4
Question Question 4
State the various physical changes that occur during adolescence.
The various physical changes that occur during adolescence are:
- Sexual maturation — In males testes start producing testosterone and sperms. In females, the ovaries start releasing eggs and produce the female hormones, oestrogen and progesterone. Sex organs develop fully and secondary sexual characteristics like enlargement of external genital organs in males and enlargement of breasts in females also start.
- Increase in height — There is a spurt in growth hormone leading to sudden increase in height due to the elongation of the bones of the legs and arms. Age by which full height is attained is 14 to 15 years for girls and 18 to 19 years for boys.
- Change in body appearance — In males, the shoulders become broad and the chest becomes wide.The muscles also grow and develop more than in girls. In females, there is widening of the pelvic region and broadening of the hips. The breasts also develop and enlarge in size. Also in both males and females, hair starts growing in the armpit and pubic area. In males, facial hair (as beard and mustache) grows.
- Change in voice — There is growth in the voice box or larynx. It grows more in males than in females. As a result, males develop deep voice whereas females develop a high-pitched voice.
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ICSE Class VIII | Academic Year 2026-2027
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Biology | Chapter 7: Endocrine SystemWeb Content
Endocrine System – Interactive Study Guide
Quick Overview
The endocrine system consists of ductless glands that secrete hormones into the blood. Hormones are chemical messengers that regulate growth, metabolism, reproduction, and response to stress.
Endocrine vs Exocrine at a Glance
| Feature | Endocrine | Exocrine |
|---|---|---|
| Ducts | Ductless | Have ducts |
| Secretion | Hormones (into blood) | Enzymes, sweat (through ducts) |
| Examples | Pituitary, thyroid, adrenal | Salivary, sweat, liver |
Master Table: Glands, Hormones, Functions
| Gland | Hormone | Function | Disorder |
|---|---|---|---|
| Pituitary | GH | Growth | Dwarfism / Gigantism |
| Thyroid | Thyroxine | Metabolism (needs iodine) | Goitre / Cretinism |
| Parathyroid | Parathormone | Calcium regulation | Tetany |
| Adrenal | Adrenaline | Fight-or-flight | Addison's disease |
| Pancreas | Insulin / Glucagon | Blood sugar regulation | Diabetes mellitus |
| Testes | Testosterone | Male characters | — |
| Ovaries | Oestrogen | Female characters | — |
Feedback Mechanism
How It Works
High hormone level → Gland reduces production. Low hormone level → Gland increases production.
Example: High blood sugar → Insulin released → Sugar absorbed by cells → Sugar drops → Insulin production stops.
Self-Test Questions
Test Yourself
- Why is the pituitary gland called the master gland?
- What is goitre? How can it be prevented?
- Differentiate between insulin and glucagon.
- What happens during a fight-or-flight response?
- Explain the feedback mechanism with the example of blood sugar.