Archive for the ‘REPRODUCTIVE SYSTEM’ Tag

HUMAN DISEASES (Part 6 of 7)   Leave a comment

Other Metabolic Diseases

Gout is faulty metabolism of purine, an amino acid, resulting in the accumulation of uric acid in the blood and urate salts in the tissues, especially the joints where they cause painful arthritis. It may stem from an inborn error of metabolism or from other diseases. It usually strikes middle-aged men. The joint at the base of the big toe is the typical site of a sudden acute attack of gout. The affected joint becomes red, hot, swollen, and painful. Fever accompanies the attack. Joints of other limbs might become similarly affected. Attacks of gout recur, but the sufferer enjoys complete relief in between them. Some patients develop chronic arthritis from gout. Gout is treated with low-purine foods and such drugs as allopurinol that lower the uric acid level of the blood.

Cystic fibrosis, an inherited disease in which the pancreas fails to provide secretions necessary for normal digestion of food; commonly associated with chronic lung disease.

Cystic fibrosis is a genetic disorder involving the pancreas and the lungs. It appears during the first 10 years of life, although sometimes it is not discovered until later. Certain glands of the pancreas become plugged by thick mucus, which bottles important digestive enzymes. Intestinal troubles result.

Furthermore, the lungs suffer scarring, infection, and eventual emphysema. Cystic fibrosis is treated with substitute pancreatic enzymes, vitamins, and a high-calorie diet. Antibiotics are given to fight the lung troubles.

Other metabolic disorders include phenylketonuria (PKU) and galactosemia. PKU is an inherited inability to metabolize phenylalanine, an amino acid. Galactosemia is an inherited inability to change galactose, one type of sugar, into sucrose, another, because a necessary enzyme is missing. Both diseases can result in mental retardation of children if not corrected in time.

Arthritis and Lupus

Rheumatoid arthritis (RA), chronic disease of the connective tissue, causing painful sensations in joints and muscles.

When the body fails to recognize itself, it makes antibodies against its own tissues. Rheumatoid arthritis and systemic lupus erythematosus are two among a rising number of such autoimmune diseases.

Rheumatoid arthritis is a chronic crippling disease that deforms bone joints and their adjacent tissues. It can strike nearly anyone. Although arthritis is not especially prevalent in damp climates, its symptoms are more bothersome there. It is marked by inflammation of an entire joint, including its synovial lining. Tendon coverings and bursas, or fluid-filled cushions, can become inflamed too. Cartilage in the joint and adjacent bone are destroyed, causing painful stiffness and eventual ankylosis, or “freezing,” of the joint. Skin over the joint is taut, shiny, and clammy. Arthritics often suffer aches and pains. The rheumatoid factor, a large protein molecule, is present in the blood of so many adult patients that it aids in the diagnosis of the disease. Rheumatoid arthritis is usually treated with rest, physical therapy, and aspirin and other salicylates.

Systemic lupus erythematosus (SLE), or lupus, is a serious degenerative disease that can strike one or many body systems over a period of years. The blood serum of afflicted persons contains a number of peculiar proteins, including the so-called L.E. factor, the antibody characteristic of the disease. Symptoms of SLE resemble other diseases, including cancer and tuberculosis, but lesions around the nail beds and fingertips that destroy the skin in those areas earmark lupus. In addition, the spleen and lymph glands of the neck and armpits may enlarge. The pericardium and heart valves are affected too. The kidneys and portions of the central nervous system may also become damaged. Although anyone may be affected, females between the ages of 20 and 40 years most often develop this incurable disease.

Osteoarthritis is a painfully disabling disease of the spine and other weight-bearing joints. Cartilage in the joint is destroyed, followed by overgrowth of nearby bone. The incurable but non deforming disease develops with advancing age.

Ankylosing spondylitis is a disabling and deforming disease of the spine, sacroiliac joints, and sometimes the shoulders, hips, and knees. The synovial lining of the affected joint becomes inflamed, the bone is weakened by loss of calcium, and the spine is bent forward. Eventually, the spinal vertebrae fuse and the spine becomes locked in the deformed position.

KIDNEY AND GENITAL DISEASES

Disease can affect any of the parts of the closely related urinary and genital systems. Both can be infected or malfunction because of a shortcoming in development.

Kidney Inflammations

Kidney disease, commonly result of inflammation or damage to blood vessels of kidneys; severe forms lead to breakdown of normal elimination of waste products.

