Chapter 35: Structure and Function of the Pulmonary System
peripheral chemoreceptors
located in the aorta and carotid bodies and is stimulated by hypoxemia (PaO2), which results in an increase in ventilation in response to arterial hypoxemia
parietal pleura
outer layer of pleura lying closer to the ribs and chest wall; line the thoracic cavity
What mechanism promotes rapid diffusion from the alveolus into the capillary?
partial pressure of oxygen molecules (PO2)
What is the pulmonary artery pressure?
18
Causes of oxyhemoglobin disassociation curve shifting to the left
Alkalosis hypocapnia hypothermia
Where does gas exchange occur?
Alveolocapillary membrane
What role does the lymphatic system play in the respiratory system?
It keeps the lung free of fluid and providing immune defense
Oxyhemoglobin
Hgb bind to O2
What happens to lungs and chest wall when there is high compliance?
Increased work of expiration
structures of the lower respiratory tract
bronchi, bronchioles, alveolar ducts, alveoli, carina, trachea, larynx
How does alveolar ventilation or distention made possible?
by surfactant
pulmonary C-fiber receptors (juxtapulmonary capillary (J) receptors)
causes an increase in pulmonary capillary pressure, which stimulates rapid, shallow breathing; laryngeal constriction on expiration and mucus secretion; hypotension; and bradycardia
Central chemoreceptors located in the medulla provide feedback to increase the rate and depth of breathing when they sense:
central chemoreceptors
What are the two types of chemoreceptors?
central chemoreceptors and peripheral chemoreceptors
What needs to occur for even gas exchange?
even distribution of gas (ventilation) and blood (perfusion) in all parts of the lungs
When smooth muscle contracts (vasoconstriction), does pulmonary artery pressure increase or decrease?
increase
What happens when academia is present in the pulmonary artery?
it causes constriction
How to calculate effective ventilation?
ventilatory rate (breaths per min) x volume of air per breath (liters per breath, tidal volume)
Can low PAO2 be reversible?
yes, PAO2 is reversible as long as levels are corrected
What are the two types of epithelial cells found on alveoli and its functions?
- Type 1 Alveolar cells: provides structure of the alveoli - Type 2 Alveolar cells: surfactant production, which prevents lung from collapsing
functions of alveoli
- air sacs that exchange gases - site where O2 enters the blood and CO2 removed - prevent lung collapse - prevent foreign substances from entering - provide structure - secretes surfactant - promote collateral ventilation between alveoli
What two structures of the lower respiratory tract help to prevent infection?
- alveolar macrophages -surfactant
Causes of muscular effort
- decreased lung and chest wall compliance - airway obstruction caused by bronchospasm or mucous plugs
What are the function of the pulmonary circulation system?
- facilitate gas exchange - delivers nutrients to lung tissues - acts as a blood reservoir for the left ventricle - filters by removing clots, air, and other debris from circulation
What is the primary function of the pulmonary system?
- gas exchange between air and blood - ventilation - diffusion - perfusion
Name the lung sensory receptors to stimulate breathing (DRG)
- irritant receptors - stretch receptors - pulmonary C-fiber receptors (juxtapulmonary capillary (J) receptors)
What are alveolar macrophages?
- phagocytic cells in alveoli of lungs - macrophages most abundant in the lungs to provide immune support
What are the benefits of surfactant of the alveoli?
- prevents the lung from collapsing (atelectasis) - control lung inflammation - prevent oxidative injury - regulating the role of fibroblasts in airway - ingest foreign material and remove it through the lymphatic system
Pores of Kohn
- small openings in the alveolar walls that allow gases and macrophages to travel between the alveoli - promotes collateral ventilation and even air distribution between alveoli
What are the 3 functions of the pulmonary system?
