📚 GCSE CCEA Science: Human Body Key Points | GCSE CCEA 科学：人体 考点精讲
In GCSE CCEA Single Award and Double Award Science, the 'Human Body' topic explores how the major organ systems work together to keep us alive and healthy. You will need to understand the structures and functions of the digestive, circulatory, respiratory, nervous, hormonal and reproductive systems, as well as the role of homeostasis and the body's defences against disease. This revision guide breaks down every key specification point, with clear explanations in both English and Chinese, to help you succeed in your exams.
在 GCSE CCEA 单奖和双奖科学课程中，“人体”主题探讨主要器官系统如何协同工作以维持生命和健康。你需要理解消化系统、循环系统、呼吸系统、神经系统、激素系统和生殖系统的结构与功能，以及稳态的作用和人体对疾病的防御机制。这份双语复习指南逐条拆解考点，用清晰的中英文解释帮助你备考成功。
1. Organisation and Digestive System | 组织层次与消化系统
Cells are the basic building blocks of all living organisms; in humans, specialised cells group together to form tissues, tissues form organs, and organs work together in organ systems.
细胞是所有生物体的基本结构单位；在人体中，特化的细胞聚集形成组织，组织形成器官，器官再协同工作构成器官系统。
The digestive system breaks down large insoluble food molecules into small soluble molecules that can be absorbed into the blood. It includes the mouth, oesophagus, stomach, small intestine, large intestine, rectum and anus, along with associated glands such as the salivary glands, liver and pancreas.
消化系统将大分子不溶性食物分解为可溶性的小分子，以便吸收进入血液。它包括口腔、食管、胃、小肠、大肠、直肠和肛门，以及相关腺体如唾液腺、肝脏和胰腺。
Digestion involves both physical processes, like chewing in the mouth and churning in the stomach, and chemical breakdown by enzymes. Amylase in saliva begins starch digestion in the mouth; protease (pepsin) in the stomach breaks down proteins; lipase, along with bile from the liver, digests fats in the small intestine.
消化包括物理过程（如口腔咀嚼和胃的搅拌）和酶的化学分解。唾液中的淀粉酶在口腔开始消化淀粉；胃中的蛋白酶（胃蛋白酶）分解蛋白质；脂肪酶和来自肝脏的胆汁在小肠消化脂肪。
Bile is produced by the liver and stored in the gall bladder. It emulsifies fats, increasing their surface area for lipase action, and also neutralises stomach acid to create an alkaline pH suitable for enzymes in the small intestine.
胆汁由肝脏产生并储存在胆囊中。它能乳化脂肪，增大脂肪的表面积以便脂肪酶作用，同时中和胃酸，为小肠中的酶创造适宜的碱性 pH 环境。
Villi in the small intestine have a large surface area, thin walls (one cell thick), and a rich network of capillaries, which allow efficient absorption of digested products such as glucose and amino acids into the blood, and fatty acids and glycerol into the lacteal.
小肠绒毛具有巨大的表面积、薄壁（仅一层细胞）和丰富的毛细血管网，可以高效地将消化的产物如葡萄糖和氨基酸吸收到血液中，而脂肪酸和甘油则进入乳糜管。
2. Circulatory System and Blood | 循环系统与血液
The human circulatory system consists of the heart, blood vessels and blood. It is a double circulatory system: the right side pumps deoxygenated blood to the lungs (pulmonary circulation), and the left side pumps oxygenated blood to the rest of the body (systemic circulation).
人体循环系统由心脏、血管和血液组成。它是一个双循环系统：右侧将缺氧血泵入肺部（肺循环），左侧将富氧血泵往全身（体循环）。
The heart has four chambers: right atrium, right ventricle, left atrium and left ventricle. Valves prevent backflow of blood, and the septum separates oxygenated and deoxygenated blood. The heart muscle itself is supplied with blood via the coronary arteries.
心脏有四个腔室：右心房、右心室、左心房和左心室。瓣膜防止血液倒流，隔膜将富氧血和缺氧血分开。心脏自身的肌肉通过冠状动脉获得血液供应。
Arteries carry blood away from the heart. They have thick muscular and elastic walls to withstand high pressure. Veins carry blood back to the heart at low pressure and contain valves to prevent backflow. Capillaries are one-cell-thick vessels where exchange of gases, nutrients and wastes occurs at the tissues.