Glomerulonephritis is a serious inflammatory disease of the kidneys. It usually is triggered by a prior infection, often by streptococcal bacteria, which inflames the glomeruli, the tiny tufts through which blood is filtered. The inflammation may go away after a few weeks or may slowly destroy all the glomeruli. In the early stages, the inflammation may reduce filtration enough to cause blood to retain some excess fluid, salts, and wastes. Blood pressure might also rise. If the inflammation persists, the glomeruli are destroyed, blood pressure soars, and urine formation may stop. Mechanical means must be taken to cleanse the blood.

Pyelonephritis, bacterial infection of the inner portions of the kidneys and the urine.

Pyelonephritis is a bacterial infection of the inner portions of the kidneys and the urine. If quickly treated, the infection can be cured. If untreated, however, the infection may scar and eventually destroy kidney tubules, resulting in a need for mechanical cleansing of the blood. Once damaged by a bout of pyelonephritis, the kidneys are easily reinfected.

Toxaemia of pregnancy is a disorder stemming from other kidney problems experienced by some women in the last half of pregnancy. During a pregnancy, the kidneys must work more than usual. However, a woman entering pregnancy with a kidney disease such as Glomerulonephritis may not be able to step up kidney function enough to meet the new demands. In severe cases of toxaemia, the foetus may die or have to be aborted to save the mother’s life. In lesser cases, however, medical treatment poses little risk to either life. Once a woman develops toxaemia, she is likely to develop it again in later pregnancies.

Calculi and Other Urinary Disorders

Calculus disease, condition that occurs when certain substances in urine crystallize into compact stones.

Calculus disease occurs when certain substances in urine crystallize into compact stones called calculi. A stone may be formed within a kidney and become swept by urine into the ureters and the bladder. It may cause pain, obstruct urine flow, or grow large enough to damage the kidney or bladder. Small calculi may be passed in urine, and large ones can be pulverized without surgery by means of energetic sound waves. Calculi can consist of calcium, urates, cystine, or other crystals. The tendency to form kidney stones sometimes runs in families.

Polycystic disease, an inherited failure of normal kidney development, strikes infants as well as adults. Many fluid-filled cysts spring up throughout the kidneys and cause them to malfunction. Polycystic disease sufferers eventually become uraemic

Uraemia means “urine in blood.” It describes the condition in which the kidneys almost totally fail to operate. The blood then retains the nitrogenous products of protein metabolism instead of having them removed by the kidneys. Also, the concentration of many of the electrolytes, or salts, in the blood rises too high. The breath or perspiration of affected persons smells of urine. Each of the previously mentioned kidney ailments could cause uraemia Artificial kidneys have been developed to cleanse the blood of uraemic patients. In some cases, patients with destroyed kidneys can receive a human kidney transplant.

Genital Disorders

Sometimes portions of the genital system fail to develop normally. In some rare cases, the gonads male testes and female ovaries or other sex structures fail to develop at all. Without gonads, a person neither achieves puberty nor develops secondary sexual characteristics, such as breasts and uterus growth in females and penis growth and muscle development in males.

Infections such as gonorrhoea can cause sterility by blocking the oviducts, or egg passages, of females or the vas deferens, or sperm passages, of males. In males, gonorrhoea may also interfere with urination.

The prostate gland at the neck of the bladder in males enlarges slowly with age. It eventually may hamper urination and need surgical correction.

REHABILITATION

Rehabilitation is a fairly new medical speciality, although the notion of helping someone cope with a disabling disease or disorder is an old one. As an increasing number of people become disabled by stroke, paraplegia (paralysis of the lower body), limb losses, and many chronic nervous system and other physical disorders, it has been shown that medical rehabilitation can help many of them live a reasonably normal life. This is true even when the handicapping problem is not medically correctable.

Rehabilitation means getting utmost use from the limbs, senses, or other body systems that remain in operation after a chronic disability. Its goal is to help the patient become as independently active as possible. The disabling condition might result from a disease, birth defect, or severe accident. Sometimes rehabilitation involves fitting an amputee with an artificial limb, fitting a lame person with a brace, or teaching a paraplegic how to manoeuvre a wheelchair. Sometimes it only involves counselling and other psychological techniques for persons who are mentally disabled.

In its early days medical rehabilitation concentrated on helping people who had walking and other movement problems. The advances made in rehabilitating them sparked efforts to aid people who were stricken by stroke, chronic arthritis, and spinal cord disease and other chronic nervous system disorders. Afterwards, it was learned that rehabilitation could also help patients with heart disease, chronic lung disease, and a variety of conditions that slowed recovery from surgery. Bio engineers have been successful in devising artificial limbs and other life support structures that function so much like natural ones that recipients no longer suffer a disabling handicap.

