Several different types of receptors in the lungs stimulate the VRG through afferent nerves.
Thyroid cartilage
Oropharynx
The pulmonary blood and lymphatic vessels.
Yes, if the acidemia is corrected.
A serous membrane that adheres firmly to the lungs and attaches to the chest wall.
The main structures are the upper airways, two lungs, the lower airways, and the blood vessels that serve them.
The lung tissue that surrounds the airways supports them, preventing their distortion or collapse as gas moves in and out during ventilation.
The laryngeal box is formed by three large cartilages—the epiglottis, thyroid, and cricoid—and three smaller cartilages.
Stimulation of irritant receptors in the nares (nostrils) by chemical or mechanical irritants triggers the sneeze reflex, resulting in rapid removal of irritants from nasal passages.
Several pulmonary capillaries.
At the level of the terminal bronchioles.
An arterial blood gas analysis must be performed to measure PaCO2 to determine the adequacy of ventilation.
An epithelial lining, a smooth muscle layer, and a connective tissue layer.
Noxious aerosols, gases, and particulate matter.
Increases in the size or volume of the lungs.
Increased pulmonary capillary pressure.
Approximately 50 million at birth and about 480 million by adulthood.
Mononuclear phagocytes of the lungs that ingest foreign material and prepare it for removal through the lymphatics.
More vessels become perfused.
The basic automatic rhythm of respiration is set by the DRG, a cluster of inspiratory nerve cells located in the medulla.
Cuneiform tubercle
The arytenoid, corniculate, and cuneiform cartilages.
Hard palate
Vasoconstriction caused by alveolar and pulmonary venous hypoxia.
It results in decreased velocity of airflow into the gas-exchange portion of the lung and allows for optimal gas diffusion.
The three steps are ventilation, diffusion, and perfusion.
A thin layer of fluid secreted by the pleura.
The nasopharynx, oropharynx, and related structures are often called the upper airway.
Alveolar macrophages ingest and remove bacteria and other foreign material from alveoli by phagocytosis.
Across the alveolocapillary membrane.
No, it does not.
Local humoral conditions.
The lung eliminates about 10,000 milliequivalents (mEq) of carbonic acid per day in the form of CO2.
Vasoconstriction of the arterioles perfusing those areas is a positive compensatory mechanism that reduces shunt (wasted perfusion).
In the epithelium of the conducting airways.
In the proximal larger airways.
At high tidal volumes, such as with exercise and mechanical ventilation.
The vagus nerve.
About one third.
Voluntary breathing is necessary for talking, singing, laughing, and holding one’s breath.
Epiglottis
Vestibule
Nasopharynx
Because the right mainstem bronchus is slightly larger and more vertical than the left.
Yes, it is reversible if the PaO2 is corrected.
It protects the lungs from injury and performs the muscular work of breathing.
The cardiovascular system carries out the third function of gas exchange.
Bronchi are a set of conducting airways that deliver air to each section of the lung.
During quiet breathing, gas usually flows through the nose, nasopharynx, and oropharynx to the lower airways.
The endolarynx is formed by two pairs of folds that form the false vocal cords (supraglottis) and the true vocal cords.
Approximately 100 ml of blood is spread very thinly over about 140 m² of alveolar surface area.
Yes, in the same manner as the systemic circulation.
CO2 is produced at the rate of approximately 200 ml/minute.
Widespread and persistent hypoxic pulmonary vasoconstriction creates resistance to pulmonary blood flow and raises the pressure in the pulmonary artery, causing secondary pulmonary artery hypertension.
Research is in progress to inhibit and potentially reverse the remodeling of pulmonary arteriolar walls.
In the smooth muscles of airways.
Protecting against excess lung inflation.
Airway caliber by stimulating bronchial smooth muscle to contract or relax.
The parasympathetic division.
The VRG becomes active when increased ventilatory effort is required.
Arytenoid cartilage
Nasal conchae
Laryngeal pharynx
The arterioles to that segment constrict, shunting blood to other, well-ventilated portions of the lung.
Histamine, prostaglandins, endothelin, serotonin, nitric oxide, and bradykinin.
Diffusion is the movement of gases between air spaces in the lungs and the bloodstream.
It lubricates the pleural surfaces, allowing the two layers to slide over each other without separating.
The mouth and oropharynx provide for ventilation when the nose is obstructed or when increased flow is required, such as during exercise.
The upper respiratory tract mucosa maintains constant temperature and humidification of gas entering the lungs; traps and removes foreign particles, some bacteria, and noxious gases from inspired air.
The thin basement membrane of the pulmonary system.
Pulmonary veins are dispersed randomly throughout the lung, unlike pulmonary arteries which follow the branching bronchi.
No, there are no lymphatic structures in the acinus.
The pulmonary system functions to ventilate the alveoli, diffuse gases into and out of the blood, and perfuse the lungs so that the organs and tissues of the body receive blood that is rich in oxygen and low in CO2.
The thoracic cavity is divided into three subdivisions (left and right pleural divisions and mediastinum) by a partition formed by a serous membrane called the pleura.
Severe pulmonary hypertension can impede right ventricular ejection and eventually cause right heart failure known as cor pulmonale.
They become thinner.
Bronchioles from the sixteenth through the twenty-third divisions that contain increasing numbers of alveoli.
They cause smooth muscle to contract.
Near the respiratory center.
The VRG is located in the medulla and contains inspiratory and expiratory neurons.
Corniculate cartilage
Soft palate
At the carina.
Sixteen divisions.
Perfusion is the movement of blood into and out of the capillary beds of the lungs to body organs and tissues.
The lungs are divided into lobes: three in the right lung (upper, middle, lower) and two in the left lung (upper, lower).
