Chapter 37 - Pulmonary Ventilation Flashcards
Guyton, 5th Edition
Four major functions of respiration
- Pulmonary Ventilation
- Diffusion of O2 and CO2 between the alveoli and the blood
- Transport of O2 and CO2 in the blood and body fluids to and from the body’s tissue cells.
- Regulation of ventilation and other facets of respiration.
What are the 2 ways that the lung can expand and contract.
- Downward and upward movement of the diaphragm to lengthen or shorten the chest cavity.
- Elevation and depression of the ribs to increase and decrease the anteroposterior diameter of the chest cavity.
What happens to during inspiration of a normal quite breathing?
Contraction of the diaphragm pulls the the lower surfaces of the lungs downwards.
What happens during expiration of a normal quite breathing?
The diaphragm simply relaxes and the elastic recoil of the lungs, chest wall and abdominal structures compresses the lungs and expels the air.
What changes during heavy breathing?
The elastic forces are not powerful enough to cause the necessary rapid expiration, so that extra force is achieved by contraction of the abdominal muscles, which pushes the abdominal contents upward against the bottom of the diaphragm, thereby compressing the lungs.
What are the most important muscles that raise the rib cage?
External intercostas, (1) sternocleidomastoid muscles, which lift upward on the sternum, (2) anterior serrati, whch lift many of the ribs; and the (3) scaleni, which lift the first two ribs.
What are the muscles that pull the rib cage downward during expiration?
- Abdominal recti
2. Internal intercostals
What happens when there is no force to keep the lung inflated?
Collapses like a balloon and expels all its air through the trachea.
What is the Pleural pressure
The pressure of the fluid in the thin space between the lung pleura and the chest wall pleura; normally a slight suction, which means a slightly negative pressure.
What is the normal pleural pressure at the beginning of inspiration?
About -5 centimeters of water, which is the amount of suction required to hold the lungs open to their resting levels.
What is the normal pleural pressure at the during of inspiration?
Expansion of the chest cage pulls outwards on the lungs with greater force and creates more negative pressure to about -7.5 centimeters of water.
What is alveolar pressure?
Pressure of the air inside the lung alveoli.
How do you cause inward flow of air into the alveoli during inspiration?
The pressure in the alveoli must fall to a value slightly below atmospheric pressure (about -1 centimeters of water).
What is the Transpulmonary Presure?
The difference between the alveolar pressure and the pleural pressure.
What is lung compliance?
The extent to which the lungs will expand for each unit increase in trans-pulmonary pressure (if enough time is allowed to reach equilibrium).
What is recoil pressure?
The elastic force in the lungs that tend to collapse the lungs at each instant of respiration.
What is the total compliance of both lungs together in the normal adult human being?
200 milliliters of air per centimeter of water trans-pulmonary pressure.
What are the components of the compliance diagram of the lungs?
Two curves:
- Inspiratory compliance curve
- Expiratory compliance curve
What are components of the elastic forces of the lungs?
- Elastic forces of the lung tissue
- Elastic forces caused by surface tension of the fluid that lines the inside walls of the alveoli and other lungs air spaces.
What are the elastic components of the lung tissue?
Elastin and collagen fibers interwoven among the lung parenchyma.
What is a surfactant?
A surface active agent in water, which means that it greatly reduces the surface tension of water.
What secretes surfactants in the alveoli?
Type II alveolar epthelial cells. Constitutes about 10% of the surface area of the alveoli.
What are the molecular components of the surfactant?
Dipalmitoylphosphatidylcholine (the one responsible for reducing the surface tension), surfactant apoproteins, and calcium ions.
Surface tension of pure water, normal fluid lining the alveoli w/o surfactant; and normal fluid lining the alveoli w/ surfactant.
72 dynes/cm; 50 dynes/cm; 5-30 dynes/cm.
What is the formula to calculate the Pressure inside the alveolus?