Rehabilitation is a team effort. It requires the work and dedication of physicians, physical therapists, occupational therapists, psychologists, social workers, and vocational counsellors The doctor and the physical and occupational therapists work to restore those body functions impaired by the disability. The psychologist, social workers, and vocational counsellor help the patient get a mental grip on himself to better deal with the emotional and social problems brought on by the disability. Members of a coordinated rehabilitative team can do wonders in restoring a handicapped person to a functional life.

In addition, the rehabilitative team works with a disabled person to prevent the physical deterioration that takes place when muscles are not used. Furthermore, the team aims at getting the maximum output from the patient’s remaining body functions. Exercises and other means are used to develop fully the remaining physical reserves because disabled persons expend more energy and need more stamina to do ordinary things than do non disabled persons.

Teaching new tasks to the disabled is an integral part of physical rehabilitation. For example, a crippled person may be trained to use a wheelchair or other motive device well enough to manage into the driver’s seat of an auto mobile and thus achieve a measure of independence, the important goal of the entire rehabilitative process.

A chronically disabled person often suffers mental depression. The rehabilitation team tries to restore that person’s confidence so that he can take an optimistic view on resuming daily activities. Positive attitudes of patient, friends, and family toward any disability are important factors in the success of rehabilitation. During rehabilitation the patient is encouraged to find meaning in life, overcome feelings of being a “permanent patient,” and resume his place as an active member of society. Counselling is also important in rehabilitating alcoholics and the mentally ill.

Treatment for the disabled is given at special rehabilitation centres or in the rehabilitation departments of some hospitals. Rehabilitation units are designed so that patients can do many things by themselves; the quarters are built to simulate conditions the patients will encounter when discharged. As a consequence, patients get practice in dealing with such problems as opening and closing doors, going up and down stairs, and a host of other environmental situations that they will face when the rehabilitation program is over.

ANIMALS (Part 1 of 4)   Leave a comment

Cheetah

DEFINITION: 1 any living organism, excluding plants and bacteria: most animals can move about independently and have specialized sense organs that enable them to react quickly to stimuli: animals do not have cell walls, nor do they make food by photosynthesis 2 any such organism other than a human being, esp. a mammal or, often, any four-footed creature 3 a brutish, debased, or inhuman person 4 [Colloq.] a person, thing, concept, etc. thought of as a kind or type [today’s athlete is another animal altogether]

All living things are divided into two main kingdoms the animal and plant kingdoms and two or three other kingdoms that include bacteria, blue-green algae, and one-celled creatures with definite nuclei. What is the difference between a horse, for example, and grass? A horse moves about in the pasture eating grass. It trots toward you when you offer it a lump of sugar and shows pleasure when you stroke its head. The grass, however, is rooted to one place. It does not respond behaviourally to people or to the horse in any way.

Animals Move About and Sense Surroundings

Adult animals move freely from place to place during at least one phase of their life. Plants usually cannot move unless a force, such as the wind, causes them to move.

Most animals move freely from place to place and can sense their surroundings; that is, they can taste, smell, hear, see, and touch. Certain simple animals, such as the corals and barnacles, spend most of their lives fastened to one spot, but they are able to swim freely when they are young. Even these rooted animals have parts that move in order to capture food. Plants, however, cannot shift about at their own will. They react to heat, light, chemicals, and touch, but their responses are involuntary and automatic, quite different from those of animals.

All living things are made of cells. The walls of plant and animal cells are different.

Cellulose, complex carbohydrate consisting of 3,000 or more glucose units; basic structural component of plant cell walls; 90% of cotton and 50% of wood is cellulose; most abundant of all naturally occurring organic compounds; indigestible by humans; can be digested by herbivores, such as cows and horses, because they retain it long enough for digestion by micro organisms present in their digestive systems; also digestible by termites; processed to produce papers and fibres; chemically modified to yield plastics, photographic film, and rayon; other derivatives used as adhesives, explosives, thickening agents, and in moisture-proof coatings.

All living things are made up of cells of protoplasm. They may consist of a single cell, as does an amoeba, or billions of cells, as do trees and horses. The cell wall of a plant is composed of a woody material called cellulose. No true animal contains cellulose. Animal cells are bounded by a membrane composed chiefly of fat and protein.

Green plants make their own food. With the aid of the green substance called chlorophyll, they use the energy in sunlight to change carbon dioxide and water into carbohydrates and other food materials. No true animal contains chlorophyll.

Animals must eat, either directly or indirectly, the food manufactured by members of the plant kingdom. A horse cannot stand in the sun and wait for its body to make fat and proteins. It must move about the pasture in search of green grass. Even meat eaters for example, lions live on animals, such as zebras, which in turn subsist on plants.

