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Here is a term paper on ‘Sexual Reproduction in Human Beings’ for class 9, 10, 11 and 12. Find paragraphs, long and short term papers on ‘Sexual Reproduction in Human Beings’ especially written for school and college students.
Sexual Reproduction in Human Beings
Term Paper Contents:
- Term Paper on the Male Reproductive System
- Term Paper on the Female Reproductive System
- Term Paper on the Comparison Between Male and Female Gametes
- Term Paper on the Menstrual Cycle
- Term Paper on Human Fertilisation
- Term Paper on Birth Control
- Term Paper on the Sexually Transmitted Diseases
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Term Paper # 1. The Male Reproductive System:
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Although a baby is born with a full set of reproductive organs, these organs are not functional during the first 12 (or so) years of life. Under the influence of hormones from the pituitary gland, the organs become active at the time known as puberty.
The male nuclei involved in the process of human sexual reproduction are located within male gametes (sex cells) called sperms (an abbreviation for ‘spermatozoa’). The male reproductive system is designed to manufacture sperms and to deliver them to the place where one of them will be able to fuse with a female nucleus.
i. Testes (Singular: ‘Testis’):
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The testes are the gonads of the male. Gonads are the organs which produce the gametes, in this case the sperms. The testes are made of millions of tiny coiled tubes. The cells forming the walls of these tubes are constantly dividing to produce up to 100,000,000 sperms per day. The testes work more efficiently at just below body temperature, so they are held outside the body in the scrotum (or scrotal sac).
ii. Sperm Ducts:
Sperm ducts are tubes which carry the sperms away from the testes. They join with one another and with the tube bringing urine, at a position just under the bladder. Each sperm duct bears a seminal vesicle for sperm storage.
iii. Prostate Gland:
The prostate gland is about the size of a golf ball. It surrounds the junction between the sperm ducts and the tube from the bladder. It manufactures, and adds to the sperms, a nutrient fluid (seminal fluid) in which the sperms are able to swim (sperms + seminal fluid = semen).
iv. Urethra:
The urethra is a tube that carries both urine and semen along the penis to be released from the body.
v. Penis:
The penis is the organ for introducing sperms into the female. It contains spongy tissue which fills with blood to make the penis firm (an ‘erection’) so that it can more easily be guided into the female.
Term Paper # 2. The Female Reproductive System:
The female nuclei which are involved in the process of sexual reproduction are located in the female gametes called ova (singular: ‘ovum’).
The functions of the female reproductive system are:
(i) To produce ova and ensure that they are fertilised by the male gametes
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(ii) To protect and nourish the embryo until it is born.
a. Ovaries:
The ovaries are the female gonads, making and releasing the female gametes (ova). There are two ovaries, each a little smaller than a ping-pong ball, lying in the lower abdomen. The female releases one ovum every four weeks from alternate ovaries, that is, each ovary releases one ovum every eight weeks.
b. Oviducts:
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The oviducts are the tubes which carry the ova away from the ovaries. They are lined with cilia which, together with a little muscular assistance, help to move the ova gently along. If fertilisation occurs, it usually does so about one-third of the way along the oviduct.
c. Uterus:
The uterus is a pear-shaped organ lying behind and slightly above the bladder. Its walls contain involuntary muscle (i.e. muscle that cannot be consciously controlled). The embryo develops in the uterus during pregnancy.
d. Cervix:
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The cervix is the ‘neck’ of the uterus, where the uterus joins the vagina. It supplies mucus to the vagina.
e. Vagina:
The vagina is the part of the female system which receives the penis during copulation. It is muscular and stretchable (it forms part of the birth canal) and it connects the cervix with the slit-like vulva opening to the outside.
Term Paper # 3. A Comparison Between Male and Female Gametes:
Term Paper # 4. The Menstrual Cycle:
Once a female reaches puberty, she will start to release ova from her ovaries (i.e. she will start to ovulate).
Ovulation is one stage in her menstrual or monthly cycle, described below:
1. Over a period of about 14 days, the walls of the female’s uterus develop a spongy lining, containing many blood capillaries.
2. When the spongy lining is ready, ovulation occurs. The ovum passes down the oviduct. If the ovum is not fertilised by a sperm, it passes through the uterus and vagina and out of the vulva.