动脉将血液带离心脏，它们有厚实的肌肉和弹性壁以承受高压。静脉以低压将血液送回心脏，并含有瓣膜以防止回流。毛细血管是仅一层细胞厚的血管，在组织处进行气体、营养物质和废物的交换。
Blood is composed of red blood cells, white blood cells, platelets and plasma. Red blood cells contain haemoglobin which binds to oxygen in the lungs and releases it in the tissues; they have no nucleus to maximise space for haemoglobin. White blood cells are part of the immune system, platelets help blood clotting, and plasma transports dissolved substances including carbon dioxide, hormones, urea and heat.
血液由红细胞、白细胞、血小板和血浆组成。红细胞含有血红蛋白，能在肺部结合氧并在组织释放氧；它们没有细胞核以最大化血红蛋白的空间。白细胞是免疫系统的一部分，血小板帮助凝血，血浆运输溶解的物质，包括二氧化碳、激素、尿素和热量。
3. Respiratory System and Gas Exchange | 呼吸系统与气体交换
The respiratory system moves air in and out of the lungs and provides a surface for gas exchange. Air travels through the trachea, bronchi and bronchioles before reaching the alveoli, the tiny air sacs where oxygen diffuses into the blood and carbon dioxide diffuses out.
呼吸系统将空气吸入和呼出肺部，并提供气体交换的表面。空气通过气管、支气管和细支气管，最终到达肺泡。在肺泡这个微小的气囊中，氧气扩散进入血液，二氧化碳扩散出去。
Alveoli are adapted for efficient gas exchange: they have a large total surface area, thin walls (one cell thick), and are surrounded by a dense network of capillaries. They are also moist, which helps gases dissolve before diffusing. Breathing movements ventilate the lungs, maintaining a steep concentration gradient for oxygen and carbon dioxide.
肺泡适应高效气体交换：它们有巨大的总表面积、薄壁（仅一层细胞），并被密集的毛细血管网包围。肺泡表面湿润，有助于气体在扩散前溶解。呼吸运动为肺部通风，维持了氧气和二氧化碳的陡峭浓度梯度。
Inhalation is an active process where the diaphragm contracts and flattens, and the intercostal muscles contract to raise the ribcage. This increases the volume of the thoracic cavity, decreasing pressure and drawing air in. Exhalation is mainly passive: the diaphragm and intercostal muscles relax, reducing volume and increasing pressure, pushing air out.
吸气是一个主动过程：膈肌收缩变平，肋间肌收缩提升胸廓。这增大了胸腔容积，降低了压力，将空气吸入。呼气主要是被动的：膈肌和肋间肌放松，容积减小、压力升高，将空气推出。
The composition of inhaled and exhaled air differs. Exhaled air contains less oxygen (about 16% compared to 21% in inhaled air), more carbon dioxide (about 4% compared to 0.04%), and is warmer and saturated with water vapour.
吸入和呼出空气的成分不同。呼出气含氧较少（约 16%，吸入气约 21%），二氧化碳更多（约 4%，吸入气约 0.04%），并且更温暖，富含水蒸气。
4. Nervous System and Reflexes | 神经系统与反射
The nervous system detects changes in the environment (stimuli) and coordinates responses. It is made up of the central nervous system (CNS), which consists of the brain and spinal cord, and the peripheral nervous system, which comprises nerves connecting the CNS to receptors and effectors.
神经系统检测环境变化（刺激）并协调反应。它由中枢神经系统（脑和脊髓）以及周围神经系统组成，周围神经系统由连接中枢神经系统与感受器和效应器的神经构成。
Receptors are specialised cells that detect stimuli; examples include thermoreceptors in the skin for temperature, photoreceptors in the eyes for light, and chemoreceptors on the tongue for chemicals (taste). Effectors are muscles or glands that bring about a response.
感受器是检测刺激的特化细胞，例如皮肤中的温度感受器检测温度，眼中的光感受器检测光线，舌上的化学感受器检测化学物质（味道）。效应器是产生反应的肌肉或腺体。
Neurones (nerve cells) transmit electrical impulses. Sensory neurones carry impulses from receptors to the CNS; motor neurones carry impulses from the CNS to effectors; relay neurones are found within the CNS and connect sensory neurones to motor neurones. The junction between two neurones is called a synapse, where chemicals (neurotransmitters) are released to transmit the signal.
神经元（神经细胞）传递电脉冲。感觉神经元将脉冲从感受器传到中枢神经系统；运动神经元将脉冲从中枢神经系统传到效应器；中间神经元位于中枢神经系统内，连接感觉神经元和运动神经元。两个神经元之间的连接点称为突触，在此处释放化学物质（神经递质）来传递信号。
timulus → receptor → sensory neurone → relay neurone in spinal cord (or brain) → motor neurone → effector → response. Examples include pulling your hand away from a hot object and the knee-jerk reflex. Reflexes protect the body from harm.
