Difference Between Endocrine and Exocrine Glands

Before we can understand what is the difference between Endocrine and Exocrine glands, let’s first define what glands are. Glands are special cells or organs that secrete chemical compounds. These are the two types of glands:

Endocrine Glands

These glands secrete chemicals into the bloodstream and tissues of the body. The endocrine glands do not have ducts. They don’t go to any ducts before releasing chemical substances, also known as hormones, into the bloodstream. Hormones can be thought of as messengers. They are responsible for telling a part of the body what to do or not to do.

Examples of Endocrine Glands

  • The brain’s pineal gland secretes melatonin to induce sleep in response to dark environments. It regulates the female reproductive cycles and initiates puberty. The hormones responsible for puberty are estrogen, progesterone, and testosterone.
  • The glands responsible for releasing estrogen and progesterone in female characteristics are called the ovaries.
  • Testes are glands that produce testosterone to encourage male characteristics.

Exocrine Glands

These glands secrete chemicals into ducts which help in the release of the secretions. Many of these glands release their secretions outside the body, while others release them onto a surface within the body. These glands can also synthesize their products and release them onto a surface via a tube/duct. It is also known that some ducts can modify secretions.

Exocrine Glands: Examples

  • Pancreatic acinar cells: The secretions are stored in the vesicles, transported to the apical surfaces and released (exocytosis). This is known as merocrine secretion.
  • The secretion of lactating mammary glands is made with some cytoplasm and plasma membrane. This is known as apocrine secretion.
  • The programmed cell death of the sebaceous gland is where secretions and debris are released. This is known as holocrine secretion.

What is the Difference Between Endocrine and Exocrine Glands

The hormones produced by an endocrine gland are secreted directly into the bloodstream. The adrenal gland, which secretes the hormone adenaline from the adrenal medulla into the blood, is an example of an endocrine organ.

Exocrine glands secrete their products, such as enzymes, into ducts which lead to the target tissues. The salivary gland secretes saliva in the collecting duct that leads to the mouth.

It is important to remember that the pancreas has both exocrine and endocrine functions. It releases insulin and glucose directly into the blood (endocrine), and also secretes pancreatic liquid into the pacreatic tube which leads to the duodenum.