Exocrine Glands

What are exocrine glands?

Exocrine glands release (secrete) substances through openings (ducts) onto your body surfaces. Exocrine glands secrete sweat, tears, saliva, milk and digestive juices. A gland is a unit of cells that work together to create and secrete these substances. Exocrine glands can be found in many different organs in your body. They have a variety of functions.

What’s the difference between endocrine and exocrine glands?

Exocrine glands secrete their substances through ducts onto your body's surfaces. On the other hand, endocrine glands secrete their substances directly into your bloodstream. They’re called ductless glands. Endocrine glands are part of your endocrine system, and they secrete hormones. Examples of endocrine glands include your pituitary gland, thyroid gland and adrenal glands.

What are the different types of exocrine glands?

Many organs in your body use exocrine glands to function properly. Examples of exocrine glands include:

• Sweat glands: Your sweat glands create and secrete sweat. A type of sweat gland called eccrine sweat glands covers almost your entire body surface. These sweat glands produce clear, non-oily sweat that helps control your body temperature.
• Sebaceous glands: Your sebaceous glands are also on your skin. But they open into your hair follicles. Sebaceous glands secrete sebum. Sebum is an oily substance that lubricates and protects your hair and skin.
• Salivary glands: Your salivary glands create and secrete saliva. Salvia helps you chew, swallow and digest your food. It also helps lubricate and protect the inner lining of your tissues.
• Lacrimal glands: Your lacrimal glands are your tear glands. Your lacrimal glands are located above your upper eyelids. They create and secrete a fluid that gets into your eyes every time you blink. This fluid helps keep your eyes moisturized.
• Mammary glands: Your mammary glands produce milk. Your milk is nutrient-rich and helps protect your baby’s developing immune system.
• Ceruminous glands: Your 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 your stomach release enzymes that help break down food. They also help your body absorb important nutrients.
• Brunner glands: The Brunner glands are located in the first part of your small intestine. This is called your duodenum. The Brunner glands produce mucus that protects your duodenum from stomach acid. They also help your body digest food and absorb nutrients.

Your liver and pancreas are exocrine glands too. Your liver secretes bile through ducts into your gastrointestinal tract. Your pancreas secretes pancreatic juices through ducts into your gastrointestinal tract. But your liver and pancreas are also considered endocrine glands. They have dual roles. They also secrete hormones directly into your bloodstream.

What is the function of exocrine glands?

Your exocrine glands have any different functions. The function of each depends on the organ in your body they’re associated with. The main purpose of all exocrine glands is to make and release substances to assist your body in some way. They help your body:

• Digest your food.
• Absorb nutrients.
• Protect the inner lining of your organs.
• Control your body temperature.
• Lubricate your hair and skin.

How do exocrine glands work?

Your exocrine glands release their substances in different ways. The three main ways exocrine glands can secrete their substances are:

• Merocrine glands: Merocrine glands release their substances through a process called exocytosis. With exocytosis, the cells aren’t damaged at all. Your eccrine sweat glands are a kind of merocrine glands.
• Apocrine glands: Apocrine glands make buds of the cell membranes, which break off into the duct. This causes them to lose part of the membrane in the process. Your mammary glands are a kind of apocrine glands.
• Holocrine glands: With holocrine glands, the cell membrane bursts to release its substance. Your sebaceous glands are a kind of holocrine glands.

What are common conditions and disorders that affect exocrine glands?

Many conditions can affect your exocrine glands because they're located throughout your body. These conditions include:

• Hyperhydrosis: Hyperhydrosis is also called excessive sweating. It occurs when your body’s sweat glands produce more sweat than it needs.
• Bromhidrosis: Bromhidrosis is also called excessive body odor. It occurs when bacteria on your skin starts to break down dried sweat.
• Acne vulgaris: Acne occurs when your sebaceous glands plug up with sebum. This releases free fatty acids, which trigger an inflammatory response that creates pimples.
• Sjögren's syndrome: Sjögren's syndrome is an autoimmune disorder. It reduces the amount of moisture your salivary glands and lacrimal glands produce. This can lead to dry mouth and dry eyes.
• Mammary duct ectasia: Mammary duct ectasia is the swelling and thickening of your milk ducts. This condition can cause blockages in your milk ducts.
• Cystic fibrosis: Cystic fibrosis is a disease that causes sticky, thick mucus to build up in organs including your lungs and pancreas. It’s caused by a mutation of a protein involved in the production of your sweat, mucus and digestive fluids.
• Brunner’s gland hyperplasia: Brunner’s gland hyperplasia is a noncancerous (benign) tumor on your duodenum.
• Pancreatitis: Pancreatitis can cause your pancreas to stop producing digestive enzymes. Your small intestine needs the enzymes to help break down food.

A note from Cleveland Clinic

Your exocrine glands make and release many of the important substances your body needs to function properly. Exocrine glands can be found all over your body, from your skin to your breasts to your pancreas. Since they’re found all over your body, there’s a wide range of conditions they can affect. If you’re experiencing any new or concerning symptoms, talk to your healthcare provider. They can assess your health and make sure you’re on the right track.