Physiology 2058 Respiratory Flashcards
(39 cards)
Bronchioles
Smooth muscle, diameter alters, SNS controls
Pulmonary ventilation
mechanics of breathing, air from higher pressure area to lower pressure area, causes changes in volume of the lungs
Mechanics of breathing
inspiration- diaphragm contracts, volume of thorax increases and pressure within it falls, air to flow from outside into lungs
expiration- process reversed, aided by elastic recoil, passive
Lung compliance
Ease of lung expansion, healthy- highly compliant, for a given change in pressure, large change in volume, reduces WOB
over- compliant- emphysema
under - compliant - fibrosis
increase air way resistance reduces air flow- hard to breath
Surfactant
liquid produced by certain alveolar cells and lines in inner surface of alveoli, begins in utero, reduces surface tension, keeps airways open increasing compliance, in RDS preterm infants lack of surfactant increasing WOB
Lung volume and capacities
Measured using spirometry, varies, tidal volume, inspiratory reserve volume, expiratory reserve volume, functional residual capacity, vital capacity, residual volume
Tidal volume
volume of air moved in and out of lungs during a normal breath - minute volume= TV x RR
Expiratory reserve volume ERV
volume of extra air breathed out after normal expiration
Inspiratory reserve volume IRV
volume of extra air breathed in after normal inhalation
Functional residual capacity FRC
The volume of air in the lungs after a normal exhalation
Residual volume
Total volume of air left in lungs after maximum exhalation
Vital capacity
Maximum amount of air that can be moved in and out of the lungs in a single breath
Forced vital capacity
speed is important, peak flow meter
Atmospheric pressure
Air as gases, nitrogen, oxygen , carbon dioxide and water vapour exerting certain amount of total
Partial pressure
Each gas exerts an individual partial pressure
Inhaled air partial pressures
Nitrogen 79%, oxygen 20.9%, CO2 20.9%, water vapour .5%
Alveolar Air
Nitrogen 75.4%, Oxygen 13.2%, CO2 5.2%, Water vapour 6.2%
Gas exchange
diffusion, intimate relationship between alveoli and pulmonary capillaries, pulmonary vascular resistance is low facilitating good lung perfusion
Criteria for Gas exchange across the resp membrane
Factors influencing diffusion- SA available, thickness of resp membrane (0.5microns), partial pressure gradient of the gases, lipid solubility of the gases, good ventilation/perfusion needed
Pulmonary gas exchange
O2 diffuses down conc gradient across resp membrane from alveoli to pulmonary capillaries, around circulation bound to haemoglobin, small amount dissolved in plasma
CO2 diffuses down conc gradient across resp membrane from pulmonary capillaries into alveoli to be expelled
O2 transport in blood
bound to haemoglobin, oxyhaemoglobin - reversible rxn, some dissolved in blood - partial pressure of O2, normal PO2 of arterial blood is 95-100mmHg, when blood reaches tissues, oxygen is released from Hb and diffuses into cells
Amount of O2 bound to Hb is influenced by PCO2, blood Ph, Temp
Internal respiration
involves the diffusion of O2 acorss the capillary membrane into the cells
CO2 transport in blood
23% as carbaminohemoglobin- venous side of circulation
70% as bicarbonate ions, through formation of carbonic acid
Small amount dissolved in plasma
The resp centre
Medulla oblongata and Pons of brainstem, basic rhythm set by rhytmicity centre - involuntary
Inspiratory area- dorsal respiratory group neurones
Expiratory area- ventral respiratory group neurones
