Glands

What is a gland?

One or more cells that make and secrete an aqueous fluid called a secretion.

How are glands classified?

By site of product release and by the relative number of cells forming the gland.

What is an endocrine gland?

An internally secreting gland; for example, one that releases hormones into interstitial fluid and then blood.

What is an exocrine gland?

An externally secreting gland that uses a duct to transport secretions to an epithelial surface; sweat glands are an example.

What are unicellular glands?

Single secretory cells; goblet cells are an example.

What are multicellular glands?

Glands formed by many cells; salivary glands are an example and multicellular glands may be endocrine or exocrine.

What type of gland is a goblet cell?

A unicellular exocrine gland.

Where are goblet cells found in this module?

In the epithelium of the intestines.

What do goblet cells secrete and what does it become?

They secrete mucin, which mixes with water to form mucus.

How do multicellular epithelial glands begin to form?

By invagination, or inward growth, of an epithelial sheet.

What happens to connecting cells during exocrine-gland development?

They remain and form a duct connecting the gland to the epithelial surface.

What happens to connecting cells during endocrine-gland development?

They are lost; the gland releases hormones into interstitial fluid, and the hormones enter the blood.

What are the two main ways multicellular glands are classified?

By structure and mode of secretion.

What is the difference between a simple and compound gland?

A simple gland has an unbranched duct; a compound gland has a branched duct system.

What is an example of a simple tubular gland?

Intestinal glands.

What is an example of a simple coiled tubular gland?

Merocrine sweat glands.

What are examples of simple branched tubular glands?

Gastric glands and mucous glands of the esophagus, tongue, and duodenum.

Where is the simple alveolar (acinar) form found?

It is not found as a mature adult gland; it is a developmental stage of simple branched glands.

What is an example of a simple branched alveolar gland?

Sebaceous (oil) glands.

What are examples of compound tubular glands?

Mucous glands in the mouth, bulbourethral glands, and testes/seminiferous tubules.

What is an example of a compound alveolar (acinar) gland?

Mammary glands.

What are examples of compound tubulo-alveolar glands?

Salivary glands, glands of respiratory passages, and the pancreas.

What is merocrine secretion?

Release of product from secretory vesicles at the apical surface by exocytosis.

What is apocrine secretion?

Release involving loss of apical cytoplasm; inclusions, vesicles, and other cytoplasmic components are shed, then the cell grows and repairs itself.

What is holocrine secretion?

Superficial gland cells burst and release their cytoplasmic contents; underlying stem cells replace the lost cells by mitosis.

Which gland is shown as an example of merocrine secretion?

A salivary gland.

Which gland is shown as an example of holocrine secretion?

A sebaceous gland associated with a hair follicle.