and males?

    <p>Ovaries and testes</p> Signup and view all the answers

    What does the SRY gene on the Y chromosome encode?

    <p>Testis Determining Factor (TDF)</p> Signup and view all the answers

    What happens if Testis Determining Factor (TDF) is present during fetal development?

    <p>The testes develop, and male external genitalia form</p> Signup and view all the answers

    What is the role of Anti-Müllerian Hormone (AMH) in males?

    <p>It induces the regression of the paramesonephric duct</p> Signup and view all the answers

    In female embryos, which structure remains and forms the uterus and fallopian tubes?

    <p>Paramesonephric duct</p> Signup and view all the answers

    What happens in female embryos during the early stages of development (6-8 weeks)?

    <p>The absence of testosterone and AMH allows the paramesonephric duct to persist and develop female reproductive organs</p> Signup and view all the answers

    What distinguishes the development of male external genitalia from female structures?

    <p>The presence of the SRY gene</p> Signup and view all the answers

    What is the consequence of the presence of testosterone during fetal development?

    <p>Causes the regression of female reproductive structures</p> Signup and view all the answers

    During which developmental phase is the absence of AMH critical for female development?

    <p>From 6 to 8 weeks</p> Signup and view all the answers

    What physiological function of the reproductive system is primarily controlled by the nervous system?

    <p>Erection and ejaculation</p> Signup and view all the answers

    Which hormone significantly influences the menstrual cycle and female sexual characteristics?

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

    How does Follicle-stimulating hormone (FSH) affect reproductive processes in both sexes?

    <p>Stimulates follicle growth in females and spermatogenesis in males</p> Signup and view all the answers

    What specific role does Luteinizing hormone (LH) play in women's reproductive health?

    <p>Triggers ovulation</p> Signup and view all the answers

    Which of the following functions is not controlled by hormones within the reproductive system?

    <p>Erection and ejaculation</p> Signup and view all the answers

    What is a primary effect of hormones on sexual behavior?

    <p>They influence sexual drive and behavior, in part</p> Signup and view all the answers

    Which of the following hormones directly triggers the release of an egg from the ovary?

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

    What happens during the male reproductive process when Follicle-stimulating hormone (FSH) is present?

    <p>Promotes the growth of sperm production</p> Signup and view all the answers

    What is the typical length of a testis?

    <p>4 cm</p> Signup and view all the answers

    Which part of the testis is responsible for sperm production?

    <p>Seminiferous tubules</p> Signup and view all the answers

    Where is sperm stored and matured?

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

    What is the function of the ductus deferens?

    <p>It transports sperm from the epididymis to the urethra</p> Signup and view all the answers

    What is the role of myoid cells in the seminiferous tubules?

    <p>They help move sperm through the tubules</p> Signup and view all the answers

    What is the role of the tunica albuginea in the testes?

    <p>It provides structural support</p> Signup and view all the answers

    What structure is primarily responsible for the maturation of sperm?

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

    Which cells are known to surround and support the seminiferous tubules during sperm production?

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

    What is the primary function of the ductus deferens?

    <p>Sperm transportation</p> Signup and view all the answers

    Which structure directly provides a protective layer around the testes?

    <p>Tunica vaginalis</p> Signup and view all the answers

    What is the primary function of the epididymis?

    <p>To store and mature sperm</p> Signup and view all the answers

    How long does it typically take for sperm to gain motility in the epididymis?

    <p>20 days</p> Signup and view all the answers

    What is the length of the ductus deferens (vas deferens)?

    <p>45 cm</p> Signup and view all the answers

    What type of epithelium lines the ductus deferens?

    <p>Stratified epithelium</p> Signup and view all the answers

    What happens to sperm in the epididymis if they are not ejaculated?

    <p>They are stored for several months</p> Signup and view all the answers

    What is the primary function of the male urethra?

    <p>To carry both urine and semen, but not simultaneously</p> Signup and view all the answers

    What is the function of the mucus secreted by the spongy urethra before ejaculation?

    <p>To lubricate the passage</p> Signup and view all the answers

    What is the function of the ejaculatory duct?

    <p>It empties sperm into the urethra for ejaculation</p> Signup and view all the answers

    What is the primary function of the ductus deferens?

    <p>To transport sperm from the epididymis to the urethra during ejaculation</p> Signup and view all the answers

    What type of muscle constitutes the ductus deferens?

    <p>Smooth muscle</p> Signup and view all the answers

    How does the smooth muscle of the ductus deferens function in sperm transport?

    <p>It uses peristalsis to propel sperm towards the urethra</p> Signup and view all the answers

    What occurs during a vasectomy?

    <p>The ductus deferens is cut and sealed to prevent sperm from entering the urethra</p> Signup and view all the answers

    In which anatomical relationship is the ductus deferens found with respect to the spermatic cord?

    <p>It runs through the spermatic cord</p> Signup and view all the answers

    What is the significance of the smooth muscle contractions in the ductus deferens?

    <p>They facilitate the movement of sperm towards the urethra during ejaculation</p> Signup and view all the answers

    Which structure does the ductus deferens directly connect?

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

    What is the primary function of the seminal gland (seminal vesicle)?

    <p>To produce seminal fluid that combines with sperm during ejaculation</p> Signup and view all the answers

    What is the main energy source provided by the seminal fluid produced by the seminal glands?

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

    What role do prostaglandins in the seminal fluid play during ejaculation?

    <p>They stimulate contractions in the female reproductive tract to aid sperm transport</p> Signup and view all the answers

    What does the prostatic fluid contribute to sperm function?

    <p>It activates sperm and helps maintain their motility</p> Signup and view all the answers

    What is the primary role of the bulbo-urethral glands (Cowper’s glands)?

    <p>To produce a clear mucus that neutralizes acidic urine and lubricates the penis</p> Signup and view all the answers

    Where is the seminal gland located?

    <p>On the surface of the bladder</p> Signup and view all the answers

    What does the prostatic fluid look like?

    <p>Thick and milky</p> Signup and view all the answers

    What section of the urethra runs through the penis and allows sperm to pass?

    <p>Spongy urethra</p> Signup and view all the answers

    How long is each seminal vesicle typically?

    <p>5 cm</p> Signup and view all the answers

    What is the main function of the seminal vesicles?

    <p>To produce an alkaline fluid that makes up most of the ejaculate</p> Signup and view all the answers

    What substance found in the fluid produced by the seminal vesicles provides energy for sperm?

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

    What role do prostaglandins in the seminal vesicle fluid play?

    <p>They stimulate contractions in the female reproductive tract to aid sperm transport</p> Signup and view all the answers

    What type of muscle is present in the seminal vesicles?

    <p>Smooth muscle</p> Signup and view all the answers

    What is the role of smooth muscle in the seminal vesicles?

    <p>To propel the fluid into the ejaculatory duct during ejaculation</p> Signup and view all the answers

    How do the seminal vesicles contribute to sperm transport?

    <p>By combining their duct with the ductus deferens to form the ejaculatory duct</p> Signup and view all the answers

    Where are the seminal vesicles located in relation to other structures in the male reproductive system?

    <p>Between the bladder and the rectum</p> Signup and view all the answers

    What is the primary function of the glandular tissue in the prostate?

    <p>To produce seminal fluid</p> Signup and view all the answers

    What percentage of seminal fluid is produced by the prostate gland?

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

    What is the main function of the ejaculatory ducts?

    <p>To transport prostatic fluid into the urethra during ejaculation</p> Signup and view all the answers

    Which zone of the prostate is most commonly associated with prostate cancer?

    <p>Peripheral zone (PZ)</p> Signup and view all the answers

    What clinical procedure is commonly used to check for abnormalities in the prostate?

