Difference Between Exocrine and Endocrine Glands

Let's begin with straightening up the basics. There are two types of glands in our body - those with ducts and those without. We all know that the glands in our bodies secrete hormones and enzymes that act as chemical signals which oversee and regulate the performance of a wide variety of essential physiological functions.

While glands with ducts release their secretions into the ducts that project from them and the secreted enzymes are carried directly to the target regions (cells, tissues or any other specific organ) of the body. Ductless glands, on the other hand, release their secretions directly into the bloodstream as they have no ducts to carry their secretions to specific biological sites.

The blood carries the hormones released by these ductless glands all over the body, allowing the concerned organs or functions to utilize these when this hormone laden blood reaches them. The glands that have ducts are known as Exocrine Glands while their ductless counterparts are known as Endocrine Glands.

So, what is the main difference between exocrine and endocrine glands? Well, apart from the different chemicals, enzymes and hormones produced by each gland (which sets each gland apart), the sole factor that differentiates exocrine glands from endocrine glands is the presence or absence of the glandular ducts.

Let's take a closer look at endocrine and exocrine glands to understand the finer differences between the two, now that the basic and most obvious difference is clear. Description of each category of glands will be followed by a listing of all glands that fall under each category for clearer understanding of the subject.

Endocrine glands are the primary hormone producing glands of the body that release various hormones and similar chemical messengers directly into the blood stream. Sometimes, hormones and chemical enzymes meant for specific organs are secreted to these organs directly by endocrine glands that are located in proximity to the organs in question. 

For instance, in case of paracrine signaling which occurs to stimulate cellular growth (known as growth factor) as well as to trigger the formation of blood clots, chemical signal cells that are located within close proximity of target organs and cells act upon the latter directly.

Here's a list of major endocrine glands that secrete some of the most significant hormones that regulate our physiological as well as psychological chemistry.

• Thyroid Gland
• Pineal Gland
• Thalamus Gland
• Pituitary Gland
• Liver
• Pancreas
• Adrenal Glands
• Ovaries (in females only)
• Testes (in males only)

Although not specifically known as a part of the endocrine system, the stomach also secretes a hormone, known as Ghrelin, which is what induces the feeling of hunger that gets the brain to believe that the stomach is empty.

Exocrine glands are glands that have ducts via which they release various liquid and semi liquid compounds that are neither hormones nor any kind of chemical signals. Different exocrine glands produce different secretions that are carried by the ducts to their target destinations.

Some of the major exocrine gland secretions include milk, sweat, saliva, mucus, bile, gastric acid, pepsinogen, sebum, pancreatic juice, etc.

The various major exocrine glands of the body are as follows:-

• Salivary Glands
• Sebaceous Glands
• Sudoriferous Glands (sweat glands)
• Mammary Glands
• Stomach
• Pancreas
• Liver

I guess that pretty much clears all doubts, whatsoever, that you might have harbored regarding the differentiating factors that set exocrine and endocrine glands in the human body apart.

Certain glands perform both exocrine and endocrine functions as they secrete both hormone and non-hormone enzymes. Prominent examples of such double-function glands include the stomach (exocrine secretion = gastric acid; endocrine secretion = ghrelin) and pancreas (exocrine secretion = pancreatic juice; endocrine secretion = insulin).