B3.1 Gas Exchange Flashcards
Define gas exchange.
The exchange of oxygen and carbon dioxide between the alveoli and bloodstream
State the role of diffusion in gas exchange.
Gas exchange occurs via diffusion - the random net movement of particles from an area of higher conc. to an area of lower conc. leading to equilibrium (an equal distribution of particles)
Explain the need for structures of larger organisms to maintain a large enough surface area for gas exchange.
As organisms increase in size, the SA:V ratio decreases thus, there is a greater need for specialised structures to facilitate efficient gas exchange having properties such as: being highly folded, branched, in structure, increasing the SA available across which gases can be exchanged.
- The larger the organism, the smaller the SA:V ratio, the greater the distance betw. the surface of the organism and the cells in the interior thus, rate of diffusion decreases.
Outline the function of the following properties of gas-exchange surfaces: permeability, thin tissue layer, moisture and large surface area.
- Permeability: The exchange surface must have pores allowing gases to be exchanged across its surface
- Thin Tissue Layer: provides a short distance across which gases need to move
- Moisture: helps dissolve gases before they diffuse across the exchange surface
- Large SA: more membrane surface available for gases to diffuse across
State the reason why concentration gradients must be maintained at exchange surfaces.
The bigger the difference in the conc., the steeper the conc. gradient, the faster the rate of diffusion
Explain dense networks of blood vessels as a mechanism for maintaining concentration gradients at exchange surfaces in animals.
- Dense network of blood vessels: Lots of opportunity for substances to be exchanged betw. the surface and the blood thus maintaining a low concentration gradient
Explain continuous blood flow as a mechanism for maintaining concentration gradients at exchange surfaces in animals.
- Continuous blood flow: As soon as substances flow into blood, they’re transported away thus, ensuring a low conc. of that substance in the blood supply adjacent to the exchange surface.
Explain ventilation with air for lungs for maintaining concentration gradients at exchange surfaces in animals.
- Ventilation: movement of air into and out of the lungs driven by respiratory muscles
- MAMMALS WITH LUNGS: Inhale air into the lungs and exhale air out from the lungs
Explain ventilation with water for gills as mechanisms for maintaining concentration gradients at exchange surfaces in animals.
- Ventilation: numberof breaths per minute
- MAMMALS WITH GILLS: One of the various mechanisms is to pump water over the gills through the mouth.
Explain how mammals are able to maintain steep concentration gradients?
- Double circulatory system separates oxygenated and deoxygenated blood
- This ensures that blood transported to respiring cells is highly oxygenated
State the locations of gas exchange in humans.
Lungs
Outline the structures of mammalian lungs that are adapted to maximizing gas exchange.
- Alveoli: Tiny air sacs w/ large surface areas
- Bronchioles: Branches of bronchi leading into alveoli
- Bronchi (plural for bronchus): Airways that lead from trachea into bronchioles
- Trachea: Contains cartilaginous rings providing structure to the trachea, the smooth muscle regulates airflow, mucous membrane lining produces mucus trapping dust and bacteria before reaching the lungs
Describe the features of alveoli that adapt them to gas exchange (TRIM)
Thin wall: Made of a single layer of flattened cells so that diffusion distance is small
Rich capillary network: Alveoli are covered by a dense network of capillaries that help to maintain a concentration gradient
Increased SA:Vol ratio: High numbers of spherically-shaped alveoli optimise surface area for gas exchange
Moist: Pneumocytes type II in the lining secrete fluid to allow gases to dissolve and to prevent alveoli from collapsing (through cohesion)
State what pneumocytes are
Cells inside the lungs
Function of Type II Pneumocytes?
- Surfactants Secrete alveolar fluid that moistens the surface of the alveoli allowing gases to dissolve into the surfactant before diffusing across the wall of the alveoli and capillary into the blood.