反射是对刺激的快速、自动反应，不需要意识参与。反射弧通常遵循这条路线：刺激 → 感受器 → 感觉神经元 → 脊髓（或脑）中的中间神经元 → 运动神经元 → 效应器 → 反应。例子包括手碰到烫物时迅速缩回和膝跳反射。反射保护身体免受伤害。
5. Hormonal Control and Homeostasis | 激素控制与稳态
Hormones are chemical messengers produced by endocrine glands and transported in the blood to target organs. Compared to the nervous system, hormonal responses are slower but longer-lasting. Key glands include the pituitary (master gland), thyroid, pancreas, adrenal glands, ovaries and testes.
激素是由内分泌腺产生的化学信使，通过血液运送到靶器官。与神经系统相比，激素反应较慢但持续时间更长。主要的内分泌腺包括垂体（主腺）、甲状腺、胰腺、肾上腺、卵巢和睾丸。
Homeostasis is the maintenance of a constant internal environment, including body temperature, blood glucose level and water balance. It relies on negative feedback, where a change in a condition triggers a response that counteracts the change to restore the set point.
稳态是维持恒定内环境，包括体温、血糖水平和水分平衡。它依靠负反馈机制：某一条件的变化触发一个抵消该变化并恢复设定点的反应。
Blood glucose regulation involves the pancreas. When blood glucose rises, the pancreas releases insulin, causing liver and muscle cells to take up glucose and convert it to glycogen for storage. When blood glucose falls, the pancreas releases glucagon, which stimulates the liver to break down glycogen back into glucose. Diabetes is a condition where this control fails; Type 1 diabetes is often due to the pancreas not producing enough insulin, while Type 2 involves body cells becoming resistant to insulin.
血糖调节涉及胰腺。当血糖升高时，胰腺释放胰岛素，促使肝细胞和肌细胞摄取葡萄糖并转化为糖原储存。当血糖降低时，胰腺释放胰高血糖素，刺激肝脏将糖原分解为葡萄糖。糖尿病是这种控制机制失效的疾病；1 型糖尿病常因胰腺无法产生足够胰岛素，2 型则涉及身体细胞对胰岛素产生抵抗。
Thermoregulation keeps core body temperature around 37 °C. The thermoregulatory centre in the hypothalamus receives information from skin receptors and the blood. In response to cold, vasoconstriction of skin arterioles reduces heat loss, shivering generates heat, and hairs stand on end to trap an insulating layer of air. In response to heat, vasodilation increases blood flow to the skin, sweating increases heat loss by evaporation, and hairs lie flat.
体温调节将核心体温保持在约 37 °C。下丘脑中的体温调节中枢接收来自皮肤感受器和血液的信息。应对寒冷时，皮肤小动脉收缩减少散热，颤抖产热，毛发竖立以形成隔热空气层。应对炎热时，血管舒张增加皮肤血流量，出汗通过蒸发增加散热，毛发平伏。
6. Human Reproduction and Development | 人类生殖与发育
In males, the testes produce sperm and the hormone testosterone. Sperm travel through the sperm ducts and are mixed with fluids from the seminal vesicles and prostate gland to form semen, which is ejaculated through the urethra in the penis.
在男性体内，睾丸产生精子和激素睾酮。精子通过输精管运送，并与精囊和前列腺分泌的液体混合形成精液，经阴茎中的尿道射出。
In females, the ovaries release eggs (ova) and produce oestrogen and progesterone. Eggs travel down the oviducts to the uterus, where a fertilised egg can implant into the thick lining and grow into a foetus. The cervix is the opening to the uterus, and the vagina receives sperm during intercourse and acts as the birth canal.
在女性体内，卵巢释放卵子并产生雌激素和孕激素。卵子沿输卵管下行到达子宫，受精卵可在此处植入增厚的内膜并发育成胎儿。子宫颈是子宫的开口，阴道在性交时接收精子并作为产道。
The menstrual cycle (approximately 28 days) is controlled by hormones. FSH (follicle-stimulating hormone) from the pituitary causes an egg to mature and stimulates oestrogen production. Oestrogen causes repair of the uterine lining and triggers a surge of LH (luteinising hormone), which brings about ovulation around day 14. After ovulation, the follicle becomes the corpus luteum and releases progesterone, which maintains the uterine lining. If fertilisation does not occur, progesterone levels drop, causing menstruation.
