Part A: Endocrine Glands

ASE109 Structure and Function of the Human Body

The Endocrine System (I)

Major Endocrine Glands and Their Hormones

• Hypothalamus

  • Produces hormones that control the release of other hormones from the pituitary gland.

  • Example: Thyrotropin-releasing hormone (TRH).

• Pituitary Gland

  • Often referred to as the "master gland"; produces multiple hormones that regulate other endocrine glands.

  • Example: Growth hormone (GH), Adrenocorticotropic hormone (ACTH).

• Thyroid Gland

  • Produces hormones that regulate the body's metabolic rate, heart and digestive function, muscle control, brain development, and bone maintenance.

  • Example: Thyroxine (T4) and Triiodothyronine (T3).

• Parathyroid Glands

  • Produce parathyroid hormone (PTH), which regulates calcium levels in the blood.

• Adrenal Glands

  • Produce hormones involved in stress responses, metabolism, and immune response.

  • Examples: Cortisol (regulates metabolism and response to stress), Aldosterone (regulates sodium and potassium levels).

• Thymus

  • Produces thymosin, which is important for T-cell development and immune response.

• Pancreas

  • Produces insulin (lowers blood glucose levels) and glucagon (raises blood glucose levels).

• Gonads

  • Testes produce testosterone (regulates male reproductive functions).

  • Ovaries produce estrogen and progesterone (regulate female reproductive functions).

• Pineal Gland

  • Produces melatonin, which regulates sleep-wake cycles.

• Hormonal Action

  • Hormones are secreted into the bloodstream and bind to specific receptors on target cells.

  • Target cells respond by either initiating a cellular response or modifying their function based on the hormone's signal.

Learning Outcomes

• At the end of this section, you should be able to:

  • Distinguish between the mode of action of a neurotransmitter and that of a hormone.

  • Distinguish between endocrine and exocrine glands.

  • Identify the organs and glands of the endocrine system.

  • Compare the actions of peptide and steroid hormones.

Endocrine Glands

• The organs of the endocrine system produce chemical signals known as hormones, which are vital for the regulation of other organs.

• The endocrine system operates in tandem with the nervous system to uphold homeostasis.

Major Endocrine Glands

• The major endocrine glands include:

  • Hypothalamus and pituitary glands (located in the brain)

  • Thyroid and parathyroid glands (located in the throat with parathyroids being 4 tiny glands attached to the thyroid)

  • Thymus (attached to the heart)

  • Adrenal glands (one attached to each kidney)

  • Pancreas (horizontal structure between adrenal glands)

  • Gonads (testes in males and ovaries in females located in the groin)

Other Hormone-Producing Organs

• Other organs that produce hormones include:

  • Kidneys

  • Gastrointestinal tract

  • Heart

• However, these organs do not primarily function as hormone producers.

• In the context of the endocrine system, the hormone-secreting functions of these organs are called endocrine tissue.

Overview of the Endocrine System

• The endocrine system encompasses all endocrine organs and tissues within the body.

  • Endocrine organ: The primary function is endocrine secretion.

  • Endocrine tissue: These are tissues with multiple functions in addition to hormone secretion.

Major Endocrine Organs and Tissues

Major Endocrine Organs

• Hypothalamus

• Pituitary gland

• Thyroid gland

• Parathyroid glands

• Adrenal glands

• Thymus

• Reproductive system (testes, ovaries)

• Pineal gland

Major Endocrine Tissues

• Pancreas

• Kidneys

• Heart

• Gastrointestinal tract (pancreas)