Exchange and Transport Flashcards
what are the reasons for gas exchange?
- because multicellular organisms have a small SA:V ratio, cells in the centre of the organism would not receive any materials if multicellular organisms survived on diffusion alone as they have too big of a diffusion distance.
- multicellular organisms have a high metabolic rate so gas exchange systems are needed
what are the features of efficient gas exchange?
- large surface area to maximise rate of diffusion
- good blood supply (to maintain a steep concentration gradient)
- thin cells (short diffusion distance)
- ventilation (maintains the diffusion gradient)
- moist surfaces (allows gases to dissolve and diffuse more easily and stops walls of alveoli from sticking together
what are examples of good exchange surfaces?
alveoli, villi, root hair cell
what are the four main body parts involved in the human gas exchange system?
nasal cavity, trachea, bronchi, bronchioles and alveoli
adaptations of the nasal cavity function
large surface area and good blood supply - this warms the air as it passes the body
hairy lining - hairs trap dust and bacteria in mucus and prevent them from reaching the lungs
moist surfaces - increases the humidity of the incoming air, this reduces the evaporation of water in the lungs
adaptations of the trachea
this pipe is supported by a layer of cartilage that holds the trachea open and prevents it from collapsing
the rings are incomplete to allow it to bend when food is swallowed in the oesophagus behind
the trachea is lined with ciliated epithelial and goblet cells (produces mucus) to prevent dust and bacteria from entering
adaptations of the bronchi
extensions of the trachea that split into two for the left and right lung
cartilage rings hold the airway open
smooth muscle can contract or relax to constrict or dilate the airway and change airflow.
adaptations of the bronchioles
they have no cartilage so they can change shape
the walls of the bronchioles are lined with a layer of smooth muscle to alter the diameter of the bronchiole tubes.
This helps to regulate the flow of air into the lungs by dilating when more air is needed and constricting when e.g. an allergen is present.
adaptations of the alveoli
made up of a thin layer of flattened epithelial cells as well as collagen and elastic fibres
the elastic fibres cause recoil which helps move air out of the alveoli
the thin cell walls create a short diffusion distance
moist surface so the gases can dissolve and then diffuse more quickly
The constant flow of blood through the capillaries means that oxygenated blood is brought away from the alveoli and deoxygenated blood is brought to them
This maintains the concentration gradient necessary for gas exchange to occur
The large number of alveoli increases the surface area available for oxygen and carbon dioxide to diffuse across
what causes ventilation in mammals?
pressure changes in the thoracic cavity bring about ventilation
what are the scientific names for inhalation and exhalation?
inspiration and expiration
explain the process of inspiration
it’s an active process (so requires energy)
1) diaphragm contracts (moves down)
2) external intercostal muscles contract (causing ribcage to move up and out)
3) the thoracic volume increases
4) the thoracic pressure decreases
5) air flow into lungs which equalises the pressure difference
explain the process of expiration
passive process (so doesn’t require energy)
1) diaphragm relaxes (moves up)
2) external intercostal muscles relax (causing ribcage to move down and in)
3) the thoracic volume decreases
4) the thoracic pressure increases
5) air flow out of lungs
what is a spirometer?
measures volume of gas breathed in and out in different conditions
-the static lower half of tank is full of water
-mobile upper half of tank is full of oxygen
-breathe out into the tank and the upper half will rise
-breathe in from the tank and the upper half will fall
-trace marker (pencil) is attached to the mobile upper half
how to read a spirometer graph?
-when inspiring the trace will be going downwards
-when expiring, the trace will climb up
-the peak of expiration to low of inspiration shows the volume of a single breath
tidal volume definition
the volume of air that moves into and out of the lungs with each resting breath
- 15% of the vital capacity
- 0.5 dm^3 in an average adult
vital capacity definition
the largest volume of air that can be breathed in
- when the strongest exhale is followed by the strongest possible inhale
- 5dm^3 in an average adult
inspiratory reserve volume definition
the maximum volume of air you can breathe in over and above normal inhalation
expiratory reserve volume definition
maximum volume of air you can force out of your lungs over and above the normal tidal volume of air you breathe out
residual volume definition
the volume of air that is left in your lungs when you have exhaled as hard as possible
- cannot be directly measured
- we need a residual volume because otherwise, the lungs would collapse and the alveoli would stick together
total lung capacity
the sum of the vital capacity and the residual volume
- the total amount of air in the lungs at any one time
what is the formula for ventilation rate?
ventilation rate = tidal volume x breathing rate
What are the characteristics of gaseous exchange systems in insects?
Insects have a tough exoskeleton that prevents simple diffusion.
They use a tracheal system with spiracles to transport oxygen directly to cells.
They don’t rely on blood pigments like haemoglobin to carry oxygen.
How does gas exchange occur in insects?
they have a tracheal system which supplies air directly to the respiring tissues. air enters via a spiracle and it is transported into the body through trachea, which divide into smaller tubes called tracheoles. the ends of the tracheoles are open and filled with tracheal fluid. gas exchange happens between the air in the tracheole and the tracheal fluid.
What is the role of the tracheoles in insects?
Tracheoles have thin, permeable walls for effective gas exchange.
They provide a large surface area for diffusion.
Oxygen dissolves in fluid at the tracheole ends and diffuses into cells.
what happens to gas exchange when the insects are active?
the tracheal fluid can be withdrawn into the body fluid in order to increase the surface area of the tracheole wall exposed to air so that more oxygen can be absorbed when the insect is active
What adaptations do some insects (e.g. locusts) have for higher oxygen demands?
Mechanical ventilation: Active pumping of the thorax to draw air in.
Collapsible air sacs: Store extra air to increase oxygen supply.
movement of wings alter the volume of the thorax. as the thorax volume decreases, air is put under pressure and is pushed out of the tracheal system. vice versa for when the thorax volume increases
What is the primary function of gills in bony fish?
To facilitate gas exchange by absorbing oxygen from water and releasing carbon dioxide.
What is the structure that covers and protects the gills in bony fish?
The operculum.
Describe the structure of gill filaments.
Gill filaments are thin structures attached to a bony arch, with many secondary lamellae that increase the surface area for gas exchange.
What mechanism allows bony fish to maximise oxygen absorption from water?
Countercurrent flow, where blood flows in the opposite direction to water passing over the gills.
Explain how the buccal-opercular pump helps bony fish with ventilation.
The fish moves the floor of its mouth downward to draw water in, then raises it to push water through the gills, while the operculum movements coordinate to maintain water flow.
What is the role of secondary lamellae in gills?
They provide a large surface area for blood capillaries to facilitate efficient gas exchange.
How does the operculum reduce pressure in the opercular cavity?
By moving outward, it helps water flow through the gills.
What is countercurrent flow in the context of bony fish?
Countercurrent flow is when water flows over the gills in the opposite direction to the flow of blood in the capillaries.
Why is countercurrent flow advantageous for bony fish?
It maintains a steep concentration gradient across the entire gill, allowing maximum oxygen diffusion from water into the blood.
How does countercurrent flow maximise oxygen absorption?
Blood with a lower oxygen concentration meets water with a higher oxygen concentration, ensuring continuous diffusion of oxygen into the blood.
What would happen if bony fish used parallel flow instead of countercurrent flow?
Oxygen diffusion would stop once equilibrium is reached, resulting in less efficient oxygen absorption.
