thereproductivesystem-ppt

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THE REPRODUCTIVE SYSTEM

Reproduction


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The reproductive system consists of the organs

that enable human beings to create new life

and to reproduce themselves. The human

species is divided into two sexes: male and

female. Each individual produces basic sex

cells; when male and female sex cells unite,

the product will develop into a new individual.


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Reproduction

• Reproduction means the process by which a

living entity or organism produces a new

individual of the same kind. The gonads, or

sex glands – the ovaries in the female and the

testes in the male – produce the germ cells

(gametes) that unite and grow into a new

individual. Reproduction begins when thegerm cells unite, which is a process called

fertilization.


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• The germ cells are the male spermatozoon andthe female ovum, or egg. These are specializedcells differing primarily from normal body cells in

one important way. Each sex cell contains exactlyhalf the number of chromosomes that a normalbody cell contains. When the ovum andspermatozoon unite, the cell produced receives

half of its genetic material from its female parent,and half from its male parent; thus it contains afull, normal complement of hereditary material.


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The Male Reproductive System

The organs of the male reproductive system arespecialized for the following functions:

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To produce, maintain and transport sperm (the malereproductive cells) and protective fluid (semen)

• To discharge sperm within the female reproductivetract

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To produce and secrete male sex hormonesThe male reproductive anatomy includes internal and

external structures.


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The External Reproductive Structures

Most of the male reproductive system is located outside ofthe man’s body. The external structures of the malereproductive system are the penis, the scrotum and thetesticles.

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Penis — The penis is the male organ for sexual intercourse.It has three parts: the root, which attaches to the wall ofthe abdomen; the body, or shaft; and the glans, which isthe cone-shaped end of the penis. The glans, which also iscalled the head of the penis, is covered with a loose layer ofskin called foreskin. (This skin is sometimes removed in a

procedure called circumcision.) The opening of the urethra,the tube that transports semen and urine, is at the tip ofthe glans penis. The penis also contains a number ofsensitive nerve endings.


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• The body of the penis is cylindrical in shape and consists ofthree internal chambers. These chambers are made up ofspecial, sponge-like erectile tissue. This tissue contains

thousands of large spaces that fill with blood when the manis sexually aroused. As the penis fills with blood, it becomesrigid and erect, which allows for penetration during sexualintercourse. The skin of the penis is loose and elastic toaccommodate changes in penis size during an erection.

• Semen, which contains sperm, is expelled (ejaculated)through the end of the penis when the man reaches sexualclimax (orgasm). When the penis is erect, the flow of urineis blocked from the urethra, allowing only semen to beejaculated at orgasm.


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• Scrotum — The scrotum is the loose pouch-like sac ofskin that hangs behind the penis. It contains thetesticles (also called testes), as well as many nerves and

blood vessels. The scrotum has a protective functionand acts as a climate control system for the testes. Fornormal sperm development, the testes must be at atemperature slightly cooler than the bodytemperature. Special muscles in the wall of the

scrotum allow it to contract and relax, moving thetesticles closer to the body for warmth and protectionor farther away from the body to cool the temperature.


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Testicles (testes) — The testes are oval organs about thesize of large olives that lie in the scrotum, secured ateither end by a structure called the spermatic cord.Most men have two testes. The testes are responsiblefor making testosterone, the primary male sexhormone, and for generating sperm. Within the testesare coiled masses of tubes called seminiferous tubules.

These tubules are responsible for producing the spermcells through a process called spermatogenesis.


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Epididymis — The epididymis is a long, coiled tubethat rests on the backside of each testicle. It

functions in the transport and storage of thesperm cells that are produced in the testes. It alsois the job of the epididymis to bring the sperm tomaturity, since the sperm that emerge from the

testes are immature and incapable of fertilization.During sexual arousal, contractions force thesperm into the vas deferens.


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The Internal Reproductive Organs

• Vas deferens — The vas deferens is a long, muscular tube thattravels from the epididymis into the pelvic cavity, to just behind thebladder. The vas deferens transports mature sperm to the urethrain preparation for ejaculation.

• Ejaculatory ducts — These are formed by the fusion of the vasdeferens and the seminal vesicles. The ejaculatory ducts empty intothe urethra.

• Urethra — The urethra is the tube that carries urine from thebladder to outside of the body. In males, it has the additionalfunction of expelling (ejaculating) semen when the man reaches

orgasm. When the penis is erect during sex, the flow of urine isblocked from the urethra, allowing only semen to be ejaculated atorgasm.


