science

Mesonephros

Mesonephros 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 Mesonephros rather than just read about it. In short: The mesonephros (Greek: middle kidney) is one of three excretory organs that develop in vertebrates. It serves as the main excretory organ of aquatic vertebrates and as a temporary kidney in reptiles, birds, and mammals.

Key takeaways

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

Reference excerpt

The mesonephros (Greek: middle kidney) is one of three excretory organs that develop in vertebrates. It serves as the main excretory organ of aquatic vertebrates and as a temporary kidney in reptiles, birds, and mammals. The mesonephros is also known as the Wolffian body after Caspar Friedrich Wolff who described it in 1759. (The Wolffian body is composed of: mesonephros + paramesonephrotic blastema)

Structure The mesonephros acts as a structure similar to the kidney that, in humans, functions between the sixth and tenth weeks of embryonic development. Despite the similarity in structure, function, and terminology, however, the mesonephric nephrons do not form any part of the mature kidney or nephrons. In humans, the mesonephros consists of units which are similar in structure and function to nephrons of the adult kidney. Each of these consists of a glomerulus, a tuft of capillaries which arises from lateral branches of dorsal aorta and drains into the inferior cardinal vein; a Bowman's capsule, a funnel like structure which surrounds the glomerulus; and a mesonephric tubule, a tube which connects the Bowman's capsule to the mesonephric duct. A unit consisting of a single glomerulus and the Bowman's capsule surrounding it is called a renal corpuscle, and a unit consisting of single renal corpuscle with its associated mesonephric tubule is called a nephron or "excretory mesonephric unit".

Development

Mesonephric vesicle The formation of each mesonephric nephron begins when a part of the intermediate mesoderm adjacent to the mesonephric duct differentiates to form a mesonephric vesicle.

Mesonephric tubules

This vesicle then elongates to form the mesonephric tubule, attaching to the mesonephric duct on one side. Meanwhile, an artery from the dorsal aorta begins extending towards the mesonephric tubule. When these two structures contact each other, they form the glomerulus and the Bowman's capsule surrounding it. The mesonephric tubule is also known as the Wolffian tubules (or Kobelt's tubules). On the medial side of the mesonephric duct, from the sixth cervical to the third lumbar segments, a series of mesonephric tubules develop. They increase in number by outgrowths from the original tubules. They change from solid masses of cells to become hollowed in the center. One end grows toward and finally opens into the mesonephric duct, the other dilates and is invaginated by a tuft of capillary bloodvessels to form a glomerulus.

Formation The tubules collectively constitute the mesonephros.

Function The mesonephros as a whole produces urine from the 6th through the 10th week of development. Despite the similarity in structure, function, and terminology, however, the mesonephric nephrons do not form any part of the mature kidney or nephrons. As the more caudal nephrons form, the more cranial nephrons are already degenerating. In females, the mesonephros degenerates entirely, though vestigial structures such as Gartner's ducts, the epoophoron, and paroophoron are common. In males, a few of the more caudal tubules will survive and give rise to the efferent ductules of the testis, the epididymis, vas deferens, seminal vesicle, as well as vestigial structures such as the appendix testis, appendix epididymis, and paradidymis.

Other animals

The mesonephros persists and forms the anterior portion of the permanent kidneys in fish and amphibians, but in reptiles, birds, and mammals, it atrophies and for the most part disappears rapidly as the permanent kidney (metanephros) begins to develop during the sixth or seventh week. By the beginning of the fifth month of human development, only the ducts and a few of the tubules of the mesonephros remain.

Additional images

See also pronephros metanephros paramesonephric ducts, ducts beside (para-) the mesonephros

References

Illustrations

Worked examples

Example 1 — a first encounter with Mesonephros

Start with the simplest possible case. Write down what Mesonephros 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 Mesonephros 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 Mesonephros 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 Mesonephros

In research: Mesonephros 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 Mesonephros 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: Mesonephros is common in secondary-school and first-year university syllabi. It links to neighbouring topics Embryology of urogenital system, Kidney, Scrotum, so understanding it makes those chapters shorter.
In everyday life: Look for Mesonephros 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 Mesonephros in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Mesonephros 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 Mesonephros out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Mesonephros in simple terms?

Why does Mesonephros 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 Mesonephros?

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 Mesonephros.