Exocrine Glands: Function, Structure, Mechanism of Action, Classification and Associated Disorders

They are cellular substructures in a body that provides a system to secrete substances outward and inward of the body.

They are different from the endocrine glands; while the secretions of the exocrine gland end up outside the body, endocrine secretions enter the bloodstream.

The exocrine glands secrete their substances through a ductal system.

Most of the glands in the body are of the exocrine type. The other major category of glands in the body consists of the endocrine glands.

The function of the exocrine glands

The exocrine glands perform a variety of bodily functions.

They regulate body temperature by producing sweat, feeding babies milk, cleaning, moistening, and lubricating the eye to make tears helping start digestion and lubricating the mouth, producing saliva.

The oil (sebum) of the sebaceous glands keeps the skin and hair conditioned and protected.


The wax (cerumen) of the ceruminous glands in the outer ear protects the ears from foreign substances.

The exocrine glands in the testicles produce seminal fluid, which transports and nourishes the sperm.

The secretions of the exocrine gland also help in the defense against bacterial infection by carrying special enzymes, forming protective films, or washing microbes.

Humans are not the only living beings that have exocrine glands.

The exocrine glands in plant life produce water, sticky protective fluids, and nectars.

The substances needed to make bird eggs, caterpillar buds, spider webs, and beeswax are all produced by exocrine glands.

Silk is a product of the secretion of the salivary gland of the silkworm.


The structure of the exocrine gland is divided into the ductal portion and the glandular portion.

The glandular portion is around an elongated set of cells producing the secreted substance.

Different types of cells are found in the glandular portion depending on the substance secreted.

Common cell types include serous cells (protein excretion) and mucous cells (mucus/fluid excretion).

The tubular portion is often a single thick wall of cuboid cells that helps move the secretion.

The tubular conduit may be of simple structure (unbranched) or complex with many branches of pipes.

The tubular conduit can also be observed in a simple spiral structure.

Mechanism of action of the exocrine glands

Secretions of exocrine glands eventually lead to the outside of the body, so the inner surface of the glands and the ducts that drain them are similar to the skin.

Although this collection of glands is considered a system, they do not work together in the way that the parts of the digestive system or the respiratory system function.

Instead, they work independently, each with their work to do and respond to the body’s needs at any particular time.


By secretion method:

  • The holocrine glands: will release whole broken cells broken in your ductal system. These cells contain reserves of substance that the gland will remove. This secretion method requires frequent cell rotation and replacement.
  • The eccrine or merocrine glands: release their substances directly into the duct, through cellular channels or pores, without loss of cell structure or membrane. This is the most common type of exocrine gland.
  • The apocrine glands: release their secretion by budding a part of its membrane and cell cytoplasm. This outbreak contains the secreted substance and is released into the ductal system.

By secreted product:

  • Serous cells: secrete proteins, often enzymes. Examples include gastric central cells.
  • Mucous cells: secrete mucus. Examples include Brunner glands, esophageal glands, and pyloric glands.
  • The mixed glands: secrete proteins and mucus. Examples of the salivary glands: are the parotid gland, the sublingual gland, and the submandibular gland.
  • The sebaceous glands: secrete sebum, a lipid product. These glands are also called sebaceous, Fordyce points, and meibomian glands.

Diseases and disorders associated with the exocrine system

Many conditions can affect the exocrine system, such as infections, ulcers, cancer, tumors, some obstruction, genetic disorders, and cysts.

The exocrine system and the endocrine system are closely related, so some of the disorders observed in the endocrine system are also observed in the exocrine system.

Some disorders of the exocrine system include:

  • Acromegaly: too much growth hormone is produced in adults, which causes an enlargement of the bones and thickening of the skin.
  • Addison’s disease: the adrenal gland does not have enough corticosteroids.
  • Cretinism: an extreme form of hypothyroidism present before or after birth.
  • Cushing’s disease: overproduction of cortisol.
  • Dwarfism: Minimal growth hormone produced during childhood.
  • Gigantism: too much growth hormone made during childhood.
  • Goiter: an enlargement of the thyroid gland, which generates a swelling in the neck.
  • Hyperthyroidism: a disorder in which an overactive thyroid produces too much thyroxine.
  • Hypothyroidism: a condition in which an underactive thyroid produces too little thyroxine.
  • Cystic fibrosis: this hereditary disorder causes the production of abnormally thick mucus that leads to obstruction of the pancreatic ducts, intestines, and bronchi. Respiratory infections are common.
  • Diabetes: is a disease characterized by the alteration of blood glucose levels.