Exchange and Transport Flashcards
Factors affecting
exchange system
Size
SA: V ratio
Metabolic activity
How does size affect
the need for an
exchange system
In single-celled organisms, the cytoplasm is very close to its environment. Diffusion will supply enough 02 and nutrients to keep the cells alive and active In multicellular organisms have several layers of cells, so there's a longer diffusion pathway. Diffusion is too slow to enable a sufficient supply to the innermost cells
How does SA:V affect
the need for an
exchange system
When organisms have a large SA:V their SA is large enough to supply all the cells with sufficient 02 Volume increases more quickly than SA so the SA:V is smaller in larger organisms so a specialised exchange surface is needed
How does metabolic
activity affect the
need for an exchange
system
Metabolically active organisms need good supplies of 02 and nutrients to supply energy for movement and warmth so the exchange of substances need to be efficient
Features of a good
exchange surface
Large surface area achieved by folding walls and membranes Thin, permeable barrier - shorter diffusion distance Good blood supply maintain steep concentration gradient (brings molecules to supply side and removes from demand side)
How are lungs
adapted
Many alveoli - large SA:V Thin barrier - short diffusion pathway Good blood supply capillaries to carry dissolved gases to and from alveoli Ventilation refreshes air in alveoli Elastic tissue to stretch/ recoil to help expel air
Function of
goblet cells
Produce mucus
Function of cartilage
Prevent collapse
of airways
Why do the walls of
alveoli contain elastic
fibres
Expand (inhalation) to increase lung volume
Prevent alveoli bursting
Elastic fibres recoil
Inspiration
Diaphragm contracts to move down and become flat. Displaces digestive organs downwards External intercostal muscles contract moving the ribs outward and upward Volume of thorax increases Pressure in thorax < atmospheric pressure Air is drawn in through the nasal passages, trachea, bronchi and bronchioles into lungs
Thorax
Chest cavity Lined with pleural membranes - space between these membranes is the pleural cavity - usually filled with lubricating fluid
Expiration
Diaphragm relaxes and is pushed up by displaced organs underneath External intercostal muscles relax and ribs fall Volume of thorax decreases Pressure in thorax > atmospheric pressure Air is moved out of the lungs
What does the alveoli
consist of
Thin, flattened
epithelial cells alone
with some collagen
and elastic fibres
Elastic recoil
When the elastic fibres in the alveoli return to their resting size, they help squeeze the air out
What is the inner
surface of the alveoli
covered in
A thin layer of solution of water, salts and lung surfactant When 02 diffuses out of the alveoli, it first dissolves in the water before diffusing into the blood. Water can also evaporate into the air in the alveoli
Lung surfactant
Phospholipid that coats the surfaces of the lungs Without it, watery lining of alveoli would have surface tension ->collapse
Collagen in alveoli
Ensures alveoli aren’t
deformed as they
stretch (support)
Distribution and function of capillaries
Over surface of alveoli
To provide a large
surface area for
exchange
Distribution and function of cartilage
In walls of bronchi and trachea To hold the airways open and provide structural support
Distribution and
function of goblet
cells
In ciliated epithelium
To produce and
release mucus
Distribution and
function of smooth
muscle
In walls of airways
Contracts to constrict
or narrow the airways
Loose tissue
Contains elastic
fibres, glands and
blood vessels
Peak flow meter
Simple device that measures how much air can move out of (and therefore into) the lungs
Spirometer
Device that measures the movement of air in and out of the lungs as the person breathes Also measures oxygen consumption as the chamber of soda lime absorbs carbon dioxide
