Respiratory Systems Flashcards
What is internal respiration?
Metabolism
Energy being made available to cells
What is external respiration?
Delivery of oxygen to tissues and cells
Removal of carbon dioxide
How does gas move across biological membranes?
Diffusion
Define partial pressure.
Pressure of a single gas in a gas mixture
What are physical factors influencing the rate of diffusion?
Partial pressure gradient Diameter of the gas molecules Temperature Solubility of the gas in liquid Thickness of the gas exchange surface Surface area of the gas exchange surface
What does a respiratory system consist of?
Specialised body surfaces for gas exchange
Mechanisms to ventilate the environmental face of this surface
Mechanisms to perfuse the internal face of this surface
What is the primary role of a respiratory system?
Meet the metabolic demands of the organisms
What is ventilation?
Convection of respiratory medium over the gas exchange surfaces (active or passive)
What is the purpose of ventilation?
Maintain partial pressure gradient at respiratory system
Fresh oxygen delivered and carbon dioxide removed
What is the intrapleural pressure at rest (with respect to atmospheric pressure)?
Negative with respect to atmospheric pressure
When does ventilation occur?
When active muscle force is applied to the relaxed respiratory system
Is inspiration active or passive?
Active process
In inspiration, what changes?
Volume of thorax increases
Diaphragm contracts
External intercostal muscles contract
As the volume of the thorax increases, the intrapleural pressure … ?
Falls
What is Boyle’s law?
P1 x V1 = P2 x V2
pressure x volume is constant
As the volume of the thorax increases, what happens to alveoli and alveolar pressure?
Alveoli expand
Air flows into lungs until alveolar pressure equals atmospheric pressure (before it was negative wrt atmospheric pressure)
Is expiration largely passive or active?
Passive
What happens in expiration?
Elastic recoil of lungs and chest wall reduces volume of thorax (passive mechanism) Intrapleural pressure rises Alveoli recoil Alveolar pressure > atmospheric pressure Air expelled from lungs
Air moves … from a region of … to … pressure
Air moves passively from a region of high to low pressure
Pressure-volume graph:
Why does the curve deviate to the right in inspiration?
Because of resistive forces which oppose airflow
Pressure-volume graph:
Why does the curve deviate to the left in expiration?
Resistive forces assist airflow
Describe ventilation in birds.
Birds lung volume changes less than in mammals
Air moves through lungs from interconnected air sacs
Sacs do not participate in gas exchange
Describe ventilation in frogs.
Air forced into lungs
Lungs emptied by abdominal contraction
Describe air movement in insects.
Airways penetrate each body segment, allowing diffusion
Abdominal muscles pump air through tracheae
Describe water movement across gills.
Energy is required to pump water across gills
Water pulled across gills when opercular cavity expands and opercular flaps open
Water pulled across gills when opercular cavity expands and opercular flaps open
Water pushed over gills when fish closes mouth
Describe laminar flow.
Slow flow rate
Parallel stream lines
Describe turbulent flow.
High flow rate
Disorganised strwam lines
Describe transitional flow.
intermediate flow rate
eddy currents
What is radial traction?
As lung expands, connective tissue pulls on bronchioles, so their diameter expands and the airway resistance falls
As lung volume is reduced, airway resistance rises rapidly because radial traction is relieved
What is dynamic compression?
Occurs at low lung volume, or when intrathoracic pressure > alveolar pressure (forced expiration)
Airways are compressed and may close
What is bronchioconstriction?
Irritants cause reflex constriction: trachea, large bronchi
Parasympathetic stimulation
Fall in PCO2
Asthma
What is bronchiodilation?
Autonomic stimulation
Sympathomimetic agents
How does infection impact airway resistance?
Infection can significantly increase
Inflammation of the tissues lining the upper airways
Overproduction/ accumulation of mucus
What is elastic recoil determined by?
Elastic properties of the lung tissue
Surface tension in the alveoli
What elastic tissues are in the lung and where?
Elastin and collagen fibres in alveolar wall and around vessels and bronchi
What does the network of fibres in the lungs do?
Allows distension but recovers geometry the pressure is released
What are alveoli lined with?
Fluid
Why does the presence of an air-fluid interface create potential problems? How can these problems by minimised?
Attractive forces in liquid (surface tension) oppose expansion by inspired air
Promotes collapse of smaller alveoli
Causes transudation of fluid form capillaries
These problems are minimised by surfactant
What is surfactant?
Substance that reduces surface tension between two liquids; a gas and a liquid or a solid and a liquid
