Flashcards in Physiology Deck (252)
what is the internal respiration equation?
food + oxygen = energy + carbon dioxide (+ water)
consumption of oxygen and production of carbon dioxide
what does external respiration refer to?
the exchange of oxygen and carbon dioxide between external environment and the cells of the body
how many steps are involved in external respiration?
what is the 1st step of external respiration?
what is the 2nd step of external respiration?
gas exchange between alveoli and blood
what is the 3rd step of external respiration?
gas transport in the blood
what is the 4th step of external respiration?
gas exchange at tissue level
what does ventilation (1st step of external respiration) involve?
the mechanical process of gas exchange between the armosphere and the alveoli
what does 'gas exchange between alveoli and blood' (2nd step of external respiration) involve?
exchange of oxygen and carbon dioxide between the air in the alveoli and the blood in the pulmonary capillaries
what does 'gas transport in the blood' (3rd step of external respiration) involve?
the binding and transport of oxygen and carbon dioxide in the circulating blood
what does 'gas exchange at tissue level' (4th step of external respiration) involve?
the exchange of oxygen and carbon dioxide between the blood in the systemic circulation and the body cells
what 3 body systems are involved in external respiration?
What is Boyle's Law?
for a given mass of gas -at a certain temperature- as the volume of the gas increases, the pressure exerted by the gas decreases.
air flows down a pressure gradient ___ pressure to a region of ___ pressure
high pressure to a region of low pressure
when is the intra-alveolar pressure equivalent to the atmospheric pressure?
What does expansion of the thorax and lungs do to the intra-alveolar pressure?
makes it fall below atmospheric pressure (Boyle's Law)
this allows air to move from atmosphere into lungs down pressure gradient
what 2 forces hold the thoracic wall and the lungs in close opposition?
1. intrapleural fluid cohesiveness
2. the negative intrapleural pressure
how does the intrapleural fluid keep thoracic wall and lungs in close opposition?
the water molecules in the intrapleural fluid are attracted to each other and resist being pulled apart, therefore pleural membranes tend to stick together
how does the negative intrapleural pressure keep the thoracic wall and lungs in close opposition?
the sub-atmospheric intrapleural pressure creates a transmural pressure gradient across the lung wall and chest wall, therefore lungs are forced to expand outwards while the chest is forced to squeeze inwards
what 3 pressures are important in ventilation?
what is the atmospheric pressure at sea level?
what is usually the intrapleural pressure?
when the external intercostal muscle contract what do they cause?
elevation of the ribs, causing the sternum to move upwards and forwards- increases AP dimension of thoracic cavity
what type of process is inspiration?
(brought about by contraction of inspiratory muscles)
what type of process is normal expiration?
(brought about by relaxation of inspiratory muscles)
what 2 properties allows the lung to recoil to their preinspiratory size during expiration?
elastic connective tissue in the lungs
alveolar surface tension
what does the recoil of lungs do to the intra-alveolar pressure?
makes it rise above atmospheric pressure
this allows air to move from lungs to atmosphere down a pressure gradientq
what is a traumatic pneumothorax?
a puncture wound in the chest wall causing a collapsed lung
what is a spontaneous pneumothrax?
a hole in the lung itself causing a collapsed lung