Module 10 Flashcards
List the main functions of the respiratory system
Transport of O2 from air into blood Removal of CO2 from blood into air Control of blood acidity (pH) Temperature regulation Forming a line of defense to airborne particles
Describe the path of air into the lungs
Airway starts at nasal cavity and mouth, joining at the pharynx, leading to larynx (voice box), which becomes the trachea, which divides into two main bronchi (left and right) into the lungs, dividing into smaller bronchioles until becoming alveoli, the site of gas exchange
Describe the blood vessels from entering the lungs to leaving the lungs
Pulmonary artery brings deoxygenated blood to the lungs, branches into capillaries around each alveolus, whose structure maximizes gas exchange (thin endothelial walls, large cross-sectional area, low blood velocity). O2 diffuses in, CO2 diffuses out, then pulmonary vein brings oxygenated blood back to the heart
Describe the anatomical relationship of the lungs to the chest wall, pleural membrane, and diaphragm
Lungs are inside the thoracic cavity surrounded by the rib cage (laterally, posteriorly and anteriorly) and the diaphragm (inferiorly), with two thin pleural membranes, one lining the ribs (parietal) and one on the lungs (visceral)
Describe the histological structure of an alveolus (type I vs type II cells)
An alveolus is toughly 0.3mm in diameter, with walls one cell thick made of alveolar epithelial cells (type I cells)
Tyle II cells secrete surfactant, which lines the alveoli
Fibers of elastin and collagen are present in walls of the alveoli and around blood vessels and bronchi
Lots of capillaries surround the alveoli closely
Describe the pleural membranes and intrapleural space, and their functions
Parietal pleura lines and sticks to the ribs, visceral pleura lines and sticks to the lungs
Between them is intrapleural space, containing a small amount of pleural fluid, which reduces friction between the two pleura during breathing
Define alveolar/intrapulmonary pressure
Pressure inside the lungs
Define intrapleural pressure
Pressure in the intrapleural space
Define atmospheric pressure
Pressure outside the body (760mmHg at sea level)
Define transpulmonary pressure
Difference between the alveolar and intrapleural pressures
Explain the significance of a low intrapleural pressure compared to the alveolar pressure
This would be a positive transpulmonary pressure
Important because the difference in pressure holds the lungs open, in healthy lungs, transpulmonary pressure is positive (outwards) to keep the lungs and alveoli open (they want to collapse)
Describe what happens during a pneumothorax
If both alveolar and intrapleural pressures were equal, transpulmonary would be 0, no pressure holding lungs open, causing collapse
Occurs when intrapleural space is punctured, causing the pressures to equalize
Generally only one lung collapses because the intrapleural spaces are isolated from each other
Define Boyle’s Law
When the volume of a container decreases, the pressure inside increases, and vice versa
Important for ventilation
Basically pressure varies inversely with volume
Describe the process of inspiration
To decrease pressure, lung volume must increase, so diaphragm contracts, moving downward, and external intercostal muscles of ribs contract, lifting ribcage up and out
This drops alveolar pressure, pressure gradient now exists (low in lungs, higher outside), so air flows into lungs
This is an active process, requires signals from brain stem to contract muscles
Describe the process of expiration at rest
Diaphragm and external intercostal muscles relax, causing lungs to recoil to original size; volume decreases, alveolar pressure increases above outside pressure, so pressure gradient is now reversed and air flows out
This is a passive process, no muscle contractions
Describe the process of expiration during exercise
Air must be forced out of lungs, requiring contraction of abdominal and internal intercostal muscles. When they contract, decreases volume of lungs, creating larger pressure gradient and forcing air out
This is an active process
Define pulmonary compliance
Stretchability of the lungs (more stretchable is more compliant); the volume change that happens as a result of a change in pressure
Explain the importance of pulmonary compliance
Equation: compliance = volume change / pressure change
Important because it determines the ease of breathing, a lung with decreased compliance is difficult to inflate, but one with high compliance is difficult to deflate
List two major factors that influence compliance of lungs
The amount of elastic tissue found in the walls of the alveoli, blood vessels, and bronchi
The surface tension of film of liquid lining the alveoli
Describe pulmonary fibrosis
A disease causing decrease in compliance, caused by constant inhalation of fine particles (asbestos, air pollution, coal dust). Immune cells can’t destroy them, so they form large inelastic collagen deposits that form fibrous scars
List two factors that cause an increase in pulmonary compliance
Normal aging and pulmonary emphysema
Describe pulmonary emphysema
A chronic condition from smoking, destroys elastin fibers in the lungs (elastin decreases compliance), so without them compliance increases, inhalation is easy, but without elastin its hard to recoil the lungs, exhalation requires muscular contraction even at rest
Describe the two elastic tissue components in the lungs
Fibers of elastin and collagen are arranged in special geometric arrangements where elastin are easily stretchable but collagen are not, contributes to 1/3 of total compliance of healthy lungs
Elastin - adding more makes lungs less compliant because it takes energy to stretch, inspiration becomes more difficult, expiration becomes less difficult
Collagen - inelastic, forms deposits in pulmonary fibrosis, decrease in collagen causes increase in compliance
Define surface tension
Force developed at the surface of a liquid due to attractive forces between water molecules
Explain how surface tension affects lung compliance/elastic behaviour
2/3 of elastic behaviour of lungs is attributed to surface tension of the liquid film lining alveoli, which tends to collapse alveoli, decreasing compliance and making inflation difficult
The majority of forces between water molecules are inward in a drop, no outward balancing force on surface, so the inward forces would cause alveoli to collapse
Define pulmonary surfactant
A lipoprotein substance produced by type II alveolar cells, consisting mostly of phospholipids (hydrophilic head, hydrophobic tail)
Explain the function of pulmonary surfactant
When surfactant is added to water, it lies on the surface. Phospholipid head groups are attracted to water, and balance the inward forces of the water drop with an outward one. Forces now equal in every direction, water drop will flatten due to decreased surface tension, so alveoli won’t collapse.
Surfactant is released during deep breathing, so important to breathe deeply after surgeries in thoracic cavity to stimulate production
List the four basic lung volumes
Tidal volume
Inspiratory reserve volume
Expiratory reserve volume
Residual volume
Define tidal volume
The volume of air entering or leaving the lungs during one breath at rest
Usually 500mL
