Male Reproductive System
Introduction
The reproductive system ensures the continuation of the species. The major difference between the reproductive system and other systems such as the urinary system, cardiovascular system, respiratory system, etc. is that other systems function for the survival of the individual but the reproductive system (producing offspring) is not necessary for the survival of the individual.
Table of Contents
An individual can live a long and healthy life without reproducing offspring. However, a continuation of generation depends only on the reproductive system.
Read And Learn More: Medical Physiology Notes
Four processes execute the function of the reproductive system:
- Production of egg and sperm
- Transport and maintenance of egg and sperm
- Nurturing of developing offspring
- Secretion of male and female sex hormones.
- The organs of the reproductive system are divided into two groups namely internal reproductive organs and external genital organs. Gonads are the main organs that produce the gametes – sperm and egg or ovum. A pair of testes (singular testis) produces sperms in males and a pair of ovaries produces ovum in females.
- Normally, most of the animals including humans are either definite males or definite females. However, in some organisms like earthworms and snails, both sexes may be present in the same organism and this condition is known as hermaphroditism.
- In humans and most of the higher animals, reproduction occurs sexually, i.e. by mating. However, there are some species like insects which can produce offspring without mating.
Male Reproductive Organs
Male reproductive organs include the primary sex organs and accessory sex organs.
Primary Sex Organs
Testis
- Testis is the primary sex organ or gonad in males. It corresponds with the ovary in females. There are two testes in almost all species. In human beings both the testes are situated in the scrotum.
- Each testis weighs about 15-19 g and measures about 5×3 cm. Testis contains about 900 coiled tubules known as seminiferous tubules which produce sperms.
- Seminiferous tubules continue as the vas efferent, which forms the epi didymous. It is continued as vas deferens. The terminal portion of the vas deferens is called the ampulla.
Accessory Sex Organs
Accessory sex organs in males are
- Seminal vesicles
- Prostate gland
- Urethra
- Penis
Seminal Vesicles
The seminal vesicles are situated on either side of the prostate gland. Secretions of seminal vesicles are emptied into the ampulla of the vas deferens. The ampulla of the vas deferens is continued as the ejaculatory duct, which passes through the prostate to form the internal urethra.
Prostate Gland
The prostate gland is constituted of many secretory glands. Secretion from these glands is emptied into the internal urethra through the utriculus prostaticus.
Urethra
Urethra has two parts namely, internal urethra and external urethra. The internal urethra is the continuation of the ejaculatory duct. The internal urethra passes through the penis as the external urethra, Urethra contains mucus glands throughout its length, which are called glands of Littre. The bilateral bulbourethral glands also open into the urethra.
Penis
Penis is the male genital organ. Urethra passes through the penis and opens to the exterior. Penis is formed by three erectile tissue masses, i.e. a paired corpora cavernosa and an unpaired corpus spongiosum. The corpus spongiosum surrounds the urethra and terminates distally to form a glans penis.
External and Internal Genitalia
The external genital organs in males are the scrotum, penis, and urethra. The remaining sex organs constitute the internal genitalia.
Functional Anatomy Of Testis
The testes are ovoid or walnut-shaped bodies having the organization of compound tubular glands. Both the testes are located in the sac-like structure called the scrotum and are suspended.
Coverings Of Testis
Each testis is enclosed by three coverings.
1. Tunica vasculosa
Tunica vasculosa is the innermost covering. It is made up of connective tissue and it is rich in blood vessels
2. Tunica Albuginea
Tunica albuginea is the middle covering. It is a dense fibrous capsule
3. Tunica Vaginalis
- It is the outermost closed cleft-like covering which is constituted by mesothelial cells. The tunica vaginalis is formed by visceral and parietal layers.
- Beth these layers glide on one another and allow free movement of testes. The visceral layer of tunica vaginalis adheres to tunica albuginea and the parietal layer lines the inner surface of the scrotum.
- All three layers cover the anterior and lateral surfaces of the testis and the posterior surface is covered by tunica albuginea only.
- The tunica albuginea on the posterior surface of the testis is thickened to form the mediastinum testis. From this, the connective tissue septa called septula testis radiate into the testis and bind with tunica albuginea at various points.
