science

Hamburger–Hamilton stages

Hamburger–Hamilton stages 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 Hamburger–Hamilton stages rather than just read about it. In short: In developmental biology, the Hamburger–Hamilton stages (HH) are a series of 46 chronological stages in chick development, starting from laying of the egg and ending with a newly hatched chick. It is named for its creators, Viktor Hamburger and Howard L.

Key takeaways

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

Reference excerpt

In developmental biology, the Hamburger–Hamilton stages (HH) are a series of 46 chronological stages in chick development, starting from laying of the egg and ending with a newly hatched chick. It is named for its creators, Viktor Hamburger and Howard L. Hamilton. Chicken embryos are a useful model organism in experimental embryology for a number of reasons. Their domestication as poultry makes them more readily available than other vertebrates (such as mice), and being oviparous, the embryos are easily accessible. However, the rate of development can be affected by a range of factors; including the specific breed, the temperature of incubation, the delay between laying and incubation, and the time of year, raising the need to create a standardised system based on morphology rather than chronological age. There had been a previous attempt to create a morphological system for staging chick development by the German embryologists Keibel and Abraham in 1900, but this system lacked detail and was not widely used, with most researchers relying on somite number or age to identify the stage of development. Hamburger and Hamilton aimed to provide a detailed description of developmental events, modeled on an earlier system for Axolotl by Harrison. The Hamburger–Hamilton system provides advantages over the Carnegie system in that it allows the developing chick to be accurately characterized during all embryonic stages, and is used universally in chick embryology.

Stages of development Chick embryos can be "staged" according to the different morphological landmarks. Although most organ systems have a stereotypical appearance at each stage, there are a few which particularly lend themselves to use in staging chick development.

In the very early embryo, the primitive streak is the only visible landmark, and its shape and size are used to stage HH1-6 embryos. The nervous system is formed by a process of neurulation. Stages 5–8 may be defined by the formation of a head fold, the neural folds, and their fusion to form the neural tube. The expansion of the anterior neural tube to form the brain may also be used to identify later stages. Somitogenesis – the progressive segmentation of the paraxial mesoderm provides a convenient method for staging embryos between stages 6 and 14. Somites form with regularity every 90 minutes. Stage 10 embryos have 10 somites, and as a rule of thumb, the embryo gains 3 somites during each stage (i.e. Stage 11 embryos have 13 somites, Stage 12 embryos have 16, etc.). However, beyond 22 somites (HH14) it is better to rely on other markers. Formation of the branchial arches; which will give rise to the structures of the jaw, pharynx and larynx; begins at HH14 and is used as a marker throughout development. The morphology of the limbs, starting with the appearance of wing bud at stage 16, is a useful landmark for staging chick embryos until hatching. Between stages 15 and 35, the appearance of specific structures within the limbs (such as joints and digits); at later stages the length of the toes are used. The formation and development of the eyelids, primordial feathers and beak is used in a similar way to stage later development.

References Hamburger, V; Hamilton, HL (1951). "A series of normal stages in the development of the chick embryo". Journal of Morphology. 88 (1): 49–92. doi:10.1002/jmor.1050880104. PMID 24539719. UNSW page on Chick Development

Worked examples

Example 1 — a first encounter with Hamburger–Hamilton stages

Start with the simplest possible case. Write down what Hamburger–Hamilton stages 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 Hamburger–Hamilton stages 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 Hamburger–Hamilton stages 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 Hamburger–Hamilton stages

In research: Hamburger–Hamilton stages 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 Hamburger–Hamilton stages 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: Hamburger–Hamilton stages is common in secondary-school and first-year university syllabi. It links to neighbouring topics Embryology, Poultry, so understanding it makes those chapters shorter.
In everyday life: Look for Hamburger–Hamilton stages 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 Hamburger–Hamilton stages in 20 minutes

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

Frequently asked questions

What is Hamburger–Hamilton stages in simple terms?

Why does Hamburger–Hamilton stages 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 Hamburger–Hamilton stages?

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 Hamburger–Hamilton stages.