B3.1 Gas Exchange human

Gas exchange definition 

Process allows organisms to obtain gases for metabolism and release its waste products.

occurs via diffusion, where gases travel from a high concentration to a low concentration until equilibrium.

gas exchange need to have a what sa:v

high

Consequences of Decreased SA:V Ratio

•  limit the rate of gas exchange and potentially hinder the cell's ability to function properly. 

Adaptations for Gas Exchange in terms of sa:v

Specialized respiratory surfaces to increase sa:v

Thin respiratory surfaces reduces the distance that gases need to diffuse, enhancing the rate of exchange.

Circulatory systems transport gases and nutrients to and from cells, compensating for the increased diffusion distances caused by a lower surface area to volume ratio.

Large organisms have evolved specialised structures to facilitate gas exchange such as 

Large SA in relation to volume of organism

Permeability to O2 and CO2

Thin tissue layer to minimise diffusion distance

Moist surface allows fo gases to dissolve

The higher the concentration gradient, the () the rate of diffusion

faster

how is a high concentration gradient maintained during gas exchange?

Dense capillary network around gas exchange surfaces

Continuous blood flow

Ventilation

With air for lungs

With water for gills

adaptations of mammalian lungs

surfactant, bronchioles, many alveol, extensive capilary network

alveoli are made of

Type I and II pneumocytes.

Type I pneumocytes

involved in the process of gas exchange between the alveoli and the capillaries

minimising diffusion distance for respiratory gases.

Type II pneumocytes

secrete alveolar fluid, which contains surfactant.

surfactant function

reduces the surface tension to prevent alveoli collapse during exhalation.

alveoli attached to where and why

ends of the bronchioles

increase sirface area forgas exchange

small diameter of bronchioles can

slows down air flow to increase efficiency

Many alveoli can

increase surface area for gas exchange

Extensive capillary network around alveoli

diffusion distance for gases is always short.

ventilation definition

movement of air into and out of alveoli through breathing

breathing depends on

inverse relationship between pressure and volume

is lung tissue muscular

no

gas moves from what to waht pressure

higher to lower

what force air into and out of the lungs

Muscles surrounding the lungs contract and the pressure changes in the thorax

muscles facilitate ventilation

Antagonistic muscles

Inhalation/inspiration

External intercostal muscles contract

Ribcage moves up and out

Diaphragm contracts

It flattens and moves downward

Volume of thorax ⇧

Pressure in thorax ⇩ (below atmospheric pressure)

Air flows into the lungs from outside until it reaches atmospheric pressure

Exhalation/expiration

Internal intercostal muscles contract

Ribcage moves down and in

Abdominals contract

Pushes diaphragm up into dome shape

Volume of thorax ⇩

Pressure in thorax ⇧ (above) atmospheric pressure)

Air flows out of the lungs from outside until it reaches atmospheric pressure

Spirometry Practical

involves measuring the amount (volume) and/or speed (flow) at which air can be inhaled or exhaled.

detects the changes in ventilation and presents the data on a digital display

Total capacity

Volume of air in the lungs after a maximal inhalation

Tidal capacity 

Volume of air that can be exchanged by the lungs via a maximal inhalation and exhalation.

residual volume

volume of air that is always present in the lungvolume

tidal volume

Volume of air that is exchanged via normal breathing

expiratory reserve volume

Additional volume of air exhaled after normal exhale

inspiratory reserve volume

Additional volume of air inhaled after normal inhale

factors affecting ventilation rate

height location lifestyle

lung condition where the walls of the alveoli lose their elasticity due to damage to the alveolar walls.

emphysema

causes of lung cancer

smoking pollution environmental factors eg radon has

Structure of an Alveolus

site of gas exchange

very thin epithelial layer (one cell thick) to minimize diffusion distances for respiratory gases.

surrounded by a rich capillary network to increase the capacity for gas exchange with the blood.

roughly spherical in shape, in order to maximize the available surface area for gas exchange.

internal surface is covered with a layer of fluid (surfactant) , as dissolved gases are better able to diffuse into the

bloodstream.