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What is the primary function of prostaglandins in fertilization?
What is the primary function of prostaglandins in fertilization?
What is the primary function of the fluid secreted by the prostate gland?
What is the primary function of the fluid secreted by the prostate gland?
What is the pH range required for optimal sperm motility?
What is the pH range required for optimal sperm motility?
What is the primary source of seminal fluid in semen?
What is the primary source of seminal fluid in semen?
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What is the primary function of testosterone in regulating fertility?
What is the primary function of testosterone in regulating fertility?
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What is the primary function of GnRH in regulating fertility?
What is the primary function of GnRH in regulating fertility?
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What is the primary function of the bulbourethral glands in semen?
What is the primary function of the bulbourethral glands in semen?
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What is the purpose of the slightly alkaline prostatic fluid in fertilization?
What is the purpose of the slightly alkaline prostatic fluid in fertilization?
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What is the primary function of inhibin in the context of spermatogenesis?
What is the primary function of inhibin in the context of spermatogenesis?
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What is the effect of high concentrations of estrogens on spermatogenesis?
What is the effect of high concentrations of estrogens on spermatogenesis?
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What is the role of growth hormone in spermatogenesis?
What is the role of growth hormone in spermatogenesis?
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What is the optimal pH range for sperm motility?
What is the optimal pH range for sperm motility?
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What is the primary function of the seminal vesicles?
What is the primary function of the seminal vesicles?
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What is the role of prostaglandins in the seminal vesicle secretion?
What is the role of prostaglandins in the seminal vesicle secretion?
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What is the effect of increased temperature on sperm activity?
What is the effect of increased temperature on sperm activity?
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What is the typical lifespan of sperm in the female genital tract?
What is the typical lifespan of sperm in the female genital tract?
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What is the primary function of androgen binding protein in the seminiferous tubules?
What is the primary function of androgen binding protein in the seminiferous tubules?
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Which hormone regulates the production of inhibin by Sertoli cells?
Which hormone regulates the production of inhibin by Sertoli cells?
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What is the primary function of Leydig cells in the testis?
What is the primary function of Leydig cells in the testis?
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What is the result of high levels of testosterone and dihydrotestosterone in the seminiferous tubules?
What is the result of high levels of testosterone and dihydrotestosterone in the seminiferous tubules?
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Which hormone stimulates the production of testosterone by Leydig cells?
Which hormone stimulates the production of testosterone by Leydig cells?
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What is the primary function of Sertoli cells in the seminiferous tubules?
What is the primary function of Sertoli cells in the seminiferous tubules?
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What is the result of low levels of sperm production in the seminiferous tubules?
What is the result of low levels of sperm production in the seminiferous tubules?
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What is the primary function of inhibin in the seminiferous tubules?
What is the primary function of inhibin in the seminiferous tubules?
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What is the primary function of the mucus derived from the urethral glands and bulbourethral glands?
What is the primary function of the mucus derived from the urethral glands and bulbourethral glands?
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What is the role of the cavernous smooth musculature in the erectile process?
What is the role of the cavernous smooth musculature in the erectile process?
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What is the typical partial pressure of oxygen (PO2) in the flaccid penis?
What is the typical partial pressure of oxygen (PO2) in the flaccid penis?
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What is the effect of nutritional deprivation on puberty?
What is the effect of nutritional deprivation on puberty?
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What is the function of kisspeptin in the infundibular nucleus of the medium basal hypothalamus (MBH)?
What is the function of kisspeptin in the infundibular nucleus of the medium basal hypothalamus (MBH)?
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What is the location of spermatogonia in the testes?
What is the location of spermatogonia in the testes?
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What is the main function of the blood-testis barrier?
What is the main function of the blood-testis barrier?
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What is the role of the smooth muscles of the arteriolar and arterial walls in the erectile process?
What is the role of the smooth muscles of the arteriolar and arterial walls in the erectile process?
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What is the location of spermatogonia with doubled DNA?
What is the location of spermatogonia with doubled DNA?
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What is the state of the smooth muscles in the flaccid penis?
What is the state of the smooth muscles in the flaccid penis?
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What is the fate of completely transformed sperm?
What is the fate of completely transformed sperm?
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What is the function of the seminal vesicles?
What is the function of the seminal vesicles?
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What is the path of spermatozoa after leaving the epididymis?
What is the path of spermatozoa after leaving the epididymis?
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What is the purpose of the blood-testis barrier?
