respiratory system 3 (mechanisms of breathing)

negative intrapleural pressure

-4 mm Hg, due to tendency of the alveoli to recoil and get smaller, the tendency of the thoracic cage to expand, and the suction created by the pleural fluid (which makes the visceral pleura cling to the parietal pleura, and causes the lungs to adhere to the thoracic wall)

restrictive pulmonary disease

a disease in which the patient experiences a decrease in total lung capacity. includes, tuberculosis, pneumonia, or fibrosis, where there is an increase in non-elastic tissue in the lungs, so it is harder to inflate the lungs. cause a decline in vital capacity, total lung capacity, functional residual capacity, and residual volume

obstructive pulmonary disease

a disease in which the patient experiences increased airway resistance, the air stays in the lungs because it is harder to push out. patients might exhibit increased total lung capacity, increased functional residual capacity, and increased residual volume. includes, chronic bronchitis, emphysema, asthma, and cystic fibrosis.

deep, slow breathing

a greater percentage of each inspired breath reaches the alveoli, enhancing the flow of fresh air

spirometry

a measurement of breathing

quiet expiration

a passive process that only requires the relaxation of the diaphragm and external intercostal muscles. the natural recoil of the lungs and thoracic wall cause an increase in intrapulmonary pressure, causing air to flow out of the lungs

when intrapulmonary pressure is less than atmospheric pressure

air flows into the lungs

when intrapulmonary pressure is greater than atmospheric pressure

air moves out of the lungs

what factors affect the efficiency of pulmonary ventilation?

airway resistance, alveolar surface tension, and lung compliance

quiet inspiration

an active process that requires contraction of the diaphragm and external intercostal muscles, which cause an increase in the thoracic cavity volume, a decrease in intrapulmonary pressure, and airflow into the lungs

forced inspiration

an active process that requires the recruitment of additional muscles including the sternocleidomastoid, scalenes, and serratus anterior. these muscles help increase the volume of the thoracic cavity beyond what is seen in quiet inspiration, allowing for the greater movement of air

forced expiration

an active process that requires the recruitment of the internal intercostal muscles and abdominal wall muscles. contraction of these muscles helps decrease the volume of the thoracic cavity beyond what is achieved with quiet expiration, allowing for a greater movement of air

contraction of the muscles of inspiration most directly cause...

an increase in thoracic volume

surfactant

any substance that interferes with the hydrogen bonding between water molecules and thereby reduces surface tension, produced by type 2 alveolar cells

how does anatomical dead space affect respiratory efficiency?

approximately 150 mL of air moved during tidal volume is within the anatomical dead space, which means that only 350 mL of air is actually participating in gas exchange. by considering this in pulmonary ventilation, you will have a better understanding of how much air is reaching the alveoli for gas exchange.

Patm

atmospheric pressure

how does puncturing the parietal pleura result in pneumothorax in only one lung?

because each lung is encased in its own pleural cavity, each lung can operate somewhat independently

pulmonary ventilation

breathing, movement of air in and out of lungs

bronchoconstriction

causes a reduction in the diameter of the airway, increasing resistance, and decreasing airflow

bronchodilation

causes a widening of the diameter of the airway, decreasing resistance, and increasing airflow

pneumothorax

collapsed lung

pulmonary ventilation related to boyle's law

container - thoracic cavity and lungs pressure - intrapulmonary pressure within the lungs and alveolar air spaces

airway resistance

controlled by smooth muscles that line the bronchioles. contraction of the smooth muscles causes bronchoconstriction and relaxation causes bronchodilation

air flows

down its pressure gradient

inspiration

during pulmonary ventilation, contraction of inspiratory muscles cause expansion of the thoracic cavity. at the same time, the negative intrapleural pressure is creating a suction, or vacuum, which tends to cause the lungs to follow the movement of the thoracic wall. as the volume of the lungs expands, there is a decrease in intrapulmonary pressure. this causes air to move into the lungs. at first, the lungs expand, and the negative pressure is getting bigger, but as more air enters the lungs, this pressure difference is not as great. these pressures continue to equilibrate until the lungs stop expanding, at which point the difference between intrapulmonary pressure and atmospheric pressure is 0. during the entire inspiration phase, the intrapleural pressure continues to become more negative (until it reaches -6 mm Hg), which is necessary to keep the lungs inflated. transpulmonary pressure is the greatest when the lungs are expanded the most, which occurs at the peak of the breath (tidal volume).

lung compliance

how easy it is for the lungs to stretch or expand at a given transpulmonary pressure

example of transpulmonary pressure

if the intrapulmonary pressure is 760 mm Hg and the intrapleural pressure is 756 mm Hg, or -4 mm Hg compared to the intrapulmonary pressure, then it would be equal to 4 mm Hg

when it atmospheric pressure the same as intrapulmonary pressure

in between breaths, because the air in the lungs equilibrates with the outside air

factors that decrease lung compliance

increasing alveolar surface tension (making the alveoli harder to inflate), limiting chest wall movement (broken ribs or weak muscles), or inhibiting lung movement within the thoracic cavity