3. The spongy lining then peels away from the uterus wall, damaging the blood capillaries. The lining is passed out of the vagina and vulva, together with blood. This is menstruation or the monthly period. Menstruation lasts for about four days, and occurs about two weeks after ovulation.
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4. Once the uterus wall has recovered, it begins to rebuild its spongy lining, under the influence of a hormone from the ovary. Meanwhile, a new ovum is maturing in the ovary, under the influence of a hormone from the pituitary gland. When mature, the ovum is released (ovulation), at around two weeks after menstruation. The cycle continues in this way as long as the female remains healthy.
If an ovum is fertilised, and the woman becomes pregnant, her menstrual cycle stops until after the baby is born. When a female reaches the menopause, usually at around 50 years of age, she stops ovulating and can no longer become pregnant.
Factors Affecting the Menstrual Cycle:
i. Stress:
At times of emotional stress the menstrual cycle may become irregular.
ii. Diet:
An inadequate diet can lead to an irregular cycle, and starvation can suppress the cycle completely.
Fertile and Infertile Phases of the Menstrual Cycle:
When there is no ovum in the oviducts, fertilisation cannot occur. It is unlikely to occur if the ovum is not in the correct position in the oviduct; however, sperms can live in the oviduct for a few days, allowing the ovum a chance to arrive. A woman’s most fertile period is therefore from a few days before ovulation (allowing for the possible survival of sperms in the oviduct) to a few days after ovulation. Outside this time, she is less likely to become pregnant.
Term Paper # 5. Human Fertilisation:
During copulation, sensitive cells near the end (glans) of the penis are the receptors for a reflex action leading to the release (ejaculation) of semen. The sperms are deposited near the cervix of the female, and then swim through the uterus and up the oviducts. If they meet an ovum, around one-third of its way from the ovary, one of the sperms may fuse with the ovum to form a zygote. This is the moment of fertilisation.
Development of the Embryo:
The zygote, a single cell formed from equal nuclear contributions from both parents, now begins to divide, eventually to form a hollow ball of cells. This stage in embryonic development is called the blastocyst.
The embryo initially absorbs nourishment secreted by the cells of the uterus, but it soon embeds itself (implantation) in the spongy lining of the uterus. Further division of the cells turns the blastocyst into a fetus. The fetus is surrounded by a membrane (the amnion) which forms the amniotic sac enclosing the fetus in a water bath (the amniotic fluid).
Functions of the Amniotic Fluid:
(i) To protect the embryo from physical damage, e.g. if mother falls over.
(ii) To support the embryo, keeping even pressure all round it, allowing organs to develop without restriction.
(iii) To allow the fetus some restricted movement.
The Nutrition and Excretion of the Fetus:
Both nutrition and excretion are carried out through a special structure called the placenta. This is made up partly of material from the fetus and partly of material from the spongy lining of the uterus. In the placenta, blood in the mother’s capillaries runs very close to blood in the capillaries of the fetus. However, their blood does not mix – mother and child may be different blood groups.
Diffusion of substances takes place between the two blood systems:
The placenta is connected to the fetus by the umbilical cord, inside which run fetal blood vessels. The umbilical vein brings substances to the fetus; the umbilical artery carries substances from the fetus.
The Dietary Needs of a Pregnant Woman:
An embryo’s development depends on the food eaten by its mother, so a pregnant woman must adjust her diet accordingly.
She should ensure that the levels of the following constituents are higher than in her normal intake:
(i) Protein for the manufacture of embryonic tissues.
(ii) Carbohydrate for additional respiration in embryonic tissues.
(iii) Vitamin C for making proteins in the embryo.
(iv) Vitamin D and calcium for making bones and teeth of embryo.
(v) Iron for making embryo’s blood.
These should be raised to the approximate levels required by a very active woman who is not pregnant.
The Value of Breast Feeding:
After the birth of the baby, milk from the mother’s mammary glands supplies the ideal food for the first months of development.
The Milk:
(i) Is cheap
(ii) Readily available
(iii) Contains all the necessary constituents, in the correct proportions
(iv) Is at the correct temperature
(v) Contains some antibodies which protect the baby against disease.
Breast feeding also helps to develop the bond between mother and baby.
Some babies may suffer harmful reactions to the substitute formula milk powders which are used in bottle feeding.
Term Paper # 6. Birth Control:
The world population has risen alarmingly over the last few decades. It is already difficult to supply enough food to all areas of the world. A solution lies in birth control.