2 x Surface Tension
__________________
Radius
= Surface tension of the alveoli is inversely affected by the radius of the alveolus, which means that the smaller the alveolus, the greater the alveolar pressure caused by the surface tension.
What is the radius of the average-sized alveolus and its pressure with and w/o surfactant?
About 100 micrometers. Lined with normal surfactant, about 4 centimeters of water pressure (3mmHg). Without, about 18 centimeters of water pressure; about 4.5 times greater.
What causes Respiratiory distress syndrome of the newborn?
The smaller raidus of the alveoli and the small or absence of secretion of surfactants.
The work of inspiration can be divided into three factions:
- Compliance or Elastic work
- Tissue resistance work
- Airway resistance work
What is Compliance or Elastic work
The work required to expand the lungs against the lung and chest elastic forces
What is Tissue resistance work
Work required to overcome the viscosity of the lung and chest structures
What is Airway resistance work
Work required to overcome airway resistance to movement of air into the lungs.
During normal quite respiration, how much of the body’s total energy expenditure is required? How much can this increase in heavy exercise?
3 to 5 percent; 50-fold.
How does one measure and study pulmonary ventilation?
Record the volume movement of air into and out of the lungs using a spirometer.
What are the four pulmonary elements, when added together, equal the maximum volume to which the lungs can be expanded?
- Tidal volume
- Inspiratory reserve volume
- Expiratory reserve volume
- Residual Volume
What is Tidal wave and how much does it measure?
The volume of air inspired or expired with each normal breath; it amounts to about 500 milliliters in the adults male.
What is Inspiratory reserve volume and how much does it measure?
The extra volume of air that can be inspired over and above the normal tidal volume when the person inspires with full force; about 3000 milliliters.
What is Expiratory reserve volume and how much does it measure?
The maximum extra volume of air that can be expired by forceful expiration after the end of a normal tidal expiration; about 1100 milliliters.
What is Residual Volume and how much does it measure?
The volume of air remaining in the lungs after the most forceful expiration; about 1200 milliliters.
What are the Pulmonary capacities
- Insipiration capacity
- Functional residual capacity
- Vital Capacity
- Total lung capacity
What is Insipiration capacity
This is the amount of air a person can breathe in, beginning at the normal expiratory level and distending the lungs to the maximum amount (about 3500 milliliters). [Tidal volume + inspiratory reserve volume]
What is Functional residual capacity
Amount of air that remains in the lungs at the end of normal expiration (about 2300 milliliters). [Expiratory reserve volume + residual volume]
What is Vital Capacity
The maximum amount of air a person can expel from the lungs after first filling the lungs to their maximum extent and then expiring to the maximum extent (about 4600 milliliters). [Inspiratory reserve volume + tidal wave + expiratory reserve volume]
What is Total lung capacity
Maximum volume to which the lungs can be expanded with the greatest possible effort (about 5800 milliliters). [Vital capacity + Residual volume]
What is the difference between male and females in the pulmonary system?
All pulmonary volumes and capacities are about 20-25% less in women than in men; greater in large and athletic people than small and asthenic people.
What is the anatomic dead space?
The volume of all the space of the respiratory system other than the alveoli and their other closely related gas exchange areas.
What is physiologic dead space?
The anatomic dead space with plus any alveoli with reduced or nonfunctioning gas exchange area
What is the rate of alveolar ventilation?
Alveolar ventilation per minute is the total volume of new air entering the alveoli and adjacent gas exchange areas each minute. It is equal to the respiratory rate times the amount of new air that enters these areas with each breath.
What is so special about alveolar ventilation?
One of the major factors determining the concentration of O2 and CO2 in the alveoli.
What do the cartilage rings found in five sixths of the way around the trachea do?
To keep the trachea from collapsing
When the cartilage rings stop appearing in the pulmonary system?
Bronchioles
What is the diameter of a bronchiole?
1.5 milliliters
How are bronchioles kept from collapsing?
The same transpulmonary pressures that expand the alveoli
What is a respiratory bronchiole?