- By this, the interior of the testis is divided into a number of pyramidal lobules, with bases directed towards the periphery and the apices towards the mediastinum.
- The septula do not form a complete partition. Because of this, the lobules of the testis anastomose with one another in many places.
Parenchyma Of Testis
Seminiferous Tubules
Each testis has about 200-300 lobules. Each lobule contains 1-4 coiled tubules known as seminiferous tubules. The seminiferous tubules are surrounded and supported by interlobular connective tissue. The seminiferous tubules do not end bluntly but, form single, double, or triple arches. The limbs of an arch are not in the same lobule.
Rete Testis
Towards the apex of each seminiferous lobule, the convoluted tubules unite with a narrow straight tubule. The straight tubules from all the lobules pass into the mediastinum. There, the straight tubules join and form a network of thin-walled channels called the rete testis.
Vas Efferens
From the rete testis, 8-15 tubules called vas efferents arise. Vas efferent join together and form the head of the epididymis and then converge to form the duct of the epididymis.
Epididymis
The duct of the epididymis is an enormously convoluted tubule with a length of about 4 meters. It begins at the head, where it receives vas efferent.
Vas Deferens
At the caudal pole of the testis, epididymis turns sharply upon itself and passes as vas deferens without any definite demarcation.
Interstitial Cells of Leydig
The parenchyma of the testis contains interstitial cells of Leydig in between the seminiferous tubules. The interstitial cells of Leydig are the hormone-secreting cells of the testis.
Seminiferous Tubule
Seminiferous tubules are thread-like convoluted tubular structures in which the spermatozoa or sperms are produced. There are about 400-600 seminiferous tubules in each testis. The length of each seminiferous tubule is between 30 and 70 cm. The diameter of the tubules is between 150 and 300 p. The wall of the seminiferous tubule is formed by three layers:
- The outer capsule or tunica propria is formed by fibro-elastic connective tissue
- A thin homogeneous basement membrane
- The complex stratified epithelium consists of two types of cells:
- Germ cells or spermatogenic cells
- Supporting cells called Sertoli cells.
Germ Cells
The germ cells or spermatogenic cells of seminiferous tubules are the precursor cells of spermatozoa. These cells lie in between Sertoli cells and are arranged in an orderly manner in 4-8 layers. The germ cells occupy the spaces between the basement membrane and the lumen of seminiferous tubules.
In children, the testis is not fully developed. Therefore, only the primitive germ cells called spermatogonia are present. With the onset of puberty, the spermatogenic cells are represented in all stages of differentiation.
Different stages of spermatogenic cells seen from the periphery to the lumen of seminiferous tubules are:
- Spermatogonium
- Primary spermatocytes
- Secondary spermatozyte
- Spermatid.
Sertoli Cells
- The Sertoli cells are the supporting cells that provide support, protection, and nourishment for spermatogenic cells present in seminiferous tubules. Sertoli cells are also known as sustentacular cells or nurse cells.
- Sertoli cells are large and tall irregular columnar cells extending from the basement membrane to the lumen of the seminiferous tubule. The spermatogenic cells present in the seminiferous tubule are attached to Sertoli cells by means of cytoplasmic connection.
- This attachment between germ cells and Sertoli cells exists till the matured spermatozoa are released into the lumen of seminiferous tubules.
Functions of Sertoli cells
Sertoli cells provide an environment for the development and maturation of spermatogenic cells.
Sertoli cells:
- Support and nourish the spermatogenic cells till the spermatozoa are released from them
- Convert androgens into estrogen. The enzyme aromatase which is present in Sertoli cells is responsible for the conversion of androgens into estrogen
- Secrete androgen binding protein (ABP) which is essential for testosterone activity, particularly in spermatogenesis.
- Secrete estrogen-binding protein (EBP)
- Secrete inhibin which inhibits the release of FSH from the anterior pituitary
- Secrete ucLvin which has the opposite action of inhibin
- Secrete Mcr .tan regression factor (MRF) in fetal testes sliT is also called Mullerian inhibiting substance (MLS). MRF is responsible for the regression Mullerian duct during sex differentiation in the fetus.