    <p>Digital rectal examination (DRE)</p> Signup and view all the answers

    What is the role of the fibrous capsule surrounding the prostate?

    <p>To maintain the shape and protect the prostate</p> Signup and view all the answers

    What is the prostatic utricle?

    <p>A small cavity described as a vestigial structure within the prostate</p> Signup and view all the answers

    Where does the lymphatic drainage of the prostate lead?

    <p>To the spine</p> Signup and view all the answers

    What is the primary function of spermatozoa in semen?

    <p>To fertilize the egg</p> Signup and view all the answers

    What percentage of semen volume is contributed by the seminal vesicle fluid?

    <p>50-70%</p> Signup and view all the answers

    What is the primary energy source for sperm in seminal vesicle fluid?

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

    What is the function of prostate fluid in semen?

    <p>Activates sperm and makes semen alkaline</p> Signup and view all the answers

    Which gland produces fluid that neutralizes acidity in the urethra?

    <p>Bulbourethral (Cowper's) gland</p> Signup and view all the answers

    What is the typical volume of semen ejaculated during a normal ejaculation?

    <p>2-5 mL</p> Signup and view all the answers

    What characteristic does semen have in terms of its appearance and texture?

    <p>Viscous and whitish</p> Signup and view all the answers

    Which of the following is NOT a component of semen?

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

    What component of seminal vesicle fluid primarily supplies energy to sperm?

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

    What is the main purpose of PSA (Prostate-Specific Antigen) in semen?

    <p>To liquefy semen after ejaculation</p> Signup and view all the answers

    Which gland is the largest contributor to the volume of semen?

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

    What is the primary function of pre-ejaculate fluid from the bulbourethral gland?

    <p>To lubricate and neutralize acidic urine</p> Signup and view all the answers

    Why is semen alkaline in nature?

    <p>To alleviate acidity in the female tract</p> Signup and view all the answers

    Where is sperm initially produced and stored before maturation?

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

    Which structure is responsible for transporting sperm from the epididymis to the ejaculatory duct?

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

    What is the function of the bulbo-urethral gland in the male reproductive system?

    <p>Produces pre-ejaculate fluid to lubricate the urethra and neutralize traces of urine</p> Signup and view all the answers

    The ejaculatory duct is formed by the convergence of which two structures?

    <p>Seminal vesicle and ductus deferens</p> Signup and view all the answers

    What is the final pathway through which semen exits the male body?

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

    Which of the following is NOT a component of the spermatic cord?

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

    What is the main role of the pampiniform plexus in the spermatic cord?

    <p>Cools arterial blood for optimal spermatogenesis</p> Signup and view all the answers

    Which artery within the spermatic cord is primarily responsible for supplying blood to the cremaster muscle?

    <p>Cremasteric artery</p> Signup and view all the answers

    Which nerve's genital branch is responsible for innervating the cremaster muscle?

    <p>Genitofemoral nerve</p> Signup and view all the answers

    What is the origin of the internal spermatic fascia within the spermatic cord?

    <p>Originates from the transversalis fascia</p> Signup and view all the answers

    Which nerve is primarily responsible for sensation in parts of the scrotum and groin?

    <p>Genital branch of the genitofemoral nerve</p> Signup and view all the answers

    Which components are essential for temperature regulation in the spermatic cord?

    <p>Pampiniform plexus and cremaster muscle</p> Signup and view all the answers

    What is the main function of the ductus (vas) deferens within the spermatic cord?

    <p>Transporting sperm from the testis to the urethra</p> Signup and view all the answers

    Where do the testicles initially develop before descending to the scrotum?

    <p>In the retroperitoneal space</p> Signup and view all the answers

    What structure guides the descent of the testicle from the abdomen to the scrotum?

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

    The processus vaginalis is a fold of which structure?

    <p>Parietal peritoneum</p> Signup and view all the answers

    What does the processus vaginalis form after the testicular descent is complete?

    <p>Tunica vaginalis</p> Signup and view all the answers

    What clinical condition can result from the failure of the processus vaginalis to close properly?

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

    The gubernaculum’s main role in testicle development is to:

    <p>Guide the descent of the testicle into the scrotum</p> Signup and view all the answers

    What potential condition can occur if the testicle does not descend properly?

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

    The processus vaginalis can contribute to the formation of which type of hernia if it remains open?

    <p>Indirect inguinal hernia</p> Signup and view all the answers

    What is the typical pathway for an indirect inguinal hernia?

    <p>Through the deep inguinal ring and into the inguinal canal</p> Signup and view all the answers

    Which type of inguinal hernia is more likely to extend into the scrotum?

    <p>Indirect inguinal hernia</p> Signup and view all the answers

    An indirect inguinal hernia occurs due to the failure of which structure to close?

    <p>Processus vaginalis</p> Signup and view all the answers

    A direct inguinal hernia is typically located:

    <p>Medial to the inferior epigastric vessels</p> Signup and view all the answers

    Which group is most commonly affected by indirect inguinal hernias?

    <p>Young males and infants</p> Signup and view all the answers

    What is the anatomical area called where direct inguinal hernias protrude through the abdominal wall?

    <p>Hesselbach's triangle</p> Signup and view all the answers

    Direct inguinal hernias are usually associated with:

    <p>Increased intra-abdominal pressure and weakened abdominal muscles</p> Signup and view all the answers

    Which of the following best describes the location of an indirect inguinal hernia relative to the inferior epigastric vessels?

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

    What is a varicocele?

    <p>Enlargement of the pampiniform plexus</p> Signup and view all the answers

    The primary function of the pampiniform plexus in the spermatic cord is to:

    <p>Cool the blood entering the testes</p> Signup and view all the answers

    What impact can a varicocele have on testicular temperature?

    <p>Increases temperature</p> Signup and view all the answers

    Why might a varicocele contribute to fertility issues?

    <p>It increases oxidative stress and raises testicular temperature.</p> Signup and view all the answers

    Varicoceles are more commonly found on which side of the scrotum and why?

    <p>Left side, due to anatomical differences in venous drainage</p> Signup and view all the answers

    Which diagnostic tool is commonly used to confirm the presence of a varicocele?

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

    What is a common surgical treatment for varicocele?

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

    Which of the following is NOT a potential symptom of a varicocele?

    <p>No symptoms at all</p> Signup and view all the answers

    Which structures are primarily responsible for enabling penile rigidity during an erection?

    <p>Corpora cavernosa</p> Signup and view all the answers

    Where is the corpus spongiosum located in relation to the penis?

    <p>On the ventral side</p> Signup and view all the answers

    What is the primary function of the corpus spongiosum during erection?

    <p>To prevent compression of the urethra during erection</p> Signup and view all the answers

    Which part of the penis extends to form the glans?

    <p>Corpus spongiosum</p> Signup and view all the answers

    Hypospadias is a condition where the urethral opening is located:

    <p>On the underside of the penis</p> Signup and view all the answers

    Which type of hypospadias is considered the most severe?

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

    The root of the penis primarily serves to:

    <p>Anchor the penis to the pelvic bones</p> Signup and view all the answers

    Surgical correction for hypospadias is typically performed:

    <p>In infancy or early childhood</p> Signup and view all the answers

    Which part of the nervous system is primarily responsible for initiating an erection?

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

    What role does nitric oxide (NO) play during the process of erection?

    <p>It relaxes smooth muscle cells to enable blood vessel dilation</p> Signup and view all the answers

    During an erection, what happens to the arterioles supplying blood to the penis?

    <p>They dilate</p> Signup and view all the answers

    Which structure(s) in the penis are filled with blood during an erection?

