Respiratory System Flashcards
Point at which the bronchus enters the lung
Hilum
Bronchodilation
When sympathetic stimulation relaxes the smooth muscle, dilating or enlarging the bronchioles
How does the respiratory mucosa change as it moves towards the terminal respiratory bronchioles?
From pseudostratified columnar to simple columnar then to simple cuboidal
Surfactant
The inside surfaces of the alveoli are coated with a very small amount of fluid. Has a detergent action that reduces surface tension (the tendency for fluid to reduce its surface area by forming droplets). This facilitates inspiration and prevents total collapse of alveoli during expiration
Parietal pleura
Lines the inside of the thoracic cavity, adhering to the chest wall and diaphragm.
Pleural cavity
Small space, slightly negative pressure (less than atmospheric pressure) assists in holding the pleura in close approximation and promoting lung expansion. Provides lubrication during respiratory movements and a force that provides cohesion (high surface tension)
True ribs and false ribs
Upper seven pairs of ribs articulate with the vertebrae and are attached to the sternum by costal (hyaline) cartilage. . The next three are connected to the costal cartilage of the seventh rib, not directly to the sternum. Last two (11th and 12th) are attached only to vertebrae (floating)
How does airflow on inspiration and exhalation work?
Depends on a pressure gradient, air always moves from high pressure to low pressure area. If atmospheric pressure is higher than air pressure inside the lungs, air will move from the atmosphere into the lungs.
Boyle’s law
As the size of the cavity decreases, the pressure inside the cavity increases.
Process of normal quiet inhalation
Contraction of diaphragm and external intercostal muscles
Eternal intercostals raise the ribs and sternum up and out
Increased size of thoracic cavity results in decreased pressure in the pleural cavity
As ribs and diaphragm move, the attached parietal pleura pulls the adhering visceral pleura and lungs along with it
As visceral pleura moves outward, elastic lungs expand with it, resulting in a decrease in air pressure inside the lungs
Air flows from atmosphere down airways into the alveoli.
Inhalation is active and requires energy, exhalation is passive
What muscles are involved in forced inspiration or expiration?
Sternocleiodmastoid, scalene, pectoralis minor, serratus muscles during inhalation
Abdominal muscles contract during forceful expiration and intercostals
Compliance
Refers to ability of the lungs to expand, depends on elasticity of the tissues, alveolar surface tension and shape, size, flexibility of thorax
Why do we measure pulmonary volumes?
They can change with disease processes and are helpful in monitoring a patient’s progress or response to treatment.
Residual volume
The volume of air remaining in the lungs after maximum expiration. This air continues to provide gas exchange and maintains partial inflation of the lungs
Vital capacity
Maximal amount of air that can be moved in and out of the lungs - can be altered by disease, size of thorax, amount of blood in lungs, body position
Dead space
Passageways or areas where gas exchange cannot take place. Bronchi and bronchioles
Tidal volume
500 mL - amount of air entering lungs with each normal breath
Residual volume
1200 mL - amount of air in lungs after forced expiration
Inspiratory reserve (IRV)
3000 mL - Max amount of air that can be inhaled in excess of normal quiet inspiration
Expiratory reserve (ERV)
1100 mL - Max volume of air expired following a passive expiration
Vital Capacity (VC)
Max amount of air expired following max inspiration
Total Lung Capacity
Total volume of air in lungs after max inspiration
Primary control centers for breathing
Medulla and pons - inspiratory center controls the basic rhythm by stimulating the phrenic nerves to the diaphragm and the intercostal nerves to the external intercostal muscles.
The expiratory center in the medulla appears to function primarily when forced expiration is required
Additional centers in the pons play a role in coordinating inspiration, expiration and intervals for each
Factors that can depress central nervous system activity
Drugs like morphine
Activity of hypothalamus - perhaps in response to emotions
Stretch receptors in the lungs
Hering-Breuer reflex - prevents excessive lung expansion
Voluntary control - singing
Voluntary control is limited by levels of carbon dioxide in the blood. When the concentration or partial pressure of carbon dioxide in the blood rises, breathing resumes automatically.
Central chemoreceptors
In medulla - respond quickly to slight elevations in CO2 (40-43mmHg) or a decrease in pH (increased H+) of cerebrospinal fluid.
Peripheral chemoreceptors
Located in the carotid bodies at the bifurcation of the common carotid arteries and in the aortic body in the aortic arch, sensitive to decreased oxygen levels in arterial blood as well as to low pH.
Hypoxemia
A marked decrease in oxygen (105 to 60 mmHg) is necessary before chemoreceptors respond to hypoxemia.
Hypoxic drive
Individuals with chronic lung disease adapt to sustained elevation in PCO2 and move to hypoxic drive, such individuals are dependent on low oxygen levels rather than the normal slight elevation in carbon dioxide to stimulate inspiration. The medullary chemoreceptors become insensitive to high PCO2. Therefore it is important for these patients always to remain slightly hypoxic and not be given excessive amounts of oxygen.
Hypercapnia
When carbon dioxide levels in the blood increase, gas diffuses into the cerebrospinal fluid. lowers pH and stimulates the respiratory center, results in increased rate and depth of respirations (hyperventilation)
Causes respiratory acidosis which depresses the nervous system.
Hypocapnia
Low PCO2 may be caused by hyperventilation after excessive amounts of CO2 have been expired. Causes respiratory alkalosis.
Dalton’s law
Each gas in a mixture moves or diffuses according to its own partial pressure gradient and independent of other gases
What does atmospheric air contain?
Oxygen, carbon dioxide, nitrogen and water
Factors effecting diffusion
Thickness of the respiratory membrane. When fluid accumulates in the alveoli or interstitial tissue, diffusion is greatly impaired. Presence of extra fluid may also impede blood flow through the pulmonary capillaries and increase surface tension in the alveoli, restricting expansion of the lung.
Total surface area available for diffusion and the thickness of the alveolar membranes.
Ventilation perfusion ration (Va / Q)
An autoregulatory mechanism in the lungs can adjust ventilation and blood flow in an attempt to produce a good match.
E.g. if PO2 is low because of poor ventilation in an area, vasoconstriction occurs in the pulmonary arterioles, shunting the blood to other areas of the lungs where ventilation may be better.
How much total oxygen is dissolved in plasma?
1% because oxygen is relatively insoluble in water, which also limits the ease that oxygen can diffuse.
Where is the dissolved form of oxygen found?
That which diffuses from the alveolar air into the blood in the pulmonary capillaries, diffuses into the interstitial fluid and the cells during internal respiration.
Fully saturated hemoglobin
When all four heme molecules have taken up oxygen
What effects the rate that hemoglobin binds or releases oxygen?
Partial pressure of dissolved oxygen Partial pressure of carbon dioxide Temperature Plasma pH Normally approx 25% of the bound oxygen is released to the cells for metabolism during the erythrocyte's trip through the systemic circulation, leaving 75% of the hemoglobin in the venous blood still saturated with oxygen.
