Reproductive System: Spermatogenesis, Prostate Cancer, and Testicular Cancer | Assignments Philosophy

Spermatogenesis

Spermatogenesis is the process of sperm

cell production in the seminiferous tubules

of the testes.

It begins at puberty (when a boy is about

11 to 15 years old) and continues

throughout life with 100 to 200 million

sperms being made each day.

Spermatogonia (singular,

spermatogonium) develop from primordial

germ cells that migrate into the testes early

in embryogenesis.

(i) Spermatogonia are immature cells that

remain dormant until puberty.

(ii) They are diploid cells with each

containing 46 chromosomes (23 pairs).

(iii) They are located surrounding the

periphery of the seminiferous tubules.

At puberty, hormones stimulate these cells

to divide by mitosis.

(i) Some of the daughter cells produced will

remain at the periphery of the seminiferous

tubules as spermatogonia while some are

pushed towards the lumen and undergo

some changes to become primary

spermatocytes.

(ii) Primary spermatocytes are diploid cells

with 46 chromosomes.

Each primary spermatocyte undergoes the

first meiotic division to produce two

secondary spermatocytes, which

are haploid cells with 23 chromosomes.

In the second meiotic division, each

secondary spermatocyte divides to produce

two spermatids. Thus, four spermatids are

produced from the original primary

spermatocyte.

In the final stage of spermatogenesis, the

spermatids differentiate into spermatozoa

(singular, spermatozoon) or sperm.

The sperm are then released into the lumen

of the seminiferous tubule and leave the

testes into the epididymis.

Below is a transverse section of

seminiferous tubules showing that it is

packed with cells in various stages of

development. Interspersed among these

cells are large cells that extend from the

periphery of the tubule to the lumen. These

cells are called the Sertoli cells or nurse

cells which function in supporting and

nourishing the developing sperm.

(a) Sertoli cells help convert the spermatids

into spermatozoa by engulfing their extra

cytoplasm.

(b) Sertoli cells are joined to one another by

tight junctions which form a blood–testis

barrier and also form compartments that

separate sperm cells at various stages of

development.

At puberty, the gonadotropin releasing

hormone (GnRH) from the hypothalamus of

the brain will stimulate the anterior pituitary

gland to secrete

two gonadotropic hormones, namely,

the follicle- stimulating hormone (FSH)

and luteinizing hormone (LH) .

FSH initiates spermatogenesis while LH sti

mulates the production of testosterone by

Leydig cells.

Testosterone and FSH stimulate Sertoli

cells to secrete androgen binding

protein and other signaling molecules that

are necessary for spermatogenesis.

Testosterone is the main sex hormone in

males.

(a) Testosterone is responsible for initiating

and maintaining the secondary sexual

characteristics of the human male such as

the growth of the sex organs and body hair,

deepening of the voice, protein

synthesis/production in skeletal muscle

(why boys have bigger built), sex drive

(aggresiveness at times) and general

muscular and skeletal development.

(b) It is also necessary for

the maturation of sperm.

Hormonal actions in spermatogenesis

are regulated by a negative feedback

mechanism

Overproduction of testosterone inhibits t

he secretion of LH by acting on the

hypothalamus which decreases the

secretion of GnRH.

This results in decreased FSH and LH

secretion by the anterior pituitary.

Sertoli cells also release inhibin , a

hormone which inhibits the secretion of FSH

by the anterior pituitary gland.

FSH itself stimulates inhibin secretion.