What is the purpose of the blood-testis barrier?
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Where do spermatocytes, spermatids, and spermatozoa reside?
Where do spermatocytes, spermatids, and spermatozoa reside?
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What is the final connecting link from the testis to the exterior?
What is the final connecting link from the testis to the exterior?
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What is the primary function of the septa in the testis?
What is the primary function of the septa in the testis?
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What is the function of the tight junctions between Sertoli cells?
What is the function of the tight junctions between Sertoli cells?
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Where do the mitotic spermatogonia remain in the seminiferous tubules?
Where do the mitotic spermatogonia remain in the seminiferous tubules?
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What is the role of Leydig cells in the testis?
What is the role of Leydig cells in the testis?
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Where are the Leydig cells located in the testis?
Where are the Leydig cells located in the testis?
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What is the result of the action of testosterone on the accessory sex glands?
What is the result of the action of testosterone on the accessory sex glands?
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What is the significance of the mediastinum testis in the testis?
What is the significance of the mediastinum testis in the testis?
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What is the role of the stroma in the testis?
What is the role of the stroma in the testis?
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What is the primary function of the mitochondria in the proximal portion of the sperm tail?
What is the primary function of the mitochondria in the proximal portion of the sperm tail?
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During which stage of spermatogenesis do sperm develop the capability of motility?
During which stage of spermatogenesis do sperm develop the capability of motility?
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What is the purpose of the fluid secreted by the Sertoli cells and the epithelium of the epididymis?
What is the purpose of the fluid secreted by the Sertoli cells and the epithelium of the epididymis?
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How many chromosomes are found in each spermatogonium?
How many chromosomes are found in each spermatogonium?
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Where are sperm stored after formation in the seminiferous tubules?
Where are sperm stored after formation in the seminiferous tubules?
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What is the result of maturation of the sperm in the Epydidimi?
What is the result of maturation of the sperm in the Epydidimi?
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What is the purpose of the axoneme in the sperm tail?
What is the purpose of the axoneme in the sperm tail?
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How long can sperm remain fertile in the vas deferens?
How long can sperm remain fertile in the vas deferens?
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During spermatogenesis, what is the main function of the acrosome in the head of the sperm?
During spermatogenesis, what is the main function of the acrosome in the head of the sperm?
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What is the significance of the Sertoli cells in the seminiferous tubules?
What is the significance of the Sertoli cells in the seminiferous tubules?
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What is the purpose of the blood-testis barrier in the seminiferous tubules?
What is the purpose of the blood-testis barrier in the seminiferous tubules?
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During spermatogenesis, what is the result of meiotic division in primary spermatocytes?
During spermatogenesis, what is the result of meiotic division in primary spermatocytes?
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What is the duration of the entire process of spermatogenesis from spermatogonia to spermatozoa?
What is the duration of the entire process of spermatogenesis from spermatogonia to spermatozoa?
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What is the characteristic of the cells in the seminiferous tubules?
What is the characteristic of the cells in the seminiferous tubules?
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Where do spermatogonia migrate to during the first stage of spermatogenesis?
Where do spermatogonia migrate to during the first stage of spermatogenesis?
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What is the significance of the Sertoli cells in the formation of the blood-testis barrier?
What is the significance of the Sertoli cells in the formation of the blood-testis barrier?
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What is the primary function of androgen-binding protein in the seminiferous tubules?
What is the primary function of androgen-binding protein in the seminiferous tubules?
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Which hormone Stimulates the production of testosterone by Leydig cells?
Which hormone Stimulates the production of testosterone by Leydig cells?
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What is the result of low levels of sperm production in the seminiferous tubules?
What is the result of low levels of sperm production in the seminiferous tubules?
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What is the primary function of Sertoli cells in the seminiferous tubules?
What is the primary function of Sertoli cells in the seminiferous tubules?
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What is the role of inhibin in the seminiferous tubules?
What is the role of inhibin in the seminiferous tubules?
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What is the effect of high levels of testosterone and dihydrotestosterone in the seminiferous tubules?
What is the effect of high levels of testosterone and dihydrotestosterone in the seminiferous tubules?
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Which hormone regulates the production of inhibin by Sertoli cells?
Which hormone regulates the production of inhibin by Sertoli cells?
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What is the function of the blood-testis barrier?
What is the function of the blood-testis barrier?
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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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Learn about the role of prostaglandins in fertilization, including their effects on cervical mucus, uterine and fallopian tube contractions, and sperm motility.