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• Seminal vesicles — The seminal vesicles are sac-like pouches that attach to the vasdeferens near the base of the bladder. The seminal vesicles produce a sugar-richfluid (fructose) that provides sperm with a source of energy and helps with thesperms’ motility (ability to move). The fluid of the seminal vesicles makes up mostof the volume of a man’s ejaculatory fluid, or ejaculate.

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Prostate gland — The prostate gland is a walnut-sized structure that is locatedbelow the urinary bladder in front of the rectum. The prostate gland contributesadditional fluid to the ejaculate. Prostate fluids also help to nourish the sperm. Theurethra, which carries the ejaculate to be expelled during orgasm, runs throughthe center of the prostate gland.

• Bulbourethral glands — The bulbourethral glands, or Cowper’s glands, are pea-sized structures located on the sides of the urethra just below the prostate gland.

These glands produce a clear, slippery fluid that empties directly into the urethra.This fluid serves to lubricate the urethra and to neutralize any acidity that may bepresent due to residual drops of urine in the urethra.


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Functioning

• The entire male reproductive system is dependent onhormones, which are chemicals that stimulate or regulatethe activity of cells or organs. The primary hormonesinvolved in the functioning of the male reproductive systemare follicle-stimulating hormone (FSH), luteinizing hormone

(LH) and testosterone.• FSH and LH are produced by the pituitary gland located at

the base of the brain. FSH is necessary for spermproduction (spermatogenesis), and LH stimulates theproduction of testosterone, which is necessary to continue

the process of spermatogenesis. Testosterone also isimportant in the development of male characteristics,including muscle mass and strength, fat distribution, bonemass and sex drive.


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The Female Reproductive System

FUNCTIONS:

• The female reproductive system is designed to carry out severalfunctions. It produces the female egg cells necessary forreproduction, called the ova. The system is designed to transportthe ova to the site of fertilization. Conception, the fertilization of an

egg by a sperm, normally occurs in the fallopian tubes. Afterconception, the uterus offers a safe and favorable environment fora baby to develop before it is time for it to make its way into theoutside world. If fertilization does not take place, the system isdesigned to menstruate (the monthly shedding of the uterinelining). In addition, the female reproductive system produces

female sex hormones that maintain the reproductive cycle.• During menopause the female reproductive system gradually stops

making the female hormones necessary for the reproductive cycleto work. When the body no longer produces these hormones awoman is considered to be menopausal.


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Parts

The female reproductive anatomy includes internal

and external structures.

The function of the external female reproductive

structures (the genital) is twofold: To enable

sperm to enter the body and to protect the

internal genital organs from infectious organisms.The main external structures of the female

reproductive system include:


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The External Structures of the Female

Reproductive System• Labia majora: The labia majora enclose and protect the

other external reproductive organs. Literally translated as"large lips," the labia majora are relatively large and fleshy,and are comparable to the scrotum in males. The labiamajora contain sweat and oil-secreting glands. After

puberty, the labia majora are covered with hair.• Labia minora: Literally translated as "small lips," the labia

minora can be very small or up to 2 inches wide. They lie just inside the labia majora, and surround the openings tothe vagina (the canal that joins the lower part of the uterus

to the outside of the body) and urethra (the tube thatcarries urine from the bladder to the outside of the body).


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• Bartholin’s glands: These glands are located nextto the vaginal opening and produce a fluid(mucus) secretion.

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Clitoris: The two labia minora meet at the clitoris,a small, sensitive protrusion that is comparable tothe penis in males. The clitoris is covered by afold of skin, called the prepuce, which is similar to

the foreskin at the end of the penis. Like thepenis, the clitoris is very sensitive to stimulationand can become erect.


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The Internal Reproductive Organs

• Vagina: The vagina is a fibromuscular tube that extendsfrom the cervix to the vestibule of the vulva. The vaginareceives the penis and semen during sexual intercourse andalso provides a passageway for menstrual blood flow toleave the body. It also is known as the birth canal.

• Uterus (womb): The uterus is a hollow cavity about the sizeof a pear (in women who have never been pregnant) thatexists to house a developing fertilized egg. The main part ofthe uterus (which sits in the pelvic cavity) is called the bodyof the uterus, while the rounded region above the entrance

of the fallopian tubes is the fundus and its narrow outlet,which protrudes into the vagina, is the cervix.


