Samacheer Class 8 Science - Reaching the Age of Adolescence

The correct matching of terms with their definitions is as follows: Puberty refers to the period of sexual maturity when reproductive organs become functional. Testosterone is the male hormone responsible for the development of male secondary sex characteristics. Adam's apple is the change in voice that occurs in boys during puberty due to the enlargement of the larynx. Androgen is the group of male hormones that promote muscle development and other male characteristics. ICSH, or Interstitial Cell Stimulating Hormone, stimulates the production of testosterone in males. Menopause is the cessation of menstrual cycles that occurs in females at 45 to 50 years of age, marking the end of the reproductive years.

Puberty is the period during which the body of a child transforms into that of an adult. This transformation involves several significant changes that occur over a period of time. The changes that occur during puberty include changes in body size, where there is a rapid increase in height and weight due to the growth spurt. Changes in body proportion occur as different parts of the body grow at different rates, altering the overall shape and structure. Development of primary sex characteristics takes place, which involves the maturation of reproductive organs such as the ovaries and uterus in females and testes in males. Development of secondary sex characteristics also occurs, which includes features like the growth of body hair, development of breasts in females, deepening of voice in males, and changes in skin texture. All these changes are triggered by hormonal changes, particularly the release of sex hormones during adolescence.

Menarche is the first menstrual flow that begins at puberty in females and marks an important milestone in adolescence. It is the beginning of the menstrual cycle and indicates that the reproductive system has matured and become functional. Menarche typically occurs between the ages of 10 to 14 years, though this can vary among individuals. The onset of menarche signals the beginning of adolescence, during which significant mental and emotional maturation occurs alongside physical growth. During this period, girls experience pronounced physical growth, hormonal changes, and the development of secondary sex characteristics. Menarche is an important biological event that indicates a girl has entered her reproductive years, though it does not necessarily mean she is emotionally or socially ready for reproduction. The menstrual cycle that begins with menarche continues throughout a woman's reproductive years until menopause.

Pregnancy is the process that begins after fertilization of the ovum by a sperm cell. After ovulation, the mature ovum is released from the ovary and enters the fallopian tube, where fertilization takes place if a sperm cell is present. The fertilized egg, now called a zygote, begins to undergo cell division and development as it travels through the fallopian tube towards the uterus. Once the developing embryo reaches the uterus, it undergoes implantation, embedding itself into the uterine lining where it will continue to develop. During pregnancy, the corpus luteum continues to grow and produces large amounts of progesterone and estrogen, which are essential for maintaining the pregnancy and preventing further ovulation. The developing embryo gradually transforms into a fetus and continues to grow and develop within the uterus. Normally, pregnancy lasts for approximately 280 days or about nine months, at the end of which parturition, or childbirth, takes place. During this entire period, the fetus receives nutrients and oxygen from the mother through the placenta and umbilical cord.

Girls should take special care of cleanliness and hygiene during the menstrual cycle as it is an important aspect of health and well-being. Making use of disposable napkins or tampons may reduce the chances of infections by maintaining cleanliness and preventing bacterial growth. These products should be changed frequently depending upon the menstrual flow to ensure maximum hygiene and comfort. In addition to using clean menstrual products, girls should wash their genital area regularly with clean water and maintain overall body cleanliness during menstruation. Using clean toilets for defecation is also an important practice during this time. Proper hygiene during menstruation helps prevent various infections such as urinary tract infections and other bacterial infections. Girls should also avoid using unhygienic materials and should dispose of used napkins or tampons properly. Maintaining cleanliness during menstruation is not only important for physical health but also contributes to emotional well-being and confidence during adolescence.

Adolescence and childhood are two distinct periods in human development with significant differences. Childhood is the period of life from birth until approximately 12 years of age, during which children grow and develop but experience relatively gradual physical changes. Adolescence begins around 12 to 13 years of age and extends into the late teenage years, marking a period of rapid and dramatic transformation. During adolescence, numerous significant changes occur in the body, including a sudden increase in height and weight known as the growth spurt. Changes in body proportions take place as different parts of the body grow at different rates. The sex organs mature and become functional during adolescence, which does not occur during childhood. Muscle mass increases significantly, particularly in males, due to hormonal changes. Secondary sex characteristics develop during adolescence, including the growth of body hair, development of breasts in females, and deepening of voice in males. Additionally, adolescence is characterized by significant mental, emotional, and social development, whereas childhood involves more gradual cognitive and emotional growth. Hormonal changes during adolescence trigger these physical and psychological changes, making adolescence a unique and transformative period distinct from childhood.

Secondary sex characteristics are the physical features which distinguish male from female and develop during adolescence. In girls, several important physical changes occur: height and weight increase significantly, fatty and subcutaneous tissues develop beneath the skin, the hips broaden, hair grows in the armpits and pubic area, the voice becomes shrill or higher-pitched, and the breasts develop. In boys, the physical changes include an increase in height and weight, development of muscles throughout the body, broadening of the shoulders, growth of hair in the armpits and pubic area as well as facial hair on the face, a voice break that occurs due to the lengthening of the vocal cords and enlargement of the larynx, and an increase in the size of the penis. These changes are controlled by hormones and mark the transition from childhood to adulthood, preparing the body for reproductive functions.

