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Slide 1

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Lungs and Lung Disease
Biology Unit 1…read more

Slide 2

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Structure of the human gas-
exchange system
Organisms need oxygen in order to
respire and release ATP and they
need to remove carbon dioxide
which is a waste product of
respiration. Mammals are large
organisms and have high body
temperatures so have high
metabolic rates and respiratory
rates. This means they absorb lots
of 02 and remove lots of co2.
Mammals have evolved specialised
surfaces, lungs for efficient gas
exchange. They are located inside
the body because;
Air is not dense enough to support
the delicate structure
They would lose a lot of water and
dry out.…read more

Slide 3

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Structure of the human gas-
exchange system
Rib cage ­ this protects ribs and can be moved by intercostal
muscles enabling ventilation.
Lungs ­ pair of lobed structures made up of lots of branches
Trachea ­ flexible airway supported by rings of cartilage
which prevent trachea from collapsing when air pressure falls
when inhaling. Tracheal walls are made up of muscle, lined
with ciliated epithelium and goblet cells. Goblet cells produce
mucus that traps dirt and bacteria. Cilia move mucus
containing the dirt up throat to oesophagus into stomach.
Bronchi ­ two divisions of trachea each leading to one lung.
Similar structure to trachea (cartilage + goblet cells).
Bronchioles ­ series of subdivisions of bronchi. Walls are
made of muscle lined with epithelial cells. This allows them to
constrict so they can control air flow into alveoli.
Alveoli ­ tiny air sacs at the end of bronchioles. Contain some
collagen and elastic fibre and are lined with epithelium. Elastic
fibres allow them to stretch as they fill with air and spring back
during exhale. The alveolar membrane is gas exchange surface.…read more

Slide 4

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Mechanism of Breathing
To maintain diffusion gradient air must be constantly
moved in and out of lungs, ventilation.
Inspiration (inhalation) ­ when air pressure of
atmosphere is greater than air pressure inside lungs, air is
forced into alveoli.
External intercostal muscles contract, while internal intercostal muscles
Ribs are pulled up and out increasing volume of thorax
Diaphragm contracts causing it to flatten which also increases volume of
Increased volume results in lower pressure in lungs
Atmospheric pressure is greater than pulmonary pressure so air is forced
into lungs.
Expiration (exhalation)- when air pressure in
lungs is greater than atmosphere and air is forced
Internal intercostal muscles contract, while external intercostal muscles
Ribs move down and in, decreasing volume of thorax…read more

Slide 5

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Mechanism of breathing
Pulmonary ventilation
Pulmonary ventilation(dm3 min-1) = tidal volume(dm3) x vetilation rate
(min -1)
Pulmonary ventilation is total volume of air moved into lungs
during one minute.
Tidal volume is volume of air normally taken in at each breath
when body is at rest
Ventilation rate is number of breaths taken in one minute.…read more

Slide 6

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Exchange of gases in lungs
Essential features of gas exchange surface
Large surface area to volume ratio
Thin diffusion pathway
Partially permeable ­ selected materials can
diffuse through easily
Movement of the enviromental medium e.g air
Movement of internal medium e.g blood…read more

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