Key Words

It is important that you know the meanings of all the key scientific words as this will make it easier for you to understand what quesitons are asking and you may be tested on the meanings of some of these.

Look at the words below. Do you know a meaning for each? Click/Tap on the word to check that you know the correct definition.

 

Alveoli

The smallest air sac in the lungs. There are around 700 million of these. They are the exchange surface for gases in mammals.

Alveolar sacs

Found at the end of the bronchioles. These are a collection of alveoli.

Bronchi

The main airway that carries air from the trachea into the lungs.

Bronchioles

A smaller version of the bronchi, the bronchioles get smaller and smaller until they reach the alveolar sacs.

Buccal cavity

The mouth of a fish.

Carbon dioxide

The gas that diffuses through the phospholipid bilayer of the capillary wall and into the alveoli.

Ciliated epithelium

A cell which contains cilia which move (beat) to remove mucus and any trapped particles or pathogens out of the lungs.

Counter current flow

When two fluids move in opposite directions – eg the water moves in the opposite direction of blood flow in a fish.

Diaphragm

A large dome shaped muscle found at the bottom of the lungs separating the thorax from the abdomen. This contracts and flattens to push the ribcage outwards increasing its volume.

Elastic tissue

A tissue made out of cells which can stretch and recoil.

Erythrocyte

A red blood cell.

Expiration

Another term for breathing out.

Expiratory Reserve Volume

The amount of extra air that can be breathed out above a normal breath (breathing all the way out.)

External intercostal muscles

The intercostal muscles which are used in inspiration.

Folding

A process that increases the surface area of a structure – for example root hair cells, alveoli and villi all increase surface area.

Goblet cells

Epithelial cells which release mucus to trap pathogens and any other particles which have entered the lungs

Inspiration

Another term for breathing in.

Inspiratory Reserve Volume

The amount of extra air that can be breathed in above a normal breath (taking a deep breath).

Intercostal muscles

The muscles found between the ribs. There are two sets – internal and external which move the ribs in different directions during breathing.

Internal intercostal muscles

The intercostal muscles which are used in inspiration.

Lamellae

Folds of a filament to increase the surface area – eg fish gills.

Operculum

A bony flap that covers and protects the gills.

Oxygen

The gas that diffuses through the phospholipid bilayer of the alveoli and capillary wall and into erythrocytes.

Residual volume

The volume of air which is kept inside the lungs after forced expiration. This is usually around 1.5 dm³.

Smooth muscle

A muscle which we have no voluntary control over.

Spiracle

An external opening that allows gas into or out of the tracheae in insects.

Spirometer

The equipment which is used to measure lung volume.

Squamous

A cell that is very thin, these are useful in exchange surfaces as they reduce the distance that a particle has to diffuse over.

Surfactant

A chemical which reduces the cohesive forces between the water molecules and prevent the alveoli from collapsing.

Tidal volume

The volume of air (around 0.5dm³) which is moved during normal breathing.

Trachea

The term for the windpipe. This is held open by C shaped rings of cartilage.

Tracheae

An air filled tube in an insect.

Tracheael fluid

The fluid which is found at the end of the tracheoles. Gases can diffuse into this liquid which speeds up the gaseous exchange.

Ventilation

The process of breathing.

Vital capacity

The maximum volume of air that can be moved by one big breath in the lungs (form breathing all the way out to breathing all the way in).
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