MA Exam Help Male Reproductive System For Medical Assistants
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Male Reproductive System
Male Reproductive System
Male Reproductive System...
Male Reproductive System:
The major function of the reproductive system is to produce offspring. Many of our other systems strive for a constant state of homeostasis, while the reproductive system functions for the survival of the species.
In both men and women, the organs of the reproductive system are adapted for the specific functions that permit the development of sperm or ova followed by the successful fertilization and the normal development and birth of a baby.
Both male and female reproductive systems include:
reproductive organs or gonads that produce gametes (reproductive cells) and hormones
ducts that transport and receive the gametes
accessory glands and organs that secrete fluids into these or excretory ducts
perineal structures associated with the reproductive system, collectively known as external genitalia.
Also, production of hormones that permit the secondary sex characteristics, such as breast development in women and beard growth in men, is a result of normal system activity.
The male reproductive system, sustains, and transports sperm, introduces sperm into the female vagina and produces hormones.
Reproductive organs can be classified as essential or accessory.
Essential organs in both men and women are called gonads. The gonads of men consist of a pair of testes. In the adult male, the testes secrete androgens, which are principally testosterone and they produce one half billion sperm cells called spermatozoa each day.
After storage, mature sperm travel along a lengthy duct system, where they are mixed with the secretions of accessory glands, creating semen. During ejaculation, the semen is expelled from the body.
The female gonads or ovaries usually release one egg per month. This gamete travels along short uterine tubes called Fallopian tubes or oviducts that end in a muscular chamber called the uterus. A short passageway, called the vagina, connects the uterus with the exterior.
During intercourse, the male ejaculation introduces semen into the vagina and the sperm cells travel into the female reproductive tract. If a single sperm fuses or joins with an egg, fertilization occurs.
Testes begin their development high in the abdominal cavity, near the kidneys. During the last 2 months before birth, or shortly after birth, they descend through the inguinal canal into the scrotum. A condition in which testes do not descend is called cryptorchidism. This may result in sterility if not corrected before puberty. Cooler temp is needed for sperm production. The inguinal canal represents a weakened area-intestine may pass through this opening into the scrotum. Painful, dangerous-blood supply to the intestine is constricted. There is a higher incidence in men, and a surgical repair called a herniorrhaphy is needed. The scrotum is the pouch that extends below the abdomen, posterior to the penis.. This exposed location provides an environment about 3 degrees F cooler than normal body temperature, which is an important requirement for the normal production and survival of the sperm. Unfortunately, this also makes them very vulnerable to injury.
The scrotum consists of a thin layer of skin, loose connective tissue and a smooth muscle layer. Beneath the dermis is a layer of skeletal muscle called the cremaster muscle, which can contract to pull the testes closer to the body. When temperatures rise this muscle relaxes and the testes move away from the body with the excess heat being lost across the surface of the scrotum. When the scrotum is cooled, like in an icy swimming pool, the cremasteric contractions pull the scrotum closer to the body to keep them warm for survival of the sperm.
Inside each testis are approximately 250 lobules that subdivide each of the male gonads. Inside these lobes are about 800 slender, tightly coiled seminiferous tubules where sperm production occurs. Amazingly each testis contains nearly one half mile of these tubules!!!!!
The interstitial cells of the testes, which secrete testosterone, may be found in the tissue that separates or the septa, which separates each testis.
Sperm production is called spermatogenesis. From puberty on, the seminiferous tubules produce sperm. The number of sperm produced each day diminishes with age but are still produced in significant numbers throughout the normal male life span.
Spermatogenesis or sperm production takes place in three integrated processes:
· Mitosis- stem cells of the sperm or spermatogonia undergo cello divisions throughout adult life. The cell divisions produce daughter cells, which contain copy of the genetic material of a normal number of 46 chromosomes. These daughter cells are pushed to the lumen of the seminiferous tubule. When a boy enters puberty, under the influence of FSH (hiccup) the sperm cell undergoes a unique or one of a kind cell division. The product of this division from a parent cell is 2 daughter cells. One of the daughter cells becomes a more specialized cell called a spermatocyte. These spermatocytes then undergo a special type of cell division called meiosis, which is the next step in the process.
· Meiosis- means to make smaller. This is a special form of cell division involved in gamete production. Remember what gamete is....forgot already it is a reproductive cell. Gametes contain half the number of chromosomes found in other cells. As a result, the joining of a sperm and an egg cell results in a single cell with the normal number of chromosomes. Look at page 510 in your A&P book for a good graphic on the way the cells divide. An important aspect of meiosis is the fact that during this process there are two episodes of cell division. In the seminiferous tubules, the meiotic divisions of the spermatocytes produce immature gametes called spermatids.
Spermiogenesis- is when spermatids differentiate into mature spermatozoa.
Spermatozoa are among the smallest and most highly specialized cells in the body. All of the characteristics that a baby will inherit from its father at fertilization are contained in the small concentrated genetic material found in each sperm head.
Genetic material from the father can fuse with the material from the mother only when successful fertilization occurs. The mature sperm has a head, mid piece, and a tail.