The Variety of Animal Life

More than a million different kinds of animals inhabit the Earth. The exact number is not known, for new kinds are continually being discovered. They live in the seas, from the surface down to the black depths where no ray of light penetrates. On mountaintops and in deserts, in mud and in hot pools some form of animal life may be found.

Animals are infinitely varied in form, size, and habits. The smallest animals are bits of protoplasm that can be seen only with a microscope. The largest, the blue whales, may be more than 100 feet (30 meters) long and weigh 300,000 pounds (136,000 kilograms).

Some of the most familiar animals, such as dogs, birds, frogs, and fish, have a backbone and a central nervous system. They are called vertebrates, meaning animals with backbones. Animals without backbones are called invertebrates and include arthropods, worms, molluscs, and many other groups. Most of the vertebrates and many invertebrates have a head where sense organs are concentrated and have legs, wings, or fins for locomotion. Vertebrates and many invertebrates, such as the arthropods and worms, have bilateral, or two-sided, symmetry. This means that they have two mirror-image sides (a right side and a left side), distinct upper and lower surfaces of the body, and a distinct front and rear.

Some invertebrates, such as jellyfish, sea anemones, and starfish, display radial symmetry, in which the parts of the body are arranged around a central axis, similar to a wheel. Animals with radial symmetry live in marine or freshwater aquatic environments. Some drift with the currents, unable to swim in any definite direction. Others become attached to a solid object by one end and float with the mouth end upright. Tentacles arranged in a circle around the mouth sweep in food particles and ward off enemies.

One-celled animals called protozoans live in fresh and salt water. Many are shapeless creatures and cannot swim toward their food. They move along by squeezing out a finger like projection from the body. This is called a pseudopod, from the Greek meaning “false foot.” The pseudopod fastens to something solid, and the rest of the body flows into the fastened projection. The amoeba also moves in this manner. One-celled animals are very small. They are single blobs of liquid enclosed in a thin membrane and as such cannot attain a large size or a very definite shape.

Animals with Outside Skeletons and Feet

Molluscs have soft bodies that are not divided into specialized sections such as head, thorax, and abdomen. Many molluscs are enclosed in hard, hinged shells. Snails have a single large, fleshy foot located on the stomach side.

The heads of the octopus and the squid are surrounded by a circle of eight or ten tentacles that act as arms and feet. Oysters, clams, mussels, and scallops all have a single axe-shaped foot which they burrow into sand.

Most molluscs do not move around efficiently. Oysters fasten themselves to something solid and settle down for life, letting food drift to them. Scallops may move in zigzag leaps by clapping their shells together.

Joint-Legged Animals

Arthropod, animal of the phylum Arthropoda comprising invertebrates with external skeleton, segmented body, and jointed appendages.

Joint-legged animals, or arthropods, have bodies divided into segments that have specialized functions. These animals also have many jointed legs. Most arthropods are covered with a jointed skeleton made of a horny material. This outside skeleton is lighter than the shells of the molluscs The legs and muscles and many organs of the arthropod are attached to the outside skeleton.

The arthropods include insects, lobsters, crabs, centipedes, millipedes, scorpions, and spiders. They can run, jump, swim, and crawl. Some live mostly on land, while others live mostly in water. Many of the insects have wings and can fly. Arthropods inhabit most of the Earth’s environments, from the poles to the tropics, and are found in fresh and marine water and in terrestrial habitats.

How Back boned Animals Move

Vertebrates move through water and air and over the ground with great speed and skill. Birds, with their feathered wings, are the best fliers. Fish are the best swimmers. However, other vertebrates also can fly and swim. Bats fly on wings of membrane like skin. The flying squirrel glides on a broad membrane between its legs. The flying fish soars over the surface of the ocean by using its fins. Neither the fish nor the squirrel can soar great distances, however.

Some turtles swim with paddle like front legs. Some water birds can swim underwater with their wings. The mud skipper and walking catfish are fishes that walk on mud by pulling themselves along on their front fins.

Frogs, kangaroos, various cats, and some fishes are superior jumpers. Salmon leap up waterfalls when they travel from the sea to their home streams to lay their eggs. Tarpon, swordfish, and sailfish make great leaps out of the water when pursuing their prey or trying to escape an enemy.

Breathing

Animals breathe in different ways:

  • Some animals, like amoeba and sponges, let oxygen move through their cell walls.

  • Fish and tadpoles breathe with their gills.

  • Insects bring air in through pores, or holes, called spiracles.

  • Mammals, birds, and reptiles breathe with lungs.

