Respiratory System Flashcards
Compare and contrast how 02 and CO2 are carried in the blood. What are the approximate partial pressures of these gases in the right atrium, and the left ventricle?
Almost all oxygen in the blood is bound to haemoglobin in RBCs. Specifically, it is bound to the iron or the haeme group of each haemoglobin subunit. Very little is dissolved in the fluid components of blood. Most (70-85%) carbon dioxide is present as bicarbonate HCO3-, about 10-20% is bound to haemoglobin and plasma proteins as carbamino (binds to NH2 groups of these proteins), and about 5-10% is dissolved as gas in the fluid of the blood. Right atrial blood is ‘mixed venous’ blood returning from the body, so PCO2, is about 45 mm Hg, and P02 is about 40 mm Hg. Left ventricular blood has returned from the lungs, so PCO2 is about 40 mm Hg, and P02 is about 100 mm Hg.
What are the main respiratory muscles?
The main respiratory muscles are the diaphragm which is located between the thoracic wall and the abdominal cavities and the intercostal muscles, which are located between the ribs. Both are skeletal muscles
Describe the process of inhalation.
During inspiration the vertical, lateral and anteroposteroir diameters of the thoracic cavity increase, therefore increasing volume due to the decent of the diaphragm and the elevation of the ribs. The lung volume increases because the pleural fluid holds the lungs to the surrounding thoracic wall structures. Inspiration results in movement of air into the lungs as air moves from high pressure to low pressure.
Describe recoil in the lungs.
Recoil is caused by two factors: elastic fibres and surface tension.
Elastic fibres are located throughout the lung connective tissue ECM and try to ‘recoil’ making the lung want to collapse.
Surface tension due to a thin film of fluid in the alveoli tends to cause alveoli to collapse (reduce in diameter). The surface tension, however, is reduced by surfactant, without which the alveoli would collapse on expirations.
What does pulmonary gas exchange by diffusion depend on?
Pulmonary gas exchange by diffusion depends on:
• Ventilation and perfusion maintaining the partial pressure difference between air and blood.
• Pulmonary ventilation: breathing to keep ‘fresh’ air moving into alveoli, and ‘used’ air out.
• Pulmonary perfusion: right ventricle of heart pumping blood to pulmonary capillaries
• Partial pressure difference = concentration gradient
• Total surface area of alveoli
• Time available
• Distance: thickness of blood-air barrier (respiratory membrane)
• Solubility of gas in water
• Molecular weight
Compare and contrast how oxygen and carbon dioxide are carried in the blood.
Oxygen is poorly soluble in water, and thus 98% of O2 is bound to haemoglobin (Hb) in RBCs.
Carbon dioxide (CO2) mainly occurs as bicarbonate ion (HCO3-, 70-85%), with 10-20% bound to haemoglobin and plasma proteins (forms carbamino) and 5-10% dissolved in plasma.
How is breathing controlled?
Breathing is controlled by brainstem respiratory centres, with the rhythm of breathing, the coordination of neurons innervating the respiratory muscles. Various nervous system inputs regulate these.
How are oxygen and carbon dioxide concentrations controlled?
Chemoreceptors in the CNS (brainstem) and PNS (carotoid and aortic bodies) detect CO2 and O2 partial pressures and pH. A small increase in CO2 and [H+], or a large decrease in O2 increases the respiratory rate.
What is tidal volume, inspiratory reserve volume, expiratory reserve volume, residual volume, and lung capacity?
Tidal volume is the volume of air that moves in and out of the respiratory tract during resting respiration (approx. 0.5L).
After normal inspiration, it is possible to inhale additional are, this is the ‘inspiration reserve volume’ (1.9-3.1L).
After normal exhalation is it possible to exhale additional air, this is the ‘expiratory reserve volume’ (0.7-1.2L).
After you have blown all the air you can out of your respiratory tract, there is still a ‘residual volume’ of air in the tract (1.1-1.2L).
Capacities are sums of two or more lung volumes. The vital capacity is the volume of air that can be blown out after a maximal inhalation (=expiratory reserve volume + tidal volume + inspiratory reserve volume = 4.8L).
Circle the correct term in the following statements:
The ribs are [medial / lateral] to the vertebral bodies.
The heart is [superficial / deep] and [anterior / posterior] to the sternum.
The oesophagus is [anterior / posterior] to the heart, and [ventral / dorsal] to the
trachea.
LATERAL
DEEP, POSTERIOR
POSTERIOR, DORSAL
Which specific tissue types comprise a serous membrane?
Serous membrane is composed of an simple squamous epithelial layer known as the mesothelium and a loose connective tissue layer.
