Exocrine glands are collections of cells that produce substances and release them through ducts to a specific location, such as the skin or the surface of internal organs. The primary purpose of these glands is to deliver secretions that help the body with digestion, temperature control, and lubrication. Their structure consists of a glandular portion, where substances are made, and a duct portion for transport.
Exocrine Glands vs. Endocrine Glands
The body has two main types of glands: exocrine and endocrine. The fundamental difference is how they release their products. Exocrine glands secrete substances like sweat, saliva, and digestive juices through a ductal system that leads directly to a specific surface.
In contrast, endocrine glands are ductless. They release their chemical messengers, known as hormones, directly into the bloodstream. The circulatory system then carries these hormones throughout the body to reach distant target cells and organs. The pituitary and thyroid glands are examples of endocrine glands.
Major Exocrine Glands and Their Secretions
The salivary glands in the mouth produce saliva, which contains enzymes that begin the breakdown of carbohydrates and lubricates food for easier swallowing. The pancreas has a significant exocrine role, producing a variety of digestive enzymes that are released into the small intestine to break down fats, proteins, and carbohydrates. The liver, another large gland, produces bile, which is secreted into the small intestine to aid in fat digestion.
Other exocrine glands function on the body’s surface. Sweat glands are distributed across the skin and produce sweat, a watery secretion that helps control body temperature by evaporating and cooling the skin. Sebaceous glands are typically attached to hair follicles and secrete an oily substance called sebum, which lubricates the hair and skin, preventing them from drying out. The lacrimal glands, located above each eyeball, produce tears that lubricate the eyes, wash away debris, and contain enzymes to protect against infection.
Another type of exocrine gland is the mammary gland. These glands are responsible for producing milk to provide nutrition for offspring.
Conditions Related to Exocrine Gland Dysfunction
When exocrine glands do not function correctly, it can lead to various health problems. The specific condition depends on which glands are affected and the nature of the dysfunction. The role these glands play in digestion, lubrication, and protection means that any disruption can have noticeable consequences throughout the body.
One prominent example of a disease affecting exocrine glands is cystic fibrosis. This genetic condition causes the body to produce unusually thick and sticky mucus. This mucus clogs the ducts of many exocrine glands, particularly in the pancreas and lungs. The blockage prevents the release of digestive enzymes from the pancreas, leading to malabsorption of nutrients.
Another condition is Sjögren’s syndrome, an autoimmune disorder. In this disease, the body’s immune system mistakenly attacks its own moisture-producing glands. The primary targets are the lacrimal and salivary glands, resulting in significantly reduced production of tears and saliva. This leads to persistent symptoms of dry eyes and dry mouth.