science

Gland

Gland is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Gland rather than just read about it. In short: A gland is a cell or an organ in an animal's body that produces and secretes different substances that the organism needs, either into the bloodstream or into a body cavity or outer surface. A gland may also function to remove unwanted substances such as urine from the body.

Key takeaways

Gland belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Gland to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Gland from memory before moving on to harder problems.

Reference excerpt

A gland is a cell or an organ in an animal's body that produces and secretes different substances that the organism needs, either into the bloodstream or into a body cavity or outer surface. A gland may also function to remove unwanted substances such as urine from the body. There are two types of gland, each with a different method of secretion. Endocrine glands are ductless and secrete their products, hormones, directly into interstitial spaces to be taken up into the bloodstream. Exocrine glands secrete their products through a duct into a body cavity or outer surface. Glands are mostly composed of epithelial tissue, and typically have a supporting framework of connective tissue, and a capsule.

Structure

Development

Every gland is formed by an ingrowth from an epithelial surface. This ingrowth may in the beginning possess a tubular structure, but in other instances glands may start as a solid column of cells which subsequently becomes tubulated. As growth proceeds, the column of cells may split or give off offshoots, in which case a compound gland is formed. In many glands, the number of branches is limited, in others (salivary, pancreas) a very large structure is finally formed by repeated growth and sub-division. As a rule, the branches do not unite with one another. One exception to this rule is the liver; this occurs when a reticulated compound gland is produced. In compound glands the more typical or secretory epithelium is found forming the terminal portion of each branch, and the uniting portions form ducts and are lined with a less modified type of epithelial cell. Glands are classified according to their shape.

If the gland retains its shape as a tube throughout it is termed a tubular gland. In the second main variety of gland the secretory portion is enlarged and the lumens variously increased in size. These are termed alveolar or saccular glands.

Types of glands

Glands are divided based on their function into two groups: endocrine and exocrine.

Endocrine glands

Endocrine glands secrete substances that circulate in the blood. The glands secrete their products through basal lamina into the bloodstream. Basal lamina typically can be seen as a layer around the glands to which more than a million tiny blood vessels are attached. These glands often secrete hormones which play an important role in maintaining homeostasis. The pineal gland, thymus, pituitary gland, thyroid gland, and the two adrenal glands are all endocrine glands.

Exocrine glands

Exocrine glands secrete their products through a duct onto an outer or inner surface of the body, such as the skin or the gastrointestinal tract. Secretion is directly onto the apical surface. The glands in this group can be divided into three groups:

Merocrine glands – cells secrete their substances by exocytosis. (e.g. mucous and serous glands; also called "eccrine", e.g. major sweat glands of humans, goblet cells, salivary gland, tear gland and intestinal glands) Apocrine glands – a portion of the secreting cell's body is lost during secretion. The term Apocrine gland is often used to refer to the apocrine sweat glands, however it is thought that apocrine sweat glands may not be true apocrine glands as they may not use the apocrine method of secretion. (e.g. mammary gland, sweat gland of arm pit, pubic region, skin around anus, lips and nipples) Holocrine glands – the entire cell disintegrates to secrete its substances. (e.g. sebaceous glands: meibomian and zeis glands) Exocrine glands can further be categorized by their product:

Serous glands secrete a watery, often protein-rich, fluid-like product, e.g. sweat glands. Mucous glands secrete a viscous product, rich in carbohydrates (such as glycoproteins), e.g. goblet cells. Sebaceous glands secrete a lipid product. These glands are also known as oil glands, e.g. Fordyce spots and meibomian glands.

Clinical significance

Adenosis is any disease of a gland. The diseased gland has abnormal formation or development of glandular tissue which is sometimes tumorous.

References

External links Media related to Glands at Wikimedia Commons The dictionary definition of gland at Wiktionary

Illustrations

Worked examples

Example 1 — a first encounter with Gland

Start with the simplest possible case. Write down what Gland claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Gland before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Gland ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Gland

In research: Gland appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Gland in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Gland is common in secondary-school and first-year university syllabi. It links to neighbouring topics Glands, so understanding it makes those chapters shorter.
In everyday life: Look for Gland outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Gland in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Gland means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Gland out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Gland in simple terms?

Why does Gland matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Gland?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Gland.