Blood-testis Barrier
Blood-testis barrier is a mechanical barrier that separates blood from the seminiferous tubules of the testes. It is formed by tight junctions between the adjacent Sertoli cells near the basal membrane of the seminiferous tubule.
Functions of blood-testes barrier
Blood-testes barrier prevents the entry of many substances into the lumen of seminiferous tubule from blood and the fluid of surrounding tissues viz.
- Large molecules including proteins, polysaccharides, and cytotoxic substances
- Medium-sized molecules like galactose.
However, the blood-testes barrier permits some substances:
- Water and very small water-soluble molecules like urea
- Nutritive substances essential for the developing spermatozoa
- Hormones are necessary for spermatogenesis.
Damage of blood-testes barrier
Blood-testes barrier is commonly damaged by trauma or viral infection like mumps. Whenever the blood-testes barrier is damaged the sperms enter the blood. The immune system of the body is activated resulting in the production of autoantibodies against sperms. The antibodies destroy the germ cells leading to consequent sterility.
Functions Of Testis
Testis performs two functions:
- Gametogenic function: It is the general term that refers to the production of gametes in the gonads
- Endocrine function: It is the secretion of male sex hormones.
Gametogenic Functions Of Testis – Spermatogenesis
Spermatogenesis is the process by which the male gametes called spermatozoa (sperms) are formed from the Primitive Germ Cells (Spermatogonia) In The Testis.
It Takes 74 Days For The Formation of sperm from a primitive germ cell. Throughout the process of spermatogenesis, the germ cells have cytoplasmic attachment with Sertoli cells. Sertoli cells supply all the necessary materials for spermatogenesis through the cytoplasmic attachment.
Stages Of Spermatogenesis
Spermatogenesis occurs in four stages:
- Stage of proliferation
- Stage of growth
- Stage of maturation
- Stage of transformation.
1. Stage of Proliferation
- Each spermatogonium contains a diploid number of chromosomes. In man, there are 23 pairs of chromosomes. One member of each pair is from maternal origin and the other one is from paternal origin.
- The 23 pairs include 22 pairs of autosomal chromosomes and one pair of sex chromosomes. The sex chromosomes are one X chromosome and one Y chromosome.
- The spermatogonia near the basement membrane of the seminiferous tubule are larger in size. During the proliferative stage, spermatogonia divide by mitosis without any change in chromosomal number. In man, there are usually seven generations of spermatogonia.
- The last generation enters the stage of growth as the primary spermatocyte. During this stage, the spermatogonia migrate along with Sertoli cells towards the lumen of the seminiferous tubule.
2. Stage of Growth
In this stage, the primary spermatocyte grows into a large cell. Apart from growth, there is no other change in spermatocyte during this stage.
3. Stage of Maturation
After reaching the full size, each primary spermatocyte quickly undergoes meiotic or maturation division, which occurs in two phases:
First phase
In the first phase, each primary spermatocyte divides into two secondary spermatocytes. The significance of the first meiotic division is that each secondary spermatocyte receives only the haploid or half the number of chromosomes. 23 chromosomes include 22 autosomes and an X or a Y chromosome.
Second phase
During this phase, each secondary spermatocyte undergoes a second meiotic division resulting in two smaller cells called spermatids. Each spermatid has a haploid number of chromosomes.
4. Stage of Transformation
There is no further division. The spermatids are transformed into matured spermatozoa (sperms) by means of spermatogenesis and released by termination.
Spermiogenesis
It is the process by which spermatids become matured spermatozoa.
The changes taking place during spermiogenesis are:
- Condensation of nuclear material
- Formation of the acrosome, mitochondrial spiral filament, and tail structures
- Removal of extraneous (extra volume of nonessential) cytoplasm.
Termination
Termination is the process by which the matured sperms are released from Sertoli cells into the lumen of seminiferous tubules.
Role Of Sertoli Cells In Spermatogenesis
Sertoli cells influence spermatogenesis in four ways.
Sertoli cells:
- Support and nourish the germ cells
- Provide hormonal substances necessary for spermatogenesis
- Secrete androgen binding protein (ABP) which is essential for testosterone activity, particularly on spermatogenesis
- Release sperm into the lumen of seminiferous tubules (spermination).
