Connect a body structure to its function, from molecules to a whole person.
Begin with your hand. You can describe its shape, and you can watch it move. These are two different ways of asking about the same body part.
Read one idea at a time1 / 7
Anatomy / physiology
Anatomy asks what a part is and where it is. Physiology asks what it does and how it works.
For example
The shape of a finger bone is anatomy. How muscles bend the finger is physiology.
Read all notes for this section
Anatomy / physiology
Anatomy asks what a part is and where it is. Physiology asks what it does and how it works. The shape of a finger bone is anatomy. How muscles bend the finger is physiology.
Cell
A cell is the smallest unit that performs the basic activities of life. It has a boundary and organised contents. A muscle cell can shorten. A nerve cell can carry a signal.
Tissue
A tissue is a group of cells and surrounding material organised for a shared job. Many muscle cells together form muscle tissue.
Organ / system
An organ combines tissues into a body part. A system is a group of organs working towards related functions. The stomach is an organ. The stomach and intestines belong to the digestive system.
Two questions about one body part
Anatomy asks: what is this part, and where is it? Physiology asks: what does it do? The heart has muscular walls (anatomy). Those walls squeeze to push blood through vessels (physiology). Learn the name and the job together.
Build from small to large
Atoms are tiny building blocks of matter. They join into molecules, such as water. Molecules help make cells, the smallest living units. Cells and the material around them form tissues. Several tissues form an organ; organs cooperate in systems; all systems belong to one organism, a whole living person.
One organ, several jobs
The stomach is an organ made of several tissues. Its lining protects it, muscle mixes food, supporting tissue holds it together, and nervous tissue helps control its activity. A muscle cell and a nerve cell have different structures suited to their jobs. This specialisation is called differentiation.
Explore the illustration
Look at the whole view first. Then select one label and connect it to the idea you just read.
From molecules to a person
Follow the arrows through six levels. Each larger level contains and organises the smaller ones.
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01 / 6 Chemical level
Atoms bond into molecules. Water is one example.
Watch the sequence grow in scale: molecules → cell → tissue → organ → system → whole person. The tour changes focus; these levels do not physically transform into one another. Reduced motion is enabled. Use the arrows to study one step at a time, or choose Play.
Chemical level
Atoms join into molecules. Proteins, water and DNA are examples of molecules found in cells.
Adapted for this lesson: labels removed, artwork cropped or recoloured, and interactive teaching overlays added. Adapted artwork retains its source licence.
Go deeper
In-depth reading
Follow this example step by step, then try explaining it yourself. The extra reading is optional: you can return to it after exploring the illustration.
Worked example: why the stomach needs different tissues
Start with the job: a swallowed meal must be mixed. Muscle tissue in the stomach wall produces the movement. A single muscle cell is only one small part of that tissue.
Mixing is not the only job. The inner covering, called epithelium, helps protect the wall and produces secretions. Connective tissue supports the layers, while nervous tissue helps coordinate their activity.
Together these tissues form the stomach. The stomach then works with the intestines and other digestive organs. Follow the levels: cell → tissue → organ → system. Each step adds cooperation, not just size.
Explain it yourself
Why is the stomach an organ rather than a tissue?
Show the explanation
It combines several tissue types that work together. Muscle tissue is one component of the stomach, not the whole organ.
More detail — when you are ready
These notes expand the mechanisms and vocabulary. Read one topic at a time and find the structures in the illustration.
How structure enables function
Anatomy can be studied at several scales. Gross anatomy examines structures visible without a microscope; microscopic anatomy examines cells and tissues.
Physiology explains their activities, while pathology studies disease and pathophysiology explains disturbed function. A thin epithelial lining can support exchange; a thick muscular wall can generate force.
Start with a structure, describe its material and arrangement, and then explain what that arrangement permits. Appearance alone is not a complete account of function.
From a cell to a working organ
A cell membrane separates the cell interior from its surroundings and controls many exchanges. Organelles are small working structures inside a cell; each performs particular tasks.
Differentiation changes the structures and proteins a cell produces, enabling specialised functions. The four broad tissue families are epithelial, connective, muscular and nervous.
Epithelium is a covering or lining, like the lining inside the gut. Connective tissue supports and joins structures.
Muscle tissue contracts to generate force. Nervous tissue receives and passes on information.
An organ contains interacting tissues, not just many copies of one specialised cell.
Worked example: a meal needs several systems
Food entering the stomach is mixed by smooth muscle while the lining secretes substances and protects deeper tissues. Nerves and hormones adjust this activity.
Absorbed nutrients then depend on transport to reach distant cells, and those cells need oxygen supplied through the respiratory and cardiovascular systems. Wastes leave through several routes.
This illustrates three linked survival tasks: communication and transport, intake and waste removal, and protection. Reproduction maintains a species across generations rather than supplying a daily requirement of every individual.
Further reading — optional
Free external resources in English. Internet connection required to open the links. Choose the topic you want to explore; these readings are not required to complete the section.
Follow the negative-feedback diagram. Identify the detector, control centre and effector before reading about positive feedback.
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Sources and illustration notes
Bilingual teaching notes organised from your supplied anatomy reference pages. Medical SVG artwork is credited beneath each illustration; guided sequences and process overlays support slow, step-by-step study. Anatomy and translation await expert review.
