Exocrine Glands: Definition, Types, Functions & Disorders

Exocrine glands are one important type of glands in the human body. Glands are organs that secrete chemical substances such as hormones, digestive juices, and other secretions for the future use of the body in a particular function. There are two main types of glands in the human body: Endocrine Glands and Exocrine Glands. 

• Exocrine glands has two portion; Ductul and Glandular.
• There are three types of exocrine glands; Apocrine, Holocrine and Eccrine gland.
• these glands are involved in regulation of temperature, lactation and digestion.

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Key Terms: Exocrine Glands, Ductal System, Endocrine, Hormones, Ductal, Glandular

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Exocrine Glands

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Exocrine glands secrete their substances on the surface of the body through a duct. Examples- Salivary glands, Mammary glands, and sweat glands, are some of the exocrine glands. Both saliva, secreted by the salivary glands, and sweat, secreted by the sweat glands, act on local tissues near the duct openings.

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Structure of the Exocrine Glands

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The Exocrine glands consist of two main parts:

Ductal portion

The ductal portion is shaped like a tube. It is a single, thick, cuboidal cell wall that aids in secretion transport. The duct may or may not be branched. It's also present in a simple coiled form.

Glandular portion

The glandular region is in charge of the production of the secreted chemical. The cell cluster may be circular or elongated. The cells of the glandular portion are dependent on the substance released. Serous cells, for example, release proteins, while mucous cells exude fluids.

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Types of Exocrine Glands

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The exocrine glands are of three types:

• Holocrine Glands
• Merocrine or Eccrine Glands
• Apocrine Glands

Holocrine Glands

These are released by the rupture of the plasma membrane. They are produced in the cytoplasm of the cell by the disintegration of the entire cell, destroying them and as a result secreting the product in the lumen. For example, sebaceous glands of the skin and nose, meibomian gland, Zeis gland, etc.

Merocrine or Eccrine Glands

The cells of these glands secrete their chemical substances by a process named exocytosis. It is a form of transport wherein the cells transmit the substances out of the cell and into the duct through the cellular channels. There is no rupturing of the cell wall involved. For example, pancreatic acinar cells, most sweat glands of the human body, salivary glands, goblet cells, intestinal glands, tear glands, etc.

Apocrine Glands

They bud off an apical part of their cellular cytoplasm and membrane and release the substance into the ductal system. For example, pancreatic acinar cells, salivary glands, goblet cells, intestinal glands, tear glands, etc.

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Product Secreted

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The glands secrete chemical substances, such as hormones, digestive juices, and other secretions, that will be used by the body in the future.

• Serous cells secrete proteins and enzymes. Examples are gastric chief cells and Paneth cells
• Mucous cells secrete mucus.
• Examples include Brunner's glands, oesophagal glands, and pyloric glands
• Seromucous glands secrete both protein and mucus.
• Examples are the salivary glands.
• Sebaceous glands secrete sebum, a lipid product.
• These glands are also known as oil glands, for example, Fordyce spots, and Meibomian glands.

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Functions Of Exocrine Glands

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Exocrine glands perform the following functions:

• Regulate body temperature
• Lubrication hair and skin
• Lactation
• Helps in digestion
• Helps in reproduction
• Protect the inner lining of your organs.
• Absorb nutrients.
• Protect the inner lining of your organs.

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Examples of Exocrine Glands

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Many organs in our body use exocrine glands to function efficiently. Examples of exocrine glands include

Sweat glands:

Sweat glands produce and secrete sweat on the surface of body. A type of sweat gland called eccrine sweat glands is covered over our entire body surface. These sweat glands produce clear, non-oily sweat that helps control our body temperature.

Sebaceous glands:

Sebaceous glands are on  skin. But they open into hair follicles. Sebaceous glands secrete sebum. It is an oily substance that lubricates and protects the hair and skin.

Salivary glands:

Salivary glands create and secrete saliva. Salvia helps us chew, swallow and digest our food. It also helps lubricate and protect the inner lining of our tissues.

Lacrimal glands:

Lacrimal glands are also called tear glands. Lacrimal glands are located above upper eyelids. They create and secrete a fluid that gets into eyes every time a person blink. This fluid helps keep your eyes moisturized.

Mammary glands:

Mammary glands produce milk. Milk is nutrient-rich and helps protect the baby’s developing immune system.

Ceruminous glands:

Ceruminous glands are glands in your ears. They help produce ear wax (cerumen). Ear wax protects your ears from physical damage and infection.

Stomach glands:

Glands in stomach release enzymes that help break down food. They also help body absorb important nutrients.

Brunner glands:

The Brunner glands are located in the first part of small intestine. This is called the duodenum. The Brunner glands produce mucus that protects the duodenum from stomach acid. They also help the body digest food and absorb nutrients.

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Conditions and Disorders Associated with Exocrine Glands

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There are a few disorders and conditions associated with the exocrine glands since they are present throughout the body:

Hyperhydrosis

Hyperhydrosis is frequently referred to as excessive sweating. It develops when sweat glands create more sweat than your body requires.

Bromhidrosis

It is another name for excessive body odour. When bacteria on skin begins to break down dried sweat, it causes acne.

Acne vulgaris

Acne vulgaris occurs when the sebaceous glands become clogged with sebum. This produces pimples by releasing free fatty acids, which cause an inflammatory response.

Sjögren's syndrome

Sjögren's syndrome is an autoimmune illness that affects people. It lowers the quantity of moisture produced by your salivary and lacrimal glands. This can result in a dry mouth and eyes.

Mammary duct ectasia

The swelling and thickening of your milk ducts are known as mammary duct ectasia. Milk ducts may get blocked as a result of this problem.

Cystic fibrosis

Cystic fibrosis is a disease that causes sticky, thick mucus to accumulate in organs such as the lungs and pancreas. It is caused by a mutation in a protein implicated in perspiration, mucus, and digestive fluid production.

Brunner's gland hyperplasia

Brunner's gland hyperplasia is a benign (noncancerous) growth of the duodenum.

Pancreatitis

The pancreas may cease generating digestive enzymes as a result of pancreatitis. The enzymes in your small intestine aid in the digestion of meals.

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Things to Remember

• The exocrine glands are cellular structures or organs that emit substances outside the body via ducts.
• Some examples are Sweat glands, Salivary glands, Sebaceous glands, Lacrimal glands, and Mammary glands
• The exocrine glands are mainly composed of two main parts - the ductal portion and the glandular portion.
• There are three types of exocrine glands: Holocrine Glands, Merocrine or Eccrine Glands, and Apocrine Glands
• Functions of these glands are Digestion, Lubrication, Aid in reproduction, Lactation, Protection of inner linings of our body organs, and Regulation of our body temperature.