Methods of Secretion

Glands are classified as merocrine or holocrine depending on how they produce their secretions. Merocrine34 (MERR-oh-crin) glands, also called eccrine35 (EC-rin) glands, have vesicles that release their secretion by exocytosis, as described in chapter 3 (fig. 5.32a). These include the tear glands, pancreas, gastric glands, and many others. In holocrine36 glands, cells accumulate a product and then the entire cell disintegrates, so the secretion is a mixture of cell fragments and the substance the cell had synthesized prior to its disintegration (fig. 5.32b). The oil-producing glands of the scalp are an example. Holocrine secretions tend to be thicker than merocrine secretions.

1 acinus = berry

2alveol = cavity, pit

3cyto = cell + genic = producing

4mero = part + crin = to separate, secrete

6holo = whole, entire

Saladin: Anatomy & I 5. Histology I Text I I © The McGraw-Hill

Physiology: The Unity of Companies, 2003 Form and Function, Third Edition

Chapter 5 Histology 181

Compound Tubuloacinar Gland

Figure 5.31 Some Types of Exocrine Glands. Glands are simple if their ducts do not branch and compound if they do; they are tubular if they have a uniform diameter, acinar if their secretory cells are limited to saccular acini, and tubuloacinar if they have secretory cells in both the acinar and tubular regions.

Predict and sketch the appearance of a simple acinar gland.

Figure 5.31 Some Types of Exocrine Glands. Glands are simple if their ducts do not branch and compound if they do; they are tubular if they have a uniform diameter, acinar if their secretory cells are limited to saccular acini, and tubuloacinar if they have secretory cells in both the acinar and tubular regions.

Predict and sketch the appearance of a simple acinar gland.

Holocrine Glands

Figure 5.32 Modes of Exocrine Secretion. (a) A merocrine gland, which secretes its product by means of exocytosis at the apical surfaces of the secretory cells. (b) A holocrine gland, whose secretion is composed of disintegrated secretory cells. Which of these glands would require a higher rate of mitosis in its parenchymal cells?

Figure 5.32 Modes of Exocrine Secretion. (a) A merocrine gland, which secretes its product by means of exocytosis at the apical surfaces of the secretory cells. (b) A holocrine gland, whose secretion is composed of disintegrated secretory cells. Which of these glands would require a higher rate of mitosis in its parenchymal cells?

Saladin: Anatomy & I 5. Histology I Text I I © The McGraw-Hill

Physiology: The Unity of Companies, 2003 Form and Function, Third Edition

182 Part One Organization of the Body

Some glands, such as the axillary (armpit) sweat glands and mammary glands, are named apocrine37 glands from a former belief that the secretion was composed of bits of apical cytoplasm that broke away from the cell surface. Closer study showed this to be untrue; these glands are primarily merocrine in their mode of secretion. These glands are nevertheless different from other merocrine glands in function and histological appearance, and they are still referred to as apocrine glands even though their mode of secretion is not unique.

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Responses

  • Aimee-leigh
    Which of the following glands have the highest rate of mitosis in its parenchymel cells?
    8 years ago
  • FIORI ABRHA
    Which glands have secretions that have cell fragments?
    8 years ago

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