Role Of Hormones In Spermatogenesis
Spermatogenesis is influenced by many hormones which act either directly or indirectly: Table 74-1 gives the hormones essential for each stage of spermatogenesis. The hormones necessary for spermatogenesis are:
- Follicle-stimulating hormone
- Testosterone
- Estrogen
- Luteinizing hormone
- Growth hormone
- Inrtibln
- Activin
1. Follicular Stimulating Hormone
The follicular stimulating hormone is responsible for the initiation of spermatogenesis. It binds with Sertoli cells and spermatogonia and induces the proliferation of spermatogonia. It also stimulates the formation of estrogen and androgen binding protein from Sertoli cells.
2. Testosterone
Testosterone is responsible for the sequence of remaining stages in spermatogenesis. It is also responsible for the maintenance of spermatogenesis. Testosterone activity is largely influenced by androgen-binding protein.
3. Estrogen
It is formed from testosterone in Sertoli cells. It is necessary for spermiogenesis.
4. Luteinizing Hormone
In males, this hormone is called interstitial cell stimulate- ” ing hormone. It is essential for the secretion of testosterone from Leydig cells.
5. Growth Hormone
Growth hormone is essential for the general metabolic processes in the testis. It is also necessary for the proliferation of spermatogonia. In pituitary dwarfs, spermatogenesis is severely affected.
6. Inhibin
- Inhibin is a peptide hormone and serves as a transforming growth factor. It is secreted by Sertoli cells In females, it is secreted by granulosa cells of ovarian follicles. Its secretion is stimulated by FSH.
- Inhibin plays an important role in the regulation of spermatogenesis by inhibiting FSH secretion through a feedback mechanism. FSH secreted from the anterior pituitary induces spermatogenesis by stimulating Sertoli cells.
- It also stimulates the secretion of inhibin from Sertoli cells. So, when the rate of spermatogenesis increases, there is a simultaneous increase in inhibin secretion also.
- Inhibin in turn acts on the anterior pituitary and inhibits secretion of FSH leading to a decrease in the pace of spermatogenesis. It is believed that inhibin also inhibits FSH secretion indirectly by inhibiting GnRH secretion from the hypothalamus.
7. Activin
- It is also a peptide hormone secreted in gonads along with inhibin. The exact location of its secretion in the testis is not known. It is suggested that it is secreted by Sertoli cafe -md Leydig cells.
- Activin has the opposite actions of inhibin. It increases FSH and accelerates spermatogenesis.
Other Factors Affecting Spermatogenesis
Spermatogenesis is also influenced by some other factors:
- An increase in the body temperature prevents spermatogenesis. Normally, the temperature in the scrotum is about 2°C less than the body temperature. The low temperature in the scrotum is essential for spermatogenesis. When the temperature increases, spermatogenesis stops.
- It is very common in cryptorchidism (undescended testes). In cryptorchidism, the testes are in the abdomen where the temperature is always higher than that of the scrotum. The high temperature in the abdomen results in the degeneration of seminiferous tubules and the absence of spermatogenesis.
- Infectious diseases such as mumps cause the degeneration of seminiferous tubules and the absence of spermatogenesis.
Endocrine Functions Of Testis
Testis secretes male sex hormones which are collectively called the androgens. Androgens secreted by the testis are:
- Testosterone
- Dihydrotestosterone
- Androstenedione.
Among these three androgens, testosterone is secreted in large quantities. However, dihydrotestosterone is more active. Two more hormones activin and inhibin are also secreted in the testis. However, these two hormones do not have an androgenic effect.
Source of Secretion of Androgens
The androgens are secreted in large quantities by the testes and in small quantities by the adrenal cortex.
Testes
In testes, the androgens are secreted by the interstitial cells of Leydig which form 20% of the mass of adult testis. Leydig cells are numerous in newborn male babies and in adult males. But in childhood, these cells are scanty or non-existing. So, the secretion of androgens occurs in newborn babies and after puberty.
Adrenal cortex
Androgens secreted by the zona reticularis of the adrenal cortex are testosterone, androstenedione, and de- hydroepiandrosterone. The adrenal androgens do not have any significant physiological actions because of their small quantity. In abnormal conditions, the hypersecretion of adrenal androgens results in sexual disorders.