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Spermatogenesis

Spermatogenesis is the process of sperm cell production in the seminiferous tubules of the testes. It begins at puberty (when a boy is about 11 to 15 years old) and continues throughout life with 100 to 200 million sperms being made each day. Spermatogonia (singular, spermatogonium) develop from primordial germ cells that migrate into the testes early in embryogenesis. (i) Spermatogonia are immature cells that remain dormant until puberty. (ii) They are diploid cells with each containing 46 chromosomes (23 pairs). (iii) They are located surrounding the periphery of the seminiferous tubules. At puberty, hormones stimulate these cells to divide by mitosis. (i) Some of the daughter cells produced will remain at the periphery of the seminiferous tubules as spermatogonia while some are pushed towards the lumen and undergo some changes to become primary spermatocytes. (ii) Primary spermatocytes are diploid cells with 46 chromosomes. Each primary spermatocyte undergoes the first meiotic division to produce two secondary spermatocytes, which are haploid cells with 23 chromosomes. In the second meiotic division, each secondary spermatocyte divides to produce two spermatids. Thus, four spermatids are produced from the original primary spermatocyte. In the final stage of spermatogenesis, the spermatids differentiate into spermatozoa (singular, spermatozoon) or sperm. The sperm are then released into the lumen of the seminiferous tubule and leave the testes into the epididymis. Below is a transverse section of seminiferous tubules showing that it is packed with cells in various stages of development. Interspersed among these cells are large cells that extend from the periphery of the tubule to the lumen. These cells are called the Sertoli cells or nurse cells which function in supporting and nourishing the developing sperm. (a) Sertoli cells help convert the spermatids into spermatozoa by engulfing their extra cytoplasm. (b) Sertoli cells are joined to one another by tight junctions which form a blood–testis barrier and also form compartments that separate sperm cells at various stages of development. At puberty, the gonadotropin releasing hormone (GnRH) from the hypothalamus of the brain will stimulate the anterior pituitary gland to secrete two gonadotropic hormones, namely, the follicle- stimulating hormone (FSH) and luteinizing hormone (LH). FSH initiates spermatogenesis while LH sti mulates the production of testosterone by Leydig cells. Testosterone and FSH stimulate Sertoli cells to secrete androgen binding protein and other signaling molecules that are necessary for spermatogenesis. Testosterone is the main sex hormone in males. (a) Testosterone is responsible for initiating and maintaining the secondary sexual characteristics of the human male such as the growth of the sex organs and body hair, deepening of the voice, protein synthesis/production in skeletal muscle (why boys have bigger built), sex drive (aggresiveness at times) and general muscular and skeletal development. (b) It is also necessary for the maturation of sperm. Hormonal actions in spermatogenesis are regulated by a negative feedback mechanism Overproduction of testosterone inhibits t he secretion of LH by acting on the hypothalamus which decreases the secretion of GnRH. This results in decreased FSH and LH secretion by the anterior pituitary. Sertoli cells also release inhibin , a hormone which inhibits the secretion of FSH by the anterior pituitary gland. FSH itself stimulates inhibin secretion.