    <p>Corpus cavernosa and corpus spongiosum</p> Signup and view all the answers

    What effect does increased blood flow have on the veins draining the penis during an erection?

    <p>It compresses the veins, restricting blood outflow</p> Signup and view all the answers

    Which nervous system response primarily controls ejaculation and contrasts with the erection process?

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

    In the non-aroused state, what is the condition of the arterioles supplying the erectile tissue?

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

    What type of stimuli can activate the central nervous system's response to initiate an erection?

    <p>Sexual stimuli including touch, sound, and mental activity</p> Signup and view all the answers

    Which part of the nervous system mediates the process of ejaculation?

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

    What prevents semen from entering the bladder during ejaculation?

    <p>Constriction of the bladder sphincter muscle</p> Signup and view all the answers

    Which muscle contracts rhythmically to propel semen out of the body?

    <p>Bulbospongiosus muscle</p> Signup and view all the answers

    Which glands contribute to the formation of semen during ejaculation?

    <p>Seminal vesicles, prostate, and bulbourethral glands</p> Signup and view all the answers

    What occurs during the resolution phase after ejaculation?

    <p>The penis returns to a flaccid state.</p> Signup and view all the answers

    How fast can semen be expelled during ejaculation?

    <p>Up to 500 cm/s</p> Signup and view all the answers

    The refractory period after ejaculation refers to:

    <p>The time when another orgasm cannot be achieved temporarily</p> Signup and view all the answers

    Which of the following statements is true about ejaculation?

    <p>It involves the contraction of penile muscles to expel semen.</p> Signup and view all the answers

    What is the main function of the corpora cavernosa in the penis?

    <p>To enable penile rigidity during erection</p> Signup and view all the answers

    Which artery is primarily responsible for supplying blood to the corpora cavernosa?

    <p>Cavernous artery</p> Signup and view all the answers

    What triggers the relaxation of the trabecular smooth muscle in the corpora cavernosa during an erection?

    <p>Release of nitric oxide (NO)</p> Signup and view all the answers

    During an erection, what happens to the deep dorsal vein?

    <p>It becomes compressed, reducing venous drainage</p> Signup and view all the answers

    Which structure remains softer during an erection to ensure the urethra stays open?

    <p>Corpus spongiosum</p> Signup and view all the answers

    What surrounds the corpora cavernosa and helps trap blood within it during an erection?

    <p>Tunica albuginea</p> Signup and view all the answers

    In the flaccid state, what happens to the helicine arteries?

    <p>They constrict, limiting blood flow</p> Signup and view all the answers

    What is the role of Buck's fascia in the penis?

    <p>Surrounds and provides support to the corpora cavernosa and corpus spongiosum</p> Signup and view all the answers

    Where is sperm produced in the male reproductive system?

    <p>Seminiferous tubules in the testes</p> Signup and view all the answers

    What is the main function of the epididymis?

    <p>To mature and store sperm</p> Signup and view all the answers

    What structure propels sperm from the epididymis to the ejaculatory duct during ejaculation?

    <p>Vas (ductus) deferens</p> Signup and view all the answers

    Which structure produces a significant portion of seminal fluid that provides nutrients for sperm?

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

    What is the role of the prostate gland in the reproductive system?

    <p>To add a milky, alkaline fluid that nourishes and protects sperm</p> Signup and view all the answers

    Which gland produces a lubricating fluid that neutralizes acidic residue in the urethra before ejaculation?

    <p>Bulbourethral (Cowper’s) gland</p> Signup and view all the answers

    Which structure carries semen out of the body during ejaculation?

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

    Which part of the male reproductive system stores sperm before they are expelled?

    <p>Ampulla of the vas deferens</p> Signup and view all the answers

    Which part of the nervous system is primarily responsible for initiating the erection process?

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

    What effect does nitric oxide (NO) have during the erection phase?

    <p>It promotes blood vessel dilation to increase blood flow.</p> Signup and view all the answers

    Which type of response is predominantly involved in the ejaculation process?

    <p>Sympathetic response</p> Signup and view all the answers

    What structure is responsible for transporting sperm from the epididymis to the urethra during ejaculation?

    <p>Vas (ductus) deferens</p> Signup and view all the answers

    During ejaculation, what mechanism prevents semen from re-entering the bladder?

    <p>Constricting the bladder sphincter muscle</p> Signup and view all the answers

    Which muscle's rhythmic contractions are vital for expelling semen during ejaculation?

    <p>Bulbospongiosus muscle</p> Signup and view all the answers

    What physiological change occurs during the resolution phase after ejaculation?

    <p>The penis becomes flaccid, entering a refractory stage.</p> Signup and view all the answers

    Which phase of ejaculation is characterized by the addition of seminal fluid to sperm?

    <p>Emission phase</p> Signup and view all the answers

    What is the definition of erectile dysfunction (ED)?

    <p>The inability to achieve or maintain an erection sufficient for satisfactory sexual performance</p> Signup and view all the answers

    Approximately what percentage of men aged 40-70 years are affected by ED?

    <p>50%</p> Signup and view all the answers

    Which of the following is a common physical cause of ED?

    <p>Diabetes and cardiovascular disease</p> Signup and view all the answers

    Which psychological factor can contribute to ED?

    <p>Stress and performance anxiety</p> Signup and view all the answers

    What type of medication is known to potentially cause or exacerbate ED?

    <p>SSRIs (antidepressants)</p> Signup and view all the answers

    How does sildenafil (Viagra) help in treating ED?

    <p>By promoting relaxation of blood vessels through PDE5 inhibition</p> Signup and view all the answers

    What is an important reason for addressing ED besides improving quality of life?

    <p>It is often a marker for broader cardiovascular health issues.</p> Signup and view all the answers

    What molecule does sildenafil help maintain in higher levels to promote the relaxation of smooth muscle in the penis?

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

    Where does spermatogenesis occur within the male reproductive system?

    <p>Seminiferous tubules</p> Signup and view all the answers

    At what age does spermatogenesis typically begin in males?

    <p>Around age 14</p> Signup and view all the answers

    What type of cell division is involved in the formation of sperm cells?

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

    What is the function of Sertoli cells during spermatogenesis?

    <p>Support and nourish developing sperm cells</p> Signup and view all the answers

    Which hormones are crucial for regulating spermatogenesis?

    <p>Testosterone and follicle-stimulating hormone (FSH)</p> Signup and view all the answers

    Which phase of spermatogenesis involves primary spermatocytes dividing to form secondary spermatocytes?

    <p>Meiosis I</p> Signup and view all the answers

    What is the final stage of spermatogenesis called, during which spermatids mature into spermatozoa?

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

    What is the role of the blood-testis barrier formed by Sertoli cells?

    <p>Protects developing sperm from immune system attacks</p> Signup and view all the answers

    What hormone does the hypothalamus release to stimulate the anterior pituitary gland in the HPG axis?

    <p>Gonadotropin-releasing hormone (GnRH)</p> Signup and view all the answers

    Which hormones are secreted by the anterior pituitary gland in response to GnRH?

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

    What is the role of FSH in male spermatogenesis?

    <p>Supports Sertoli cells to promote spermatogenesis and produce androgen-binding protein (ABP)</p> Signup and view all the answers

    How do high levels of testosterone or oestrogen affect the hypothalamus and anterior pituitary gland?

    <p>Exert a negative feedback to decrease GnRH, FSH, and LH secretion</p> Signup and view all the answers

    Which hormone produced by the ovaries exerts negative feedback on the hypothalamus and anterior pituitary?

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

    What can a disruption in the negative feedback loop of the HPG axis lead to?

    <p>Conditions such as hypogonadism or PCOS</p> Signup and view all the answers

    What do Sertoli cells produce to help maintain high local concentrations of testosterone?