1. Ventilate the alveoli 2. diffuse gases in and out of blood 3. perfuses the lungs to provide organs and tissues oxygen rich blood and low in CO2
Diseases associated with low lung and chest wall compliance
ARDS, Pneumonia, Pulmonary edema, Fibrosis
Causes of oxyhemoglobin disassociation curve shifting to the right
Acidosis hypercapnia hyperthermia
Where is the respiratory center located and what does it do?
Brainstem; controls respirations by transmitting impulses to the respiratory muscles, causing them to contract and relax
How does the nervous system control breathing?
Breathing is involuntary and it automatically adjusts ventilatory rate and volume to maintain normal gas exchange this is called neurochemical control of ventilation
What are the mechanisms of the neurochemical control of ventilation?
Chemoreceptors and lung innervation (supply of nerves)
What are the two groups involved in medullary rhythmic functions?
Dorsal Respiratory Group (DRG) Ventral Respiratory Group (VRG) * located in the medulla
chest radiograph
Evaluates air trapping, consolidation, cavity formation, or presence of tumors
diffusion capacity
Measures the gas diffusion rate at the alveolocapillary membrane
Perfusion
Movement of blood into and out of the capillary beds of the lungs to body organs and tissues
ventilation-perfusion ratio
Perfusion > ventilation in bases Ventilation > perfusion in the apices
Gas velocity increases as gas passes through a restricted area, whose law is expressed?
Poiseuille's Law
central chemoreceptors
Receptors in the central nervous system that monitor the pH of cerebrospinal fluid to help regulate ventilation rate.and depth
oxyhemoglobin dissociation curve
Relationship between available oxygen and amount of oxygen carried by hemoglobin.
Bohr effect
Shift in the oxyhemoglobin dissociation curve caused by changes in CO2 and H+ concentration in the blood
Cause of low lung and chest wall compliance
Stiff lungs- difficult to inflate
What type of cells produce surfactant?
Type II alveolar cells
pulmonary circulation
The passage of venous blood from the right atrium of the heart through the right ventricle and pulmonary arteries to the lungs where it is oxygenated and its return via the pulmonary veins to enter the left atrium and participate in systemic circulation.
Minute Volume (MV)
The volume of air breathed in one minute; tidal volume (TV) x RR = MV
function of surfactant
Thin layer of fluid that covers the alveoli. Reduces surface tension of the fluid layer lining the alveoli, preventing the alveoli from collapsing during exhalation.
True or False: The bronchial circulation is part of the systemic circulation and does not participate in gas exchange?
True
Compliance
a measure of the ease of expansion of the lungs and thorax.
arterial blood gases (ABGs)
a test performed on arterial blood to determine levels of oxygen, carbon dioxide, and pH concentrations
Mechanisms that contribute to airway resistance
airway size gas velocity (Poiseullille's Law) normally low bronchoconstriction bronchodilation
dorsal respiratory group (DRG)
alters breathing patterns to restore normal blood gases
Where is surfactant located?
alveolocapillary membrane
How to measure alveolar ventilation?
arterial blood gas analysis to measure PaCO2
What happens when one lobe is obstructed from hypoxic pulmonary vasoconstriction?
blood shunts to the well-ventilated portions of the lung, called reflex, to better match ventilation and perfusion
How does diffusion of CO2 occur?
diffusion from systemic capillaries into the cells >>> perfusion of systemic capillaries into the cells >>> diffusion of O2 from the alveoli into the capillary blood >>> ventilation of the lungs
What determines compliance of lungs?
elastic recoil and alveolar surface tension
Pulmonary hypertension
elevated pulmonary artery pressure resulting from an increase in pulmonary vascular resistance to blood flow through small arteries and arterioles.
Disease associated with high lung and chest wall compliance
emphysema
Acinus
functional respiratory unit that consists of the bronchioles, alveolar ducts, alveolar sacs, and the alveoli.
