topic 6.4 - ventilation Flashcards
what is the function of ventilation?
it maintains concentration gradients of oxygen and carbon dioxide between air in alveoli and blood flowing in adjacent capillaries
draw a labelled diagram of an alveolus
pg311
- type 1 pneumocystis in alveolus walls
- phagocyte
- network of blood capillaries
- type 2 pneumocystis in alveolus walls
give 4 ways of monitoring ventilation in humans at rest and after mild and vigorous exercise
- ventilation rate
- observation of number of times air is exhaled and inhaled in a minute
- data logging with inflatable chest belt that is placed around the thorax - tidal volume
- one normal breath is exhaled through a delivery tube into a vessel and the volume is measured. it is not safe to use this apparatus for repeatedly inhaling/exhaling air as the co2 concentration will rise too high
- spirometers measure flow rate into and out of lungs and from these measurements lung volumes can be deduced
structure and function of type 1 pneumocytes
extremely thin alveolar cells that are adapted to carry out gas exchange
- located in epithelium, in wall of alveolus
- flattened cells
- distance over which co2 and o2 have to diffuse is very small, which increases the rate of gas exchange
structure and function of type 2 pneumocytes
secrete a solution containing surfactant that creates a moist surface:
- allows oxygen to dissolve and diffuse to blood
- provides area from which co2 can evaporate into the air and be exhaled
hydrophobic heads face the water and the hydrophobic tails face the air:
- reduces surface tension and prevents water from causing the sides of the alveoli to adhere when air is exhaled from lungs, helping prevent the collapse of the lung
give a flow diagram describing airways for ventilation
nose/mouth -> trachea -> two bronchi -> lung -> tree-like bronchioles -> groups of alveoli
give the structure and function of trachea and bronchi
rings of cartilage in their walls to keep it open even when air pressure inside is low or pressure in surrounding tissues is high
structure and function of bronchioles
smooth muscle fibres in their walls, allowing the width of these airways to vary
draw a diagram for inspiration
- ribs upwards and outwards
- air in
- diaphragm down
draw a diagram for expiration
- ribcage inwards and downwards
- air out
- diaphragm up
describe the basic physics involved in ventilation
- if particles of gas spread out to occupy a larger volume, the pressure of gas becomes lower
- if gas is compressed to occupy a smaller volume, the pressure rises
- if gas is free to move, it will flow from regions of higher pressure to regions of lower pressure
describe the process of ventilation and how pressure is linked with it
- muscle contractions cause pressure inside the thorax to drop below atmospheric pressure
- air is drawn into the lungs from the atmosphere (inspiration) until lung pressure has risen to atmospheric pressure
- muscle contractions then cause pressure inside the thorax to rise above atmospheric, so air is forced out from the lungs to the atmosphere (expiration)
muscles can be in two states
contracting and relaxing
contracting
- muscles do work
- exert a pulling force (tension) that causes a particular movement
- become shorter
relaxing
- muscles lengthen passively
- pulled into an elongated state by the contraction of another muscle
- do not exert a pushing force (compression) while relaxing so do no work
describe an antagonistic pair of muscles
when one muscle contracts and causes a movement the second muscle relaxes and is elongated by the first . the opposite movement is caused by the second muscle contracting while the first relaxes
why are antagonistic pairs of muscles needed?
muscles can only cause movement in one direction. if movement in opposite directions is needed at different timed, at least two muscles will be required
draw a table for
diaphragm, ribcage
inspiration, expiration
p315
draw a table for
volume and pressure changes, movement of diaphragm, movement of ribcage
inspiration, expiration
p.316
causes of lung cancer
- smoking: tobacco contains many mutagenic chemicals.
- passive smoking
- air pollution from diesel exhaust fumes, nitrogen oxides from all vehicle exhaust fumes, smoke from burning coal, wood, or other organic matter
- radon gas: radioactive gas that leaks out of rocks like granite. accumulates in badly ventilated buildings so people inhale it
- asbestos, silica, some other solids if dust or particles of them are inhaled, in construction sites, quarries, mines, or factories
consequences of lung cancer
- difficulties with breathing, persistent coughing, coughing up blood, chest pain, loss of appetite, weight loss, general fatigue
- may lead to secondary tumours
- chemotherapy or radiotherapy
emphysema
Emphysema is a lung condition whereby the walls of the alveoli lose their elasticity due to damage to the alveolar walls
- The loss of elasticity results in the abnormal enlargement of the alveoli, leading to a lower total surface area for gas exchange
- The degradation of the alveolar walls can cause holes to develop and alveoli to merge into huge air spaces (pulmonary bullae)
theories for formation of emphysema
in smokers, the number of phagocytes in the lungs increases and they produce more elastase.
- phagocytes inside alveoli normally prevent lung infections by engulfing bacteria and produce elastase, a protein-digesting enzyme, to kill them inside the vesicles formed by endocytosis.
- alpha 1-antitrypsin (A1AT) is an enzyme inhibitor and prevents elastase and other proteases from digesting lung tissue.
- genetic factors affect the quantity and effectiveness of A1AT produced in the lungs
symptoms of emphysema
- irreversible, chronic disease
- low oxygen saturation in the blood and higher than normal co2 concentrations.
- patient lacks energy
- shortness of breath
- ventilation laboured and more rapid than usual
volume and pressure changes
- inspiration
- expiration
volume in thorax increases and pressure consequently decreases
volume in thorax decreases and pressure consequently increases
movement of the diaphragm and abdomen wall muscles
- inspiration
- expiration
inspiration:
- diaphragm contracts and so it moves downwards and pushes the abdomen wall out
- muscles in the abdomen wall relax allowing pressure from the diaphragm to push it out
expiration:
- diaphragm relaxes so it can be pushed upwards into a more domed shape
- muscles in the abdomen wall contract pushing the abdominal organs and diaphragm upwards
movement of the ribcage for the external intercostal muscles and internal intercostal muscles
- inspiration
- expiration
inspiration:
- the external intercostal muscles contract, pulling the ribcage upwards and outwards
- internal intercostal muscles relax and are pulled back into their elongated state
expiration:
- external intercostal muscles relax and are pulled back into their elongated state
- internal intercostal muscles contract, pulling the ribcage inwards and downwards
