7 - Exchange surfaces & breathing Flashcards
Describe 3 characteristics of specialised exchange surfaces.
Increased SA: Provides large enough are to increase exchange and overcome limits of low SA:V ratio of large multicellular organisms (e.g. root hairs, villi)
Thin Layers: Diffuse distance decreased, increasing rate.
Good blood supply: Good blood supply increases conc. gradient, of gases in mammals.
E.g. fish gills, lung alveoli
Why is diffusion enough to supply unicellular organism?
Low metabolic activity - O2 requirement and CO2 production is low
Large SA:V ratio - gases exchanged fast enough
Name the key structures in the human gas exchange system.
Nasal cavity
Trachea
Bronchus
Bronchioles
Alveoli
Describe the features, functions and structure of the nasal cavity.
Large SA, good blood supply - warms the air to body temperature
Hair lining that secretes mucus to trap dust and bacteria - protects lung tissue from infection
Moist surfaces - increasing incoming air’s humidity, reducing evaporation from exchange surfaces
Describe the features, functions and structure of the trachea.
Wide tube supported by incomplete rings of flexible cartilage stopping trachea collapsing.
Lined with ciliated epithelium with goblet cells in between.
What are the functions of goblet cells?
Secrete mucus onto the trachea to trap dust and microorganisms that escape the nasal lining.
Most of mucus is swallowed and digested, some gets beat and moved along by cilia away from the lung.
Give adaptations of alveoli for gaseous exchange.
Good blood supply - maintain steep concentration gradient between CO2 and O2 in air and in blood of capillaries
Good ventilation - maintains conc. gradient
Large SA (300-500million alveoli per adult lung) - speed up diffusion
Thin layers - shorter diffusion distance
Alveoli & surrounding capillaries are 1 cell thick, shortening diffusion distance.
Describe the process of inspiration.
Breathing in - energy using process
1) Dome shaped diaphragm contracts (flattens and lowers)
2) External intercostal muscles contract - moves ribs UP AND OUT
3) Volume of thorax increases, lowering pressure in thorax. (Lower than atmospheric air)
4) Therefore, air is drawn in through nasal passage, trachea and bronchi/bronchioles.
Equalising pressure in and out of chest
Describe the process of forced expiration.
-Internal intercostal muscles contract, pulling ribs down hard and fast
- Abdominal muscles contract forcing diaphragm forcing diaphragm up to increase lung pressure rapidly.
What is the function of a peak flow meter?
Measures rate at which air can be expelled from lungs.
What is a vitalograph?
Graph is produced showing volume of air produced and its speed.
How does a spirometer work and what is its function?
Subject should wear a nose clip to ensure air only comes from the mouth and system
As the subject inhales, oxygen is drawn from the chamber which in turn lowers
When the subject exhales, the chamber rises
Air returning to the chamber passes a soda lime cannister to absorb the CO2
Air movements recorded by a trace on a revolving drum
Draws a kymograph
Define:
Tidal Volume
Vital Capacity
Tidal Volume: Volume of air breathed in and out in one breath. At rest this is 0.5dm3
Vital Capacity: Maximum volume of air that can be expired after the deepest inspiration
Define:
Inspiratory reserve volume
Expiratory reserve volume
Inspiratory reserve volume: Maximum volume of air one can inspire over normal inhalation
Expiratory reserve volume: Extra amount of air you can force out of lungs over the normal amount of air you exhale
Define residual volume.
Volume of air that remains in lungs after hardest expiration (cannot be directly measured)
