Exocrine Glands – Functions, Types and Examples

Exocrine Glands are also called duct glands as they release chemicals directly into a duct. Exocrine glands are important components of the human body, serving essential functions through the secretion of substances. Examples of exocrine glands include sweat glands and salivary glands.

Understanding the function of exocrine glands is fundamental to learning about their role in overall health. In this article, we will cover a detailed overview of exocrine glands including its functions, and examples.

Exocrine gland are the glands that release chemicals directly into a duct or onto the surface. These substances are often hormones, enzymes, or other fluids including milk, saliva, tears, sweat, and digestive juices. These glands are located throughout the body in different organs and are essential to preserving homeostasis and supporting several physiological processes.

Some of the examples of exocrine glands are:

• Sweat Glands: Found throughout the skin, these glands secrete sweat to regulate body temperature and excrete waste products.
• Salivary Glands: Located in the mouth, these glands produce saliva containing enzymes that initiate the digestion of carbohydrates and lubricate the food for swallowing.
• Sebaceous Glands: Found in the skin, these glands secrete an oily substance called sebum that lubricates and waterproofs the skin and hair.
• Mammary Glands: Present in the breast tissue, these glands produce milk for nourishing infants during breastfeeding.
• Mucous Glands: Found in various mucous membranes such as the respiratory and digestive tracts, these glands secrete mucus to protect and lubricate the epithelial surfaces.

Also Read: Difference Between Sweat and Sebum

Exocrine Glands can have different structures, although they usually have similar characteristics. There are two basic parts of Exocrine Glands are:

• Duct
• Secretory unit

This is a summary of their usual structure:

Secretory unit of Exocrine Glands

• Acini: Collections of cells that make up an exocrine glands secretory unit. The particular compounds that the gland secretes are made by these cells.
• Secretory Cells: The glandular substance is produced and released by specific secretory cells found within the acini. Depending on the kind of gland, these cells might have a cuboidal, columnar, or different form.

Duct of Exocrine Glands

• Ducts: The ducts found in Exocrine Glands are tubular structures that carry the Gland’s secretions to their appropriate location. Depending on the form and function of the gland, the ducts may be simple or branching.
• Intercalated Ducts: The first secretions from the acini are transported via these small ducts, which join the acini to the larger intralobular ducts.
• Intralobular Ducts or smaller ducts: These ducts lead to more substantial interlobular ducts by collecting secretions from many acini within a lobule.
• Interlobular Ducts or larger ducts: These are the large size ducts which collects secretions from different lobules and release them to main duct.

Connective Tissue

• Stroma: The stroma, or supporting connective tissue, envelops the secretory units and ducts. In addition to containing blood arteries and neurons that control glandular activity, the stroma offers structural support.

Different Cells Based on Secretion Type

• Serous Cell: These cells secrete a fluid mixture of enzymes. Serous cells are frequently observed in some pancreatic and salivary glands.
• Mucous Cell: The secretion produced by these cells is thicker and more mucus rich. In Glands that release mucus, including the goblet cells in the respiratory and digestive systems, mucous cells are common.
• Mixed gland Cells: A mixed secretion is produced by Exocrine Glands that contain both mucous and serous cells.
• Myoepithelial Cells: The contractile myoepithelial cells, which are located between the secretory cells and the basal lamina, help in the glandular secretion’s fluid.

The classification of exocrine glands is mentioned below:

• Structural Classification:
  • Simple Exocrine Glands: These glands consist of a single unbranched duct that releases secretions directly onto the surface epithelium. Examples include sweat glands and goblet cells in the digestive tract.
  • Compound Exocrine Glands: These glands have a branched duct system that transports secretions to the surface. Examples include mammary glands and salivary glands.
• Mode of Secretion:
  • Merocrine (Eccrine) Glands: Secretions are released through exocytosis without loss of cytoplasm. Examples include sweat glands and salivary glands.
  • Apocrine Glands: Secretions are produced in the cytoplasm and are released along with a portion of the cell membrane. Examples include mammary glands.
  • Holocrine Glands: Secretions are produced by the disintegration of entire cells. Examples include sebaceous glands in the skin.
• Nature of Secretions:
  • Serous Glands: Secrete a watery fluid containing enzymes and electrolytes. Examples include salivary glands.
  • Mucous Glands: Secrete a viscous fluid rich in glycoproteins called mucins. Examples include goblet cells in the respiratory and digestive tracts.
  • Mixed Glands: Secrete both serous and mucous components. Examples include submandibular salivary glands.

