KS3 CIE Lungs Structure Mark Scheme | KS3 CIE 肺部结构评分标准

📚 KS3 CIE Lungs Structure Mark Scheme | KS3 CIE 肺部结构评分标准

Understanding the structure of the lungs is a core topic in the KS3 CIE Biology curriculum. This guide breaks down every structure you must know, explains how examiners award marks, and highlights the exact phrases that earn full credit in mark schemes.

理解肺部结构是 KS3 CIE 生物课程的核心内容。本指南将逐一解析你必须掌握的每一个结构，说明考官如何给分，并指出在评分标准中能够获得满分的准确表述。

1. Overview of the Respiratory System | 呼吸系统概述

The respiratory system is the set of organs that allows gas exchange between the body and the environment. Oxygen enters the bloodstream, while carbon dioxide is removed from it. In the CIE mark scheme, when asked to ‘name the main organs of the respiratory system’, the expected answers are: lungs, trachea, bronchi, bronchioles, diaphragm and ribcage.

呼吸系统是使身体与环境之间进行气体交换的一组器官。氧气进入血液，二氧化碳被排出体外。在 CIE 评分标准中，当题目要求”说出呼吸系统的主要器官”时，预期答案为：肺、气管、支气管、细支气管、膈肌和肋骨笼。

Trachea → Bronchi → Bronchioles → Alveoli

This is the exact order of air flow. Examiners award one mark for each correctly named structure, and a further mark for the correct sequence.

这是空气流动的准确顺序。考官对每个正确命名的结构给一分，对正确的顺序额外给一分。

2. The Trachea | 气管

The trachea, commonly called the windpipe, is a tube that carries air from the nose and mouth down towards the lungs. It is supported by C-shaped rings of cartilage that keep it open at all times.

气管，通常称为风管，是将空气从鼻和口输送至肺部的管道。它由 C 形软骨环支撑，确保气道始终保持畅通。

Key mark scheme points for the trachea:

关于气管的关键评分要点：

It is supported by cartilage rings — this prevents collapse when air pressure changes during breathing.
It is lined with ciliated cells and mucus-producing goblet cells — these trap dust and bacteria and move them upwards to be swallowed.
It divides into two bronchi at its lower end.

由软骨环支撑——防止呼吸时气压变化导致气管塌陷。
内壁衬有纤毛细胞和产生粘液的杯状细胞——这些细胞捕获灰尘和细菌，并将其向上推动以便吞咽。
其下端分支为两条支气管。

Cartilage rings ≠ bone. Examiners penalise ‘bone’ as it is not a correct scientific description.

软骨环 ≠ 骨骼。考官会因写成”骨骼”而扣分，因为这不是正确的科学描述。

3. The Bronchi and Bronchioles | 支气管与细支气管

The trachea splits into two bronchi (singular: bronchus), one entering each lung. Inside the lungs, each bronchus branches into many smaller tubes called bronchioles.

气管分成两条支气管（单数形式为 bronchus），分别进入左右肺。在肺内部，每条支气管分成许多更细小的管道，称为细支气管。

Mark scheme expectations for bronchi and bronchioles:

评分标准对支气管和细支气管的要求：

Structure	Key feature examiners reward	结构	考官给分的关键特征
Bronchus	Contains cartilage, carries air into each lung	支气管	含有软骨，将空气送入每侧肺
Bronchiole	Smaller branches, no cartilage, lead to alveoli	细支气管	更细的分支，无软骨，通向肺泡

A common CIE mark scheme phrase is ‘the bronchioles end in tiny air sacs called alveoli’. Note the spelling — ‘alveoli’ is plural, ‘alveolus’ is singular. Misspelling can lose a mark.

CIE 评分标准中常见表述为”细支气管末端是称为肺泡的微小气囊”。注意拼写——alveoli 是复数形式，alveolus 是单数形式。拼写错误可能会丢分。

4. The Alveoli: Site of Gas Exchange | 肺泡：气体交换的场所

The alveoli are tiny, balloon-like air sacs at the end of the bronchioles. They are the functional units of the lungs where oxygen enters the blood and carbon dioxide leaves it.

肺泡是细支气管末端微小气球状的气囊。它们是肺的功能单位，氧气在此进入血液，二氧化碳在此离开血液。

Examiners look for specific structural adaptations of alveoli. The six most commonly credited points are:

考官关注肺泡的具体结构适应性。最常见的六个得分点如下：

Large surface area — many alveoli provide a huge total surface for diffusion.
Thin walls — only one cell thick, so diffusion distance is very short.
Rich blood supply — maintains a steep concentration gradient.
Moist inner lining — allows gases to dissolve before diffusing.
Permeable walls — allow oxygen and carbon dioxide to pass through freely.
Close contact with capillaries — minimises the distance gases must travel.