    <p>Androgen-binding protein (ABP)</p> Signup and view all the answers

    What is the primary function of the negative feedback mechanism in the HPG axis?

    <p>To maintain homeostasis and regulate hormone levels</p> Signup and view all the answers

    What hormone does the hypothalamus release in pulses to stimulate the anterior pituitary gland?

    <p>Gonadotropin-releasing hormone (GnRH)</p> Signup and view all the answers

    How often is GnRH released by the hypothalamus to regulate the HPG axis?

    <p>Every 60-90 minutes</p> Signup and view all the answers

    What is the role of FSH in the regulation of spermatogenesis?

    <p>Triggers Sertoli cells to produce androgen-binding protein (ABP) and support spermatogenesis</p> Signup and view all the answers

    Which cells in the testes are responsible for producing testosterone?

    <p>Leydig cells</p> Signup and view all the answers

    What is the function of androgen-binding protein (ABP) produced by Sertoli cells?

    <p>Binds to testosterone to maintain high local concentrations around developing sperm cells</p> Signup and view all the answers

    Which hormone provides negative feedback specifically to the pituitary to reduce FSH release?

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

    Why is the pulsatile release of GnRH important for hormone regulation in the HPG axis?

    <p>It ensures the pituitary responds effectively to GnRH, supporting LH and FSH secretion.</p> Signup and view all the answers

    What can happen if GnRH is not released in pulses?

    <p>Reduced secretion of LH and FSH, leading to impaired spermatogenesis</p> Signup and view all the answers

    Which cells in the testes are responsible for producing inhibin?

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

    What is the primary function of inhibin in the male reproductive system?

    <p>Inhibit FSH secretion from the anterior pituitary</p> Signup and view all the answers

    When is the secretion of inhibin by Sertoli cells heightened?

    <p>When sperm maturation is sufficient and sperm counts are adequate</p> Signup and view all the answers

    What is the consequence of decreased inhibin levels in the body?

    <p>FSH secretion increases, promoting enhanced spermatogenesis</p> Signup and view all the answers

    How does inhibin influence the feedback mechanism of the HPG axis?

    <p>It acts on the anterior pituitary to specifically inhibit FSH secretion</p> Signup and view all the answers

    What hormone does inhibin regulate without directly affecting its own secretion?

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

    Why is the regulation of FSH by inhibin crucial for spermatogenesis?

    <p>It helps maintain optimal sperm production and prevents excessive spermatogenesis</p> Signup and view all the answers

    What can abnormal levels of inhibin indicate in males?

    <p>Issues such as infertility or disruptions in spermatogenesis</p> Signup and view all the answers

    Which two main functions do the testes perform?

    <p>Spermatogenesis and steroidogenesis</p> Signup and view all the answers

    What role does FSH play in the male reproductive system?

    <p>Stimulates Sertoli cells to support and nourish developing sperm cells</p> Signup and view all the answers

    Which cells in the testes produce testosterone?

    <p>Leydig cells</p> Signup and view all the answers

    What is the primary hormone responsible for the maturation of spermatozoa in the epididymis?

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

    What protein is produced by Sertoli cells to maintain high concentrations of testosterone in the seminiferous tubules?

    <p>Androgen-binding protein (ABP)</p> Signup and view all the answers

    How do androgens, such as testosterone and DHT, exert their effects on target tissues?

    <p>By binding to androgen receptors and influencing gene expression</p> Signup and view all the answers

    Which of the following is NOT a function of testosterone in males?

    <p>Stimulation of Sertoli cells to release FSH</p> Signup and view all the answers

    What can disruptions in the hormonal regulation of the testes lead to?

    <p>Infertility and hypogonadism</p> Signup and view all the answers

    Which two main functions do the testes perform?

    <p>Spermatogenesis and steroidogenesis</p> Signup and view all the answers

    What role does FSH play in the male reproductive system?

    <p>Stimulates Sertoli cells to support and nourish developing sperm cells</p> Signup and view all the answers

    Which cells in the testes produce testosterone?

    <p>Leydig cells</p> Signup and view all the answers

    What is the primary hormone responsible for the maturation of spermatozoa in the epididymis?

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

    What protein is produced by Sertoli cells to maintain high concentrations of testosterone in the seminiferous tubules?

    <p>Androgen-binding protein (ABP)</p> Signup and view all the answers

    How do androgens, such as testosterone and DHT, exert their effects on target tissues?

    <p>By binding to androgen receptors and influencing gene expression</p> Signup and view all the answers

    Which of the following is NOT a function of testosterone in males?

    <p>Stimulation of Sertoli cells to release FSH</p> Signup and view all the answers

    What type of feedback does testosterone provide to the hypothalamus and anterior pituitary?

    <p>Negative feedback</p> Signup and view all the answers

    Which of the following is considered a primary sexual characteristic influenced by testosterone?

    <p>Growth and development of the penis and testes</p> Signup and view all the answers

    What is the role of testosterone in spermatogenesis?

    <p>It initiates and maintains the production of mature sperm cells.</p> Signup and view all the answers

    Which characteristic is NOT a secondary sexual effect of testosterone?

    <p>Development of male external genitalia during fetal development</p> Signup and view all the answers

    What physical change in males is associated with the growth of the larynx due to testosterone?

    <p>Formation of the 'Adam's apple' and a deeper voice</p> Signup and view all the answers

    Which of the following does testosterone NOT directly influence?

    <p>Production of FSH in the pituitary gland</p> Signup and view all the answers

    Why is testosterone important for bone health?

    <p>It increases bone density and promotes skeletal growth.</p> Signup and view all the answers

    How does testosterone affect skin texture?

    <p>It thickens the skin and can increase oil production by stimulating sebaceous glands.</p> Signup and view all the answers

    Which of the following conditions can arise due to low testosterone levels?

    <p>Reduced fertility and decreased bone density</p> Signup and view all the answers

    Study Notes

    The Reproductive System

    • The primary function of the reproductive system is to pass genetic information from one generation to the next.
    • The reproductive system is not essential for individual survival, meaning an individual can live without it.
    • Germ cells (gametes) are the cells involved in reproduction.
    • Gonads are organs that produce gametes and reproductive hormones.
    • Ovaries are the gonads in females and testes are the gonads in males.

    Sexual Differentiation

    • The SRY gene on the Y chromosome encodes Testis Determining Factor (TDF)
    • In males, TDF initiates the development of testes, leading to the formation of male external genitalia
    • Anti-Müllerian Hormone (AMH) is secreted by testes, causing the regression of the paramesonephric duct, which would otherwise develop into the uterus and fallopian tubes in females
    • In females, the absence of TDF triggers the development of ovaries
    • The absence of testosterone and AMH allows the paramesonephric duct to persist and develop into female reproductive organs
    • The mesonephric duct degenerates in females

    Neural and Hormonal Control of Reproduction

    • Erection and ejaculation are primarily controlled by the nervous system.
    • Estrogen is crucial for the development of female reproductive structures and regulates the menstrual cycle.
    • Follicle-stimulating hormone (FSH) plays a key role in both sexes:
      • In females, it stimulates the growth of ovarian follicles.
      • In males, it stimulates spermatogenesis.
    • Luteinizing hormone (LH) triggers ovulation in females.
    • Hormones are essential for the development of reproductive structures and secondary sexual characteristics, but do not directly control erection and ejaculation.
    • Hormones play a significant role in influencing sexual drive and behavior, alongside other factors.

