Difference Between Merocrine and Apocrine Sweat Glands

The key difference between merocrine and apocrine sweat glands is that merocrine sweat glands excrete sweat directly onto the surface of the skin opening out through the sweat pore while apocrine sweat glands secrete sweat into the pilary canal of the hair follicle without opening directly onto the surface of the skin.

Glands are a type of organs that secretes substances in the body. There are two main types of glands as endocrine glands and exocrine glands. Exocrine glands secrete their products into a duct. Multicellular exocrine glands can be classified further into different types based on the secretion method. They are merocrine, apocrine and holocrine glands. Merocrine glands secrete substances via secretory vesicles through exocytosis, without damaging the cell. In contrast, apocrine glands pinch off a portion of the cell with substances. Hence, the cell loses a part of the cytoplasm. Sweat glands are sweat-producing small tubular exocrine glands. They can be merocrine (eccrine) or apocrine sweat glands.

CONTENTS

1. Overview and Key Difference
2. What are Apocrine Sweat Glands
3. What are Merocrine Sweat Glands
4. Similarities Between Merocrine and Apocrine Sweat Glands
5. Side by Side Comparison – Merocrine vs Apocrine Sweat Glands in Tabular Form
6. Summary

What are Merocrine Sweat Glands?

Merocrine or eccrine sweat glands are the common type of sweat glands distributed throughout the body. They are simple tubular exocrine glands that secrete sweat to the surface of the skin directly. They are found in the superficial hypodermis. Therefore, they do not extend to the dermis of the skin. A specialty of the merocrine sweat glands is that these glands secrete sweat by exocytosis. Sweat contains mostly water. In addition to water, it contains sodium chloride, urea, potassium, etc. When we feel fear, anxiety or stress, merocrine sweat glands secrete more sweat. Compared to apocrine sweat glands, merocrine sweat glands are smaller and have a small secretory portion as well.

Merocrine sweat glands carry out several important functions in the human body. They are thermoregulation, protection and excretion.

What are Apocrine Sweat Glands?

Apocrine sweat glands are the second type of sweat glands. They are seen in areas of axillae (armpits), areola and nipples of the breast, ear canal, eyelids, wings of the nostril, perianal region, and some parts of the external genitalia. In the skin, they are present at the junction of the dermis and subcutaneous fat. Compared to merocrine sweat glands, apocrine sweat glands are larger and have a large secretory portion. Apocrine sweat glands secrete sweat into the pilary canal of the hair follicle without opening directly onto the surface of the skin.

Secretion of apocrine sweat glands is thicker than the sweat produced by the merocrine sweat glands. Moreover, it contains nutrients for the bacteria present on the skin. When these bacteria decompose nutrients in the sweat, it gives a characteristic odour.

What are the Similarities Between Merocrine and Apocrine Sweat Glands?

• Merocrine and apocrine sweat glands are the two types of sweat glands found in the skin.
• Both produce clear, odourless sweat.
• They are exocrine glands which are multicellular.

What is the Difference Between Merocrine and Apocrine Sweat Glands?

Merocrine sweat glands are the commonest sweat glands we have. These glands secrete sweat directly onto the surface of the skin. On the other hand, apocrine sweat glands are the type of sweat glands that are present in few numbers in certain areas of the human body. These glands secrete sweat into a sac of hair follicles rather than directly opening on to the surface of the skin. So, this is the key difference between merocrine and apocrine sweat glands.

Moreover, merocrine sweat glands produce thin clear watery sweat while apocrine sweat glands produce a thick fluid which nourishes bacteria on the skin. Furthermore, structurally, the merocrine sweat glands are smaller in size while the apocrine sweat glands are larger in size having a larger secretory portion.

The below infographic summarizes the difference between merocrine and apocrine sweat glands.

Summary – Merocrine vs Apocrine Sweat Glands

Merocrine and apocrine sweat glands are two types of sweat glands that we have. Merocrine sweat glands secrete sweat directly onto the surface of the skin. But, apocrine sweat glands secrete sweat into the sac of hair follicle rather than directly opening into the surface of the skin. Moreover, merocrine sweat glands produce clear, thin watery sweat while apocrine glands produce thick, clear fluid that provides nutrients to the bacteria on the skin. Furthermore, merocrine sweat glands are present in large numbers throughout the skin of the whole body while apocrine sweat glands are restricted to certain places and they are present in few numbers. So, this summarizes the difference between merocrine and apocrine sweat glands.

Reference:

1. Hodge, Bonnie D. “Anatomy, Skin Sweat Glands.” StatPearls [Internet]., U.S. National Library of Medicine, 5 Apr. 2019, Available here.
2. “Sweat Gland.” Wikipedia, Wikimedia Foundation, 15 Oct. 2019, Available here.

Image Courtesy:

1. “Gray940 – sweat gland” By Don Bliss (Illustrator) – This image was released by the National Cancer Institute, an agency part of the National Institutes of Health, with the ID 4362 (image) (Public Domain) via Commons Wikimedia
2. “Skin (layers, glands, vessels)” By Henry Gray – Gray’s Anatomy, Public Domain) via Commons Wikimedia