Health is something that so many people want to know more about, and the exocrine system is one bodily system that is shrouded in mystery for many people. The cardiovascular and muscular systems are well understood and most people could easily name specific muscles. If you were to ask those same individuals about sebaceous glands and secretory cells they would most likely have less to say.
A large reason for this discrepancy in the knowledge of the public is that the exocrine system is a large interconnected web of smaller players like hormones and glands. Many people have never even heard of a merocrine gland before and would most likely be unable to identify what it is and what its function is.
Below is a detailed look at the merocrine gland, how it plays a role in the exocrine system, and how to promote good endocrine and exocrine health.
What is the Exocrine System?
The exocrine system and the endocrine system are often confused. Both sound remarkably similar and both deal with glands, hormones, and excretions within the body. The main difference between the two is where they act within the body.
The endocrine system is made up of glands and hormones that are directly connected to the bloodstream. Hormones like testosterone, estrogen, human growth hormone, and glands like the pituitary, adrenals, and gonads make up the endocrine system. By acting on the bloodstream these hormones are able to have far-reaching effects throughout the body.
Where the endocrine system is focused on hormones and glands that interact with the bloodstream, the exocrine system encompasses the hormones and glands that are utilized everywhere else. These include glands located on the skin like the palms of the hand, glands that line the digestive tract, and much more. Unlike the endocrine system, these functions act largely independent of one another and do not rely on one another for optimal functioning.
What Makes Up the Exocrine System?
The exocrine system is made up of many glands that line the external surfaces of the body. These external surfaces don’t only include the skin, but they also include the digestive tract.
While it may seem counterintuitive, the digestive tract is considered external because it interacts with the outside world. If you think of your digestive tract as a long tube it can be easier to understand how it can be both within you but an external surface to the body at the same time
While exocrine glands don’t have large interactions with one another, they do interact with other body systems to enable proper functioning. The digestive, respiratory, and integumentary systems of the body rely on the exocrine system to function at their best.
Within the digestive system, exocrine glands work to provide your body with digestive enzymes to break down food and mucous to protect the lining of digestive organs. Without the help of the excretions of the exocrine system, your body would be much less effective at properly digesting food.
The respiratory system utilizes exocrine glands to produce mucus that lines the air pathways to the lungs. The high viscosity and presence of degradative enzymes ensure foreign invaders and particles are filtered out before making it to the lungs.
The integumentary system heavily relies on the exocrine system to function properly. The integumentary system is essentially the skin and the exocrine glands found within it allows for it to have a protective film that retains moisture and facilitates temperature regulation for the body.
Modes of Hormonal Exocrine Secretion
Exocrine glands differ in their function, what they release, and location. One of the largest ways that these glands are distinguished is by observing how they secrete their given product.
When looking at the ways that cells can release a product there are many different ways which include diffusion, exocytosis, and more.
While cells have many ways of moving products out, there are only three main modes of secretion in the exocrine system. These different modes of secretion encompass the three different exocrine glands which are merocrine, apocrine, and holocrine glands.
While they all are responsible for releasing products to the external surfaces of the body, the way it is achieved differs.
Merocrine glands are a subset of exocrine glands that deal with the glands that secrete their products through a process known as exocytosis. This process allows for products to effectively be released to their surroundings without the need to sacrifice their membrane.
Exocytosis involves the merger of vesicles within the cell and the outer cell membrane. If you were to think of it like two bubbles the vesicle would be the smaller bubble within the larger external cellular bubble. The vesicle is the structure that contains the products that need to be excreted. This is accomplished by the inner vesicle fusing with the external membrane. When these two membranes fuse the vesicle membrane becomes a part of the external membrane and the products within that vesicle are successfully transferred outside of the cell.
The most common merocrine glands are sweat and salivary glands. It makes sense that these glands would be merocrine glands because they are constantly needed, and if the cells utilized another secretion method they would quickly deplete their membranes. Merocrine glands are able to continuously secrete with little to no change to membranes.
Apocrine glands are another subset of exocrine glands. Apocrine glands, unlike merocrine glands, resulting in the loss of the outer membrane.
The best way to think about how the apocrine glands work would be to think of a lava lamp. Initially, the blob is large and as the lamp heats up the blob begins to slowly stretch until the smaller blob buds off the original.
This is what occurs with the secretion of products in the apocrine gland cells. When the cell buds off it take the products to be secreted with it. These buds are known as vesicles and as they travel through the gland they deteriorate and the products are released to their appropriate location.
Apocrine glands make up the sweat glands connected to hair follicles and mammary glands.
Holocrine glands are one of the more drastic methods of exocrine secretion. Unlike the other recreation methods, holocrine glands work through controlled cellular death.
The molecular functioning of a holocrine involves a cavity lined by cells that produce the products required. Rather than undergoing exocytosis or forming a vesicle, the cell splits open and its contents are excreted from the gland. This method requires constant cell divisions to replenish the cells lost in the process.
The sudoriferous glands are a good example of a holocrine gland. The sudoriferous glands are responsible for the excretion of the oils on the skin which helps to protect the skin from dryness. With the complexity of oils required, a holocrine gland is best suited to deliver them.
Examples of Merocrine Glands
Merocrine glands are scattered throughout the body and play an important role in temperature regulation, fluid balance, and digestion. A large number of different bodily functions rely on merocrine exocrine glands.
Below is a look at a few examples of merocrine glands and what they do for your body.
Eccrine sweat glands are some of the most prevalent glands on the surface of the skin. Eccrine sweat glands are the excretory glands responsible for the process of sweating and are a vital component to the temperature regulation of the body.
Sweat consists of water in addition to electrolytes. Eccrine sweat glands are signaled by the brain to begin the excretion of sweat. The cells within the glands act by exocytosing the salty fluid and pushing it to the surface of the skin. The water on the surface of the skin is then evaporated which results in the surface of the skin cooling down.
The saliva in your mouth may seem like plain water, but in reality, it contains enzymes that get a head start on the breakdown of the food you eat. Because of this, the mouth is the location of the first chemical breakdown of food.
The salivary glands within the mouth are located below the tongue and in the deep parts of the mouth. Salivary glands are complex structures that result in the production of saliva. While saliva is nearly 99% water, it contains enzymes that aid in the digestion of carbohydrates.
In summary, merocrine glands are one of three different kinds of exocrine glands.
Merocrine glands make up basic sweat glands and play a role in saliva production. Merocrine glands along with apocrine and holocrine glands work together and encompass the exocrine system. Although these glands differ in the mechanisms responsible for delivering products they all are required for optimal bodily functions like digestion and skin integrity.
Knowing what the exocrine system is, what it consists of, and how it impacts the body can allow you to better understand your body, and better understanding means better health!
To learn more about all things hormones, check out the Elite HRT blog here.
Human Structure Virtual Microscopy | Indiana University
Secretions of Human Salivary Gland | Salivary Glands – New Approaches in Diagnostics and Treatment