Function of Type I Pneumocytes
- Very thin cells (also called epithelial cells) forming a single layer that make up the wall of each alveolus thus, they are adapted for gas exchange due to a short diffusion distance from the alveolar air space into the bloodstream
How does a highly branched network of bronchioles increase SA
- Each bronchiole branches into many alveoli (the exchange surface of the lungs)
- This increases SA available for gas exchange and thus, increasing the rate of gas exchange
- A high degree of branching ensures air is distributed throughout the lungs
- The small diameter of bronchioles compared w bronchi & trachea helps slow down the rate of airflow increasing the efficiency of gas exchange
Draw a diagram showing the structure of an alveolus and an adjacent capillary.
pk
Identify the structure of the airway that connects the lungs to the outside of the body.
Trachea
Define ventilation, inspiration and expiration.
Ventilation:
- The process of inhaling and exhaling into the lungs. Helps to maintain concentration gradients
Inspiration:
- Inspiration is the intake of air into the lungs
Expiration:
- Expiration is the expulsion of air from the lungs.
State the relationship between gas pressure and volume.
- Inversely proportional; as the volume of gas increases, the pressure of gas decreases
Explain why internal and external intercostal muscles are defined to be “antagonistic”
They are opposing pairs of muscles that work in opposite directions during breathing
Explain the mechanism of inspiration of the lungs in terms of volume and pressure changes caused by the internal and external intercostal muscles, the diaphragm and abdominal muscles (DETTA)
Inspiration:
- Diaphragm muscles contract and flatten downwards
- External intercostal muscles contract, pulling ribs upwards
- Internal intercostal muscles relax, pulling ribs outwards
- This increases the volume of the thoracic cavity (and therefore lung volume)
- The pressure of air in the lungs is decreased below atmospheric pressure
- Air flows into the lungs by moving down its pressure gradient to equalise the pressure
Explain the mechanism of expiration of the lungs in terms of volume and pressure changes caused by the internal and external intercostal muscles, the diaphragm and abdominal muscles. (DAEITTA)
Expiration:
- Diaphragm muscles relax and the diaphragm curves upwards
- External intercostal muscles relax, allowing the ribs to fall
- Internal intercostal muscles contract, pulling ribs downwards
- This decreases the volume of the thoracic cavity (and therefore lung volume)
- The pressure of air in the lungs is increased above atmospheric pressure
- Air flows out of the lungs by moving down its pressure gradient to equalise the pressure
Define tidal volume, vital capacity, and inspiratory and expiratory reserve.
Tidal volume: vol of air that moves into and out of your lungs with every normal breath
Vital Capacity: Volume of air you can exhale with max effort after inhaling the maximum possible vol. of air
Inspiratory reserve: The extra vol of of air can be inhaled with maximum effort beyond the volume of air inhaled in a normal inspiration
Expiratory reserve: The extra vol of air that can be exhaled with a maximum effort beyond the vol. of air exhaled after a normal exhalation
List methods for measuring tidal volume, vital capacity, and inspiratory and expiratory reserve.
- A pulmonary function test called spirometry; a person breathes into a machine called a spirometer and the volume & speed of exhaled air are measured
- Simple observation; counting the number of breaths per minute
- Breathing into a balloon: measuring the volume of air in a single breath by submerging the balloon in water and measuring the vol. displaced.
formula for ventilation rate
number of ventilations / time
State the direction of movement of gases exchanged in leaves.
Gases move from the inside of the leaves to the outside
Outline adaptations for gas exchange in leaves; Epidermis
Epidermis: Regulates the exchange of gases betw. the leaf and external air through small pores called stomata
Outline adaptations for gas exchange in leaves; epidermis
Epidermis: Regulates the exchange of gases betw. the leaf and external air through small pores called stomata
Outline adaptations for gas exchange in leaves; waxy cuticle
Waxy Cuticle: Forms a protective water-proof layer to reduce water loss
Outline adaptations for gas exchange in leaves; guard cells
Guard cell: Regulate the opening and closing of stomata by changing shape.
Outline adaptations for gas exchange in leaves; air spaces
Air spaces: allow gases to diffuse from one part of the leaf to another and a greater SA