Repiratory System Flashcards
What is he purpose of repsiration?
To constantly supply the body cells with oxygen and to remove carbon dioxide
What are the three main processes of the respiratory system?
Ventilation- movement of air into the lungs
External respiration- gas exchange between alveoli and blood
Internal repsiration- gas exchange between blood and body cells
What is ventilation?
Movement of air in and out of the lungs as a result of differing pressures between the external environment and the internal lung environment
Outline inspiration
Diaphragm and intercostal muscles contract increasing volume of thoracic cavity, causing the lungs to expand
As volume in lungs increases pressure of air in the lungs decreases this means the pressure of the air in the lungs becomes lower than the air in the envorinment outside the body
(Boyles law of pressure gradient moving down)
Air therefore moves from area of higher pressure to and area of lower pressure
Outline expiration
Diaphragm and intercostal muscles relax
Volume in thoracic cavity decreases
Lung volume decreases so pressure increases
Air is expelled down pressure gradient
What happens when you smoke in pregnancy?
Decreases the amount of oxygen that reaches the fetus
Carbon monoxide crosses the placenta and binds to haemoglobin
Associated with spontaneous abortion and pre term labour
Intrauterine growth retardation
Most significant effects in second and third trimester
Respiratory problems and asthma have been linked to children who have been exposed to excessive passive smoking
What is asthma ?
Condition in which the bronchi are narrowed inappropriately by chemical or emotional stimuli.
During an asthma, attack the airways become constricted. Inspiration is normal but expiration is difficult. Air in alveoli become trapped
What advise should be given to asthmatic pregnant women?
Medication she is prescribed does not harm baby
May increase incidence of congenital abnormalities, pre term delivery and low birth weight
Closely monitored to ensure the medication prevents asthma attacks- fetus should not be deprived of oxygen
Outline external respiration
Movement of gas across alveoli
Air is warmed as it enter the body and lungs due to body temperature. Warmed air particles are more mobile which increases pressure
Air is a mixture of gases
Needs a large SA for efficient exchange
Short diffusion distance
Depth and rate of ventilation controlled by the autonomic nervous system
Partial pressure, need pressure gradients
Outline internal respiration
Gaseous diffusion between blood and bodily tissues
Moves down pressure gradient
Short diffusion path (capillaries small, one layer)
Good blood supply
How does the respiratory system change in pregnancy?
Body cells need 20% more oxygen
Increase in the amount of carbon dioxide than needs to be removed
Demands are met by and increase in tidal volume (amount of air moving in and out of the Kung in one ventilation)
Usually no increase in ventilation rate
Progesterone causes flaring of the ribs in early pregnancy
Increased capillary engorgement makes nose breathing difficult
Progesterone can cause relaxation of airways causes minor dyspnoea
Growing uterus presses up on base of lungs so less air reaches the alveoli at the base
Increase of tidal volume causes results in decreased partial pressure of carbon dioxide in the blood stream enhancing removal of carbon dioxide from the placenta
How does the respiratory system change in labour?
Demands in labour are met by the ability to increase ventilation rate and depth
Increased dissociation of oxygen from haemoglobin in areas such as the uterus
If contractions occur too frequently with little time for relaxation the muscles will become hypoxic
How does the respiratory system change in the postnatal period?
Respiratory function rapidly returns to normal
Hormone levels return
What is respiratory distress syndrome?
Surfactant is produced from 23 weeks in the alveoli and present in sufficient quantities by 28 weeks. Prevents alveolar collapse.
If a neonate is born before 28 weeks their alveoli will lively collapse on expiration. Baby will run out of energy.
