Prostaglandins and Fertilization
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Questions and Answers

What is the primary function of prostaglandins in fertilization?

  • Neutralizing the acidity of vaginal secretions
  • Reversing the peristaltic contractions in the uterus and fallopian tubes (correct)
  • Inhibiting the secretion of GnRH
  • Increasing the motility of sperm

    • What is the primary function of the fluid secreted by the prostate gland?

  • Regulating the secretion of GnRH
  • Stimulating the secretion of testosterone
  • Acidifying the seminal fluid to prevent infections
  • Neutralizing the acidity of the seminal fluid to enhance sperm motility (correct)

    • What is the pH range required for optimal sperm motility?

  • pH 6.0 to 6.5 (correct)
  • pH 8.0 to 8.5
  • pH 3.5 to 4.0
  • pH 7.0 to 7.5

    • What is the primary source of seminal fluid in semen?

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

    What is the primary function of testosterone in regulating fertility?

    <p>Inhibiting the secretion of LH and FSH</p> Signup and view all the answers

    What is the primary function of GnRH in regulating fertility?

    <p>Regulating the secretion of LH and FSH</p> Signup and view all the answers

    What is the primary function of the bulbourethral glands in semen?

    <p>Providing a small amount of fluid to semen</p> Signup and view all the answers

    What is the purpose of the slightly alkaline prostatic fluid in fertilization?

    <p>To neutralize the acidity of vaginal secretions</p> Signup and view all the answers

    What is the primary function of inhibin in the context of spermatogenesis?

    <p>Inhibiting the secretion of FSH</p> Signup and view all the answers

    What is the effect of high concentrations of estrogens on spermatogenesis?

    <p>Induction of infertility</p> Signup and view all the answers

    What is the role of growth hormone in spermatogenesis?

    <p>Promoting the development of spermatogonia</p> Signup and view all the answers

    What is the optimal pH range for sperm motility?

    <p>Slightly alkaline</p> Signup and view all the answers

    What is the primary function of the seminal vesicles?

    <p>Providing nutrients for sperm fertilization</p> Signup and view all the answers

    What is the role of prostaglandins in the seminal vesicle secretion?

    <p>Providing nutrients for sperm fertilization</p> Signup and view all the answers

    What is the effect of increased temperature on sperm activity?

    <p>Increased motility and metabolism, but shortened lifespan</p> Signup and view all the answers

    What is the typical lifespan of sperm in the female genital tract?

    <p>1 to 2 days</p> Signup and view all the answers

    What is the primary function of androgen binding protein in the seminiferous tubules?

    <p>To facilitate the transport of testosterone and dihydrotestosterone at higher concentrations</p> Signup and view all the answers

    Which hormone regulates the production of inhibin by Sertoli cells?

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

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

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

    What is the result of high levels of testosterone and dihydrotestosterone in the seminiferous tubules?

    <p>Maturation of spermatozoa in the epididymis</p> Signup and view all the answers

    Which hormone stimulates the production of testosterone by Leydig cells?

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

    What is the primary function of Sertoli cells in the seminiferous tubules?

    <p>To synthesize inhibin and androgen-binding protein</p> Signup and view all the answers

    What is the result of low levels of sperm production in the seminiferous tubules?

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

    What is the primary function of inhibin in the seminiferous tubules?

    <p>To inhibit the secretion of FSH</p> Signup and view all the answers

    What is the primary function of the mucus derived from the urethral glands and bulbourethral glands?

    <p>To neutralize the acidic urinary pH</p> Signup and view all the answers

    What is the role of the cavernous smooth musculature in the erectile process?

    <p>To dilate blood vessels and increase blood flow</p> Signup and view all the answers

    What is the typical partial pressure of oxygen (PO2) in the flaccid penis?

    <p>35mmHg</p> Signup and view all the answers

    What is the effect of nutritional deprivation on puberty?

    <p>It delays puberty by repressing reproductive neuroendocrine function</p> Signup and view all the answers

    What is the function of kisspeptin in the infundibular nucleus of the medium basal hypothalamus (MBH)?

    <p>To stimulate GnRH pulses</p> Signup and view all the answers

    What is the location of spermatogonia in the testes?

    <p>In the seminiferous tubules</p> Signup and view all the answers

    What is the main function of the blood-testis barrier?

    <p>To prevent the immune system from producing antibodies against spermatids</p> Signup and view all the answers

    What is the role of the smooth muscles of the arteriolar and arterial walls in the erectile process?

