The Human Body: Reproductive System (1959)

[Music] throughout the centuries the male and female forms of the human body have been looked upon as expressions of great beauty and perfection the human body however is more than a thing of beauty the human body is the most complex of living things many of our body processes are regulated by a digestive system a respiratory system a circulatory system and an excretory system these are just some of the body systems which working together maintain life but life must be initiated as well as maintained and this is the essential function of the reproductive system to bring new life into the world unlike the other systems of the body the reproductive system differs in the mail and in the female yet these systems show many similarities each system has a pair of main organs these are the sex glands called gonads in each system there is also a series of tubes one function of the gonads is to produce reproductive cells the other function is to produce hormones these chemical substances hormones are particularly related to growth and development unlike the other systems that maintain life in the body from earliest childhood the reproductive system is not fully functional until that period of life known as adolescence during this time the hormones produced by the gonads cause certain changes in our bodies these changes are part of growing up of maturing these body changes in the male and female may occur during the early or later years of adolescence but they are all caused by the hormones of the gonads now let's take up the other vital function of the gonads each pair produces reproductive cells or gametes after the gametes unite the development of a new individual begins the gametes produced by the male are sperm tiny living cells here greatly magnified otherwise they would be invisible these are sperm of the human male the gamete produced by the female gonad is an ovum or egg here also highly magnified is an ovum of a human female the ovum is much larger than the sperm cell and is barely visible to the naked eye the sperm cell of the male carries certain heritable characteristics of the father and the larger ovum of the female carries certain heritable characteristics of the mother when these two cells unite a new individual with characteristics from both parents begins to develop the producing of reproductive cells or gametes is a function that is common to both the male and female gonads there are other similarities in both systems there is a pair of tubes these tubes carry the reproductive cells produced by the gonads to the place where the cells may unite in addition to such similarities there are differences for instance the organs of the male reproductive system are chiefly external outside the body while the organs of the female are chiefly internal within the body we'll see other differences as we learn more details about first the female reproductive system we've already seen the gonads of the female reproductive system these are called ovaries or egg producers near the ovaries are the tubes we've seen they are called oviducts or fallopian tubes they carry the eggs or ova into the uterus within the pear-shaped muscular uterus the new individual grows and develops until birth through its lower part called the cervix the uterus connects with the vagina this side view shows how the vagina reaches to the surface of the body close to the surface the vagina contains the hymen a thin partial membrane slightly above the opening of the vagina is an organ called the clitoris around these organs are the labia which are external folds of skin these organs of the female should not be confused with other adjacent organs such as the anus through which the body wastes are eliminated also the adjacent bladder and urethra of the urinary system are not connected with the organs of the reproductive system the urethra and the vagina have independent exits between the labia now let's see how the female reproductive system functions let's begin with this enlarged cutaway view of an ovary inside the ovary there are many reproductive cells or ova about once every 28 days one of these ova or eggs in one of the ovaries ripens and with its supporting cells bursts through the wall of the ovary the ripe ovum enters the oviduct or fallopian tube we see that the ripe ovum moves through the tube if fertilization or union with a sperm cell occurs the new individual will begin to develop as the ovum moves through the tube toward the uterus during the days the ovum approaches the uterus the lining of this organ gradually becomes thick and spongy with a rich supply of blood vessels if the ovum entering the uterus has been fertilized the extra blood supply will provide nutrients and oxygen for the developing individual if the ovum has not been fertilized it slowly disintegrates usually in the uterus some days later part of the spongy lining of the uterus also disintegrates and flows out through the vagina the fluid a mixture of blood and lining cells of the uterus is discharged this is called the menstrual flow this process menstruation occurs about every 28 days and is a normal process menstruation does not occur however if fertilization takes place to understand fertilization we must also understand the male reproductive system as in the female the gonads are the main organs in the male they are called testes there are two testes enclosed in a pouch of skin the scrotum located outside the body by looking closer at a single testis we see that it is made up of a mass of tiny coiled tubules or small tubes the cells lining these tubules produce sperm the reproductive cells or gametes of the male here in cross-section we see that these sperm-producing tubules empty into other tubules outside the testis which store the sperm these sperm storing tubules empty into a larger tube called the vas deferens the vast deference carries the sperm up into the body cavity at the end of the vas deferens lie two glands the prostate gland and the seminal vesicles the prostate gland and the seminal vesicles produce a fluid sperm cells are mixed with this fluid as they pass into the next tube the urethra the sperm laden fluid is called semen although the urethra carries semen it is also attached to the bladder of the urinary system however it's important for us to remember that in the human male the urethra does not function in both systems at the same time the urethra passes through an external organ the penis through this organ semen with its sperm leaves the male body sometimes during adolescence semen may be released during sleep this is a normal occurrence now that we've learned something about the function of the male system let's see how both systems contribute to the process of fertilization semen usually containing two or three hundred million sperm is deposited within the vagina of the female each sperm consists of a head or nucleus which carries the heritable characteristics of the male parent and a tail which propels the cell sperm move from the vagina into the uterus after passing through the vagina and uterus the sperm continue to move into the oviducts it is also the oviduct that receives a ripe ovum or egg about every 28 days a ripe ovum passes from one of the ovaries and enters an oviduct fertilization of the ovum takes place in the upper part of the oviduct it occurs when one of the millions of sperm cells seen here under the microscope moves through the surrounding cells of the ovum as shown in this simplified diagram the sperm cell then penetrates the ovum the position of the sperm and ovum in this diagram are similar to what we'll see in the next scene a microscopic view of human fertilization of the many sperm cells only the one at the upper right in this picture enters the ovum after the head of one sperm enters the surface of the ovum changes and prevents any other sperm cells from entering during the next few days the fertilized ovum or zygote begins to develop by dividing into many cells here we see only the first stage of two cells the zygote is the beginning of a new individual as the zygote grows and develops it is called an embryo the embryo passing from the oviduct enters the uterus and after several days embeds itself in the thick blood-enriched lining of this organ here the embryo gets its nourishment and continues to develop after a period of development usually nine months a new individual is born a new human being who in turn will continue human life for another generation this new individual is the result of the combined functions of the male and female reproductive systems these systems consist of main organs called gonads which produce hormones an equally important function of the gonads is to produce and store reproductive cells called gametes we learned that the systems include tubes which carry the reproductive cells to the place where fertilization occurs we saw human fertilization actually occur fertilization produces a zygote or the beginnings of a new individual which is nourished and developed within the uterus these systems which account for the differences in male and female are vital parts of the human body the reproductive systems make possible the continuance of human life understanding the functions of these systems is important in preparing for family life as well as in maintaining your physical and mental health [Music]