The main methods are:
A. ‘Natural’ Method (or Rhythm Method):
Sexual intercourse (copulation) is limited only to those times in the menstrual cycle when fertilisation is less likely.
However, a woman’s menstrual pattern may not be a reliable indicator of her fertility. Severe anxiety and malnutrition can suppress the menstrual cycle completely. Varying degrees of anxiety and dietary deficiency can lead to an erratic menstrual pattern.
Not all healthy and perfectly happy women have predictable and regular periods – particularly when teenagers or when approaching the menopause. Often the most accurate prediction can only be that ovulation usually occurs somewhere between 12 and 16 days before the start of menstruation.
The ‘natural’ method of birth control is therefore not a reliable method of avoiding pregnancy.
B. Chemical Method:
Chemicals which kill sperms (‘spermicides’) are put into the vagina of the female before intercourse. This is not a very effective method of birth control when used on its own.
C. Mechanical Methods:
(i) Where some form of barrier is put between the sperms and the ova.
The barrier may take the form of:
(a) A condom, a sheath placed over the penis before intercourse to catch the sperms when ejaculated
(b) A femidom which lines the vagina of the female with the same result
(c) A diaphragm which fits over the cervix of the uterus, preventing the entry of sperms. A diaphragm is usually used with a spermicide.
Barrier methods are popular and quite effective.
(ii) Where there is no barrier between the sperms and the ovum, an intra-uterine device (IUD) which is fitted inside the uterus. It does not stop fertilisation, but it prevents implantation of the blastocyst. This is an effective method of birth control.
D. Hormonal Method:
This method is otherwise known as the pill. The woman takes a tablet which contains a hormone. When taken regularly, the pill prevents ovulation, so that no ova are present to be fertilised. This is an effective method of birth control if the routine is followed carefully.
E. Surgical Methods:
(i) In the Male:
Cutting the sperm ducts (the operation is called vasectomy) – an effective method but rarely reversible.
(ii) In the Female:
Tying the oviducts to prevent the passage of ova – an effective method and usually reversible.
Term Paper # 7. Sexually Transmitted Diseases:
During the act of sexual intercourse, the bodies of the partners are brought into close contact. Pathogens can easily pass from one infected person to another. Diseases spread through sexual contact are called sexually transmitted diseases (STDs).
Three examples are:
A. Syphilis,
B. Gonorrhoea and
C. AIDS .
A. Syphilis:
Syphilis is caused by a bacterium. Symptoms of the disease include – sores on the penis, or around the vulva, a slightly raised temperature, rash and headache. This disease can eventually destroy the tissues of the brain, skeleton and other major organs. However, it may be treated with antibiotics.
Syphilis can be controlled by limiting sexual contact to one partner, and using a condom during intercourse.
B. Gonorrhoea:
Gonorrhoea is caused by a bacterium. Symptoms include severe pain on urination (particularly in the male) since the bacterium invades the tissues of the urethra. There is a discharge of pus from the urethra (from the end of the penis in the male).
The infection may spread to produce inflammation of the uterus in the female and of the epididymis in the male. The disease is not life- threatening, but it may lead to sterility. Methods of treatment, prevention and control are similar to those described for syphilis.
C. AIDS:
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Acquired immune deficiency syndrome (AIDS) is caused by the human immuno-deficiency virus (HIV). The virus affects the body’s ability to fight infection. It lives in body fluids such as blood and semen.
Transmission:
HIV may be transmitted in the following ways:
(i) From host to host when intravenous drug users share unsterilised needles. A small amount of blood may enter the needle and syringe when a person injects a drug. If another person uses the same, unsterilised needle, they will receive the blood of the first user, who may be infected.
(ii) In semen, from one partner to the blood of another, if there is any tearing of tissues during intercourse.
(iii) From an infected mother’s blood to her baby’s blood during the birth process.
(iv) In untreated blood during blood transfusion.
Disease Control:
Although the drug AZT can slow the progress of the disease, there is, as yet, no cure for AIDS.
It can, however, be controlled by:
(i) Educating the public about how it is spread, and what precautions can be taken.
(ii) Never sharing needles.
(iii) Avoiding sex with prostitutes because they are often carriers of the disease. Staying with one STD-free partner.
(iv) Always using a condom or other barrier method of contraception which prevents direct contact between the body fluids of the two partners.
(v) Treating all blood and blood products used in transfusions to destroy the AIDS virus.
