Learning Objectives
- Understand the changes that occur during adolescence
- Learn about puberty and secondary sexual characters
- Understand the role of hormones in growth and development
- Learn about the human reproductive cycle and healthy habits
Key Concepts
Adolescence and Puberty
Adolescence: The period of life from roughly 11 to 18-19 years, during which the body undergoes changes leading to reproductive maturity. Adolescents are also called teenagers (13-19 years).
Puberty: The period during adolescence when the body becomes capable of reproduction. It is marked by the appearance of secondary sexual characters.
Changes During Puberty
- Increase in height: Rapid growth spurt occurs. Long bones elongate. Full height is usually reached by 18 years of age.
- Change in body shape: Boys develop broader shoulders and more muscular bodies. Girls develop wider hips.
- Voice change: Boys develop a deeper voice (voice box/larynx grows larger, producing Adam's apple). Girls develop a higher-pitched voice.
- Increased activity of sweat and sebaceous glands: Can lead to acne and pimples.
- Development of sex organs: Male and female reproductive organs become fully developed and functional.
- Mental and emotional changes: Increased self-awareness, mood swings, desire for independence.
Secondary Sexual Characters
In boys: Growth of facial hair (moustache, beard), body hair, deeper voice, broadening of shoulders.
In girls: Development of breasts, widening of hips, growth of body hair.
Role of Hormones
Hormones are chemical substances produced by endocrine glands that regulate body functions.
- Testosterone: Male hormone produced by testes. Controls development of male sexual characters.
- Oestrogen (Estrogen): Female hormone produced by ovaries. Controls development of female sexual characters.
- Growth hormone: Secreted by the pituitary gland. Controls growth of the body.
- Thyroxine: Secreted by the thyroid gland. Controls metabolism. Iodine is needed for its production.
- Insulin: Secreted by the pancreas. Controls blood sugar levels. Deficiency causes diabetes.
- Adrenaline: Secreted by the adrenal glands. Prepares the body for emergency situations.
Reproductive Phase and Menstruation
In females, the reproductive phase begins at puberty (menarche) and lasts until about 45-50 years (menopause). The ovaries release one ovum every 28 days. If the ovum is not fertilised, the uterus lining breaks down and is shed along with blood. This is called menstruation. The menstrual cycle repeats approximately every 28 days.
Sex Determination
Humans have 23 pairs of chromosomes. The 23rd pair determines sex: XX in females, XY in males. The sex of the baby is determined by the father's chromosome (X or Y sperm).
Summary
Adolescence is marked by puberty, during which hormones drive physical, emotional, and reproductive changes. Secondary sexual characters distinguish males from females. Hormones from endocrine glands regulate growth, metabolism, and reproduction. Sex is determined by the chromosomes inherited from the father.
Important Terms
- Adolescence: The period between childhood and adulthood (11-19 years)
- Puberty: The age at which sex hormones begin to produce changes
- Hormone: Chemical messenger secreted by endocrine glands
- Adam's Apple: The enlarged voice box (larynx) visible in boys' throats
- Menstruation: Monthly shedding of the uterine lining in females
- Chromosomes: Thread-like structures carrying genetic information
- Endocrine Gland: A ductless gland that secretes hormones into the blood
Quick Revision
- Adolescence: 11-18/19 years; puberty marks onset of reproductive maturity
- Changes: height increase, voice change, body shape, sex organ development
- Testosterone (male) and oestrogen (female) control sexual development
- Menstruation cycle ≈ 28 days; menarche to menopause
- Sex determination: XX = female, XY = male (father determines sex)
- Balanced diet, exercise, personal hygiene are essential during adolescence