The primary hormones that regulate reproduction are the steroids such as androgens, estrogens and progesterone. which have masculinizing, feminizing and gestational effects respectively.
These hormones are secreted from the gonads which are regulated by the anterior pituitary (adenohypophysis).
Follicle Stimulating Hormone (FSH):
FSH in a female influences the development of the Graafian follicle and secretion of estrogens. In a male, it is necessary for the development of seminiferous tubules, and for spermatogenesis.
Luteinizing Hormone (LH):
In a female, it is the hormone necessary for ovulation, and the secretion of the luteal hormone progesterone, and for the final maturation of the Graafian follicle. In a male, it stimulates the interstitial (Leydig) cells of testes and the secretion of testosterone, and is referred to as the Interstitial Cell Stimulating Hormone (ICSH).
Prolactin (PRL) or Lactogenic Hormone:
The main function of this hormone is milk secretion during lactation.
Oxytocin Hormone:
Oxytocin causes expulsion of milk from the breast and it is also involved in the contraction of smooth muscles of uterus during child birth.

The beginning of the menstrual cycle marks the onset of puberty in human females. Menstruation occurs if an ovum released by the ovary of a woman is not fertilized during ovulation. This is described below.
1. When a girl reaches puberty at the age of about 10, the sex hormones released into her blood cause some of the ova (or egg cells) in her ovaries to become mature (or ripe).
2. Usually one mature ovum (or egg) is released ff(jm one of the ovaries into the oviduct once in every 28 days. This is called ovulation.
3. Before ovulation (or release of ovum), the inner wall of uterus becomes thick and spongy, and full of tiny blood vessels to receive the fertilized ovum.
4. If the ovum does not get fertilized then the thick and soft inner lining of uterus breaks. So, the thick and soft inner lining of uterus along with the blood vessels and the dead ovum comes out of the vagina in the form of a bleeding called menstruation.
5. Menstruation usually occurs 14 days after ovulation and usually lasts for about 3 to 5 days.
6. After menstruation is over, the inner lining of the uterus starts building up again so that it may become ready to receive the next ovum.
7. If the ovum does not get fertilized even now, then menstruation takes place again. This cycle of menstruation is repeated again and again in women after every 28 days. The menstrual cycle is controlled by hormones.
Menstruation stops temporarily when the ovum gets fertilized and the women gets pregnant. Menstruation also stops due to nutritional deficiencies, low body weight, stress, eating disorder, excessive weight gain etc.

Adolescence is a stage of rapid growth and development.
Balanced diet is very much important during adolescence. Balanced diet includes proteins, carbohydrates, fats and vitamins in requisite proportions.
A very good amount of proteins and carbohydrates is necessary during this growth period. Apart from that, adolescents need the following dietary components.
Minerals:
Since there is an increase in skeletal mass and blood volume during adolescence, the body needs calcium, phosphorus and iron.
Calcium:
Calcium intake needs to be increased to prevent osteoporosis in later life.
It is present in milk and milk products or other equivalents.
Iodine:
It helps to prevent thyroid gland related diseases.
Iron:
Iron builds blood and iron-rich foods such as green leafy vegetables, jaggery, meat, dates, fish, chicken, citrus, Indian gooseberry (Nelli) and whole pulses are good for adolescents.
Lack of iron in the diet results in anemia.
In boys, iron deficiency occurs due to muscle spurt whereas in girls it occurs due to menstruation in addition to the muscular growth.

Shower or bath daily.
Always wash your hands before and after meals.
Keep fingernails clean and dipped.
Wash your teeth and mouth before and after each meal.
Avoid touching your face, nose or mouth while preparing food.
Avoid coughing or sneezing around food and close your mouth by using hand kerchief while you cough in public places.
If you want to taste the food, use a clean spoon.
Change your clothes regularly and wash them cleanly, especially undergarments.
Do not defecate in open field. Use clean toilets for defecation.
If you are not well, avoid self-medication, consult a doctor.
In case of girls, menstrual hygiene can be explained to them.

Adolescence is an energetic and critical stage of life, and developing healthy and good habits during this period is essential for overall well-being. One should eat a balanced diet that includes all necessary nutrients and avoid junk food to prevent obesity and related health problems. Regular physical exercise is important as it helps to build a strong and healthy body, improves cardiovascular fitness, and enhances mental well-being. Maintaining personal hygiene by bathing regularly, cutting hair, trimming nails, and wearing clean clothes prevents infections and promotes good health. It is crucial to keep away from abusive substances, drugs, smoking, and other bad habits that can harm physical and mental health. Girls should observe proper menstrual hygiene during their menstrual cycle to prevent infections and maintain health. Being aware of the various problems and changes related to adolescence and taking care of both physical and mental health through proper nutrition, exercise, sleep, and stress management helps adolescents develop into healthy and responsible adults.