    Testis Structure and Function

    • The testes are oval-shaped organs located in the scrotum, responsible for sperm production and testosterone secretion.
    • Each testis is about 4 cm in length.
    • The seminiferous tubules are the sites of sperm production.
    • Columnar cells lining the seminiferous tubules aid in sperm development.
    • Myoid cells surrounding the tubules help move sperm through the tubules.
    • Epididymis is a coiled tube attached to the testis where sperm are stored and mature.
    • Ductus deferens is a long tube that carries sperm from the epididymis to the urethra.
    • Tunica albuginea is a fibrous capsule surrounding the testes and providing support.
    • Tunica vaginalis is a membrane surrounding the testes for protection.

    Testis Structure and Function

    • The testis, also known as the testicle, is the male reproductive organ responsible for producing sperm and testosterone.
    • The average length of a testis is 4 cm.
    • The testis is divided into lobules by connective tissue septa.
    • The seminiferous tubules are the site of sperm production, a complex process involving numerous cell types.
    • Columnar cells, also called Sertoli cells, line the seminiferous tubules and support and nourish developing sperm cells.
    • Myoid cells surrounding the seminiferous tubules are responsible for contraction and the movement of sperm through the tubules.
    • The epididymis is a long coiled tube that connects the seminiferous tubules to the ductus deferens.
    • The epididymis serves as a storage and maturation site for sperm, allowing them to gain motility and fertilization capacity.
    • The ductus deferens, a muscular tube, transports mature sperm from the epididymis to the urethra, the final passageway for semen.
    • The tunica vaginalis, a serous membrane, surrounds the testes and provides support and protection.
    • The tunica albuginea, a fibrous capsule, surrounds the testis, providing structural support.

    Epididymis

    • The epididymis is a coiled tube attached to the testes, where sperm are stored and mature into their fully functional state.
    • It takes about 20 days for sperm to become motile and fully mature in the epididymis.
    • If sperm are not ejaculated, they can be stored in the epididymis for several months.

    Ductus Deferens

    • The ductus deferens, also known as the vas deferens, is a long muscular tube that transports sperm from the epididymis to the ejaculatory duct.
    • It measures approximately 45 cm in length.
    • The ductus deferens is lined with stratified epithelium.

    Ejaculatory Duct

    • The ejaculatory duct is a short, narrow passage that connects the ductus deferens to the urethra.
    • It is the final part of the male reproductive tract, where sperm are released into the urethra for ejaculation.

    Urethra

    • The urethra is a tube that carries both urine and semen, although not simultaneously.
    • The urethra is divided into three parts: the prostatic urethra, the membranous urethra, and the spongy urethra.
    • The spongy urethra, the shortest part of the urethra, measures approximately 15 cm in length.
    • Mucus secreted by the spongy urethra before ejaculation helps to lubricate the passage.

    Seminal Vesicles

    • The seminal vesicles are two small glands adjacent to the prostate gland.
    • They produce seminal fluid, a thick, yellowish liquid that comprises the majority of the ejaculate.
    • Seminal fluid contributes to the nourishment and transportation of sperm during ejaculation.

    Male Reproductive System - Seminal Glands, Prostate & Bulbo-Urethral Glands

    • Seminal Glands (Seminal Vesicles) are responsible for producing most of the seminal fluid which combines with sperm during ejaculation
    • Seminal Fluid provides fructose as the primary energy source for sperm
    • Prostaglandins in seminal fluid stimulate contractions in the female reproductive tract to help transport sperm
    • Seminal Glands are located on the surface of the bladder
    • Prostate Gland contributes prostatic fluid to sperm that activates sperm and helps maintain motility.
    • Prostatic fluid is thick and milky
    • Prostate Gland is located beneath the bladder and surrounds the urethra
    • Bulbo-Urethral Glands (Cowper’s Glands) produce a clear mucus that neutralizes the acidic urine and lubricates the penis
    • The Spongy Urethra section of the urethra runs through the penis and allows sperm to pass
    • The Seminal Fluid provides energy for sperm, stimulates sperm motility but does NOT neutralize acidic urine in the urethra. This is the role of the bulbo-urethral glands.

    Ductus Deferens (Vas Deferens)

    • The ductus deferens is responsible for transporting sperm from the epididymis to the urethra during ejaculation.
    • It consists of smooth muscle, which contracts using peristalsis to propel the sperm forward.
    • The ductus deferens is part of the spermatic cord and travels up through the inguinal canal into the pelvic cavity.
    • A vasectomy is a surgical procedure where the ductus deferens is cut and sealed, preventing sperm from reaching the urethra and resulting in sterility.
    • The ductus deferens connects to the ejaculatory duct before joining the urethra.

    Seminal Vesicles: The Key Players in Male Reproduction

    • The seminal vesicles are a pair of elongated, sac-like structures located between the bladder and the rectum.
    • They are approximately 5 cm in length and contribute significantly to the production of seminal fluid, which makes up the majority of ejaculate volume (70-80%).
    • The primary function of the seminal vesicles is to produce an alkaline fluid containing fructose, prostaglandins, and other substances essential for sperm viability and transport.
    • The fluid produced by the seminal vesicles provides energy for sperm motility through the presence of fructose.
    • Prostaglandins in the fluid stimulate contractions in the female reproductive tract to aid sperm transport.
    • The seminal vesicles are lined with smooth muscle, which contracts during ejaculation, propelling the fluid into the ejaculatory duct, the channel formed by the fusion of the ductus deferens and the seminal vesicle duct.
    • This combination allows the transfer of sperm and seminal fluid to the urethra and ultimately into the female reproductive tract.

    Prostate Gland Anatomy & Function

    • Primary function: Production of seminal fluid, which makes up approximately 20% of the total.
    • Location: Positioned between the bladder and the rectum.
    • Prostatic Ducts and Ejaculatory Ducts: Transport prostatic fluid into the urethra during ejaculation.

    Zones of the Prostate

    • Peripheral Zone (PZ): Most commonly associated with prostate cancer.
    • Central Zone (CZ): Located in the central part of the gland, rarely affected by prostate cancer.
    • Transitional Zone (TZ): Most prone to Benign Prostatic Hyperplasia (BPH), causing enlargement of the prostate.
    • Prostatic Utricle: A small, vestigial structure within the prostate.

    Clinical Procedures

    • Digital Rectal Examination (DRE): Used to check for abnormalities in the prostate, commonly employed in routine check-ups.

    Prostate Gland Health

    • Benign Prostatic Hyperplasia (BPH): Enlargement of the prostate, primarily affecting the transitional zone.
    • Prostatitis: Inflammation of the prostate gland.

    Lymphatic Drainage

    • The prostate's lymphatic drainage system leads to the spine.

    Fibrous Capsule

    • The fibrous capsule surrounds the prostate, providing structural support and protection.

    Semen Composition and Characteristics

    • Semen, also known as seminal fluid, is a biological fluid produced by males and plays a vital role in reproduction.

    • Semen is a complex mixture of fluids and cells from various male reproductive organs, primarily:

      • Spermatozoa (sperm): The primary function is to fertilize the egg.
      • Seminal Vesicle Fluid: Contributes significantly (50-70%) to semen volume and provides fructose, the primary energy source for sperm.
      • Prostate Fluid: Contributes (20-30%) to semen volume, helps to activate sperm and make semen alkaline (less acidic) for sperm survival.
      • Bulbourethral Gland Fluid: Neutralizes the acidity in the urethra, preparing it for the passage of semen.

    • Typical semen characteristics:

      • Volume: 2-5 mL per ejaculation
      • Appearance: Viscous and whitish
      • Components: Spermatozoa, seminal vesicle fluid, prostate fluid, bulbourethral gland fluid (Cowper's gland). Oocytes (eggs) are not a component of semen.

    Seminal Vesicle Fluid

    • Fructose is a key component of seminal vesicle fluid, providing energy for sperm.
    • Prostaglandins contribute to stimulating uterine contractions, aiding sperm movement.

