Merocrine and apocrine glands are two types of exocrine glands found in the human body. Both types of glands are responsible for secreting substances onto the surface of the skin or into ducts. However, there are distinct differences in their structure, location, and mode of secretion.
MEROCRINE GLANDS
a). Structure: Merocrine glands are simple tubular glands composed of a secretory portion and a duct. The secretory portion consists of secretory cells that release their products into the duct without losing any part of their cytoplasm.
b). Location: Merocrine glands are widely distributed throughout the body and can be found in the skin, respiratory tract, digestive system, and other organs.
c). Mode of secretion: Merocrine glands release their secretions through exocytosis, where the secretory vesicles fuse with the plasma membrane, expelling their contents. This process does not involve any loss of cellular material.
d). Examples: Sweat glands (eccrine glands) found in the skin are a common example of merocrine glands. They secrete sweat, which helps regulate body temperature.
APOCRINE GLANDS
a). Structure: Apocrine glands are more complex than merocrine glands. They have a larger secretory portion and a narrower duct. The secretory portion consists of cells that accumulate secretory products and then release them by shedding a part of their cytoplasm along with the secretory material.
b). Location: Apocrine glands are primarily found in specific regions of the body, such as the axillary (armpit) and pubic regions, mammary glands, and certain sweat glands in the ear canal.
c). Mode of secretion: Apocrine glands release their secretions through a process called apocrine secretion. This involves the pinching off of the apical portion of the glandular cells, which contains the secretory material, and its subsequent release into the duct.
d). Examples: The mammary glands, which produce milk, are an example of apocrine glands. Similarly, the apocrine sweat glands in the axillary and pubic regions produce a thicker, odorous sweat compared to merocrine sweat glands.
It's worth noting that the classification of apocrine glands has been a subject of debate among researchers, and some argue that what were traditionally considered apocrine glands are actually a modified form of merocrine glands.
In summary, merocrine glands release their secretions through exocytosis without losing cellular material, while apocrine glands shed a part of their cytoplasm along with the secretory material. Merocrine glands are more widespread, while apocrine glands are localized in specific regions of the body.
Other examples of merocrine glands besides sweat glands
In addition to sweat glands, there are several other examples of merocrine glands in the human body. Here are a few notable examples:
i). Salivary glands: The salivary glands, including the parotid, submandibular, and sublingual glands, are merocrine glands. They produce and secrete saliva, which aids in digestion and lubrication of food during chewing and swallowing.
ii). Lacrimal glands: The lacrimal glands, located in the upper outer part of each orbit, are merocrine glands that produce tears. Tears help keep the eyes lubricated, protect them from foreign particles, and contain enzymes that help fight against infections.
iii). Pancreas: The pancreas contains both exocrine and endocrine glands. The exocrine portion of the pancreas consists of merocrine glands called pancreatic acinar cells. These cells secrete digestive enzymes, such as amylase, lipase, and proteases, into the pancreatic ducts, which ultimately reach the small intestine to aid in the digestion of carbohydrates, fats, and proteins.
iv). Gastric glands: The gastric glands in the lining of the stomach are another example of merocrine glands. They secrete gastric juice, which contains hydrochloric acid and digestive enzymes like pepsinogen. These secretions help break down food in the stomach during the process of digestion.
v). Intestinal glands: The small intestine has numerous merocrine glands called intestinal glands (or crypts of Lieberkühn). These glands secrete mucus, digestive enzymes, and other substances that aid in the digestion and absorption of nutrients.
vi). Brunner's glands: Brunner's glands are specialized merocrine glands found in the submucosa of the duodenum (the first part of the small intestine). These glands secrete alkaline mucus, which helps neutralize the acidic chyme coming from the stomach and provides an optimal pH for the action of digestive enzymes.
These are just a few examples of merocrine glands in the human body. Merocrine glands are diverse and can be found in various organs and tissues, playing crucial roles in maintaining homeostasis and facilitating bodily functions.