Structure of a sperm Mature sperm or spermatozoa consist of three parts—the head, middle piece and a tail. The head is flattened and oval in shape. The nucleus, enclosed in a thin membrane, is contained within the head. The acrosome forms a cap at the anterior end of the nucleus. It secretes hydrolytic enzymes which help the head to penetrate the oocyte. The middle piece consists of a tightly coiled spiral sheath of elongated mitochondria. The mitochondria provide energy for sperm motility The tail or flagellum has the typical ‘9 + 2’ microtubule arrangement. It allows the sperm to swim towards the egg. Erectile Dysfunction Erectile dysfunction (ED) is sexual dysfunction characterized by the regular and repeated inability of a sexually mature individual to obtain or maintain an erection. It is a common disorder that affects about 40 percent of people with penises. Causes of Erectile Dysfunction The penis normally stiffens and becomes erect when the columns of spongy tissue within the shaft of the penis (the corpora cavernosa and corpus spongiosum) become engorged with blood. Anything that hampers normal blood flow to the penis may, therefore, interfere with its potential to fill with blood and become erect. The normal nervous control of sexual arousal or penile engorgement may also fail and lead to problems obtaining or maintaining an erection Specific causes of ED include both physiological and psychological causes. Physiological causes include the use of therapeutic drugs (such as antidepressants), aging, kidney failure, diseases (such as diabetes or multiple sclerosis), tobacco smoking, and treatments for other disorders (such as prostate cancer). Psychological causes are less common but may include stress, performance anxiety, or mental disorders. The risk of ED may also be greater in people with obesity, cardiovascular disease, poor dietary habits, and overall poor physical health. Having an untreated hernia in the groin may also lead to ED. Treatments for Erectile Dysfunction Treatment of ED depends on its cause or contributing factors. For example, for tobacco smokers, smoking cessation may bring significant improvement in ED. Improving overall physical health by losing weight and exercising regularly may also be beneficial. The most common first-line treatment for ED, however, is the use of oral prescription drugs, known by brand names such as Viagra® and Cialis®. These drugs help ED by increasing blood flow to the penis. Other potential treatments include topical creams applied to the penis, injection of drugs into the penis, or the use of a vacuum pump that helps draw blood into the penis by applying negative pressure. More invasive approaches may be used as a last resort if other treatments fail. These usually involve surgery to implant inflatable tubes or rigid rods into the penis. Epididymitis Epididymitis is inflammation of the epididymis. The epididymis is one of the paired organs within the scrotum where sperms mature and are stored. Discomfort or pain and swelling in the scrotum are typical symptoms of epididymitis, which is a relatively common condition, especially in young individuals. In the U.S. alone, more than half a million cases of epididymitis are diagnosed annually between the ages of 18 to 35. Acute vs. Chronic Epididymitis Epididymitis may be acute or chronic. Acute diseases are generally short-term conditions, whereas chronic diseases may last years — or even lifelong. Acute Epididymitis Acute epididymitis generally has a fairly rapid onset and is most often caused by a bacterial infection. Bacteria in the urethra can back-flow through the urinary and reproductive structures to the epididymis. In sexually active individuals, many cases of acute epididymitis are caused by sexually transmitted bacteria. Besides pain and swelling, common symptoms of acute epididymitis include redness, warmth in the scrotum, and a fever. There may also be a urethral discharge. Chronic Epididymitis Chronic epididymitis is epididymitis that lasts for more than three months. In some, the condition may last for years. It may

before their prostate cancer causes symptoms. Treatment of younger patients — or those with more aggressively growing tumors — may include surgery to remove the prostate, chemotherapy, and/or radiation therapy (such as brachytherapy, see photo below). All of these treatment options can have significant side effects, such as erectile dysfunction or urinary incontinence. Patients should learn the risks and benefits of the different treatments, and discuss them with their healthcare provider to decide on the best treatment options for their particular case. Testicular Cancer Reproductive cancer that is rare and most commonly affects young individuals is testicular cancer. The testes are the paired reproductive organs in the scrotum that produce sperm and secrete testosterone. The risk of testicular cancer is about four to five times greater in individuals of European than African ancestry. The cause of this difference is unknown. Signs and Symptoms of Testicular Cancer One of the first signs of testicular cancer is often a lump or swelling in one of the two testes. The lump may or may not be painful. If pain is present, it may occur as a sharp pain or a dull ache in the lower abdomen or scrotum. Some people with testicular cancer report a feeling of heaviness in the scrotum. Testicular cancer does not commonly spread beyond the testis, but if it does, it most often spreads to the lungs, where it may cause shortness of breath or a cough. Diagnosis of Testicular Cancer The main way that testicular cancer is diagnosed is by detection of a lump in the testis. This is likely followed by further diagnostic tests. An ultrasound may be done to determine the exact location, size, and characteristics of the lump. Blood tests may be done to identify and measure tumor- marker proteins in the blood that are specific to testicular cancer. CT scans may also be done to determine whether the disease has spread beyond the testis. However, unlike the case with prostate cancer, a biopsy is not recommended, because it increases the risk of cancer cells spreading into the scrotum. Treatment of Testicular Cancer Testicular cancer has one of the highest cure rates of all cancers. Three basic types of treatment for testicular cancer are surgery, radiation therapy, and/or chemotherapy. Generally, the initial treatment is surgery to remove the affected testis. If the cancer is caught at an early stage, the surgery is likely to cure the cancer, and has nearly a 100 percent five- year survival rate. When just one testis is removed, the remaining testis (if healthy) is adequate to maintain fertility, hormone production, and other normal functions. Radiation therapy and/or chemotherapy may follow surgery to kill any tumor cells that might exist outside the affected testis, even when there is no indication that the cancer has spread. In many cases, however, surgery is followed by surveillance instead of additional treatments. Summary Erectile dysfunction (ED) is a disorder characterized by the regular and repeated inability of a sexually mature male to obtain and maintain an erection. ED is a common disorder that occurs when normal blood flow to the penis is disturbed, or when there are problems with the nervous control of penile engorgement or arousal. Possible physiological causes of ED include aging, illness, drug use, tobacco smoking, and obesity, among others. Possible psychological causes of ED include stress, performance anxiety, and mental disorders. Treatments for ED may include lifestyle changes, such as stopping smoking, adopting a healthier diet, and regular exercise. The first-line treatment, however, is prescription drugs such as Viagra® or Cialis® that increase blood flow to the penis. Vacuum pumps or penile implants may be used to treat ED if other types of treatment fail. Epididymitis is inflammation of the epididymis. It is a common disorder, especially in young people. It may be acute or chronic and is often caused by a bacterial infection. Treatments may include antibiotics, anti-inflammatory drugs, and painkillers. Treatment is important to prevent the possible spread of infection, permanent damage to the epididymis or testes, and even infertility. Prostate cancer is the most common type of cancer and the second leading cause of cancer death in prostate carrying individuals. If there are symptoms, they typically involve urination, such as frequent or painful urination. Risk factors for prostate cancer include older age, family history, high-meat diet, and sedentary lifestyle, among others. Prostate cancer may be detected by a physical exam or a high level of prostate- specific antigen (PSA) in the blood, but a biopsy is required for a definitive diagnosis. Prostate cancer is typically diagnosed

