Alveolar vs. Tubular Glands: Definition, Shapes & Examples

Lesson Transcript
Instructor: Sarah Phenix
In this lesson, we will explore what a gland is and the function that it performs. We'll also look at the many varied shapes that the tubular and alveolar structures take.

Understanding Glands

I'm sure you probably don't think of glands in your everyday life. In fact, some of you may even be thinking, 'Glands, what are those? Aren't those the things that swell when you get sick?' You would be right but those aren't the only type of glands in your body, and they do so much more than just swell when you get sick! They're responsible for everything from excreting sweat and tears to hormones and digestive enzymes. And, just to keep things interesting, they come in a few different shapes.

So, what's a gland? Glands are a collection of cells or an organ responsible for secretions and excretions. Secretion refers to the act of a substance moving internally from one part of your body to another, like when the lining of your stomach secretes digestive juices. Excretion describes how a substance leaves the body, such as when tears excrete from your tear ducts or sweat excretes from your sweat glands. Okay, so, now that we know what a gland is, let's explore some tubular and alveolar glands.

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  • 0:00 Understanding Glands
  • 1:02 Gland Shapes
  • 1:43 Simple Glands
  • 3:41 Compound Glands
  • 5:09 Lesson Summary
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Gland Shapes

gland shapes

The glands in our bodies come in three overarching shapes. Acinar, meaning 'grape,' are ducts that have a large, bulbous collection of secretory and excretory cells within a small lumen, or interior space. They look something like a cluster of grapes in the body, hence their name. Tubular glands have cells of a consistent shape that form a uniform tubular lumen, while alveolar glands have cells of a similarly uniform size within a large, sac-like lumen. Tubular and alveolar glands can be further subdivided by their shape into simple, or non-branching glands, and compound, or branching glands.

Simple Glands

Thankfully, the terminology for these glands is fairly self-explanatory, which should make them relatively easy to remember. Simple glands are exactly what you would think of in relation to shape: they have a simple straight duct, or opening, that connects the secretory and excretory cells, and where the exterior of the tissue is straight, without any complex branching systems. Tubular glands come in three simple shapes: simple tubular, simple coiled tubular, and simple branched tubular. Alveolar glands only have two simple shapes: simple alveolar and simple branched alveolar. Let's take a quick look at what these glands look like and where they might be found in the body.

simple glands

Simple tubular glands are one of more uncommon shapes that, in a cross section, simply look like a straight test tube submerged in the tissue. These glands are found in the lining of the intestines, where they secrete mucous to help the byproducts of digestion pass through the intestinal tract.

Simple coiled tubular glands are like coiled tubes. They basically look like a garden hose tangled or coiled around itself at one end. The sweat glands in your skin are simple coiled tubular glands.

Simple branched tubular glands have a straight duct opening with branched clusters of secretory glands. They include the gastric glands of your stomach that produce acid, as well as the mucous secreting glands lining your esophagus, tongue, and duodenum of your small intestines.

Simple alveolar glands have a simple duct and a sac-like base. They are found in the paraurethral and periruethral glands of the urethra.

Simple branched alveolar glands have a simple duct and branched alveolar sacs. The oil-producing sebaceous glands in your skin, as well as the mucous secreting glands in your stomach that protect your stomach lining from the highly acidic gastric juices, are both examples of simple branched alveolar glands.

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