Hormonal Regulation and Physical Development in Adolescence

Human Development: Puberty and Sexual Characteristics

Gametes and Reproductive Capability

Gametes are the reproductive cells: sperm (male) and eggs (female). Humans acquire this ability during the first stage of adolescence, known as puberty.

Sexual Characteristics

Primary Sex Characteristics

These include the gonads and internal structures that house the embryo (the uterus) until the individual is born.

Secondary Sexual Characteristics

Secondary sexual characteristics are external features unique to either sex, which appear at puberty.

Changes in Males

• Shoulders widen.
• Hair appears (axillary, pubic, facial).
• The voice deepens (becomes lower pitched).
• The penis and testes increase in size.

Changes in Females

• Hips widen and the waist narrows.
• Hair appears in the armpits and pubic area.
• The secretion of vaginal fluid begins.
• Menstruation (menarche) starts.

Adolescence: Key Changes

Adolescence is characterized by significant changes:

• Physiological and Anatomical Changes: Including the appearance of the first menstrual period (menarche).
• Psychological Changes.
• Social Changes.

The Endocrine System: Glands and Hormones

Pituitary Gland Regulation

The pituitary gland regulates the activity of other glands. If the pituitary detects a low concentration of a hormone, it releases a stimulating hormone, thereby synthesizing the required hormone. When the concentration increases, the pituitary detects this and stops producing the stimulating hormone.

Key Endocrine Glands and Functions

Hypothalamus

This is a neural structure at the base of the brain formed by neurons that synthesize hormones. It reacts to external stimuli and changes in hormone levels in the bloodstream, stimulating or inhibiting the secretion of endocrine glands.

Thyroid

The thyroid is an H-shaped gland located in the neck. It produces thyroxine, which regulates metabolism and promotes growth (orgasm).

Parathyroid Glands

Four small cellular masses located inside the thyroid. They secrete parathormone, which controls the amount of calcium and phosphorus in the blood.

Pancreas

The pancreas is a mixed gland (both exocrine and endocrine). It secretes:

• Glucagon: Increases the amount of glucose in the blood.
• Insulin: Decreases blood glucose levels.

Gonads (Ovaries and Testes)

• Ovaries: Secrete female sex hormones (estrogen and progesterone) that regulate female characteristics and the menstrual cycle.
• Testes: Produce androgens that promote the formation of sperm.

Pituitary Gland (Detailed Functions)

Located at the base of the brain, the pituitary is divided into two parts:

• Anterior Pituitary (Adenohypophysis): Secretes:
  • Growth hormone.
  • Prolactin (causes milk secretion).
  • Follicle-Stimulating Hormone (FSH) (stimulates egg production).
  • Luteinizing Hormone (LH) (responsible for ovulation in the menstrual cycle).
• Posterior Pituitary (Neurohypophysis): Synthesizes oxytocin, which induces uterine contractions.

Adrenal Glands

These glands are attached to the kidneys:

• Cortex: Secretes cortisol, which regulates the metabolism of proteins and buttocks.
• Medulla: Produces adrenaline, which mimics the effects of the sympathetic nervous system.