    <p>To dilate blood vessels and increase blood flow</p> Signup and view all the answers

    What is the location of spermatogonia with doubled DNA?

    <p>Basal compartment</p> Signup and view all the answers

    What is the state of the smooth muscles in the flaccid penis?

    <p>Tonic contraction</p> Signup and view all the answers

    What is the fate of completely transformed sperm?

    <p>They enter the epididymis</p> Signup and view all the answers

    What is the function of the seminal vesicles?

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

    What is the path of spermatozoa after leaving the epididymis?

    <p>Vas deferens, ampulla of the vas deferens, prostate gland</p> Signup and view all the answers

    What is the purpose of the blood-testis barrier?

    <p>To prevent the immune system from producing antibodies against spermatozoa</p> Signup and view all the answers

    Where do spermatocytes, spermatids, and spermatozoa reside?

    <p>Adluminal compartment</p> Signup and view all the answers

    What is the final connecting link from the testis to the exterior?

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

    What is the primary function of the septa in the testis?

    <p>To subdivide the testis into lobules</p> Signup and view all the answers

    What is the function of the tight junctions between Sertoli cells?

    <p>To divide the tubules into two separate compartments</p> Signup and view all the answers

    Where do the mitotic spermatogonia remain in the seminiferous tubules?

    <p>In the basal compartment</p> Signup and view all the answers

    What is the role of Leydig cells in the testis?

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

    Where are the Leydig cells located in the testis?

    <p>Between the seminiferous tubules</p> Signup and view all the answers

    What is the result of the action of testosterone on the accessory sex glands?

    <p>Secretion from the accessory sex glands</p> Signup and view all the answers

    What is the significance of the mediastinum testis in the testis?

    <p>It is a thickening of the tunica albuginea</p> Signup and view all the answers

    What is the role of the stroma in the testis?

    <p>To provide a connective tissue framework for the seminiferous tubules</p> Signup and view all the answers

    What is the primary function of the mitochondria in the proximal portion of the sperm tail?

    <p>To generate energy for the sperm</p> Signup and view all the answers

    During which stage of spermatogenesis do sperm develop the capability of motility?

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

    What is the purpose of the fluid secreted by the Sertoli cells and the epithelium of the epididymis?

    <p>To provide nutrients for sperm maturation</p> Signup and view all the answers

    How many chromosomes are found in each spermatogonium?

    <p>23</p> Signup and view all the answers

    Where are sperm stored after formation in the seminiferous tubules?

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

    What is the result of maturation of the sperm in the Epydidimi?

    <p>Sperm develop capability of motility</p> Signup and view all the answers

    What is the purpose of the axoneme in the sperm tail?

    <p>To regulate sperm motility</p> Signup and view all the answers

    How long can sperm remain fertile in the vas deferens?

    <p>At least a month</p> Signup and view all the answers

    During spermatogenesis, what is the main function of the acrosome in the head of the sperm?

    <p>To facilitate the entry of sperm into the ovum</p> Signup and view all the answers

    What is the significance of the Sertoli cells in the seminiferous tubules?

    <p>They support the development of sperm cells by providing nutrients and structural support</p> Signup and view all the answers

    What is the purpose of the blood-testis barrier in the seminiferous tubules?

    <p>To prevent the entry of immune cells into the tubules</p> Signup and view all the answers

    During spermatogenesis, what is the result of meiotic division in primary spermatocytes?

    <p>The formation of 2 secondary spermatocytes with 23 chromosomes each</p> Signup and view all the answers

    What is the duration of the entire process of spermatogenesis from spermatogonia to spermatozoa?

    <p>74 days</p> Signup and view all the answers

    What is the characteristic of the cells in the seminiferous tubules?

    <p>They have an epithelioid aspect</p> Signup and view all the answers

    Where do spermatogonia migrate to during the first stage of spermatogenesis?

    <p>Towards the central lumen of the seminiferous tubules</p> Signup and view all the answers

    What is the significance of the Sertoli cells in the formation of the blood-testis barrier?

    <p>They form tight junctions to prevent immune cells from entering the tubules</p> Signup and view all the answers

    What is the primary function of androgen-binding protein in the seminiferous tubules?

    <p>To bind to testosterone and dihydrotestosterone, making them less lipophilic</p> Signup and view all the answers

    Which hormone Stimulates the production of testosterone by Leydig cells?

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

    What is the result of low levels of sperm production in the seminiferous tubules?