All animals must take in oxygen in order to change food into a form that the body can use. One-celled animals that live in water absorb oxygen directly through their membranes. The sponge is a very simple many-celled animal. The surface of a sponge is covered with millions of tiny pores. Water bearing dissolved oxygen and minute food particles flows through the pores and out of the opening at the top of the sponge.

Fish and tadpoles breathe by means of gills. Insects and caterpillars take air into the body through breathing pores called spiracles.

Mammals, birds, and reptiles obtain oxygen from the air. They take it into the lungs, and the oxygen passes through membranes in the lungs into particles called red blood cells. The bloodstream then carries the oxygen to all parts of the body. Amphibians have lungs, but they also have thin, moist skins that absorb oxygen directly.

Reproduction

Sea squirt, a tunicate or saclike marine animal, so called from its habit of ejecting water when touched; belongs to the phylum Chordata.

Hydra, primitive water animal of the class Hydrozoa and the genus Hydra.

All animals reproduce their own kind. One of the most primitive forms of reproduction is by fission, in which the individual organism divides to produce a replica of itself. Some animals, such as sea squirts, reproduce by budding: lumps appear along a branchlike organ and develop into young sea squirts. Sea squirts, sponges, corals, and other creatures that bud often remain together and form large colonies. The hydra also reproduces by budding, but in time the young bud separates and goes off to live alone.

Most animals reproduce by means of eggs from the female that are fertilized by sperm from the male. The eggs of some species are deposited in a nest or in some other manner before hatching. Most species of mammal and some species of reptile and fish bear their young alive, the fertilized eggs being retained within the body of the female.

The types of reproductive behaviour among animals are almost as varied as the kinds of animals themselves. Some species, such as most insects and turtles, deposit their eggs and give them no further attention. In colonies of the social insects, such as ants and bees, a single female lays all of the eggs, and workers provide care and nourishment for the developing young in the nest. The females of some reptiles, such as the king cobra and the blue-tailed skink, and amphibians, such as the marble salamander, stay with their clutch of eggs until they hatch but provide no protection or nourishment for the young. Some fish guard their young after they are born. Crocodilians protect the eggs before hatching and the young for several months afterwards. Many birds provide not only protection but also nourishment for the developing young. Mammals, which feed their young with milk produced by the mother, provide care for their young much longer than do other classes of animals.

Posted 2012/01/29 by Stelios in Education

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SEXUALITY   Leave a comment

 Human beings are born sexual. Humans develop a strong sense of being male or female. This sense of maleness or femaleness and the behaviour exhibited because of it is called human sexuality. The characteristics of being a man or a woman involve biological, psychological, and sociological behaviours as well as the reproductive capacity and sexual functions of genital organs

Human sexuality is an integral part of life from birth until death. Throughout history people from all cultures have acted in relationships in part on the basis of both physical and emotional feelings of sexual attraction. Sexual behaviour is also influenced by cultural traditions and laws about sex.

Cultures vary greatly in what kinds of sexual behaviour is permitted. In some societies children are discouraged from knowing anything about sexuality and some children are not allowed to understand sexual reproduction. Other societies encourage children to learn about sex. Parents sometimes exercise their right to educate their children about sex and encourage or discourage sexual activity.

Whatever the practice of the society, children grow up aware of the parental, religious, cultural, and social norms of sexual behaviour Human sexuality is also physically influenced by hormones, brain centres, networks of nerves, and sex organs.

Sexual Development

Uterus (or womb), female organ for holding and nourishing young during prenatal development.

Even before birth the female ovaries develop ova, or eggs. At puberty, under the influence of chemicals called hormones that are produced within the body, the ova ripen and are periodically released from the ovaries about once a month. When this event, termed ovulation, occurs, hormones are released to begin a thickening of the lining of the uterus (endometrium). Hormones control the discharge of the lining about once a month. This is called menstruation.

If a woman becomes pregnant, menstruation does not occur; the endometrium stays in the uterus and serves as the first nourishment for the developing embryo. Ovulation and menstruation begin in girls at puberty at about age 12 and continue until menopause, sometime in middle age. Puberty in boys begins when the testes start to produce sperm continuously at about age 13. This is a life-long process in males.

When ovum and sperm come together, the first complete cell of a potential new human begins to develop. This is called conception. Sexual arousal usually precedes conception and begins when hormones are given off by endocrine glands. This causes body fluids to shift to the pelvic area. In the male the fluid goes into the tube called the penis, and in the female through the walls of the tube called the vagina. The fluid also enlarges the labia and the clitoris in females. The testes in the male enlarge and draw close to the body. Eventually the penis becomes erect and the vagina becomes lubricated.