relatively late in life and is usually slow growing, so treatment may not be necessary. In younger patients or those with faster-growing tumors, treatment is likely to include surgery to remove the prostate, followed by chemotherapy and/or radiation therapy. Testicular cancer, or cancer of the testes, is the most common cancer in individuals between the ages of 20 and 39 years. It is more common in European than African ancestry. A lump or swelling in one testis, fluid in the scrotum, and testicular pain or tenderness are possible signs and symptoms of testicular cancer. Testicular cancer can be diagnosed by a physical exam and diagnostic tests, such as ultrasound or blood tests. Testicular cancer has one of the highest cure rates of all cancers. It is typically treated with surgery to remove the affected testis, and this may be followed by radiation therapy and/or chemotherapy. If the remaining testis is healthy, normal male reproductive functions are still possible after one testis is removed. Female Reproductive System Oogenesis

Female gametes develop in the ovaries by a process called oogenesis
Oogenesis begins soon after fertilization. The primordial germ cells in the ovary begin to proliferate mitotically from a few thousand to almost 7 million and differentiate into oogonia (2n). However, after the seventh month of embryonic development, most of the oogonia (singular, oogonium) die.
The remaining oogonia divide by mitosis and mature into primary oocytes.
The primary oocytes progress through the first meiotic division but is arrested at prophase I, at which point they are maintained until puberty.
At puberty, secretion of FSH (Follicle stimulating hormone) triggers only one primary oocyte to complete meiosis I. (i) The division of the cell is unequal, producing one large cell, the secondary oocyte , and one tiny cell called the polar body. (ii) Both cells are haploid. The secondary oocyte begins the second meiotic division but the process stops at metaphase. At this point, ovulation occurs. If fertilization occurs (i.e., nuclear fusion of egg and sperm), meiosis II will be completed producing an ovum and the second polar body. The first polar body also usually divides to produce two smaller polar bodies which later degenerate. Structure of the secondary oocyte At birth, each oocyte is enveloped by a primordial follicle consisting of a single layer of epithelial granulosa cells and thecal cells. Periodically, a group of primordial follicles enters a stage of follicular growth. (a) During this time, the oocyte undergoes a 500 - fold increase in volume and it is now called a primary follicle. (b) Granulosa cells form concentric layers around the oocyte. In addition, an antrum (a cavity), which is filled with a complex mixture of proteins, hormones and other molecules, forms. The follicle now becomes a secondary follicle.
The granulosa cells also secrete a glycoprotein substance that forms a clear membrane around the oocyte known as the zona pellucida.
The oocyte lies at the edge in a mound of granulose epithelial cells, the cumulus oophorous . The cumulus is shed along with the egg at ovulation.
The fully developed ovarian follicle is also called a Graafian follicle. Read This: The ovarian and menstrual (uterine) cycles The female reproductive cycle consists of two important cycles : (a) The ovarian cycle and (b) The uterine or menstrual cycle. The ovarian cycle The ovarian cycle is a series of events in the ovaries that occur during and after the maturation of the oocyte It comprises three phases: the follicular phase, ovulatory phase and luteal phase During the follicular phase, three to thirty follicles begin to grow.