A bronchiole with pulmonary epithelium instead of smooth muscle
Where is the greatest amount of airflow resistance found in the pulmonary system in a healthy individual?
In the larger bronchioles and bronchi near the trachea.
Where is the greatest amount of airflow resistance found in the pulmonary system in a diseased individual?
Smaller bronchioles because of muscle contraction in their walls, edema occurring in the walls, or mucus collecting in the lumens of the bronchioles.
Describe the sympathetic nerve control of the pulmonary system
Weak because few of these fibers penetrate to the central portions of the lungs.
However, the bronchial tree is very much exposed to norepinephrine and epinephrine released into the blood; especially epinephrine because of its greater stimulation of beta-adrenergic receptors that cause dilation of bronchial tree.
Describe parasympathetic nerve control of the pulmonary system.
Few parasympathetic nerve fibers from the vagus nerve penetrate the lung parenchyma; acetylcholine causes mild to moderate constriction of the bronchioles (atropine blocks the effects of acetylcholine)
Can also be activated by reflexes that originate from the lungs.
What are 2 powerful local secretory factors that cause bronchial contraction?
Histamine and slow reactive substance of anaphylaxis; both are released by mast cells during an allergic reaction.
How are all the respiratory passages from the nose to the terminal bronchioles kept moist?
Layer of mucus that coats the entire surface
Which cells secrete the mucus in the respiratory passages?
Individual goblet cells in the epithelial lining of the passages and by small submucosal glands.
How many cilia are on each epithelial cell and how many times do they beat and their direction
200 cilia per cell, 10 to 20 times per second and the direction is always toward the pharynx.
How is the mucus itself removed from the respiratory passage?
Cilia beat the mucus continuously upwards to the pharynx. Then it is either swallowed or coughed to the exterior.
What is the carina?
The point where the trachea divides into the bronchi
Describe the cough reflex
- Stimuli on the bronchi or trachea
- Afferent nerve impulses pass from the respiratory passages thru the vagus to the medulla of the brain, causing the following:
- First, up to 2.5 liters of air are rapidly inspired
- Second, the epiglottis closes, and the vocal cords shut tightly to entrap the air with the lungs
- Third, abdominal muscles contract, pushing against the diaphragm while other expiratory muscles also contract
- Pressure builds up as much as 100 mmHg
- Fourth, the vocal cords and the epiglottis suddenly open widely, so that air under this high pressure in the lungs explodes outwards thru bronchial and tracheal slits
Describe the sneeze reflex
Very much like the cough reflex but stimuli starts from the nasal passageways and the uvula is depressed so that large amounts of air pass rapidly through the nose, thus helping to clear the nasal passage.
What 3 distinct normal respiratory functions are performed by the nasal cavities as air passes through the nose AKA air conditioning function?
- Air is warmed by the extensive surface of the conchae and septum, (about 160 square centimeters)
- The air is almost completely humidified even before it passes beyond the nose
- The air is partially filtered
What is turbulent precipitation and what are its components.
Means that air passing thru the nasal passageways hits many obstructing vanes to filter it. Made up by the conchae, the septum, and the pharyngeal wall.
Size of the particles that cannot enter the lungs
Anything bigger than 6 micrometers ( Size smaller than the size of a red blood cell)
Size of the particles that settle in the smaller bronchioles as a result of gravitational precipitation
1 to 5 micrometers
Size of particles that diffuse against the walls of the alveoli and adhere to the alveolar fluid
Smaller than 1 micrometers
Size of particles that remain suspended in the alveolar air and are expelled by expiration
Smaller than 0.5 micrometers
How do particles that become entrapped in the alveoli are are removed?
Alveolar macrophages
Elements that make up the ability to speak
Respiratory system, specific speech nervous control centers in the cerebral cortex, respiratory control centers in the brain and the articulation and resonance structures of the mouth and nasal cavities
What are the mechanical components of speech?
Phonation, achieved by the larynx.
Articulation, achieved by the structures of the mouth.