Many body muscles become tense during sexual arousal and stimulation. Continued stimulation of the penis and the clitoris causes a spontaneous release of this tension in a pleasurable feeling called orgasm. In the male, this is most often accompanied by ejaculation. Ejaculate is called semen, a combination of sperm and internal fluids made primarily in the prostate gland. Ejaculation during sexual intercourse places the sperm in the vagina where the spermatozoa move through the opening of the cervix into the uterus and through the fallopian tube. If an ovum is present the sperm will be drawn to it. When a sperm cell penetrates the ovum, other sperm cells are prevented from entering.

Chromosome, microscopic, threadlike part of the cell that carries hereditary information in the form of genes; among simple organisms, such as bacteria and algae, chromosomes consist entirely of DNA and are not enclosed within a membrane; among all other organisms chromosomes are contained in a membrane-bound cell nucleus and consist of both DNA and RNA; arrangement of components in the DNA molecules determines the genetic information; every species has a characteristic number of chromosomes, called the chromosome number; in species that reproduce asexually the chromosome number is the same in all the cells of the organism; among sexually reproducing organisms, each cell except the sex cell contains a pair of each chromosome.

The combination of ovum and sperm make up a complete cell, containing 23 chromosomes from the sperm and 23 from the ovum. These chromosomes carry all the genetic information needed to determine all the inherited characteristics of the potential human being. Of the 23 pairs of chromosomes, one pair, called sex chromosomes, determine male or female sex. Male sperm cells carry either an X or a Y sex chromosome and 22 non sex chromosomes, or autosomes. Ova carry only X chromosomes and 22 autosomes. If an X-carrying sperm cell unites with the ovum, the cell will develop into a female. If a Y-carrying sperm unites with the ovum, the cell will develop into a male. Future male or female body structures are thus determined at conception.

Zygote, in biology, a cell formed by the union of male and female gametes; a fertilized egg cell; earliest stage of development, preceding embryonic and fetal stages.

The new, fertilized cell, now called a zygote, divides until it becomes a ball of cells. It moves into the uterus where it implants itself in the endometrium as a blastocyst. The genital systems of humans appear by the fifth to sixth week of embryonic development. Under the influence of sex hormones, the fetal body differentiates and develops sexual structures by about the seventh week. By the fourth month the foetus’s sex is unmistakably recognizable. This happens under the influence or lack of influence of male hormones testosterone and androgens. The absence of these hormones allows the fetal body to develop as a female. The presence or absence of these hormones is directed by the genes on the XX or XY chromosome pair.

Both male and female reproductive systems develop from the same structural origins. The male fetal structures have female counterparts. (It can also be said that female fetal structures have male counterparts.) Among these structures, called homologous pairs, are the testes and ovary.

Infants experience sexual arousal, which is a biological response, before birth. Young boys experience penile erections, girls vaginal lubrication. In childhood, sex play is a common and normal behaviour When sex play involves the rubbing or self-stimulation of genital organs, it is called masturbation. Masturbation is found in all cultures and is not physically harmful. Many religious groups, however, discourage it.

Sexual arousal expressed in sex play with other children is considered childhood sexuality, not early “adult” behaviour It is a normal exploration of the body and is often pleasurable. In Western culture it is sometimes followed by feelings of guilt because of disapproval from parents or religious authorities.

Adult patterns of sexual development begin at puberty and during adolescence. Hormones cause a rapid growth in height. Sex differences occur in bone and muscle density, breast development, and body and facial-hair patterns. The vagina gradually lengthens and the uterus enlarges. The penis and testes increase in size. Both male and female voices lower. Girls’ bodies begin to grow at about age 12. They usually complete much of their growth rather quickly. Boys begin later, at about age 13, and grow for a longer period of time. Every person is unique in growth rate and development of adult sexual characteristics. It is considered within normal range for the process to begin as late as 16 years.

Feelings of sexual desire begin at puberty. This is often accompanied by fantasy, daydreams, or infatuation. Feelings of sexual attraction can generate social interaction that begins the romance and dating process. At this point, or sooner, boys begin to experience erotic dreams accompanied by orgasm and ejaculation. Girls also experience orgasms during sleep.

Dream, illusion or hallucination of real experiences that occur during sleep.

Normal sleep patterns involve rapid eye movements in about 90-minute intervals. It is during these periods that dreaming, effective rest, slight erections of the penis, and slight engorgement of the labia and clitoris in the female occur. These are biological responses and are not psychologically induced.

