Adolescence
→ The time period when the body undergoes changes to reach reproductive maturity is known as
adolescence.
→ It begins around the age of 11 and lasts till about 18 or 19 years of age.
→ Adolescence in girls can begin one or two years earlier than boys.
Puberty
→ The various changes that occur in the body during adolescence marks the onset of puberty.
→ Puberty ends when teenagers attain sexual maturity.
→ Changes that take place during puberty
Increase in height
→ It is caused by the growth in long bones of the arms and legs.
→ Girls grow faster than boys initially but both reach their maximum height by the age of 18
years.
Change in body shape
→ Boys develop broader shoulders, wider chests, and prominent muscles.
→ In girls the region below the waist becomes wider.
Change in the voice pattern
→ Voice box or larynx starts growing during puberty.
→ It protrudes in males in the neck region and is called Adam’s apple.
→ Boys develop deep low-pitched voice.
→ Girls develop high-pitched voice.
Change in activity of sweat and sebaceous glands
→ The activity of sweat glands increases during puberty, resulting in production of more sweat.
→ The oily secretions from sebaceous glands increase. The accumulation of oil and bacterial action leads to acne problems in teenagers.
Changes in sex organs
→ Testes and penis develop completely in boys.
→ Testes start producing sperms.
→ Ovaries develop completely and start producing eggs in girls.
Change in intellectual level
→ The learning capacity of brain increases.
→ Intellectual development takes place during adolescence.
→ Development of secondary sexual characteristics.
Secondary sexual characteristics in boys
→ Appearance of moustaches and beard.
→ Appearance of hair on chest.
→ Growth of hair in genital area and other parts.
Secondary sexual characteristics in girls
→ Increase in breast size
→ Growth of hair in the pubic region.
Hormones
→ Hormones are chemical secretions that bring about various changes in the body.
→ They are produced by endocrine glands.
→ These glands release hormones into blood to reach specific target site.
→ Production of hormones is under the control of hormones produced from pituitary gland.
Characteristics of hormones
→ Hormones act as chemical messengers.
→ They are secreted by living cells/tissues or organs called glands.
→ They are secreted in very small quantities by glands.
→ They act upon specific cells, tissues, or organs called the target sites.
→ They are generally slow in action, but have long lasting effects.
→ They either accelerate or inhibit a reaction.
Endocrine glands
→ Hormones are secreted by endocrine glands such as the pituitary gland, thyroid gland, adrenal gland, pancreas etc.
• Major endocrine glands in humans are
(i) Pituitary
(ii) Hypothalamus
(iii) Pineal
(iv) Thyroid
(v) Parathyroid
(vi) Thymus
(vii) Pancreas
(viii) Adrenal
(ix) Testis in men /ovary in women
→ A feedback mechanism (positive and negative) regulates the action of the hormones.
Pituitary gland
→ It is a pea sized gland situated at the base of the brain. It secretes a growth hormone (GH).
→ It is required for proper body growth.
→ The hyposecretion of growth hormone causes a condition called dwarfism.
→ The hypersecretion causes gigantism in children and acromegaly in adults.
Thyroid gland
→ It is located close to trachea in the neck. It produces a hormone called thyroxine.
→ It is required for regulating metabolism in the body.
→ The hyposecretion of thyroxine causes hypothyroidism.
→ This condition causes abnormalities like simple goitre, myxoedema and cretinism.
→ Lack of iodine leads to deficiency of thyroxine, which results in a disease called goitre.
→ The excess secretion of thyroxine causes hyperthyroidism. It results in high metabolism, protrusion of the eye balls, high BP, nervous tension, etc.
Parathyroid Gland
→ There are four parathyroid glands present on back side of thyroid glands that secrete parathyroid hormone or parathormone (PTH).
→ This hormone regulates the level of calcium ions in the bloodstream.
→ Excess of parathyroid hormone removes calcium from bones and makes them soft.
Pancreas
→ It produces two hormones- Insulin and Glucagon.
→ These hormones maintain blood sugar level.
→ Deficiency of insulin results in diabetes.
Adrenal Gland
→ There are two adrenal glands located one on upper part of each kidney.
→ It has two parts- cortex and medulla.
→ Cortex secretes the hormones like cortisol that regulates the rate of metabolism.
→ The medulla secretes a hormone like adrenaline that prepares the body to face various stressful situations.
Gonads
→ It includes testes in males and ovaries in females.
→ Male sex hormone is testosterone. It is produced by the testes on the onset of puberty.
→ Female sex hormones produced by ovaries are estrogen and progesterone.
→ Deficiency of estrogen causes infertility.
→ Process of Hormonal Action
→ Endocrine glands release their secretions (hormones) into the bloodstream.
→ Hormones, on reaching their target site, bring about necessary changes to maintain proper functioning of the body.
Historical background and Discovery of HIV
→ The first cases of AIDS were recognized in U.S.A in the year 1981.
→ The AIDS virus was first discovered by the team of French scientists lead by Luc Montagnier in1983.
→ In 1984, the American virologist named Robert Charles Gallo gave the first report on the virus causing AIDS.
→ The name HIV was suggested by the International committee on the nomenclature of viruses.
→ In India the firsts AIDS patient was identified in Chennai in the year 1987.
→ AIDS or Acquired Immune deficiency syndrome is a viral disease, caused by the deadly virus (HIV).
Structure of HIV
→ Human Immunodeficiency virus (HIV) is spherical in shape and contains RNA as its genetic material.
→ Externally, the virus is covered by the double layered membrane made up of fatty substances.
→ Inside the fatty membrane a core of proteins is found that surrounds the viral RNA along with the enzyme reverse transcriptase.
Transmission of HIV
→ Sharing of syringes during drug abuse.
→ Unsafe sexual contact.
→ Transfusion of infected blood
→ From infected mother to her infant through milk.
Prevention of HIV
→ Avoid sexual contact with infected persons
→ Ensure use of disposable syringes
→ Screening blood from blood banks
Tests for detection of HIV
→ PCR (Polymerase Chain Reaction)
→ ELISA (Enzyme linked Immuno Sorbent Assay)
→ Western Blot
Personal health and hygiene in adolescents
→ Adolescents should have a balanced diet with right proportions of various nutrients.
→ Adolescents should maintain cleanliness to prevent bacterial infections.
→ They should indulge in some physical exercises to keep their bodies fit.
→ They should avoid the consumption of drugs and alcohol.
Sex determination in humans
• Autosomes: First 22 pairs of chromosomes that do not determine the sex of an individual.
• Sex chromosomes: Last pair of chromosomes, represented as X and Y.
→ Females have two X chromosomes,so can be represented as 44+XX.
→ Males have one X and one Y chromosome, so can be represented as 44+XY.
→ Each gamete receives half of the chromosomes i.e. 22+X or 22+Y.
→ Male gametes have 22 autosomes and either X or Y sex chromosome.
→ Male gametes can be of two types, 22+X or 22+Y.
→ Female gametes can be of only one type, 22+X.
→ Sex of a baby is determined by the type of the male gamete (X or Y) that fuses with the female gamete.
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