Chemistry
Androgens are steroid hormones synthesized from cholesterol. Androgens are also synthesized directly from acetate. Testosterone is a C19 steroid.
Synthesis
The synthesis of male sex hormones is given
Plasma Level and Transport
The plasma level of testosterone in an adult male varies between 300 and 700 ng/dL. In adult females, the testosterone level is 30-60 mg/dL.
Two-thirds of testosterone is transported in plasma by gonadal steroid-binding globulin. It is p globulin in n-Tuire and it is also called sex steroid-binding globulin. The remaining one-third of testosterone is transported by ambition.
Metabolism
- In many target tissues, testosterone is converted into dihydrotestosterone which is the most active androgen. In some of the tissues such as adipose tissue, hypothalamus, and liver, testosterone is converted into estradiol.
- The major portion of testosterone is degraded in the liver. It is converted into inactive forms of androsterone and dehydroepiandrosterone. These two substances are later conjugated and excreted through urine.
Functions Of Testosterone
- In general, testosterone is responsible for the distinguishing characteristics of the masculine body. In fetal life, the testes are stimulated by human chorionic gonadotropins secreted by the placenta.
- But, in childhood, practically no testosterone is secreted approximately until 10-12 years of age. Afterward, testosterone secretion starts and, it increases rapidly at the onset of puberty and lasts through most of the remaining part of life. The secretion starts decreasing after 40 years and becomes almost zero by the age of 90 years.
Functions of Testosterone in Fetal Life
The fetal testes begin to secrete testosterone at about 2nd to 4th month of fetal life.
Testosterone performs three functions in the fetus:
- Sex differentiation in a fetus
- Development of accessory sex organs
- Descent of the testes.
1. Sex differentiation in the fetus
Sex chromosomes are responsible for the determination of the sex of the fetus. And, testosterone is responsible for the sex differentiation of the fetus.
Fetus has two genital ducts:
- The Mullerian duct gives rise to female accessory sex organs such as the vagina, uterus, and fallopian tube
- Wolffian duct which gives rise to male accessory sex organs such as epididymis, vas deferens, and seminal vesicles.
If testosterone is secreted from the genital ridge of the fetus at about the 7th week of intrauterine life, the Mullerian duct system disappears and male sex organs develop from the Wolffian duct.
In addition to testosterone, the Mullerian regression factor (MRF) secreted by Sertoli cells is also responsible for the regression of the Mullerian duct. In the absence of testosterone, the Wolffian duct regresses and female sex organs develop from the Mullerian duct
2. Development of accessory sex organs and external genitalia
Testosterone is also essential for the growth of the external genitalia viz. penis and scrotum and other accessory sex organs namely genital ducts, seminal vesicles, and prostate.
3. Descent of testes
- Descent of testes is the process by which testes enter the scrotum from the abdominal cavity. Initially, testes are developed in the abdominal cavity and are later pushed down into the scrotum through the inguinal canal just before birth.
- The process by which testes enter the scrotum is called the descent of testes. Testosterone is necessary for the descent of the testes.
Cryptorchidism
- Cryptorchidism is a congenital disorder characterized by the failure of one or both testes to descend from the abdomen into the scrotum. In such case, the testes are called undescended testes.
- Administration of testosterone or gonadotropic hormones (which stimulate Leydig cells) causes descent of the testes provided the inguinal canal is large enough to allow the passage of testes. Surgery is required if the inguinal canal is narrow. Males with untreated testes are prone to testicular cancer.
Functions of Testosterone in Adult Life
Testosterone has two important functions in adults:
- Effect on sex organs
- Effect on secondary sexual characters.
1. Effect on sex organs
Testosterone increases the size of the penis, scrotum, and testes after puberty. All these organs are enlarged at least 8 folds between the onset of puberty and the age of 20 years, under the influence of testosterone. Testosterone is also necessary for spermatogenesis.
2. Effect on secondary sexual characters
Secondary sexual characteristics are the physical and behavioral characteristics that appear at the time of puberty in humans. These characters distinguish the male from the female. Testosterone is responsible for the development of secondary sexual characteristics in males.
The secondary sexual characters in males are:
1. Effect on muscular growth
- One of the most important male sexual characteristics is the development of musculature after puberty. The mass of the muscle increases by about 50%.