Feelings of sexual attraction and attentiveness are a part of the search for self-understanding. Parents and society often guide young people about what is permissible and avoidable sexual behaviour They often caution against the risk of pregnancy, sexually transmitted diseases, and emotional injury. Adults have a desire to protect youths from adverse experiences. Even if sexual feelings are strong, humans can consciously decide whether or not to act on those feelings.

Adolescence is a time for physical, psychological, and social self-discovery. It is a period when children learn about themselves in relation to other people and the community in which they live. Conflict between adolescents and their parents can occur as the search for self-identity leads to a desire for more independence from the family. Parental response during adolescence often includes fear for the health and safety of offspring. Dating is a way in which young people learn about both themselves and the people that attract them. There is a general expectation in many societies that people will choose one marriage partner sometime in young adult years.

Gender Orientation

People grow up knowing themselves as male or female. The human behaviour associated with being a man or being a woman is called gender identity. Among the influences on gender identity are body development, sexual organs, socialization as a boy or a girl, brain hormones that determine our knowledge of our male or female nature, and pubertal hormones that affect both sexual structure and sexual function. Gender identity is related to physical appearances, feelings of arousal and attraction, and desires to dress and act socially in ways considered male or female.

People have both male and female hormones in their bodies. The balance of these hormones allows us to be one sex or the other. Hormonal imbalance in a foetus can cause abnormalities in physical sexual development prior to birth. Cultures promote acceptable behaviours for roles based on sex, called gender roles. Many of these roles are partly determined by the person’s function within the family and economy. In Western culture the family represents a unit based on love, nurture, economic interdependence, and preparation of the young for adult life. For centuries physical work outside the home was perceived as a part of the male role. The female role was to give birth and direct the maintenance of the home. Work-related gender roles have changed. Families often need the earnings of both parents for financial survival. Women work out of necessity, desire, or both. Job qualifications are no longer gender-specific but focus instead on skill, knowledge, and experience.

Sexual Orientation

Homosexuality, the manifestation of sexual desire toward a member of one’s own sex.

What determines whether or not two persons are attracted to one another? The answer to this question is sexual orientation or sexual identity. In the 1940s Alfred Kinsey studied sexual practices in the United States and devised a scale for sexual orientation. The scale ranges from heterosexuality, or basic sexual attraction to the other sex, to homosexuality, or basic sexual attraction to the same sex. Midway on the scale is bisexuality, which means sexual attraction to both sexes. Kinsey concluded that most people do not exhibit exclusively heterosexual or homosexual behaviour Many adults, however, label themselves as one or the other. About 10 percent of the people in Kinsey’s study identified themselves as homosexual. Whether homosexuality was condemned or accepted, every civilization throughout history has included homosexual men and women.

There have been many attempts to explain the origin of sexual orientation. Some believe there is evidence that it is biological. Others believe it is learned behaviour Sexual orientation is very complex and most likely a combination of many factors. There are many religious and cultural attitudes about sexual orientation. Many religions specifically allow, encourage, or condemn various sexual behaviours This may involve an attempt to encourage people to conform to heterosexuality to ensure the continuance of the reproductive family.

Sexual Fantasy

Sexual fantasy or daydreaming is another aspect of human sexuality. This commonly used outlet for sexual feeling can be pleasurable, humorous, and even satisfying. It can also include imagined hostility and behaviours that, if acted upon, would be harmful. Some people feel that portrayals of sex and violence on television and in cinema and music, encourage more sex and violence in real life. There are recorded fantasies of sexual experience with every possible object, animal, or person. During fantasy, the person becomes sexually aroused but usually has no intention of acting out the fantasy. Attempts to act out fantasies are often expressed in art, literature, and the theatre Fantasy portrayed in explicit pictures or words is called pornography.

Attitudes About Sexuality

Western cultural attitudes about sexuality have been greatly influenced by religious attitudes. These came from times of the Old Testament, the Christian church, and the Middle Ages. The Enlightenment, the Puritans in the United States, and Victorian attitudes all have had a profound influence on current sexual attitudes. One attitude, for example, forbids sex outside of marriage. Despite this, society encourages through the media acceptance of various forms of sexual expression in order to entertain. This encouragement often elicits strong reaction from religious communities. Cultural expressions of sexual attitudes are found in religion, novels, films, paintings, music, television, theatre, and formal education. All of these things influence sexual development.

A major role of sex education is to teach the positive nature of sexuality. This aspect is often neglected because priority is given to the perceived danger of pregnancy for young people and of sexually transmitted diseases. The appropriate content of a sex education program is determined by the students’ age level from kindergarten to adult. The purpose of sex education classes is to teach communication and decision-making skills and the anatomy and physiology of the sexual reproductive systems. Classes often include discussions of rape, sexual abuse, abortion, contraception, masturbation, sexually transmitted diseases, pregnancy, childbirth, dating, marriage, and family life. Many religious groups and both public and private schools have sex education programs.