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• The thick wall of the uterus is composed of 3 layers. The inner layeris known as the endometrium. If an egg has been fertilized it willburrow into the endometrium, where it will stay for the rest of itsgrowth. The uterus will expand during a pregnancy to make roomfor the growing fetus. A part of the wall of the fertilized egg, whichhas burrowed into the endometrium, develops into the placenta. Ifan egg has not been fertilized, the endometrial lining is shed at theend of each menstrual cycle.

• The myometrium is the large middle layer of the uterus, which ismade up of interlocking groups of muscle. It plays an important roleduring the birth of a baby, contracting rhythmically to move the

baby out of the body via the birth canal (vagina). The outermostlayer is called the perimetrium.


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• Ovaries: The ovaries are the main reproductive organs of a woman.The two ovaries, which are about the size and shape of almonds,produce female hormones (estrogens and progesterone) and eggs(ova). All the other female reproductive organs are there totransport, nurture and otherwise meet the needs of the egg ordeveloping fetus.

• The ovaries are held in place by various ligaments which anchorthem to the uterus and the pelvis. The ovary contains ovarian(graafian) follicles, in which eggs develop. Once a follicle is mature,it ruptures and the developing egg is ejected from the ovary intothe fallopian tubes. This is called ovulation. Ovulation occurs in the

middle of the menstrual cycle and usually takes place every 28 daysor so in a mature female. It takes place from either the right or leftovary at random.


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• Fallopian tubes: These are narrow tubes that

are attached to the upper part of the uterus

and serve as tunnels for the ova (egg cells) to

travel from the ovaries to the uterus.Conception, the fertilization of an egg by a

sperm, normally occurs in the fallopian tubes.

The fertilized egg then moves to the uterus,where it implants to the uterine wall.


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Breasts (Accessory Organ of

Reproduction)• Breasts (mammary glands) are found in a female body that has

achieved sexual maturity. They are sweat glands that are composedof mammary alveoli and the necessary ducts. Though most peoplethink that the mammary glands are part of the reproductivesystem, they are not. They are actually a part of the integumentarysystem. But, they are linked to the reproductive system becausethey help the body in attracting a mate, and they assist in lactationafter pregnancy. The size and the shape of mammary glands differ,based on age, race, body fat and pregnancy.

• During puberty, estrogen releases hormones that control thedevelopment and the functions of the mammary glands.

Hypotrophy of the glands occur among pregnant and nursingwomen. Atrophy of the breasts normally happens after the femalebody has gone through menopause


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The Menstrual Cycle

• Females of reproductive age (anywhere from

11-16 years) experience cycles of hormonal

activity that repeat at about one-month

intervals. (Menstru means "monthly"; hencethe term menstrual cycle.) With every cycle, a

woman’s body prepares for a potential

pregnancy, with or without the woman’sintention. The term menstruation refers to the

periodic shedding of the uterine lining.


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• The average menstrual cycle takes about 28days and occurs in phases: the follicular phase,the ovulatory phase (ovulation), and the luteal

phase.• There are four major hormones (chemicals

that stimulate or regulate the activity of cellsor organs) involved in the menstrual cycle:

follicle-stimulating hormone, luteinizinghormone, estrogen, and progesterone.


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Follicular Phase

This phase starts on the first day of the period. During thefollicular phase of the menstrual cycle, the followingevents occur:

• Two hormones, follicle-stimulating hormone (FSH) and

luteinizing hormone (LH) are released from the brainand travel in the blood to the ovaries.

• The hormones stimulate the growth of about 15-20eggs in the ovaries each in its own "shell," called a

follicle.• These hormones (FSH and LH) also trigger an increase

in the production of the female hormone estrogen.


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• As estrogen levels rise, like a switch, it turns offthe production of follicle-stimulating hormone.This careful balance of hormones allows the bodyto limit the number of follicles that complete

maturation, or growth.• As the follicular phase progresses, one follicle

(graafian follicle) in one ovary becomes dominantand continues to mature. This dominant follicle

suppresses all of the other follicles in the group.As a result, they stop growing and die. Thedominant follicle continues to produce estrogen.


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Ovulatory Phase

The ovulatory phase, or ovulation, starts about 14days after the follicular phase started. Theovulatory phase is the midpoint of the menstrualcycle, with the next menstrual period starting

about 2 weeks later. During this phase, thefollowing events occur:

• The rise in estrogen from the dominant follicletriggers a surge in the amount of luteinizing

hormone that is produced by the brain.• This causes the dominant follicle to release its

egg from the ovary.