- It is due to the anabolic effect of testosterone on proteins. It accelerates the transport of amino acids into the muscle cells, the synthesis of proteins, and the storage of proteins. It also decreases the breakdown of proteins.
2. Effect on bone growth
- After puberty, testosterone increases the thickness of bones with the deposition of calcium. The increase in thickness is due to an increase in the total content of the bone matrix.
- The increase in bone matrix is because of the protein anabolic activity of testosterone. The deposition of calcium is secondary to the increase in bone matrix.
- In addition to an increase in the size and strength of bones, testosterone also causes early fusion of epiphyses of long bones with shafts. So, if testes are removed before puberty, the fusion of epiphyses is delayed and the height of the person increases.
3. Effect on shoulder and pelvic bones
Testosterone causes the broadening of shoulders and it has a specific effect on the pelvis which results in:
- Lengthening of pelvis
- The funnel-like shape of the pelvis.
- Narrowing of the pelvic outlet.
Thus, the pelvis in males is different from that of females, which is broad and round or oval in shape.
4. Effect on skin
- Testosterone increases the thickness of skin over the entire body surface and the ruggedness of subcutaneous tissue. These changes in the skin are due to the deposition of proteins in the skin.
- It also increases the quantity of melanin pigment, which is responsible for the deepening of skin color. Testosterone enhances the secretory activity of sebaceous glands.
- So, at the time of puberty, when the body is exposed to a sudden increase in testosterone secretion, the excess secretion of sebum leads to the development of acne on the face. After a few years, the skin gets adapted to testosterone secretion and, the acne disappears.
5. Effect on hair distribution
- Testosterone causes a male type of hair distribution on the body, i.e. hair growth over the pubis, along linea alba up to the umbilicus, on the face, on the chest, and other parts of the body such as the back and limbs.
- In males, the pubic hair has the base of the triangle downwards whereas it is upwards. Testosterone decreases the hair growth on the head and may cause baldness if there is genetic background.
6. Effect on voice
At the time of adolescence, boys have a cracking voice. It is because of the testosterone effect which causes:
- Hypertrophy of laryngeal muscles
- Enlargement of larynx and lengthening
- Thickening of vocal cords.
Later, the cracking voice changes gradually into a typical adult male voice with a bossing sound.
7. Effect on basal metabolic rate
At the time of adolescence and earlier part of adult life, testosterone increases the basal metabolic rate to about 5-10%. It is mainly due to the anabolic effects of testosterone on protein metabolism.
8. Effect on electrolyte and water balance
Testosterone increases sodium reabsorption from renal tubules. So sodium retention increases. It leads to water retention and an increase in ECF volume.
9. Effect on blood
Testosterone has got erythropoietic action. So, after puberty, testosterone causes a mild increase in RBC count. It also increases blood volume by increasing water retention and ECF volume.
Mode Of Action Of Testosterone
- Testosterone is converted into dihydrotestosterone in the target cells of accessory sex organs — prostate, seminal vesicles, epididymis, penis, and other organs. In the brain, it is converted into estrogen (estradiol).
- The dihydrotestosterone combines with receptor proteins. The hormone receptor complex migrates to the nucleus, binds with a nuclear protein, and induces the DNA-RNA transcription process. In 30 minutes, the RNA polymer is activated and the concentration of RNA increases.
- The quantity of DNA also increases. So, testosterone primarily stimulates protein synthesis in the target cells, which are responsible for the development of secondary sexual characteristics.
Regulation Of Testosterone Secretion
In Fetus
During fetal life, the testosterone secretion from the testis is stimulated by human chorionic gonadotropin, which has properties similar to those of luteinizing hormone. Human chorionic gonadotropin stimulates the development of Leydig cells in the fetal testes and promotes testosterone secretion.
In Adults
- Luteinizing hormone (LH) or interstitial cell-stimulating hormone (ICSH) stimulates the Leydig cells and the quantity of testosterone secreted is directly proportional to the amount of LH available.
- Secretion of LH from the anterior pituitary gland is stimulated by luteinizing hormone-releasing hormone (LHRH) from the hypothalamus.