What happens when the walls of the alveolocapillary membrane thickens?
gas exchange is impaired
What happens when oxyhemoglobin disassociation curve shifts to the right?
hemoglobin has a decreased affinity to oxygen
What happens when oxyhemoglobin disassociation curve shifts to the left?
hemoglobin has an increased affinity to O2
What biochemical factors causes a decrease in diameter of the vessels in pulmonary system?
histamine, prostaglandins, endothelin, serotonin, nitric oxide, and bradykinin
What happens to lungs when there is low compliance?
increased work of inspiration d/t stiff lungs and chest wall
What happens in chronic alveolar hypoxia?
inflammation and structural remodeling in pulmonary arterioles occurs, causing permanent pulmonary artery hypertension that eventually leads to right heart failure
visceral pleura
inner layer of pleura lying closer to the lung tissue; covers the lung
oxygen transport
is the diffusion of alveolocapillary membrane
Alterations of aging pulmonary system
loss of elastic recoil stiffening of lung and chest wall alterations of gas exchange increase in flow and resistance loss of alveoli wall tissue decreased PaO2 decrease in respiratory muscle strength and endurance
Cause of high lung and chest wall compliance
loss of elastic recoil- making lungs easy to inflate
What is the main cause of pulmonary artery constriction?
low alveolar partial pressure of oxygen (PAO2)
What causes pulmonary vasoconstriction?
low partial pressure of oxygen (PAO2)
low lung and chest wall compliance
lungs and thoracic wall resist expansion
spirometry
measures volume and flow rate during forced expiration
Chemoreceptors
monitors pH, PaCO2, and PaO2
Ventilation
movement of air in and out of the lungs
Diffusion
movement of gas between air spaces and lungs
What determines work of breathing?
muscular effort required for ventilation
structures of the upper respiratory tract
nasal cavity, pharynx, larynx, oropharynx
What is the pressure in the pleural space?
negative or subatmospheric -4 to -10 mmHg
partial pressure of oxygen molecules (PO2)
pressure is greater in alveolar gas than it is in capillary blood alveoli pressure > capillary
Irritant receptors
receptors that are stimulated by noxious substances and causes cough, bronchoconstriction, and increase respiratory rate
stretch receptors
receptors that sense muscle stretch and contraction to protect against excess lung inflation, which results in decrease respiratory rate and volume
ventilatory rate
the number of times gas is inspired and expired per minute; breaths per minute
What causes academia?
respiratory acidosis and metabolic acidosis
What are the gas exchange airways?
respiratory bronchioles, alveolar ducts, alveoli
How does hypoxic pulmonary vasoconstriction occur?
results from an increase in intracellular calcium levels in smooth muscle cells in response to low O2 and the presence of charged oxygen molecules called oxygen free radicals
ventral respiratory group (VRG)
sets automatic rhythm of respiration
Tests for pulmonary function
spirometry diffusion capacity residual volume functional reserve capacity (FRC) total lung capacity arterial blood gas analysis chest radiograph
elastic recoil
tendency of the lungs to return to the resting state after inspiration
gas transport
the delivery of oxygen to the cells of the body and the removal of CO2
What happens to the diameter of the pulmonary artery when smooth muscle contracts?
the diameter of the pulmonary artery decreases
How does distribution of ventilation and perfusion achieved?
through gravity and alveolar pressure, depends on body position
What is the purpose of eliminating CO2?
to maintain a partial pressure of arterial CO2 (PaCO2) of 40 mmHg and normal acid-base balance
bronchial circulation
transports oxygenated blood to bronchi and bronchioles
Hypoxic pulmonary vasoconstriction
vasoconstriction caused by alveolar and pulmonary venous hypoxia
What happens if the whole lung is obstructed from hypoxic pulmonary vasoconstriction?
vasoconstriction occurs throughout the whole pulmonary circulation and pulmonary hypertension can result
What are the four steps of gas transport?
ventilation of the lungs >>> diffusion of O2 from the alveoli into the capillary blood >>> perfusion of systemic capillaries into the cells >>> diffusion from systemic capillaries into the cells