    Prostate Gland

    • Prostate-Specific Antigen (PSA) is an enzyme produced by the prostate gland that helps liquefy semen after ejaculation.
    • Citric acid contributes to the alkaline nature of semen.
    • Zinc plays a role in sperm maturation and function.
    • The prostate gland contributes approximately 20-30% of the total volume of semen.

    Bulbourethral Gland

    • Pre-ejaculate secreted by the bulbourethral gland serves to lubricate the sperm passage and neutralize traces of acidic urine.

    Semen Composition

    • Alkaline nature: Semen is alkaline to neutralize the acidic environment of the female genital tract, supporting sperm survival.
    • Liquefying semen: The presence of proteases (enzymes) in semen help break down clots after ejaculation.

    Male Reproductive System Structures

    • Epididymis: Stores and matures sperm cells after they are produced in the testes.
    • Ductus (Vas) Deferens: Transports mature sperm cells from the epididymis to the ejaculatory duct.
    • Ampulla: Enlarged portion of the ductus deferens where sperm is stored before ejaculation.
    • Seminal Vesicles: Contribute a fluid rich in fructose to semen, providing energy for sperm motility.
    • Prostate: Surrounds the prostatic urethra and secretes a fluid that helps activate sperm.
    • Bulbo-urethral Glands (Cowper's Glands): Produces a pre-ejaculate fluid to lubricate the urethra and neutralize any traces of urine.
    • Ejaculatory Duct: Formed by the convergence of the ductus deferens and the seminal vesicle, responsible for transporting sperm to the urethra during ejaculation.
    • Urethra: The final pathway through which semen exits the male body.

    Spermatic Cord

    • Spermatic Cord Content: The spermatic cord is a bundle of structures that connects the testes to the abdominal cavity.
      • Key Structures:
        • Ductus deferens: Transports sperm from the epididymis to the ejaculatory duct.
        • Testicular artery: Supplies blood to the testes.
        • Pampiniform plexus: A network of veins that help regulate testicular temperature by cooling arterial blood.
        • Artery to the ductus deferens: Provides blood to the ductus deferens.
        • Cremasteric artery: Supplies blood to the cremaster muscle.
      • Not a content of the spermatic cord: Seminal vesicles.
    • Temperature Regulation:
      • Pampiniform Plexus: The primary mechanism for testicular temperature regulation.
      • Cremaster Muscle: Raises and lowers the testes, further aiding temperature control.
      • Spermatic Cord Layers: The external spermatic fascia derived from the external oblique muscle, the cremasteric fascia enveloping the cremaster muscle, and the internal spermatic fascia derived from the transversalis fascia contribute to temperature regulation.
    • Innervation:
      • Genital branch of the genitofemoral nerve: Innervates the cremaster muscle and provides sensation to parts of the scrotum.
      • Ilioinguinal nerve: Provides sensation to parts of the scrotum and groin.
      • Autonomic nerves: Supply the vasculature and smooth muscle of the spermatic cord.
    • Internal Spermatic Fascia:
      • Origin: Transversalis fascia.
      • Function: Encircles the structures within the spermatic cord and provides support.

    Testicular Descent

    • Testicular development: Testicles initially develop in the pelvic cavity before descending to the scrotum.
    • Processus vaginalis: A fold of the parietal peritoneum that guides the descent of the testicles through the inguinal canal.
    • Gubernaculum: A fibrous cord that pulls the testicles through the inguinal canal and into the scrotum.
    • Tunica Vaginalis: The remnant of the processus vaginalis forms a sac-like structure around the testicle.
    • Clinical Implications: Failure of the processus vaginalis to close properly can lead to conditions like hydrocele, indirect inguinal hernia, or cryptorchidism (undescended testicle).
    • Testicular descent pathway: The path of the descending testicle includes passing through the inguinal canal.

    Cryptorchidism

    • Cryptorchidism is when a testicle does not descend properly into the scrotum.
    • Can cause infertility.
    • Increased risk of testicular cancer.

    Inguinal Hernia

    • Occurs when a portion of the intestine protrudes through a weak area in the abdominal wall.
    • There are two types: direct and indirect.
    • Indirect inguinal hernias: result from a failure of the processus vaginalis to close properly.
    • Direct inguinal hernias: result from weakness in the abdominal wall.

    Inguinal Hernias

    • Indirect Inguinal Hernias:
      • Occur through the deep inguinal ring and enter the inguinal canal.
      • Caused by a failure of the processus vaginalis to close, which is a congenital defect present at birth.
      • More likely to extend into the scrotum.
      • Often seen in young males and infants.
    • Direct Inguinal Hernias:
      • Protrude through the Hesselbach's triangle - a weakened area in the abdominal wall medial to the inferior epigastric vessels.
      • Usually associated with weakened abdominal muscles and increased intra-abdominal pressure.
      • Typically develop in older adults.
    • Comparison
      • Indirect hernias follow the path of the spermatic cord and are typically congenital.
      • Direct hernias push through a weakened area in the abdominal wall and are usually acquired.

    Varicocele

    • Definition: A varicocele is an abnormal enlargement of the veins within the pampiniform plexus of the spermatic cord.
    • Location: More common on the left side of the scrotum due to differences in venous drainage. The left testicular vein empties into the left renal vein, which is at a higher pressure than the right renal vein.
    • Function of Pampiniform Plexus: The pampiniform plexus is responsible for cooling the arterial blood entering the testes, maintaining optimal testicular temperature for sperm production.
    • Impact on Testicular Temperature: Varicoceles can disrupt this cooling mechanism, leading to an increase in testicular temperature.
    • Impact on Fertility: Increased temperature negatively impacts sperm production and quality, contributing to fertility issues. Varicoceles can also contribute to oxidative stress, further affecting sperm.
    • Diagnosis: Ultrasound is commonly used to visualize and confirm the presence of a varicocele.
    • Treatments:
      • Surgical Intervention: Varicocelectomy is a surgical procedure to repair the enlarged veins, often involving ligation or embolization.
      • Non-Surgical Procedures: Embolization involves blocking the damaged vein to improve blood flow, while angioplasty opens blocked veins.
    • Symptoms:
      • Pain or heaviness in the scrotum
      • Enlarged testicle
      • Decreased semen quality
      • Varicoceles may also be asymptomatic.

    Anatomy of the Penis

    • Corpora Cavernosa: These paired cylindrical structures are located on the dorsal side of the penis. They fill with blood during an erection, enabling rigidity.

    • Corpus Spongiosum: This single cylindrical structure is located on the ventral side of the penis, surrounding the urethra. It helps prevent compression of the urethra during an erection.

    • Glans Penis: This cone-shaped structure forms the tip of the penis and is formed by the extension of the corpus spongiosum.

    • Bulb of the Penis: This expanded base of the corpus spongiosum is located at the root of the penis. It helps support the erectile tissue.

    • Root of the Penis: This is the fixed portion of the penis that attaches to the pelvic bones. It consists of the bulb and crura.

    • External Urethral Meatus (EUM): This opening at the tip of the glans penis allows for the passage of urine and semen.

    Hypospadias

    • Hypospadias: This congenital condition occurs when the urethral opening is located on the underside of the penis, rather than at the tip. It varies in severity depending on the location of the opening:

      • Glanular Hypospadias: The opening is on the glans.
      • Distal Hypospadias: The opening is on the shaft of the penis.
      • Proximal Hypospadias: The opening is near the base of the penis.
      • Perineal Hypospadias: The most severe form, the opening is located in the perineum, the area between the rectum and the scrotum.

    • Surgical Correction: Typically performed in infancy or early childhood, depending on the severity of the condition, to improve function and appearance.