月经周期（约 28 天）受激素控制。垂体分泌的 FSH（促卵泡激素）促使卵子成熟并刺激雌激素分泌。雌激素修复子宫内膜并引发 LH（黄体生成素）激增，在约第 14 天促使排卵。排卵后，卵泡转化为黄体并释放孕激素，维持子宫内膜。若未受精，孕激素水平下降，引发月经来潮。
Fertilisation occurs when a sperm nucleus fuses with an egg nucleus in the oviduct, forming a zygote with 46 chromosomes. The zygote divides and implants into the uterus wall, developing into an embryo and then a foetus. The placenta allows exchange of oxygen, nutrients and wastes between mother and foetus without mixing blood, and the amnion surrounds the embryo with amniotic fluid for protection.
受精发生在输卵管中，当精子核与卵子核融合，形成具有 46 条染色体的受精卵。受精卵分裂并植入子宫壁，发育成胚胎，然后成为胎儿。胎盘允许母体和胎儿之间交换氧气、营养物质和废物而不混合血液，羊膜以羊水包围胚胎提供保护。
7. Health and Disease | 健康与疾病
Health is a state of physical, mental and social well-being, not simply the absence of disease. Diseases can be communicable (infectious) or non-communicable. Communicable diseases are caused by pathogens such as bacteria, viruses, fungi and protists.
健康是身体、心理和社会适应方面的完好状态，不仅仅是没有疾病。疾病可分为传染性和非传染性。传染性疾病由病原体引起，如细菌、病毒、真菌和原生生物。
Pathogens can be spread through direct contact, airborne droplets, contaminated food and water, or vectors like mosquitoes. The body has several non-specific defence mechanisms: the skin acts as a barrier, cilia and mucus in the airways trap pathogens, stomach acid destroys many microbes, and tears contain lysozyme that kills bacteria.
病原体可通过直接接触、空气飞沫、受污染的食物和水，或如蚊子等病媒传播。身体拥有多种非特异性防御机制：皮肤作为屏障，呼吸道中的纤毛和黏液捕捉病原体，胃酸杀灭许多微生物，眼泪含有溶菌酶可以杀死细菌。
The immune system provides specific defence. White blood cells called lymphocytes produce antibodies that lock onto specific antigens on a pathogen's surface, and memory cells remain in the body to trigger a rapid response if the same pathogen invades again. Phagocytes engulf and digest foreign cells and debris by phagocytosis.
免疫系统提供特异性防御。称为淋巴白细胞产生抗体，能锁定病原体表面的特定抗原，记忆细胞留在体内，若同一病原体再次入侵可快速触发反应。吞噬细胞通过吞噬作用吞噬并消化外来细胞和碎片。
Vaccination introduces a harmless form of a pathogen (or its antigens) to stimulate the production of memory cells, providing immunity without causing the disease. This is an example of active immunity. Herd immunity occurs when a large proportion of the population is vaccinated, reducing the spread of the disease and protecting those who cannot be vaccinated.
疫苗接种引入无害形式的病原体（或其抗原），刺激记忆细胞的产生，从而在不引发疾病的情况下提供免疫力，这是主动免疫的例子。当大部分人口接种疫苗，减少疾病传播并保护无法接种的个体，就形成了群体免疫。
Non-communicable diseases are not caused by pathogens and cannot be transmitted. Examples include cardiovascular disease, type 2 diabetes, cancer and chronic respiratory diseases. Risk factors include an unhealthy diet, lack of exercise, smoking, excessive alcohol consumption and genetic predisposition. Lifestyle choices play a major role in preventing many of these conditions.
非传染性疾病不由病原体引起，不能传播。例子包括心血管疾病、2 型糖尿病、癌症和慢性呼吸系统疾病。风险因素包括不健康饮食、缺乏运动、吸烟、过量饮酒和遗传倾向。生活方式的选择对预防其中许多疾病起着重要作用。
8. Enzymes in the Body | 人体内的酶
Enzymes are biological catalysts that speed up metabolic reactions without being used up. They are proteins with a specific active site where the substrate binds, forming an enzyme-substrate complex. The 'lock and key' model describes this specificity; the induced fit model suggests the active site slightly changes shape to accommodate the substrate.
