第 4 单元 - 参考

The idiom "once and for all" has roots in Middle English and can be traced back to the 14th century. It is an idiomatic expression that emerged from the combination of the individual words "once" and "for all," which have been used separately in English for much longer. This expression is used in personal situations to resolve conflicts or make firm commitments, in professional settings to establish clear guidelines or decisions, in legal matters to settle disputes conclusively, and in discussions or debates to assert a final position or settle an argument.

The origin of the phrase "sick and tired" can be traced back to the 16th century. The word "sick" in this context means weary or fed up, while "tired" means exhausted or fatigued. This idiom is used in various contexts to express profound frustration or weariness with a particular situation, person, or ongoing circumstances. This idiomatic expression is commonly used in personal conversations, informal settings, and even in written or spoken expressions of discontent.

An antibiotic is a type of medication used to treat bacterial infections by either killing bacteria or stopping their growth. Antibiotics work by targeting specific bacterial processes or structures essential for their survival, which are different from bacterial processes or structures found in human cells. They are prescribed to fight various bacterial infections such as urinary tract infections, skin infections, respiratory infections like pneumonia, and infections of the ear, throat, or sinuses.

A network refers to a group of electronic devices, such as computers, that are connected to each other to allow the sharing of data and resources. These devices can communicate with one another, enabling users to send information, access files, or use shared printers and other equipment. Networks can vary in size, from small setups in a home to large systems connecting many devices across a city or even globally. They help make tasks more efficient by allowing information to be transferred quickly between devices.

A cell is the basic structural and functional unit that forms the foundation of all living organisms. It is the smallest unit of life capable of carrying out essential processes, such as metabolism, reproduction, and responding to stimuli. Cells have specialized structures and organelles that enable them to perform specific functions, such as the nucleus containing genetic material, mitochondria producing energy, and the cell membrane regulating the exchange of substances. Together, cells make up various tissues, organs, and systems, working harmoniously to maintain the body's structure, function, and overall health.

An organ is a distinct structure composed of different types of tissues that work together to perform specific functions. Organs are vital components of the body's systems and are responsible for carrying out essential physiological processes. Examples of organs in the human body include the heart, lungs, liver, kidneys, and brain. Each organ has a unique structure and function, and their coordinated activities contribute to the overall health and homeostasis of the body. Understanding the organization and function of organs is crucial for comprehending human biology and diagnosing and treating various medical conditions.

Tissue refers to a group or collection of specialized cells that work together to perform a specific function. Tissues can be categorized into four main types: epithelial, connective, muscle, and nervous. Epithelial tissue forms protective barriers and linings, connective tissue provides support and structure, muscle tissue enables movement and contraction, and nervous tissue facilitates communication and electrical signaling. Tissues are the building blocks of organs and systems, playing a vital role in maintaining the body's structure, function, and overall homeostasis.

A gene is a segment of DNA that provides the instructions for making proteins, which are essential for the body's growth, development, and overall functioning. Genes influence traits such as eye color, blood type, and the likelihood of developing certain diseases. They are passed from parents to children and can affect how the body responds to environmental factors and treatments.

A scan is a test that uses technology to create images of the inside of the body. It helps doctors see and evaluate organs, tissues, and structures to diagnose and monitor health conditions. Different types of scans include CT scans, MRI scans, and ultrasound scans, each using different methods to produce images. The results from a scan can provide important information for diagnosing illnesses, planning treatments, and evaluating the effectiveness of ongoing treatments.