    Erection Mechanism

    • The parasympathetic nervous system controls the process of achieving an erection.
    • Nitric oxide (NO) is the primary substance responsible for vasodilation leading to an erection.
    • During an erection, the arterioles supplying blood to the penis dilate, allowing increased blood flow.
    • The corpus cavernosa and corpus spongiosum fill with blood during an erection.
    • Increased blood flow during an erection compresses the veins that drain the penis, restricting blood outflow and maintaining the engorged state.
    • The sympathetic nervous system is associated with ejaculation, which contrasts with the parasympathetic response for erection.
    • In a non-aroused state, the arterioles supplying the erectile tissue are constricted, restricting blood flow.
    • Nitric oxide (NO) relaxes smooth muscle cells in the blood vessels, leading to dilation and increased blood flow, contributing to an erection.
    • Various stimuli including physical touch, emotional arousal, sight, sound, smell, and mental activity can trigger an erection.

    Ejaculation

    • Sympathetic nervous system controls the process of ejaculation
    • The bladder sphincter muscle contracts during ejaculation to prevent semen from entering the bladder.
    • The bulbospongiosus muscle rhythmically contracts to eject semen out of the body.
    • Seminal vesicles, prostate, and bulbourethral glands all contribute to semen formation during ejaculation.
    • During the resolution phase after ejaculation, the penis returns to its flaccid state.
    • Semen can be expelled at speeds reaching up to 200 cm/s during ejaculation.
    • The refractory period is the time after ejaculation during which another orgasm cannot be achieved.
    • Ejaculation is controlled by the sympathetic nervous system and involves the contraction of penile muscles to expel semen.
    • During ejaculation, the ducts and glands contract to release their contents and contribute to semen formation.

    Penile Erection Mechanism

    • The corpora cavernosa are two cylindrical structures within the penis responsible for penile rigidity during an erection.
    • Blood flow to the corpora cavernosa is primarily supplied by the cavernous arteries.
    • During an erection, nitric oxide (NO) release triggers relaxation of the trabecular smooth muscle in the corpora cavernosa, leading to dilation of the helicine arteries and increased blood flow.
    • The deep dorsal vein becomes compressed during an erection, reducing venous drainage from the penis.
    • The corpus spongiosum encases the urethra and remains softer during an erection, ensuring the urethra stays open.
    • The tunica albuginea, a fibrous sheath that surrounds the corpora cavernosa, helps trap blood within the corpora cavernosa during an erection.
    • In the flaccid state, helicine arteries constrict, limiting blood flow to the corpora cavernosa.
    • Buck’s fascia, a fibrous sheath that surrounds both corpora cavernosa and corpus spongiosum, provides support and helps maintain penile rigidity.
    • The corpus spongiosum plays a crucial role in ensuring the passage of semen through the urethra during ejaculation.
    • Understanding the mechanism of erection is essential for diagnosing and treating erectile dysfunction.

    Male Reproductive System

    • Seminiferous tubules in the testes are where sperm is produced
    • Epididymis matures and stores sperm
    • Vas (ductus) deferens propels sperm from the epididymis to the ejaculatory duct
    • Seminal vesicles produce a significant portion of seminal fluid that nourishes sperm
    • Ejaculatory duct is where the vas deferens and the duct from the seminal vesicle converge
    • Prostate gland adds a milky, alkaline fluid that nourishes and protects sperm
    • Bulbourethral (Cowper’s) gland produces a lubricating fluid that neutralizes acidic residue in the urethra
    • Urethra carries semen out of the body during ejaculation
    • The correct sequence of sperm travel: Testis → Epididymis → Vas deferens → Ampulla → Ejaculatory duct → Prostate gland → Urethra → Penis
    • Ampulla of the vas deferens stores sperm before they are expelled

    The Nervous System and Erection

    • The parasympathetic nervous system mediates the process of erection.
    • Nitric oxide (NO) relaxes smooth muscle allowing blood to fill erectile tissues, leading to an erection.
    • The sympathetic nervous system controls the process of ejaculation.

    Ejaculation

    • Ejaculation is a two-phase process: emission and expulsion.
    • Emission: Sperm moves from the epididymis to the urethra through the vas deferens.
      • This phase also involves the addition of glandular secretions to sperm from the prostate gland and seminal vesicles.
    • Expulsion: Rhythmic contractions of the bulbospongiosus muscle propel semen out of the body.

    Other Processes

    • Resolution phase: The penis returns to a flaccid state entering a refractory period, which is a period where another erection is impossible.
    • Preventing semen backflow: The contraction of the bladder sphincter muscle prevents semen from flowing back into the bladder during ejaculation.

    Erectile Dysfunction (ED)

    • Difficulty achieving or maintaining an erection sufficient for sexual performance
    • Affects approximately 25% of men aged 40-70 years
    • Common causes include:
      • Physical conditions: Diabetes, cardiovascular disease, high blood pressure, high cholesterol, obesity, smoking, alcohol abuse, testosterone deficiency
      • Psychological factors: Stress, anxiety, depression, performance anxiety
      • Medications: SSRIs (antidepressants), antihypertensives, antihistamines
      • Lifestyle factors: Lack of exercise, smoking, alcohol consumption, drug use
    • Sildenafil (Viagra) is a medication used to treat ED
      • Initial medical purpose was to treat angina (chest pain)
      • Inhibits PDE5, an enzyme that breaks down cGMP
      • Higher cGMP levels promote relaxation of blood vessels in the penis, facilitating an erection

    Importance of Addressing ED

    • It is a marker for broader cardiovascular health issues
    • May indicate psychological problems
    • Improves quality of life

    Spermatogenesis: The Production of Sperm

    • Spermatogenesis is the process by which sperm cells are produced in the seminiferous tubules of the male reproductive system.
    • Seminiferous tubules: The location where spermatogenesis takes place.
    • Spermatogenesis begins around the age of 14 in males and continues throughout a man's life.
    • Healthy adult males can produce up to 400 million sperm per day.
    • Meiosis: The specialized cell division process involved in the formation of sperm cells.
    • Spermatogonia: The stem cells that undergo mitosis to produce more spermatogonia and differentiate into primary spermatocytes.
    • Type A cells: Stem cells that continue to undergo mitosis to replenish the spermatogonia population.
    • Type B cells: Cells that differentiate into primary spermatocytes and initiate meiosis.
    • Meiosis I: The first division of meiosis, where primary spermatocytes divide to form secondary spermatocytes.
    • Meiosis II: The second division of meiosis, where secondary spermatocytes divide to produce haploid spermatids.
    • Spermiogenesis: The final stage where spermatids mature into spermatozoa (sperm).
    • Sertoli cells: Specialized cells within the seminiferous tubules that support and nourish developing sperm cells.
    • Blood-testis barrier: A barrier formed by Sertoli cells that protects developing sperm from immune system attacks.
    • Testosterone and Follicle-stimulating hormone (FSH): Hormones crucial for regulating spermatogenesis.
    • LH (Luteinizing Hormone): Stimulates the production of testosterone by Leydig cells.
    • FSH (Follicle-Stimulating Hormone): Stimulates Sertoli cells to support spermatogenesis.

