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a walkthough

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GCSE Test Walkthrough - hormones and the Menstrual Cycle

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Label the female reproductive system

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GCSE Biology Revision: The menstrual cycle

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Complete the worksheet

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What Are Hormones | Physiology | Biology | FuseSchool

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Complete the worksheet

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Triple ONLY

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What Is Environmental Sampling? | Ecology & Environment | Biology | FuseSchool

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Insects

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Exchange surfaces

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Exchange Surfaces

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absorbing - needed for respiration - into the blood from the air

transferring - produced by respiration - from the blood into the lungs then the air

The lungs are organs enclosed within the chest or . Air needs to be breathed in to be brought into contact with the exchange surfaces within the lungs. This process is called .

The structure of the respiratory system

The lungs are enclosed in the thorax, surrounded and protected by 12 pairs of ribs. The ribs are moved by two sets of . There is a muscular below the lungs. The lungs are sealed within two airtight . These wrap around the lungs and line the rib cage.

The , or windpipe, branches into two - one bronchus to each lung. Rings of in the walls of the trachea help to keep it open as air is drawn in.

The bronchi split into smaller branches and then into smaller tubes called . Each bronchiole ends in a cluster of microscopic air sacs called .

Gaseous exchange

In cross section:

The alveoli are adapted to provide a very large surface area for gaseous exchange:

- each alveolus is a small sphere about 300 μm in diameter, giving it a larger surface area to volume ratio than larger structures

- there are around 700 million alveoli - ie 350 million per lung

The total surface area of the alveoli is around 70 square metres.

The ventilation of the lungs and the blood flow through the surrounding capillaries mean gases are being removed continually, and steep concentration gradients are set up for gases to diffuse.

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The human gas exchange system - Animal organisation - gaseous exchange systems - AQA - GCSE Biology (Single Science) Revision - AQA - BBC Bitesize

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absorbing - needed for respiration - into the blood from the air transferring - produced by respiration - from the blood into the lungs then the air The lungs are organs enclosed within the chest or . Air needs to be breathed in to be brought into contact with the exchange surfaces within the lungs.

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Organ Labels

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GCSE Biology Revision "The Heart and Circulation"

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BBC Bitesize - GCSE Biology (Single Science) - The circulatory system - Revision 1

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Learn how blood is pumped away from the heart at high pressure in arteries, and returns to the heart at low pressure in veins.

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Use the info sheets to help

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Heart diagram

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Exam Q - Mark scheme

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Complete the worksheet