Gas exchange Flashcards
How do Microorganisms Obtain Nutrients & Remove Waste?
By exchange via their surface
Nutrients (e.g. glucose, oxygen) move in by diffusion via their surface
Waste (e.g. carbon dioxide) moves out by diffusion via their surface
Why are Microorganisms able to perform exchange via their surface?
Have a large surface area to volume ratio
Have a short diffusion distance
Have low demand
Why can’t Animals/Plants perform exchange via their surface?
Have a small surface area to volume ratio
Multicellular (large diffusion distance and high demand)
Impermeable surface (prevent pathogens entering and reduce water loss)
Therefore, require specialised Exchange & Transport systems
Exchange system
Increases the rate of diffusion of nutrients in and wastes out
Transport system
Deliver nutrients and remove waste from all cells
Why do Fish have Specialised Gas Exchange Systems?
Multicellular organism so has a small surface area to volume ratio, large diffusion distance, high demand & body surface impermeable
Therefore, cannot perform gas exchange (O2 in/CO2 out) via their surface, they require a specialised gas exchange system called Gills
Structure of Gills in Fish
Many gill filaments and gill lamellae = large surface area
Gill lamellae have a thin wall (short diffusion distance) and are permeable
Ventilation brings in pure water (high oxygen, low carbon dioxide) and circulation brings in deoxygenated blood (low oxygen, high carbon dioxide), the water and blood pass over in opposite directions (countercurrent flow), which maintains a concentration gradient all the way along the gill lamellae
Why do Insects have Specialised Gas Exchange Systems?
Multicellular organism so has a small surface area to volume ratio, large diffusion distance, high demand & body surface made of exoskeleton (impermeable barrier to reduce water loss)
Therefore, cannot perform gas exchange (O2 in/CO2 out) via their surface, they require a specialised gas exchange system called Tracheal System
Structure of Tracheal System in Insects
Starts with openings on body surface called Spiracles
Spiracles contain valves, open = gas exchange, closed = prevent water loss
Spiracles connect to Trachea
Trachea connects to Tracheoles
Tracheoles connect directly to Respiring Cells (delivering oxygen, removing carbon dioxide)
How does Gas Exchange occur in Tracheal System of Insects?
at rest = down a concentration gradient, oxygen moves in & carbon dioxide moves out by simple diffusion
when active = by ventilation, air inhaled for mass flow of O2 in & air exhaled for mass flow of CO2 out
Function of Lungs
Site of gas exchange in mammals (oxygen into blood – used in cells for respiration,
carbon dioxide out of the blood – the toxic waste product of respiration)
What are Lungs made up of?
Trachea, Bronchi, Bronchioles, Alveoli (+ capillaries)
The function of trachea, bronchi, bronchioles
Transport of air and filter air, (bronchioles also controls the amount of air reaching alveoli)
Structure of trachea/bronchi
Wall made of c-shaped cartilage
Cartilage is strong so trachea/bronchi do not collapse
cartilage is c-shaped to give flexibility
lining made of goblet cells and ciliated epithelial cells
goblet cells make mucus, which traps pathogens/particles
ciliated epithelial cells have cilia, which push mucus up and out of the lungs
Structure of bronchioles
Wall made of smooth muscle
smooth muscle contracts, lumen narrows, bronchiole constricts
(occurs when surrounded by noxious gases – reduces amount reaching alveoli)
lining made of goblet cells and ciliated epithelial cells
Adaptation of alveoli
Millions of tiny alveoli that are folded (large surface area)
Thin wall/one cell thick/squamous epithelial cells (short diffusion distance)
Elastic tissue in wall (stretches when breathing in to increase surface area, recoils when breathing out to push the air out)
Ventilation maintains concentration gradient (high oxygen, low carbon dioxide)
Adaptation of capillaries
Millions of tiny capillaries (large surface area)
Thin wall/one cell thick/squamous epithelial cells (short diffusion distance)
Narrow lumen (increases diffusion time, decreases diffusion distance)
Circulation maintains concentration gradient (low oxygen, high carbon dioxide)
How O2 moves from the alveoli to the capillaries?
By simple diffusion passing thru the alveolar epithelium and capillary epithelium
How CO2 moves from capillaries to the alveoli?
By simple diffusion passing thru the capillary epithelium and alveoli epithelium
Describe the process of Breathing/Ventilation
Breathing In/Inhalation = external intercostal muscles contract (rib cage moves up and out) & diaphragm contracts (flattens), therefore increase in volume in chest and decrease in pressure, so air moves in
Breathing Out/Exhalation = external intercostal muscle relax (rib cage moves down and in) & diaphragm relaxes (back to dome shape), therefore decrease in volume in chest and increase in pressure, so air pushed out (aided by elastic recoil in the alveoli)
The formula for Pulmonary Ventilation
PV = tidal volume x ventilation rate
Tidal volume = volume of air breathed in/out in one breath
Ventilation rate = number of breaths per minute
Pulmonary Ventilation = volume of air breathed in/out per minute