巨大的表面积——众多肺泡提供了极大的总扩散面积。
薄壁——仅一层细胞厚，扩散距离非常短。
丰富的血液供应——维持陡峭的浓度梯度。
湿润的内壁——气体在扩散前能够溶解。
可渗透的壁——允许氧气和二氧化碳自由通过。
与毛细血管紧密接触——最大限度地缩短气体运输距离。

5. The Diaphragm | 膈肌

The diaphragm is a dome-shaped sheet of muscle located at the base of the chest cavity. It separates the thorax from the abdomen and plays an essential role in ventilation.

膈肌是位于胸腔底部穹顶状的肌肉片。它将胸腔与腹腔分隔开来，在通气过程中发挥重要作用。

In mark schemes, the diaphragm is described as moving downwards and flattening during inhalation, and moving upwards and becoming dome-shaped again during exhalation.

在评分标准中，膈肌被描述为吸气时向下移动并变平坦，呼气时向上移动并恢复穹顶状。

Process	Diaphragm movement	Volume of chest cavity	过程	膈肌运动	胸腔容积
Inhalation	Contracts, flattens, moves down	Increases	吸气	收缩、变平、向下移动	增大
Exhalation	Relaxes, becomes dome-shaped, moves up	Decreases	呼气	舒张、恢复穹顶状、向上移动	减小

Note that in CIE mark schemes, the word ‘contracts’ for the diaphragm is often credited, but ‘flattens’ is the most precise descriptor. A common examiner comment is: ‘Candidates who wrote “the diaphragm goes down” without mentioning flattening were not awarded the full mark.’

请注意，在 CIE 评分标准中，膈肌”收缩”一词通常可以得分，但”变平坦”是最精确的描述。考官的常见评语是：”只写’膈肌下降’而未提及变平的考生，无法获得满分。”

6. The Intercostal Muscles and Ribcage | 肋间肌与肋骨笼

The intercostal muscles are located between the ribs. They work with the diaphragm to change the volume of the chest cavity during breathing.

肋间肌位于肋骨之间。它们与膈肌协同工作，在呼吸过程中改变胸腔容积。

Ventilation involves two sets of intercostal muscles. The external intercostal muscles contract during inhalation, pulling the ribs upwards and outwards. The internal intercostal muscles contract during forced exhalation, pulling the ribs downwards and inwards.

通气涉及两组肋间肌。吸气时，肋间外肌收缩，将肋骨向上向外拉动。用力呼气时，肋间内肌收缩，将肋骨向下向内拉动。

Mark scheme phrase: ‘The ribs move up and out and the diaphragm flattens, so the volume of the thorax increases. This decreases the pressure inside the thorax, so air flows in.’

评分标准表述：”肋骨向上向外移动，膈肌变平，因此胸腔容积增大。这使得胸腔内压力降低，空气随之流入。”

Air moves because of a pressure difference — NOT because the lungs ‘suck air in’.

空气因压力差而流动——而不是因为肺”吸入空气”。

7. The Pleura | 胸膜

The pleura is a double-layered membrane that surrounds each lung. Between the two layers is a thin layer of pleural fluid.

胸膜是包裹每侧肺的双层膜。两层之间有一薄层胸膜液。

Exam questions on the pleura at KS3 level usually ask for its function. The credited answer is:

KS3 阶段关于胸膜的考试题目通常要求说明其功能。可获分的答案是：

The pleural fluid reduces friction between the lungs and the chest wall during breathing movements.
The pleura protects the lungs and helps maintain their shape.

胸膜液在呼吸运动中减少肺与胸壁之间的摩擦。
胸膜保护肺并帮助维持其形状。

Some students confuse ‘pleura’ with ‘diaphragm’. Remember: the pleura is a membrane around the lung; the diaphragm is a muscle below the lungs.

一些学生将 pleura（胸膜）与 diaphragm（膈肌）混淆。请记住：胸膜是包裹肺的膜；膈肌是肺下方的肌肉。

8. Gaseous Exchange in the Alveoli | 肺泡中的气体交换

Gaseous exchange in the alveoli occurs by diffusion. Oxygen diffuses from the alveolus, where its concentration is high, into the blood, where its concentration is low. Carbon dioxide diffuses in the opposite direction.

肺泡中的气体交换通过扩散进行。氧气从浓度高的肺泡扩散到浓度低的血液中。二氧化碳则沿相反方向扩散。

O₂ (high in alveolus) → O₂ (low in blood)

CO₂ (high in blood) → CO₂ (low in alveolus)

氧气（肺泡中高）→ 氧气（血液中低）

二氧化碳（血液中高）→ 二氧化碳（肺泡中低）

For a full mark in CIE questions, you must mention all three of the following: (1) diffusion, (2) the direction of movement for each gas, and (3) the concentration gradient as the driving force.

要在 CIE 题目中获得满分，你必须提及以下三点：(1) 扩散；(2) 每种气体的移动方向；(3) 作为驱动力的浓度梯度。

9. Diffusion: Key Definition and Conditions | 扩散：关键定义与条件

Diffusion is the net movement of particles from a region of higher concentration to a region of lower concentration. This process is passive — it requires no energy.