These sperm cells or spermatozoa, which carry the special genetic material, are equipped with tails for motility or movement. They are designed to penetrate the ovum when there is contact between the two.
As we saw in the movie, the sperm head is covered by a special structure called an acrosome, which contains enzymes that enable the sperm to break down the covering of the ovum and permit entry if contact occurs.
Production of testosterone is another function of the testes. As we stated earlier the interstitial cells of the testes carry out this function.
Testosterone serves the following general functions:
1. masculinization- hair patterns and voice changes
2. promotes and maintains the development of the male accessory organs (prostate, seminal vesicles etc.)
3. stimulates the effect of protein building in the body that is responsible for the greater muscle development and strength of the male (sorry ladies it just happens to be true)
Sperm cells pass through a series of ducts to reach the outside of the body. After they leave the body, the sperm pass through the epididymis, ductus deferens, ejaculatory duct, and the urethra. When sperm leave the testes, they are immature and incapable of fertilization. Sperm leave the testes through a series of efferent ducts. Now efferent for some of the members of this class you will have seen the term efferent used as a word to describe nerves in the nervous system and arterioles in the urinary system. What exactly does efferent mean?? To carry away from. Have you ever heard of Efferdent…this is the denture cleaner that carries away bacteria and plaque, away from the surface of the dentures?
These efferent ducts enter the epididymis. Sperm mature and become fertile as they pass through the epididymis. This is where they develop their tails and gain their motility. Sperm mature in the epididymis. Mature sperm are stored in the proximal ductus deferens.
The ductus deferens or the vas deferens is the muscular tube that is continuous with the epididymis. This duct has a dual function. It serves as a storage site for sperm cells and as the excretory duct of the testis. Each ductus runs from the epididymis up through the inguinal canal. It then runs down and backward toward the side of the urinary bladder. It then curves around the ureter and goes down to meet with the seminal vesicle duct on the posterior side of the bladder. It then travels down toward the prostate gland. Sperm are stored in the proximal portion of the ductus deferens and the peristaltic movements propel the sperm through the tube.
The proximal portion of the ductus deferens is a component of the spermatic cord. The spermatic cord contains the ductus deferens, testicular artery and veins, lymph vessels, testicular nerve and cremaster muscle.
The proximal portion of the ductus deferns joins the duct to form a short ejaculatory duct. Each ejaculatory duct passes through the prostate gland and the urethra.
The seminal vesicles are two highly convoluted membranous tubes that join the ductus deferens to the ejaculatory duct, which then empties into the urethra. Seminal vesicles are considered accessory glands. The fluid in the seminal vesicles is viscous or thick and contains fructose (which provides energy for the sperm); prostaglandins, which contribute to the motility and the viability of the sperm; and proteins, which cause slight coagulation or clotting reactions in the semen after ejaculation. The substances found in seminal fluid help to nourish and protect the sperm on its journey.
At the precise moment of ejaculation, the seminal fluid is added to the sperm cells as they leave the ejaculatory ducts.
The ejaculatory ducts are short and narrow. They begin where the ductus deferens and the seminal vesicles join. They then descend into the prostate gland to join with the urethra.
A vasectomy is a surgical procedure-tiny incision into the scrotum that severs the vas deferens. It interrupts the sperm's pathway.
The prostate gland is a firm; dense, donut shaped structure that is located just inferior to the urinary bladder. This gland surrounds the opening of the bladder leading into the urethra. The contraction of the prostate gland closes off the prostatic urethra during ejaculation, which prevents the passage of urine through the urethra. The urethra goes from the urinary bladder to the external meatus. In males it serves as the passageway for sperm, fluids from the reproductive tract, and urine.
The urethra has 3 parts:
1. prostatic urethra-proximal portion; passes through prostate.
2. membranous urethra-short; passes through pelvic floor.
3. penile urethra- longest portion; extends length of penis to urinary meatus.
The secretions of the prostate function to enhance the motility of the sperm. The fluid in the ductus deferens is very acidic as is the female vaginal secretions. Prostate fluid is very alkaline and therefore neutralizes the acidic semen and vaginal secretions. Cancer of the prostate is the 2nd most common cancer in men. PSA screening - rectal exam.
BULBOURETHRAL GLANDS OR COWPER’S GLANDS
Cowper’s glands are paired and are located neat the base of the penis. In response to sexual stimulation, the Cowper’s glands secrete an alkaline mucus-like fluid into the urethra. This alkaline like fluid helps the sperm to live longer within the acid-like medium of the female vaginal secretions. The fluid from these glands also assists in the lubrication of the urethra.
Seminal vesicles are glands posterior to the urinary bladder. The fluid from the seminal vesicles is viscous and contains fructose which is an energy source for the sperm. It also contains prostaglandins, which enhance motility and viability of sperm, and adds protein for slight coagulation.
The penis and the scrotum constitute the male external reproductive organs. The function of the penis is to transfer sperm to the vagina. The penis consists of three columns of erectile tissue that is wrapped in connective tissue and covered with skin. The erectile tissue becomes enlarged and rigid during intercourse due to an increase in the blood supply to the erectile tissue. The penis consists of three columns of erectile tissue. The two dorsal columns are the corpora cavernosa, and the ventral column is the corpus spongiosum. A new study claims it is not recommended.