Feedback Control
Testosterone regulates its own secretion by negative feedback mechanisms. It acts on the hypothalamus and inhibits the secretion of LHRH. When the LHRH secretion
is inhibited, LH is not released from the anterior pituitary resulting in a stoppage of testosterone secretion from the testes. On the other hand, when testosterone production is low, a lack of inhibition of the hypothalamus leads to the secretion of testosterone through LHRH and LH.
Male Andropause Or Climacteric
Male andropause or climacteric is a condition in men characterized by emotional and physical changes in the body due to low androgen levels with aging. It is also called viropause.
- After the age of 50, testosterone secretion starts declining. It is accompanied by a decrease in the number and secretory activity of Leydig cells. The low level of testosterone increases the secretion of FSH and LH. It leads to some changes in the body.
- It does not affect most of the men. But some men develop symptoms similar to those of female menopausal syndrome. The common symptoms are hot flashes, illusions of suffocation, and mood changes.
Applied Physiology
Effects Of Extirpation Of Testes
The removal of testes is called castration. The effects of castration depend upon the age when testes are removed.
1. Effects of Extirpation of Testes before Puberty- Eunuchism
- If a boy loses the testes before puberty, he continues to have infantile sexual characteristics throughout life. This condition is called eunuchism. The height of the person is slightly more but the bones are weak and thin. The muscles become weak and the shoulder remains narrow.
- The sex organs do not increase in size, and, the male secondary sexual characters do not develop. The voice remains like that of a child. There is an abnormal deposition of fat on the buttocks, hip, pubis, and breast, resembling the feminine distribution.
2. Effects of Extirpation of Testes Immediately after Puberty
- If testes are removed after puberty, some of the male secondary sexual characters revert to those of a child, and other masculine characters are retained. Sex organs are depressed. Seminal vesicles and prostate undergo atrophy. Penis remains smaller.
- Voice is-aiiS mostly masculine but other secondary sexual terms like masculine hair distribution, musculature sexual, and thickness of bones are lost. There may be a loss of sexual desire and sexual activities.
3. Effect of Extirpation of Testes in Adults
Removal of testis in adults does not cause loss of secondary sexual characteristics. But, accessory sex organs start degenerating. Sexual desire is not totally lost. Erection occurs but ejaculation is rare because of degeneration of accessory sex organs and lack of sperm.
Hypergonadism In Males
Hypergonadism is a condition characterized by hypersecretion of sex hormones from gonads.
Cause
Hypergonadism in males is mainly due to the tumor of Leydig cells. It is common in prepubertal boys who develop precocious pseudopuberty.
Symptoms
- There is rapid growth of musculature and bones. But, the height of the person is less because of the early closure of epiphysis.
- There is excess development of sex organs and secondary sexual characters. The tumors also secrete estrogenic hormones which cause gynecomastia (the enlargement of breasts).
Hypogonadism In Males
Hypogonadism is a condition characterized by a reduction in the functional activity of gonads.
Causes
Hypogonadism in males is due to various abnormalities of the testes:
- The congenital non-functioning of testes
- Under-developed testes due to the absence of human chorionic gonadotropins in fetal life
- Cryptorchidism is associated with partial or total degeneration of the testes
- Castration
- Absence of androgen receptors in testes
- Disorder of gonadotropes (cells secreting gonads tropins) in the anterior pituitary
- Hypothalamic disorder.
Signs And Symptoms
The clinical picture of male hypogonadism depends upon whether the testicular deficiency develops before or after puberty.
Before puberty
The features of hypogonadism are similar to those developed due to the extirpation of the testes before puberty, which are described above.
After puberty
The symptoms are similar to those developed due to the removal of testes after puberty (see above).
In adults
- The same symptoms, which develop after extirpation of testis, occur in this condition.
- Hypogonadism caused by testicular disorders increases gonadotropin secretion and the condition is called hypogonadotropic hypogonadism. Hypogonadism that occurs due to a deficiency of gonadotropins (pituitary or hypothalamic disorder) is called hypo-gonadotropic hypogonadism.
Frohlich’s Syndrome
h tne disorder characterized by obesity and hypogonadism in adolescent boys. It is also called adipose genital syndrome or hypothalamic eunuchism. Refer to for details.
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