酶是生物催化剂，能加速新陈代谢反应而自身不被消耗。它们是具有特定活性位点的蛋白质，底物在此结合形成酶-底物复合物。“锁钥”模型描述了这种特异性；诱导契合模型认为活性位点会略微改变形状以适应底物。
The rate of enzyme action is affected by temperature and pH. As temperature rises, kinetic energy increases, raising the rate of collisions and reaction, up to an optimum (around 37 °C for human enzymes). Beyond the optimum, the enzyme denatures – its active site loses shape, and the substrate can no longer fit. Each enzyme also has an optimum pH; for example, pepsin works best in the acidic stomach, while amylase prefers neutral to slightly alkaline conditions.
酶的作用速率受温度和 pH 的影响。温度升高，动能增加，碰撞频率和反应速率提高，直到最适温度（人体酶约 37 °C）。超过最适点后，酶会变性——其活性位点形状改变，底物无法再契合。每种酶也有最适 pH；例如，胃蛋白酶在酸性胃液中活性最佳，而淀粉酶偏好中性至弱碱性环境。
Digestive enzymes are crucial for breaking down large food molecules. Carbohydrases (such as amylase) break down starch into simple sugars; proteases break down proteins into amino acids; lipases break down lipids into fatty acids and glycerol. These products are small and soluble, allowing absorption into the bloodstream.
消化酶对于分解大食物分子至关重要。碳水化合物酶（如淀粉酶）将淀粉分解为简单糖类；蛋白酶将蛋白质分解为氨基酸；脂肪酶将脂类分解为脂肪酸和甘油。这些产物分子小且可溶，能吸收进入血液。
9. Hormonal Coordination of Reproduction | 生殖的激素协调
Besides controlling the menstrual cycle, hormones also drive the development of secondary sexual characteristics during puberty. In males, testosterone causes growth of facial and body hair, deepening of the voice, muscle development and sperm production. In females, oestrogen stimulates breast development, widening of hips and the start of menstrual cycles.
除了控制月经周期，激素还驱动青春期第二性征的发育。在男性中，睾酮导致胡须和体毛生长、声音低沉、肌肉发育以及精子的产生。女性中，雌激素刺激乳房发育、骨盆变宽以及月经周期的开始。
Contraceptive pills usually contain synthetic oestrogen and progesterone, which inhibit FSH and LH release, preventing egg maturation and ovulation. Other hormonal methods include injections, implants and skin patches. Non-hormonal methods include barrier methods (condoms), intrauterine devices (IUDs) and sterilisation.
避孕药通常含有合成的雌激素和孕激素，能抑制 FSH 和 LH 的释放，阻止卵子成熟和排卵。其他激素方法包括注射剂、植入剂和皮肤贴片。非激素方法包括屏障法（避孕套）、宫内节育器和绝育术。
Fertility drugs may contain FSH and LH to stimulate ovulation in women who have difficulty conceiving. In vitro fertilisation (IVF) involves collecting eggs, fertilising them with sperm in a laboratory, and implanting the resulting embryo(s) into the uterus. Both treatments raise ethical considerations regarding cost, multiple births and the status of embryos.
促生育药物可能含有 FSH 和 LH，以刺激有受孕困难女性的排卵。体外受精（IVF）包括收集卵子、在实验室中用精子使其受精，并将得到的胚胎植入子宫。这两种治疗都引发了有关费用、多胎妊娠和胚胎地位的伦理考量。
10. Homeostasis: Water Balance and the Kidneys | 稳态：水平衡与肾脏
The kidneys play a vital role in homeostasis by filtering blood and regulating water and mineral salt levels, and by removing urea, a waste product produced when the liver breaks down excess amino acids. The functional unit of the kidney is the nephron.
肾脏在稳态中起着关键作用：过滤血液，调节水分和无机盐水平，并清除尿素——肝脏在分解过量氨基酸时产生的废物。肾脏的功能单位是肾单位。
In each nephron, blood is filtered under high pressure in the Bowman's capsule, pushing water, glucose, salts and urea into the tubule. Useful substances such as all glucose and some water and salts are selectively reabsorbed back into the blood in the convoluted tubules. The remaining fluid, containing excess water, salts and urea, continues to the collecting duct and forms urine.
在每个肾单位中，血液在鲍曼囊中在高压下过滤，将水、葡萄糖、盐分和尿素压入肾小管。有用的物质，如全部葡萄糖以及部分水和盐分，在曲小管中被选择性地重新吸收回血液。剩余液体含有多余的水分、盐分和尿素，进入集合管形成尿液。
The water content of the blood is controlled by the hormone ADH (antidiuretic hormone), which is released from the pituitary gland. When blood water levels are low, the hypothalamus detects this and triggers ADH release. ADH makes the collecting ducts more permeable to water, allowing more water to be reabsorbed, producing concentrated urine. When water levels are high, less ADH is released, so less water is reabsorbed, leading to dilute urine. This is another negative feedback mechanism.