In some communities there are organized groups of adults who oppose sex education in the public schools on the basis of values. It is said that family values about sex are personal and private, that teachers will change that private nature and make statements contrary to family values and beliefs. While the right of parents to teach their children their own values about sex is recognized, there is still debate about the extent to which special interest groups can control sex education in public schools.

Sexuality and Civil Rights

Discrimination, prejudiced or prejudicial outlook, treatment, or action.

Many people concerned with discrimination in society on the basis of sex or sexual orientation become involved with specialized groups that monitor and lobby in government for the rights of all women and men as well as such specific groups as homosexuals, also called gay people. Civil rights groups work toward equal opportunity in employment, housing, and business dealings. There are also concerns about how sexual privacy laws in many states dictate what kinds of sexual practices are allowed for consenting adults or for married people. Many people express a desire to act in any way that is not destructive. The courts deal with issues of the right to mutually consenting behaviour, the sale of pornography, and various forms of discrimination in the workplace.

Sexuality and Health

There are many health concerns related to sexuality. For youths concerns often arise when their bodies begin to mature. Uneven growth, lumps, unfamiliar feelings, and aches can create fear of abnormality. A physician can usually reassure the person of normality or have abnormalities corrected.

Sterility, in biology, the inability to produce offspring; one cause is the production of non functioning sex cells.

Infertility is the inability to get pregnant or to impregnate for a period of time. A permanent state of infertility is called sterility. In men, the most common cause of infertility is low sperm count. In women, failure to ovulate or blocked fallopian tubes commonly cause infertility. Other causes include infections caused by sexually transmitted diseases that scar the tubes, or severe malnutrition, as a result of anorexia nervosa. Infertility is often treated with drugs, microsurgery or artificial insemination.

AIDS (acquired immunodeficiency syndrome), incurable disease caused by a virus that damages the human body’s immune system; believed to be transmitted through sexual contacts, blood transfusions, or contaminated needles used for intravenous drug injections; often fatal; high percentage of victims are homosexuals or drug abusers.

Sexually transmitted disease is a serious public health issue worldwide. Acquired immune deficiency syndrome, or AIDS, is usually transmitted through sexual intercourse, but it can also be transmitted at birth or with blood products. It is fatal. Other sexually transmitted diseases also require medical treatment.

Sexual abuse and molestationare health concerns that involve deliberate sexual acts, often between adults and children. The adults can be parents, older siblings, other relatives, babysitters, neighbours, or strangers. Sexual abuse and molestation occur frequently. When the child or teenager is being stroked, touched, kissed, or sexually approached in any way by an adult, there is an assumed impropriety. Adults who choose children as the object of their sexual desire are called paedophiles Sexual behaviour between close relatives is called incest. Children who grow up with sexual advances from older, more powerful strangers or relatives can get both help and understanding from school or social work professionals.

Sexual therapy. For many reasons, many of them psychological, people can become unable to function sexually. Some experiences in peoples’ lives can cause attitudes about sex that are disturbing. There can also be physical reasons for being unable to function in a sexually satisfying way. This is called sexual dysfunction. For men it commonly results in either the inability to have an erection or unplanned immediate ejaculation after the penis becomes erect. The most common sexual dysfunction in women is the inability to have an orgasm or painful constriction of the muscle at the opening of the vagina when intercourse is attempted (vaginissimus). These problems can occur occasionally or be prolonged and cause anxiety. Sexual dysfunctions are often treated by a therapist in what is called sex therapy.

Assisted by Mary Lee Tatum, teacher and consultant for family life and sex education programs in Virginia.

BIBLIOGRAPHY FOR SEXUALITY

Bell, Ruth and others. Changing Bodies, Changing Lives (Random, 1980).

Boston Women’s Health Book Collective. Our Bodies, Ourselves, rev. 2nd ed. (Simon & Schuster, 1976).

Calderone, Mary and Johson, Eric. The Family Book About Sexuality (Harper, 1981).

Kelly, Gary. Learning About Sex: The Contemporary Guide for Young Adults (Barron’s Educational Series, 1976).

Madaras, Area and Lynda. The What’s Happening to My Body? Book for Girls (Newmarket, 1983).

Madaras, Lynda and Saavedra, Dane. The What’s Happening to My Body? Book for Boys (Newmarket, 1984).

Nilsson, Lennart and others. A Child Is Born (Delacorte, 1977).