Secondary Sexual Characters: As male and female human beings are born, there are unique aspects of their biology that set them apart, which are known as primary sexual characters/characteristics. However, as they both grow and attain puberty, they both develop unique characters that helps identify the change in them. These secondary sexual characters are not necessarily useful for reproduction, but they visually define their sexuality and a stage of growth in their life cycle. In this article, we will learn what these secondary sexual characters are, and how they are different from primary sexual characters.

Primary Sexual Characters: Definition

Human sex organs or primary sexual characteristics originate at birth, whereas secondary sexual characteristics develop later, usually during puberty. During the fetal period, sex hormones produced by the body control the development of both, as do the Y-chromosome and/or the SRY gene. In males, the primary sexual organs are the testes and penis, and in females – ovaries and vaginas.

Secondary Sexual Characters: Definition

The secondary sexual characteristics are those that distinguish males from females, and they do not directly take part in reproduction. They are not present at birth but develop later during puberty. Secondary sexual characteristics in males include the development of facial and body hair, growth of genitalia, prostate and scrotum, whereas, in females, these characteristics include the enlargement of breasts, the development of pubic and under armpit hair, and menstrual cycle, etc.

Difference between Primary and Secondary Sexual Characters

Primary Sexual Characters	Secondary Sexual Characters
1. These characters are present at birth.	1. These characters are developed during puberty.
2. It shows a direct physical relationship with the reproductive system.	2. These do not necessarily have direct involvement in reproduction.
3. It involves the enlargement of genitalia and sex organs e.g., penis and vagina.	3. It involves the enlargement of breasts, hips, and shoulders, deepening of voice, appearance of facial, pubic and underarm hair.

The Onset of Secondary Sexual Characters

Adolescence

Adolescence is considered a maturation phase. It is a stage of physical and psychological development that generally occurs from puberty. It is a very critical period which is characterized by rapid physical, emotional and psychological changes in boys and girls.

Puberty

When a boy or girl reaches puberty, sex hormones (or gametes) starts getting produced, and they become sexually mature. Girls typically reach puberty earlier than boys. The females attain puberty at the age of 10 – 12 years, whereas males reach puberty at 13 – 14 years of age. 

Secondary Sexual Characters in Males

1. The maturation and development of secondary sex organs like the genitalia.
2. The growth of body hair, including underarm, chest, pubis, and axillae, takes place.
3. Moustaches and beards grow in the form of hair on the face.
4. The body becomes more muscular due to the development of muscles.
5. The shoulders and chests are broadened, shoulders are wider than hips.
6. The larynx becomes enlarged, and a deepening of voice takes place.
7. Enlargement of Adam’s apple takes place.
8. The deposition of fat takes place around the abdomen and waist.
9. The increase in height takes place due to the rapid growth of bones.
10. The testes become more prominent and start to produce sperms.
11. The increased secretions of oil and sweat glands often cause acne and body odour.
12. Heavier skull and bone structure increase bone density.
13. The stature becomes increased; adult males are generally taller than adult females.
14. Feelings and sexual drives associated with adulthood begin to develop.
15. The BMR (Basal Metabolic Rate) is high due to higher activity.

Secondary Sexual Characters in Females

1. Development and enlargement of breasts, mammary glands and erection of nipples takes place.
2. Hair growth develops under the armpits and pubic region.
3. The broadening of the hip takes place due to the widening of the pelvis.
4. The deposition of fat takes place around the thighs, buttocks, and face.
5. The enlargement of fallopian tubes, uterus, and vagina takes place.
6. The ovaries start to release eggs.
7. The increased secretions of oil and sweat glands often cause acne and body odour.
8. No hair develops on the chest or abdomen.
9. The larynx is less apparent, and the development of high-pitched voice takes place.
10. Feelings and sexual drives associated with adulthood begin to develop.
11. The BMR is less as compared to men.
12. The beginning of the menstrual cycle takes place at the onset of puberty in females.

Fig: Secondary Sexual Characteristics of Human Male and Female

Role of Hormones in Secondary Sexual Characters

1. Sex hormones help and control the development of secondary sexual characters.
2. Sex hormones help to distinguish between boys and girls. The hormones are different in males and females.
3. FSH causes follicular growth in the ovaries. It stimulates oestrogen secretion from developing follicles.
4. LH hormone causes ovulation.

The role of sex hormones are given below:

A. Testosterone

i) Testosterone is the male sex hormone that is produced from the testes.
ii) It causes prenatal development of male genitalia.
iii) It produces sperm.
iv) It helps in the development of male secondary sexual characteristics during puberty  (including body hair, muscle mass, deepening of the voice, etc.).

Fig: Roles of Testosterone Hormone

B. Oestrogen

i) The two female sex hormones are oestrogen and progesterone. They are produced from the ovaries.
ii) Oestrogen regulates breast development, widens the pelvis, and increases body fat in the hips, thighs, buttocks, and breasts. Oestrogen also helps in the growth of the uterus, proliferation of the endometrium, and menses.
iii) Progesterone helps in the development of placenta during pregnancy. Its level is high throughout the gestation period and helps in maintaining pregnancy.
iv) Progesterone hormone also provides negative feedback inhibition to GnRH hormone to stop secretion of multiple ovums.

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Fig: Roles of Oestrogen Hormone

Role of Secondary Sexual Characteristics in Reproduction

Secondary sexual characters throughout the animal world serve to identify and attract sex partners. Odours (body smells), calling sounds, skin colouration, body contour, behavioural patterns, etc., are some of characteristics. Sex hormones play an essential role in reproduction as they make the reproductive organs mature and they start functioning.

Summary

When a male or a female grows up to a certain age, their body structure shows some changes. These changes are both internal and external. When they reach puberty, the sexual hormone level begins to change, and we can see the differences in the body structure. This is the time when both sexes develop their secondary sexual characters. Adolescence is a period when boys and girls both experience a spurt of growth in all areas of development.

Frequently Asked Questions (FAQs) on Secondary Sexual Characters

Let’s look at some of the commonly asked questions about secondary sexual characters:

Q.1. What are secondary sexual characteristics?
Ans: The secondary sexual characteristics are those that distinguish males from females, and they do not directly take part in reproduction. They are not present at birth but develop later during puberty. Secondary sexual characteristics in males include the development of facial and body hair, growth of genitalia, prostate and scrotum, whereas, in females, these characteristics include the enlargement of breasts, the development of pubic and under armpit hair, and menstrual cycle, etc.

Q.2. What are secondary sexual characters in females?
Ans: 1. Development and enlargement of breasts, mammary glands and erection of nipples take place.
2. Hair growth develops under the armpits and pubic region.
3. The broadening of the hip takes place due to the widening of the pelvis.

Q.3. What are secondary sexual characters in males?
Ans: 1. The maturation and development of secondary sex organs like the penis, prostate, scrotum take place.
2. The growth of body hair, including underarm, chest, pubis, and axillae, occurs.
3. The larynx becomes enlarged, and a deepening of voice takes place.

Q.4. Are Menstruation secondary sexual characteristics?
Ans: Menstruation is a secondary sexual characteristic.

Q.5. Name the hormone responsible for secondary characteristics in females.
Ans: Oestrogen hormone is responsible for secondary characteristics in females.

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