Numerous substances with varying physiological purposes are secreted by exocrine glands. Depending on the nature and location of the gland, an exocrine glands will generate different products. Several kinds of exocrine glands release the following:

• Saliva: Saliva is produced by salivary glands which have properties like antimicrobial compounds, mucus for lubrication, and enzymes like amylase for the breakdown of carbohydrates.
• Sweat: Electrolytes (sodium, potassium, and chloride) and trace quantities of waste products are released together with water by the sweat glands. Along with removing some metabolic waste, sweating helps in controlling body temperature.
• Sebum: Sebum is an oily substance produced by sebaceous glands. Sebum keeps the skin from drying out and cracking by helping to waterproof and moisturise it.
• Milk: Milk, which is abundant in proteins, lipids, carbohydrates, vitamins, and antibodies, is produced by the mammary glands in the breasts.
• Pancreatic juice: Pancreatic juice, which includes digestive enzymes including lipases, amylases, and proteases, is produced by the Exocrine cells of the pancreas. These digestive enzymes help break down proteins, lipids, and carbohydrates in the small intestine.
• Bile: The liver produces bile, which accumulates in the gallbladder. The bile ducts allow it to be expelled into the small intestine. Bile aids in the emulsification of lipids, increasing their accessibility to the digestive enzymes.
• Gastric juice: The stomach’s gastric Glands secrete gastric juice, which has pepsin and other digestive enzymes for breaking down protein and hydrochloric acid (HCl) for breaking down food.
• Secretion of duodenal: The duodenum, the first segment of the small intestine, has Glands that secrete alkaline secretions that counteract the acidic chyme from the stomach, so establishing an environment that is more conducive to the activity of digestive enzymes.
• Mucus: Mucus is a sticky fluid secreted by goblet cells, coats and shields the lining of the digestive and respiratory systems.

Exocrine Glands have the following essential functions:

• Digestion: Enteroenzymes (amylases, lipases, and proteases) are secreted into the small intestine by the pancreatic exocrine cells. In order to improve nutritional absorption, these enzymes help in the breakdown of proteins, lipids, and carbs.
• Lubrication: Saliva is produced by the salivary glands and contains enzymes, mucus, and water. Food is lubricated and moistened by saliva, which facilitates chewing and swallowing.
• Regulation of Temperature: Sweat is released by apocrine and eccrine sweat glands. Sweat plays a critical function in temperature control and heat dissipation by assisting in the body’s cooling process as it evaporates.
• Protection: Sebum is an oily material secreted by sebaceous glands. It creates a barrier of defence for the skin. Sebum keeps skin and hair healthy, guards against dangerous germs, and helps avoid dehydration.
• Defense: Milk, which is produced by mammary glands, includes immunological components and antibodies. Breast milk prevents babies from illnesses and gives them passive immunity.
• Acid Neutrilization: Enzyme activity in the small intestine is enhanced by the duodenum’s Glands secreting alkaline chemicals that neutralise the acidic chyme coming from the stomach.
• Mucus: Mucus is a sticky fluid secreted by goblet cells, coats and shields the lining of the digestive and respiratory systems.
• Fat Emulsification: Bile is produced by the liver and then transported via the bile ducts into the small intestine. Bile helps break down fats into tiny droplets so that lipases can digest them more quickly.
• Electrolyte imbalance: Excretory sweat glands help the body stay properly hydrated by eliminating excess salt and assisting in the regulation of water and electrolyte balance.

Endocrine vs exocrine gland is given in the table below:

Also Read: Difference Between Endocrine and Exocrine Glands

In conclusion, exocrine glands play crucial roles in the human body by releasing chemicals directly into ducts or onto surfaces. They produce substances such as hormones, enzymes, and fluids like milk, saliva, tears, sweat, and digestive juices. These glands are dispersed throughout the body, each serving specific functions crucial for maintaining homeostasis and supporting various physiological processes. Understanding the structure, classification, and functions of exocrine glands provides valuable insights into their significance in overall health and well-being.

Also Read:

• Difference Between Nervous System And Endocrine System
• Difference Between Secretion And Excretion
• Epithelial Tissue
• Endocrine Glands – Parts and Functions
• Types of Endocrine System
• What is Thymus Gland?

What is Difference Between Endocrine and Exocrine Glands?

Two main Gland types exist: Exocrine and endocrine. Exocrine Glands release substances through ducts to an epithelial surface, while endocrine Glands release products directly into the bloodstream.

Which Organ is Exocrine and Endocrine?

The pancreas, situated in the abdomen, functions as both an endocrine and Exocrine organ. It produces blood sugar-regulating hormones and secretes pancreatic fluid with bicarbonate and digestive enzymes.

What are the 3 Types of Exocrine Glands?

Exocrine Glands come in three types: Holocrine, Merocrine (Eccrine), and Apocrine.

What is an Example of an Exocrine Gland?

Exocrine Glands release substances onto epithelial surfaces through ducts. Examples include sweat, salivary, mammary, ceruminous, lacrimal, sebaceous, prostate, and mucous Glands.

What is the Largest Exocrine Gland?

The liver, the largest Exocrine Glands in the human body, produces and secretes bile.

Which is the Smallest Exocrine Glands?

The smallest Gland in the human body is the Pineal Gland, located dorsally in the forebrain and derived from the embryo’s ectoderm.