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

    What is the primary function of Sertoli cells in the seminiferous tubules?

    <p>To synthesize and release proteins involved in reproduction</p> Signup and view all the answers

    What is the role of inhibin in the seminiferous tubules?

    <p>To inhibit the secretion of FSH</p> Signup and view all the answers

    What is the effect of high levels of testosterone and dihydrotestosterone in the seminiferous tubules?

    <p>Increased spermatogenesis and maturation of spermatozoa</p> Signup and view all the answers

    Which hormone regulates the production of inhibin by Sertoli cells?

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

    What is the function of the blood-testis barrier?

    <p>To provide a physical barrier between the seminiferous tubules and the bloodstream</p> Signup and view all the answers

    Study Notes

    Prostaglandins and Fertilization

    • Prostaglandins help fertilization by reacting with cervical mucus to make it receptive to sperm movement
    • They also possibly cause reverse peristaltic contractions in the uterus and fallopian tubes to move sperm towards the ovaries
    • Some sperm can arrive at the upper ends of the fallopian tubes within 5 minutes
    • Prostaglandins stimulate sperm motility

    Prostatic Gland Function

    • The prostate gland secretes a fluid containing calcium, citrate ion, phosphate ion, clotting enzyme, and profibrinolysin
    • Prostatic fluid is more alkaline, neutralizing the acidity of the fluid from the vas deferens
    • This helps fertilization of the ovum by enhancing sperm motility

    Semen Composition

    • Semen contains fluid and sperm from the vas deferens (10%), fluid from the seminal vesicles (60%), fluid from the prostate gland (30%), and small amounts from mucous glands
    • The bulk of the semen is seminal vesicle fluid, which is the last to be ejaculated and serves to wash the sperm through the ejaculatory duct and urethra

    Testosterone and GnRH Regulation

    • Testosterone inhibits anterior pituitary secretion of LH, mainly by decreasing GnRH secretion
    • This produces a decrease in secretion of both LH and FSH by the anterior pituitary
    • Testosterone levels are automatically regulated

    Hormonal Stimuli to Spermatogenesis

    • Inhibin, a glycoprotein, inhibits the secretion of FSH
    • Estrogens, produced by Sertoli cells, stimulate FSH in low concentrations, inducing spermiogenesis
    • Growth hormone promotes early division of spermatogonia, and thyroid hormones control metabolic functions of the testes

    Physiology of Mature Sperm

    • Mature sperm are capable of flagellated movement through fluid medium at velocities of 1-4 mm/min
    • Activity is enhanced in a slightly alkaline medium, but greatly depressed in a mildly acidic medium
    • Sperm activity increases with increasing temperature, but also does the rate of metabolism, shortening their life

    Function of Seminal Vesicles

    • Seminal vesicles secrete a mucoid material containing fructose, citric acid, and prostaglandins
    • During ejaculation, the seminal vesicles empty their contents into the ejaculatory duct, providing nutrients for sperm

    Sex Determination

    • The sex of the offspring is determined by which type of sperm (X or Y chromosome) fertilizes the ovum

    Hormonal Control of Spermatogenesis

    • Testosterone, secreted by Leydig cells, is essential for growth and division of testicular germinal cells
    • LH, secreted by the anterior pituitary gland, induces secretion of testosterone by Leydig cells
    • FSH, secreted by the anterior pituitary gland, induces spermiogenesis
    • Sertoli cells synthesize ca. 60 proteins related to reproduction, including inhibin, androgen-binding protein, and antimüllerian hormone

    Urethra and Its Functions

    • The urethra is supplied with alkaline mucus from the urethral glands and bulbourethral glands (Cowper glands)
    • This mucus, called pre-ejaculate, neutralizes acidic urinary pH

    Erectile Process

    • The cavernous smooth musculature and smooth muscles of the arteriolar and arterial walls play a key role in the erectile process
    • In the flaccid state, these smooth muscles are tonically contracted, allowing only a small amount of arterial flow for nutritional purposes
    • The blood partial pressure of oxygen (PO2) is about 35mmHg range

    Puberty

    • During childhood, the hypothalamus does not secrete significant amounts of GnRH due to the inhibitory effect of circulating sex steroid hormones
    • At puberty, the secretion of GnRH increases, and adult sexual life begins
    • Nutritional deprivation delays puberty by repressing reproductive neuroendocrine function
    • Kisspeptin expression is high and increases during puberty in the infundibular nucleus of the medium basal hypothalamus (MBH) in male and female