The high level of progesterone together with estrogen, however, exerts negative feedback on the hypothalamus. These hormones inhibit the release of GnRH which, in turn, inhibit further release of FSH and LH. (note: negative feedback- inhibition) A small amount of the gonadotropin hormones are, nevertheless, required to maintain the function of the corpus luteum. If fertilization does not occur, the corpus luteum degenerates into corpus albicans. This will: decrease progesterone and estrogen levels. stop the inhibition of uterine contraction, cause follicular growth to resume and a new menstrual cycle to begin. However, if the oocyte is fertilized and begins to divide, the corpus luteum will continue to exist. It is prevented from deteriorating by the human chorionic gonadotropin (HCG) hormone produced by the chorion of the embryo. Note: The presence of HCG in urine confirms a women's pregnancy. Test kits could be bought whenever one's suspicious of being pregnant. DISORDERS Cervical cancer occurs when cells of the cervix grow abnormally and develop the ability to invade nearby tissues or spread to other parts of the body. Worldwide, cervical cancer is the second-most common type of cancer and the fourth most common cause of cancer deaths. Early on, cervical cancer often has no symptoms. Later, symptoms (such as abnormal vaginal bleeding and pain) are likely. Most cases of cervical cancer occur because of infection with human papillomavirus (HPV), so the HPV vaccine is expected to greatly reduce the incidence of the disease Other risk factors include smoking and a weakened immune system A Pap smear can diagnose cervical cancer at an early stage. Where Pap smears are done routinely, cervical cancer death rates have fallen dramatically. Treatment of cervical cancer generally includes surgery, which may be followed by radiation therapy or chemotherapy Vaginitis is an inflammation of the vagina. A discharge is likely, and there may be itching and pain. About 90 percent of cases of vaginitisare caused by infection with microorganisms, typically by the

yeast Candida albicans.

A minority of cases are caused by irritants or allergens in soaps, spermicides, or douches. Diagnosis of vaginitis may be based on characteristics of the discharge, which can be examined microscopically or cultured. Treatment of vaginitis depends on the cause and is usually an oral or topical anti-fungal or antibiotic medication. Endometriosis is a disease in which endometrial tissue grows outside the uterus. This tissue may bleed during the menstrual period and cause inflammation, pain, and scarring. The main symptom of endometriosis is pelvic pain, which may be severe. Endometriosis may also lead to Infertility. Endometriosis is thought to have multiple causes, including genetic mutations. Retrograde menstruation may be the immediate cause of endometrial tissue escaping the uterus and entering the pelvic cavity. Endometriosis is usually treated with surgery to remove the abnormal tissue and medication for pain. If surgery is more conservative than hysterectomy, endometriosis may recur.

Reproductive System: Spermatogenesis, Prostate Cancer, and Testicular Cancer, Assignments of Philosophy

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Spermatogenesis

yeast Candida albicans.