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• As the egg is released (a process called ovulation)it is captured by finger-like projections on the endof the fallopian tubes (fimbriae). The fimbriaesweep the egg into the tube.

• Also during this phase, there is an increase in theamount and thickness of mucus produced by thecervix (lower part of the uterus.) If a woman wereto have intercourse during this time, the thick

mucus captures the man's sperm, nourishes it,and helps it to move towards the egg forfertilization.


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Luteal Phase

The luteal phase begins right after ovulation andinvolves the following processes:

• Once it releases its egg, the empty follicle

develops into a new structure called thecorpus luteum.

• The corpus luteum secretes the hormonesestrogen and progesterone. Progesteroneprepares the uterus for a fertilized egg toimplant.


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• If intercourse has taken place and a man's sperm

has fertilized the egg (a process called

conception), the fertilized egg (embryo) will travel

through the fallopian tube to implant in theuterus. The woman is now considered pregnant.

• If the egg is not fertilized, it passes through the

uterus. Not needed to support a pregnancy, the

lining of the uterus breaks down and sheds, and

the next menstrual period begins.


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• During fetal life, there are about 6 million to 7 millioneggs. From this time, no new eggs are produced.

• The vast majority of the eggs within the ovariessteadily die, until they are depleted at menopause. At

birth, there are approximately 1 million eggs; and bythe time of puberty, only about 300,000 remain. Ofthese, 300 to 400 will be ovulated during a woman'sreproductive lifetime. The eggs continue to degenerate

during pregnancy, with the use of birth control pills,and in the presence or absence of regular menstrualcycles.


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Conception, Pregnancy and Labor

• Once an egg has been released from the ovaries, it will begin totravel down the fallopian (uterine) tubes towards the uterus. As itadvances towards the uterus, it begins to produce an enzyme thathelps to attract and guide any sperm that may have been ejaculatedinto the female reproductive system during sex.

• Although a man releases millions of sperm when he ejaculatesduring orgasm, only a few hundred will be able to make it all theway from the cervix up into the uterus and then into the correctfallopian tube. Just one sperm will then be able to make its waythrough your eggs tough coating to fertilize the egg. If fertilizationoccurs in the uterine tube, the fertilized egg begins to changeimmediately after. Soon the egg is divided into a cluster of two,then four, then more cells, as it makes its way down the uterinetube toward the uterus for implantation.


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• By the time the egg reaches the uterus, in 3 to 5 days, the cells areformed in the shape of a minute ball, hollow on the inside with aninternal bump at one side where the embryo will form. Theaggregation of cells, called blastocyst, quickly buries itself in thelining of the uterus.

• As soon as the blastocyst is implanted, its wall begins to change intoa structure that eventually develops into the placenta. Through theplacenta the fetus secures nourishment from the mother and ridsitself of waste products. Essentially the placenta is a filteringmechanism by which the mother’s blood is brought close to thefetal blood without the actual mixing of blood cells.

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The outermost membrane which surrounds the developing embryois called the chorion and the innermost the amnion. The amnioncontains the fetus surrounded by the amniotic fluid. The amnionand fluid are sometimes known as “the bag of water”, which breaksto signal the onset of labor.


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• The placenta, also known as the “afterbirth”because it becomes detached from the uterusafter delivery, produces its own hormone as it

develops in the uterus. This hormone is calledhuman chorionic gonadotropin – HCG (orpregnancy hormone) and it stimulates thecorpus luteum to continue producing until the

third month of pregnancy, when the placentaitself takes over the endocrine function andreleases estrogen and progesterone.


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• During the early stages of pregnancy, thefuture child grows at an extremely rapid rate.The mother’s body must undergo profound

changes to support this organism. Themuscles of the uterus grow, vaginal secretionschange, the blood volume expands, the workof the heart increases, the mother gains wait,

the breasts prepare for lactation and otheradjustments are made throughout themother’s body.


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• The average duration of pregnancy or the gastation periodis about 280 days, or 9 calendar months, although it mayvary considerably from that average.

• Labor or childbirth is the physiological process by which thefetus is expelled from the uterus. It occurs in three stages:

1) Opening or dilation of the cervix (about 10 cm);

2) The second stage is called the expulsion stage duringwhich the baby must be pushed through and out of thevagina;

3) The third stage is the stage of separation and expulsion ofthe placenta; in this final stage the placenta detachesitself from the uterine wall and is expelled.


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The End

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