Anatomy Textbooks Offline

从基础到高级学习人体解剖学

This application discusses in full about the anatomy of the human body. For those of you who want to learn, given the knowledge of the anatomy of the human body, please download this application. Human anatomy is the study of the structure of the human body, from the microscopic to the macroscopic. There are two main types of anatomy. Gross (macroscopic) anatomy is the study of anatomical structures that can be seen with the naked eye, such as the external and internal organs of the body. Microscopic anatomy is the study of small anatomical structures such as tissues and cells.

Anatomy describes the structure and location of the various components of an organism to provide a framework for understanding. Human anatomy studies the way every human part, from molecules to bones, interact to form a functional whole.

If you were a single-celled organism and you lived in a nutrient-rich place, staying alive would be pretty straightforward. For instance, if you were an amoeba living in a pond, you could absorb nutrients straight from your environment. The oxygen you would need for metabolism could diffuse in across your cell membrane, and carbon dioxide and other wastes could diffuse out. When the time came to reproduce, you could just divide yourself in two! However, odds are you are not an amoeba—given that you're using Khan Academy right now—and things aren't quite so simple for big, many-celled organisms like human beings. Your complex body has over 30 trillion cells, and most of those cells aren't in direct contact with the external environment.^11start superscript, 1, end superscript A cell deep inside your body—in one of your bones, say, or in your liver—can't get the nutrients or oxygen it needs directly from the environment. How, then, does the body nourish its cells and keep itself running? Let's take a closer look at how the organization of your amazing body makes this possible. Multicellular organisms need specialized systems Most cells in large multicellular organisms don't directly exchange substances like nutrients and wastes with the external environment, instead, they are surrounded by an internal environment of extracellular fluid—literally, fluid outside of cells.

The cells get oxygen and nutrients from this extracellular fluid and release waste products into it. Humans and other complex organisms have specialized systems that maintain the internal environment, keeping it steady and able to provide for the needs of the cells. Different systems of the body carry out different functions. For example, your digestive system is responsible for taking in and processing food, while your respiratory system—working with your circulatory system—is responsible for taking up oxygen and getting rid of carbon dioxide. The muscular and skeletal systems are crucial for movement; the reproductive system handles reproduction; and the excretory system gets rid of metabolic waste. Because of their specialization, these different systems are dependent on each other. The cells that make up the digestive, muscular, skeletal, reproductive, and excretory systems all need oxygen from the respiratory system to function, and the cells of the respiratory system—as well as all the other systems—need nutrients and must get rid of metabolic wastes. All the systems of the body work together to keep an organism up and running.