Pip

intrapleural pressure

Ppul

intrapulmonary pressure

decreased lung compliance

leads to decreased pulmonary ventilation

intrapleural pressure is always

less than intrapulmonary pressure (keeping the alveolar spaces inflated and preventing the lungs from collapsing)

shallow, fast breathing

most of the air inspired never reaches the air spaces and is stuck in the dead space

ventilation

movement of air in and out of the lungs the repeating pattern of quiet inspiration and quiet expiration

functional residual capacity

represents the amount of air remaining in the lungs after a normal tidal volume expiration expiratory reserve volume + residual volume

intrapulmonary pressure

the air pressure within the lung air spaces (alveoli) sometimes called intra-alveolar pressure

in spirometry, what is the residual volume?

the air remaining in the lungs and alveoli

residual volume

the amount of air left in the lungs even after forcefully expelling as much air as possible the amount of air that stays in the alveoli - this air helps keep the alveoli open and prevent lung collapse

expiratory reserve volume

the amount of air that can be expelled from the lungs after a normal tidal volume expiration

inspiratory reserve volume

the amount of air that can be inspired forcefully beyond tidal volume how much air you can bring into your lungs, or how much you can inflate your lungs

tidal volume

the amount of air that moves into and out of the lungs during quiet breathing and is typically about 500 mL (volume of a normal breath)

alveolar ventilation

the amount of air that reaches the alveoli (tidal volume x respiratory rate) - anatomical dead space

transpulmonary pressure

the difference between the intrapulmonary pressure and the intrapleural pressure (Ppul - Pip) expressed in an absolute value the pressure that keeps the lungs from collapsing dictates lung size

expiration

the inspiratory muscles start to relax (assuming quiet breathing). the natural recoil of the chest and the elastic tissue of the lungs start to decrease the volume of the lungs. the intrapleural pressure starts to become less negative (but still has to remain about -4 mm Hg). the decreased volume of the lungs increases intrapulmonary pressure so its greater than atmospheric pressure. air moves out of the lungs. as air moves out of the lungs, the pressure difference between intrapulmonary pressure and atmospheric pressure is not as great, until these two pressures are equal to zero.

if transpulmonary pressure equals zero

the lungs will collapse

increased alveolar surface tension

the molecular attraction (H bonding) between the water molecules creates high surface tension, which can cause the alveoli to collapse. collapsed alveoli are extremely difficult to inflate, limiting gas exchange.

the greater the transpulmonary pressure

the more inflated the lungs become

atomospheric pressure

the pressure of air on the body

boyle's law

the pressure of gas within a container is inversely related to the volume of the container P1V1 = P2V2 (p= pressure, v= volume)

if the volume of a container, containing gas, is increased (boyle's law)

the pressure of the gas decreases

if the volume of a container, containing gas, is reduced (boyle's law)

the pressure of the gas increases

intrapleural pressure

the pressure within the pleural cavity

total lung capacity

the sum of all the lung volumes, the total air that can fit into the lungs vital capacity + residual volume

decreased surface tension

the thin layer of surfactant found on the inner walls of the alveoli allows the alveoli to stay open, allowing for them to be easily inflated

when inspiratory skeletal muscles contract (boyle's law related to pulmonary ventilation)

the thoracic cavity and lungs enlarge, causing intrapulmonary pressure to decrease. since the intrapulmonary pressure is now less than the atmospheric pressure, air flows down its pressure gradient and enters the lungs

when inspiratory skeletal muscles relax (boyle's law related to pulmonary ventilation)

the thoracic wall and lungs recoil back to their original size (get smaller), and the intrapulmonary pressure increases. since the intrapulmonary pressure is now greater than atmospheric pressure, air moves out of the lungs, down its pressure gradient

inspiratory capacity

the total amount of air that can be inspired after a tidal volume or normal expiration tidal volume + inspiratory reserve volume

vital capacity

the total amount of exchangeable air tidal volume + inspiratory reserve volume + expiratory reserve volume

anatomical dead space

the volume of the conducting zone structures

puncturing the parietal pleura

this would cause the intrapleural pressure to equilibrate to the atmospheric pressure. the transpulmonary pressure wold drop to zero, resulting in a collapsed lung

minute ventilation

tidal volume x respiratory rate

alveolar surface tension

type 2 alveolar cells, found in the inner walls of alveoli, secrete surfactant, which decreases surface tension, keeping alveoli open

at which point in pulmonary ventilation is transpulmonary pressure the greatest?

when the lungs are expanded the most