At the distal end of the shaft of the penis is the enlarged glans or the glans penis. The urethra, which extends throughout the length of the corpus spongiosum, opens through the external urethral orifice at the tip of the glans penis. A loose fold of skin called the foreskin covers the glans penis.
Circumcision is the surgical removal of the prepuce of the foreskin. Sometimes this is done to correct phimosis, a condition in which the prepuce is too tight and obstructs the urine flow. In certain cultures circumcision is performed as a religious rite or ethnic custom. For others it is a matter of family preference. The medical benefits of circumcision are the subject of debate in the medical community. Some believe it is practical for hygeine reasons.
MALE SEXUAL RESPONSE
During sexual excitement, parasympathetic impulses dilate the arterioles that supply blood to the erectile tissue while constricting the veins that remove the blood. As a result, the spaces in the erectile tissue become engorged with blood causing the penis to become rigid. This is called an erection and it is necessary to allow the penis to enter the female vagina.
The erection reflex may be initiated by stimuli such as anticipation, memory, and visual sensations, or it may be the result of touch receptors on the glans penis and skin of the genital area. Emotions and thoughts can also inhibit erection.
Continued sexual stimulation causes the parasympathetic reflexes that promote an erection to become more and more intense until they reach a level that prompts a surge of sympathetic impulses to the genital organs. These sympathetic impulses stimulate rhythmic contractions of the epididymides, ductus deferens, and the ejaculatory ducts along with the accessory glands. This results in emission, which is discharge of semen into the urethra. Ejaculation immediately follows and this is considered a forceful expulsion of semen from the urethra to the exterior. During ejaculation, the sphincters of the urinary bladder constrict to prevent semen from entering the bladder and the flow of urine from the bladder.
The rhythmic muscle contractions of ejaculation are accompanied by feelings of intense pleasure, increased heart rate, elevated blood pressure, and increased respiration. Together these physiologic activities are referred to as climax or orgasm. Orgasm is followed by a variable time period during which it is not possible to achieve another erection.
DISORDERS OF THE MALE REPRODUCTIVE SYSTEM
Cryptorchidism- is the condition in which the testes do not descend into the scrotum. Cryptorchidism results in sterility if not corrected before puberty because the cooler temperature of the scrotum is necessary for sperm production.
Benign prostatic hypertrophy- is a common condition in older men. The prostate enlarges and compresses the urethra, making urination difficult. This tends to retain urine in the bladder and make the man more prone to UTI’s.
Cancer of the prostate- is the second most common cancer in men. It usually starts in one of the secretory glands and as it continues, it produces a lump on the surface of the prostate. In many cases, by the time the lump can be palpated through the wall of the rectum, the cancer has metastasized to other areas of the body. It is hoped that by using some new blood screening techniques such as a PSA (Prostate-Specific Antigen) or an ACP (prostatic acid phosphatase). Both of these tests performed on serum can be utilized to diagnose, monitor effect of prostatic cancer treatment with chemotherapy or radiation, and determine disease process and prognosis.
Prostatitis- inflammation of the prostate.
Epididymitis- inflammation of the epididymis.
Testicular cancer- malignancies of the testes are most common among men aged 25-35 years old. In addition to age this type of cancer is associated with genetic predisposition, trauma or infection of the testis, and cryptorchidism. Treatment of testicular cancer is most effective when the diagnosis is made early in the development of the tumor. TSE or testicular self exam is extremely important in the prevention of this disease.
Impotence- is the inability to achieve an erection. Psychological stresses are often blamed for impotence, but other causes can lead to the difficulty. Impotence may result from an abnormality of the erectile tissue or failure of the parasympathetic reflexes that produce an erection. Drugs and alcohol may cause temporary impotence because they can interfere with the nerve and blood vessel actions that are necessary.
Infertility- is the abnormally low ability to reproduce. If there is a complete inability to reproduce, the condition is called sterility. Infertility or sterility involve an abnormally reduced capacity to deliver healthy sperm to the female reproductive tract. There are many factors that affect reproductive capacity such as a decrease in the production of sperm, structural abnormalities in the sperm or obstruction of the reproductive ducts.
Inguinal hernia- occurs when the intestines push through a weak area of the abdominal wall that separates the pelvic cavity from the scrotum. If the intestines protrude too far into the scrotum, the digestive tract may become obstructed, resulting in death. Inguinal hernia often occurs while lifting heavy objects, because of the high internal pressure generated by contraction of abdominal muscles. Inguinal herniation may be treated with external supports or with minor surgery.
Hydrocele- is one of the most common causes of scrotal swelling. This is an accumulation of fluid in the scrotal sac. Hydrocele’s may be congenital or in an adult can be the result of trauma or infection.
Premature Ejaculation- shortly after arousal or before orgasm.
Hypospadias- condition in which the urethral opening is on the underside of the penis.
Epispadias- condition in which the urethral opening is on the top
Priapism- abnormal, painful, continued erection.
Phimosis- narrowing of the prepuce.
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