    Hypothalamic–Pituitary–Gonadal (HPG) Axis

    • The HPG axis is a complex feedback system that regulates the production of sex hormones in males and females
    • This process is essential for sexual development and reproduction

    Hormones Involved

    • Hypothalamus releases gonadotropin-releasing hormone (GnRH)
    • Anterior Pituitary releases follicle-stimulating hormone (FSH) and luteinizing hormone (LH) in response to GnRH
    • Testes (males) and Ovaries (females) produce sex hormones (e.g., testosterone and estrogen) in response to FSH and LH

    Male Reproductive System

    • Leydig cells in the testes are stimulated by LH to produce testosterone
    • Sertoli cells in the testes are stimulated by FSH to promote spermatogenesis
    • Sertoli cells produce androgen-binding protein (ABP), which helps maintain high local concentrations of testosterone

    Negative Feedback Loop

    • High levels of testosterone or estrogen exert negative feedback on the hypothalamus and anterior pituitary.
    • This inhibits the production and release of GnRH, FSH, and LH, thereby regulating hormone levels

    Disruptions to the Negative Feedback Loop

    • Disruptions can lead to conditions like hypogonadism or Polycystic Ovary Syndrome (PCOS)
    • These disruptions can affect the production and regulation of sex hormones

    Key Roles of Hormones

    • FSH: Stimulates spermatogenesis in males and follicle development in females
    • LH: Stimulates testosterone production in males and ovulation in females
    • GnRH: Regulates the release of FSH and LH from the anterior pituitary
    • Testosterone: Plays a critical role in male sexual development, muscle mass, and bone growth
    • Estrogen: Plays a crucial role in female sexual development, menstrual cycle, and pregnancy

    Hypothalamic-Pituitary-Gonadal (HPG) Axis

    • The hypothalamus releases gonadotropin-releasing hormone (GnRH) in pulses to regulate the HPG axis.
    • GnRH stimulates the anterior pituitary gland to release luteinizing hormone (LH) and follicle-stimulating hormone (FSH).
    • GnRH is released every 60-90 minutes.
    • FSH triggers Sertoli cells in the testes to produce androgen-binding protein (ABP) and support spermatogenesis.
    • LH stimulates Leydig cells in the testes to produce testosterone.
    • Testosterone acts as a negative feedback mechanism to reduce FSH release from the pituitary gland.
    • Inhibin, produced by Sertoli cells, also provides negative feedback specifically to the pituitary to reduce FSH release.
    • ABP binds to testosterone, maintaining high local concentration and contributing to ongoing spermatogenesis.
    • Pulsatile GnRH release ensures effective pituitary response and optimal LH and FSH secretion.
    • Lack of pulsatile GnRH release can lead to reduced LH and FSH secretion, causing impaired spermatogenesis.
    • Disruptions in HPG axis regulation can lead to hypogonadism.

    Inhibin in the Male Reproductive System

    • Inhibin is a hormone secreted by Sertoli cells in the testes.
    • Sertoli cells provide nourishment and support to developing sperm cells.
    • Inhibin's primary role is to inhibit the secretion of follicle-stimulating hormone (FSH) from the anterior pituitary gland.
    • FSH is crucial for the process of spermatogenesis, the production of sperm.
    • When sperm maturation is sufficient and sperm counts are adequate, inhibin secretion is increased.
    • This negative feedback mechanism ensures regulated sperm production.
    • If inhibin levels decrease, FSH secretion increases, leading to enhanced spermatogenesis.
    • Abnormally high inhibin levels may indicate issues such as infertility or disruptions in spermatogenesis.
    • Abnormally low inhibin levels may suggest decreased sperm production or testicular dysfunction.
    • Inhibin's regulation of FSH prevents excessive spermatogenesis, ensuring optimal sperm production.
    • Inhibin primarily regulates FSH and does not directly influence the secretion of other hormones like LH, testosterone, or prolactin.
    • Inhibin plays a vital role in the hypothalamic-pituitary-gonadal (HPG) axis, the complex system that regulates male reproductive function.
    • Inhibin is essential for maintaining a balanced hormonal environment within the testes, ensuring the proper development and production of healthy sperm.

    ### Male Reproductive System Hormones

    • Testes have two main functions:
      • Spermatogenesis: Production of sperm cells
      • Steroidogenesis: Production of hormones, primarily testosterone

    Hormones of the Male Reproductive System

    • FSH (Follicle-Stimulating Hormone):
      • Stimulates Sertoli cells in the testes.
      • Sertoli cells provide nutrients and support to developing sperm cells.
    • LH (Luteinizing Hormone):
      • Stimulates Leydig cells in the testes to produce testosterone.
    • Testosterone:
      • Primary male sex hormone.
      • Responsible for:
        • Development of male sex characteristics during puberty.
        • Maintenance of spermatogenesis.
        • Muscle growth and development.
        • Libido and sexual function.
    • Androgen-Binding Protein (ABP):
      • Produced by Sertoli cells.
      • Binds to testosterone, increasing its concentration in the seminiferous tubules, essential for sperm production.

    Regulation of Testosterone Production

    • Negative Feedback Loop:
      • Testosterone inhibits the release of GnRH (Gonadotropin-Releasing Hormone) from the hypothalamus.
      • GnRH stimulates the release of FSH and LH from the anterior pituitary.
      • The reduction in GnRH, caused by high testosterone levels, results in decreased FSH and LH production, consequently decreasing testosterone production.

    Disruptions in Hormonal Regulation

    • Disruptions in the hormonal regulation of the testes can lead to:
      • Infertility: Difficulty or inability to conceive.
      • Hypogonadism: Low testosterone levels, leading to reduced sperm production, decreased libido, and other symptoms.

    ### Hormones and their Functions

    • Inhibin:
      • Produced by Sertoli cells.
      • Provides negative feedback to the anterior pituitary, reducing FSH secretion.
    • DHT (Dihydrotestosterone):
      • A potent androgen derived from testosterone.
      • Plays a role in various androgen-dependent processes including prostate growth.

    Testosterone and Male Sexual Development

    • Testosterone, a male sex hormone, plays a crucial role in the development and maintenance of male sexual characteristics, both primary and secondary.

    Primary Sexual Characteristics

    • Primary sexual characteristics are those directly involved in reproduction.
    • Testosterone is responsible for the development and growth of the penis and testes.

    Secondary Sexual Characteristics

    • Secondary sexual characteristics are not directly involved in reproduction, but reflect the effects of testosterone on physical development, appearing during puberty.
    • Testosterone causes:
      • Deepening of the voice: This is due to the growth of the larynx (Adam's apple).
      • Increased muscle mass and bone density: This contributes to a more robust physique.
      • Growth of body and facial hair: This is a noticeable sign of puberty.

    Role of Testosterone in Spermatogenesis

    • Spermatogenesis refers to the process of sperm production.
    • Testosterone is essential for initiating and maintaining the production of mature sperm cells.

    Other Effects of Testosterone

    • Increased sebaceous gland activity: This can result in acne and oily skin.
    • Skeletal muscle development: Increased muscle mass is a key secondary characteristic.
    • Higher basal metabolic rate: Testosterone influences energy metabolism.
    • Increased bone density: Testosterone strengthens bones and promotes growth.

    Low Testosterone Levels

    • Low testosterone levels can lead to:
      • Reduced fertility: Decreased sperm production can impact reproductive ability.
      • Decreased bone density: This may lead to bone weakness and increased fracture risk.

    Testosterone Replacement Therapy

    • Testosterone replacement therapy may be recommended for:
      • Hypogonadism: This condition involves insufficient testosterone production.

    Key Indicators of Puberty in Males

    • The development of secondary sexual characteristics such as deepening of the voice, increased muscle mass, and growth of body hair are key signs of male puberty, all influenced by testosterone levels.

    Studying That Suits You

    Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

    Quiz Team

    Description

    Test your knowledge on the reproductive system, focusing on its primary functions and the roles of gametes and gonads. Learn about the differences between male and female reproductive organs and their significance in passing genetic information. This quiz is perfect for students exploring human biology.

    More Like This

    Use Quizgecko on...
    Browser
    Open
    Browser
    Browser