血液中的水含量由垂体释放的激素 ADH（抗利尿激素）控制。当血液水含量较低时，下丘脑检测到并触发 ADH 释放。ADH 使集合管对水更通透，让更多水被重吸收，产生浓缩尿。当水含量高时，ADH 释放减少，因此重吸收的水较少，产生稀释尿液。这是又一个负反馈机制。
11. The Skeleton and Muscles | 骨骼与肌肉
The human skeleton provides support, protection for vital organs, and allows movement in conjunction with muscles. It also produces blood cells in the bone marrow and stores minerals such as calcium. The skeleton is made up of bone, which is a living tissue, and cartilage, which covers the ends of bones at joints to reduce friction.
人体骨骼提供支撑、保护重要器官，并与肌肉配合实现运动。骨骼还能在骨髓中制造血细胞，并储存钙等矿物质。骨骼由骨组织（活组织）和软骨组成，软骨覆盖在关节处的骨端以减少摩擦。
Muscles can only contract (pull); they cannot push. Therefore, they work as antagonistic pairs. For example, in the upper arm, the biceps contracts to flex the elbow, while the triceps contracts to extend it. Tendons attach muscles to bones, and ligaments attach bones to other bones at joints, maintaining stability.
肌肉只能收缩（拉），不能推。因此它们以拮抗肌的形式成对工作。例如在上臂，肱二头肌收缩使肘关节弯曲，而肱三头肌收缩使肘关节伸展。肌腱将肌肉附着于骨骼，韧带在关节处将骨与骨连接，维持稳定性。
Synovial joints, such as the knee and elbow, are freely movable joints. They have a protective layer of cartilage, synovial fluid that lubricates the joint, a synovial membrane that produces this fluid, and tough ligaments holding the bones together. The structure minimises wear and allows smooth movement.
滑膜关节（如膝关节和肘关节）是可自由活动的关节。它们具有保护性的软骨层，滑液润滑关节，滑膜产生滑液，坚韧的韧带将骨固定在一起。该结构最大限度地减少磨损，实现平稳运动。
12. Microorganisms and Defence | 微生物与防御
Microorganisms, or microbes, include bacteria, viruses, fungi and protists. Many are harmless or beneficial (e.g., gut bacteria), but some are pathogens that cause disease. Viruses are not cells; they are smaller than bacteria and can only reproduce inside a host cell, while bacteria can reproduce rapidly on their own under suitable conditions.
微生物包括细菌、病毒、真菌和原生生物。许多是无害甚至有益的（如肠道细菌），但有些是致病的病原体。病毒不是细胞；它们比细菌小，只能在宿主细胞内繁殖，而细菌可以在适宜条件下自行快速繁殖。
The body's first line of defence includes physical and chemical barriers already described. The second line of defence is the non-specific immune response involving inflammation and phagocytosis. The third line is specific immunity with antibody production and memory cells, as covered in the vaccination section.
人体的第一道防线包括前面已描述的物理和化学屏障。第二道防线是非特异性免疫反应，涉及炎症和吞噬作用。第三道防线是特异性免疫，产生抗体和记忆细胞，如疫苗接种部分所述。
Antibiotics are medicines that kill or inhibit the growth of bacteria, but they are ineffective against viruses. The misuse and overuse of antibiotics have led to the evolution of antibiotic-resistant bacteria, such as MRSA, which are much harder to treat. To slow resistance, patients should complete the full course of prescribed antibiotics and only take them when necessary.
抗生素是杀死或抑制细菌生长的药物，但对病毒无效。抗生素的滥用和过度使用导致了耐抗生素细菌（如 MRSA）的进化，这些细菌更难治疗。为减缓耐药性，患者应完成整个疗程的处方抗生素，并仅在必要时服用。
Scientists continue to research new treatments and vaccines to combat resistant pathogens and emerging diseases. Understanding the human body's systems and defence mechanisms helps us make informed decisions about personal and public health.
科学家继续研究新疗法和疫苗，以对抗耐药病原体和新出现的疾病。了解人体系统和防御机制有助于我们对个人和公共健康做出明智的决定。
Published by TutorHao | GCSE CCEA Science Revision Series | aleveler.com
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