    Spermatogenesis

    • During formation of the embryo, primordial germ cells migrate into the testes and become spermatogonia
    • Spermatogonia, during puberty, begin to undergo mitotic division and proliferate and differentiate until forming sperm

    Male Reproductive System

    • The male reproductive system consists of two main elements: the gonads (testes) and the complex array of glands and ducts that constitute the sex accessory organs
    • The testis is composed of up to 900 coiled seminiferous tubules, in which the sperm are formed

    Testis Structure

    • The seminiferous tubules are embedded in a connective tissue stroma
    • Each lobule contains one to four seminiferous tubules
    • The septa converge towards the midline of the posterior border, meeting along a thickening of the tunica albuginea called the mediastinum testis

    Leydig Cells

    • Leydig cells are interstitial cells that contain many cholesterol-lipid droplets
    • They make and secrete testosterone in response to luteinizing hormone
    • Testosterone promotes production of spermatozoa, secretion from the accessory sex glands, and acquisition of male secondary characteristics

    Sertoli Cells

    • Sertoli cells sit on a basal membrane and stand in direct contact with one another and with the germ cells
    • They are bound together with neighboring cells through tight junctions
    • The tight junctions produce the blood-testis barrier that restricts the diffusion of substances from the interstitum and blood vessels

    Spermatogenesis Process

    • The mitotic spermatogonia remain in the basal compartment
    • Differentiating progeny enter the adluminal compartment, and are sealed off from the basal compartment
    • Meiosis and the differentiation of spermatids occur in the adluminal compartment
    • The inter-Sertoli cell junctions transiently remodel to allow germ cells to move from the basal to the adluminal compartments

    Epididymis and Vas Deferens

    • The completely transformed sperm then goes into the epididymis, which leads into the vas deferens
    • The vas deferens enlarges into the ampulla of the vas deferens immediately before entering the body of the prostate gland

    Spermatogenesis

    • Spermatogenesis takes place in the seminiferous tubules, stimulated by anterior pituitary gonadotropic hormones, beginning at around 13 years old and continuing throughout most of life, decreasing in old age.

    Formation of Sperm

    • Spermatogonia migrate among Sertoli cells toward the central lumen of the seminiferous tubule.
    • Spermatids differentiate into spermatozoa, elongating and composing of a head and a tail.
    • The head contains the nucleus with a thin cytoplasmic and cell membrane layer, and has an acrosome on the outside with enzymes like hyaluronidase and proteolytic enzymes.
    • The tail has a central skeleton (axoneme), a thin cell membrane, and a collection of mitochondria.

    Meiosis

    • Spermatogonia cross the Sertoli cell layer, modifying and enlarging to form primary spermatocytes.
    • Each primary spermatocyte undergoes meiotic division to form 2 secondary spermatocytes.
    • Secondary spermatocytes divide to form spermatids, eventually modified to become spermatozoa.
    • Each spermatid receives 23 chromosomes, with genes contributing to half of the genetic characteristics of the father.
    • The entire spermatogenesis process takes 74 days.

    Hormonal Stimulus to Spermatogenesis

    • Testosterone, secreted by Leydig cells, is essential for growth and division of testicular germinal cells.
    • LH, secreted by the anterior pituitary gland, induces testosterone secretion by Leydig cells.
    • FSH, also secreted by the anterior pituitary gland, induces spermiogenesis and controls Sertoli cell functions.

    Sertoli Cell Functions

    • Sertoli cells synthesize around 60 proteins related to reproduction, including inhibin, androgen-binding protein, and antimüllerian hormone.
    • Androgen-binding protein (ABP) has a great affinity to testosterone and dihydrotestosterone, making them less lipophilic and allowing higher concentrations in the seminiferous tubules.

    Inhibin and Feedback Mechanism

    • Inhibin, synthesized by Sertoli cells, inhibits FSH secretion and possibly GnRH secretion.
    • When sperm is not produced, FSH secretion increases, and when there is too much spermatogenesis, FSH secretion decreases.

    Sperm Maturation and Storage

    • Sperm formed in the seminiferous tubules goes to the epididymis, where they spend several days and acquire motility.
    • Sperm in the seminiferous tubules and early epididymis are non-motile and non-fertile.
    • Sperm can be stored in the vas deferens for at least a month, remaining fertile, but becoming active only during ejaculation.
    • Maturation occurs in the epididymis, where sperm develop motility and become capable of fertilizing the ovum.

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