扩散是粒子从高浓度区域到低浓度区域的净移动。该过程是被动的——不需要能量。

The rate of diffusion depends on three main factors:

扩散速率取决于三个主要因素：

Concentration gradient — the steeper the gradient, the faster the rate.
Distance — the shorter the distance, the faster the rate.
Surface area — the larger the surface area, the faster the rate.

浓度梯度——梯度越陡，速率越快。
距离——距离越短，速率越快。
表面积——表面积越大，速率越快。

In the mark scheme, students are expected to state that the alveoli are adapted to make diffusion fast and efficient, and then list the specific adaptations described in Section 4.

在评分标准中，学生需要说明肺泡的结构适应性使扩散快速高效，然后列举第 4 节中描述的具体适应性特征。

10. Common Mark Scheme Errors to Avoid | 应避免的常见评分标准错误

KS3 examiners repeatedly report the same mistakes. Avoid these to secure every available mark:

KS3 考官反复报告相同的错误。避免以下错误以确保获得每一分：

Wrong statement (no mark)	Correct statement (mark awarded)	错误表述（不得分）	正确表述（得分）
Air ‘sucks’ into the lungs	Air moves in because pressure inside is lower than outside	空气被”吸入”肺内	空气进入是因为肺内压力低于外界压力
Oxygen ‘goes into’ the blood	Oxygen diffuses across the alveolar wall into the blood	氧气”进入”血液	氧气通过扩散穿过肺泡壁进入血液
The diaphragm is made of bone	The diaphragm is a sheet of muscle	膈肌由骨骼构成	膈肌是一层肌肉

Spelling also matters. Common misspellings that lose marks include: ‘alvioli’ instead of ‘alveoli’, ‘brochi’ instead of ‘bronchi’, and ‘diaphram’ instead of ‘diaphragm’.

拼写同样重要。常见导致丢分的拼写错误包括：将 alveoli 误写为 alvioli，将 bronchi 误写为 brochi，将 diaphragm 误写为 diaphram。

11. Practice Questions with Mark Scheme | 练习题目与评分标准

Question 1: Name the pathway that air takes from the nose to the alveoli. (3 marks)

问题 1：说出空气从鼻腔到达肺泡的通路。（3 分）

Mark scheme: Trachea (1); bronchi/bronchus (1); bronchioles (1). Full marks require all three in the correct order.

评分标准：气管（1 分）；支气管（1 分）；细支气管（1 分）。满分要求三者按正确顺序写出。

Question 2: State two ways in which the alveoli are adapted for gas exchange. (2 marks)

问题 2：说出肺泡适应气体交换的两种方式。（2 分）

Mark scheme: Any two from: large surface area (1); thin walls / one cell thick (1); rich blood supply (1); moist lining (1); close contact with capillaries (1).

评分标准：以下任意两项：巨大的表面积（1 分）；薄壁／一层细胞厚（1 分）；丰富的血液供应（1 分）；湿润的内壁（1 分）；与毛细血管紧密接触（1 分）。

Question 3: Explain why air enters the lungs during inhalation. (3 marks)

问题 3：解释吸气时空气为何进入肺部。（3 分）

Mark scheme: Diaphragm contracts and flattens (1); volume of chest cavity increases (1); pressure decreases below atmospheric pressure, so air moves in (1).

评分标准：膈肌收缩并变平（1 分）；胸腔容积增大（1 分）；压力降至大气压以下，因此空气进入（1 分）。

12. Revision Summary | 复习总结

To score maximum marks on lung structure questions, remember the acronym ‘T-B-B-A’: Trachea, Bronchi, Bronchioles, Alveoli — the precise air pathway. Always pair structure with function. For every structure you name, ask yourself: what does it do, and how is it adapted for that role?

要在肺部结构题目中获得最高分，请记住首字母缩略词 T-B-B-A：Trachea（气管）、Bronchi（支气管）、Bronchioles（细支气管）、Alveoli（肺泡）——这是精确的空气通路。始终将结构与功能配对。每说出一个结构，就问自己：它的功能是什么？它如何适应这一功能？

Use the exact vocabulary of the mark scheme: ‘diffusion’, ‘concentration gradient’, ‘flattens’, ‘volume increases’, ‘pressure decreases’. These are the words examiners look for. Scientific precision earns marks; vague everyday language loses them.

使用评分标准中的精确词汇：”扩散”、”浓度梯度”、”变平”、”容积增大”、”压力降低”。这些是考官寻找的关键词。科学精确的语言得分；模糊的日常用语丢分。

With these structures memorised and these mark scheme phrases mastered, you are fully prepared for any KS3 CIE lung structure question.

牢记这些结构并掌握这些评分标准表述，你已为任何 KS3 CIE 肺部结构题目做好充分准备。

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KS3 CIE Lungs Structure Mark Scheme | KS3 CIE 肺部结构评分标准