In healthy individuals, the defense mechanisms are so effective that contamination of the lung tissue itself is unusual.
Stimulation of irritant receptors in the trachea and large airways by chemical or mechanical irritants triggers the cough reflex, resulting in removal of irritants from the trachea and large airways.
At the hila.
From the alveoli to the terminal bronchioles.
Ventilation is the mechanical movement of gas or air into and out of the lungs.
The central nervous system responds to neurochemical stimulation of ventilation and sends signals to the chest wall musculature.
They decrease ventilatory rate and volume.
Rapid, shallow breathing; laryngeal constriction on expiration and mucus secretion; hypotension; and bradycardia.
An epithelial layer and a thin, elastic basement membrane but no muscle layer.
They secrete surfactant.
Facilitates gas exchange, delivers nutrients to lung tissues, acts as a blood reservoir for the left ventricle, and serves as a filtering system that removes clots, air, and other debris from the circulation.
Through its effect on the pH (hydrogen ion content) of the CSF.
They stimulate the respiratory center to increase the depth and rate of ventilation.
The diaphragm and the external intercostal muscles.
The respiratory center in the brainstem controls respiration by transmitting impulses to the respiratory muscles, causing them to contract and relax.
Vocal cords
Intercartilaginous ligaments
They move the larynx as a whole.
It is slightly larger and more vertical, branching at about a 20° to 30° angle from the trachea.
The primary function of the pulmonary system is the exchange of gases between the environmental air and the blood.
The alveolar wall (fluid containing surfactant, epithelial cells, basement membrane), interstitial space, and wall of a pulmonary capillary (basement membrane, endothelial cells).
The diaphragm is a dome-shaped muscle that separates the thoracic and abdominal cavities and is involved in ventilation.
The structure of the larynx consists of the endolarynx and its surrounding triangular-shaped bony and cartilaginous structures.
Because they can leak plasma and blood into the alveolar space.
The normal venous admixture or right-to-left shunt.
The caliber increases, decreasing blood pressure.
CO2, the gaseous form of carbonic acid (H2CO3), is a product of cellular metabolism.
Decreases in PAO2 to less than 12% of normal induce a locally controlled constriction of preacinar arteriolar smooth muscle and endothelial cells.
Alveolar hypoxia causes the production of reactive oxygen species (toxic oxygen radicals), vasoconstrictors (such as endothelin), and vascular endothelial growth factor.
Single-celled exocrine glands (goblet cells) and ciliated cells.
They rhythmically beat the mucous blanket toward the trachea and pharynx.
In gas-exchange airways.
The alveoli.
The DRG sends efferent impulses to the diaphragm and inspiratory intercostal muscles.
Corniculate tubercle
Trachealis muscle
They are important to swallowing, respiration, and vocalization.
It can affect only one portion of the lung or the entire lung.
Acidemia.
Ventilation is the movement of air into and out of the lungs.
About 18 ml of fluid with a pH of about 7.6, a few cells, about 1 g/dl protein, and glucose and electrolyte concentrations similar to plasma.
The lungs are protected by a series of mechanical and cellular defenses.
The vestibule is the space above the false vocal cords.
An endothelial layer and a thin basement membrane.
Any disorder that thickens the alveolocapillary membrane.
Deep and superficial pulmonary lymphatic capillaries.
No, the adequacy of alveolar ventilation cannot be accurately determined by observation of ventilatory rate, pattern, or effort.
High columnar pseudostratified epithelium.
They stimulate bronchial smooth muscles to constrict.
The structures of the gas-exchange airways that participate in gas exchange.
By sensing changes in the pH of cerebrospinal fluid (CSF).
It combines with H2O to form carbonic acid, which dissociates into hydrogen ions.
Renal compensation through bicarbonate retention.
The pneumotaxic center and apneustic center, situated in the pons, act as modifiers of the inspiratory depth and rate established by the medullary centers.
Cricoid cartilage
They control vocal cord length and tension.
They contract to prevent aspiration into the trachea and contribute to voice pitch.
It can cause coughing and airway narrowing.
It improves the lung’s efficiency by better matching ventilation and perfusion.
The membrane lining the thoracic cavity.
The mucosal lining warms and humidifies inspired air to 100% and removes foreign particles from it as it passes into the lungs.
Filtering and humidifying are not as efficient with mouth breathing.
Nasal hairs and turbinates trap and remove foreign particles, some bacteria, and noxious gases from inspired air.
The fusion of the basement membrane of the pulmonary system with the basement membrane of the alveolar septum.
They have no valves.
The membrane that surrounds the lungs.
Ventilation is often misnamed as respiration, which is actually the exchange of O2 and CO2 during cellular metabolism.
The response of the respiratory system to neurochemical impulses is influenced by several factors that affect the mechanisms of breathing and therefore affect the adequacy of ventilation.
Irritant receptors, stretch receptors, and J-receptors.
The cough reflex.
They become more sparse.
They consist of an epithelial layer devoid of cilia and goblet cells, very little smooth muscle fiber, and a very thin and elastic connective tissue layer.
They cause it to relax.
Stimulation of irritant receptors by irritants in inspired air, inflammatory mediators, many drugs, and humoral substances.
Hydrogen ion concentration.
The mechanisms that control respiration are very complex.
Breathing can be modified by input from the cortex, the limbic system, and the hypothalamus.
The trachea serves as the main airway to the lungs.
Epiglottis
Vasoconstriction occurs throughout the pulmonary vasculature, and pulmonary hypertension can result.
Skin, ribs, and intercostal muscles.
The pulmonary system carries out the first two functions of gas exchange.
Negative or subatmospheric (−4 to −10 mmHg).
The larynx connects the upper and lower airways.
The mucous blanket protects the trachea and bronchi from injury; traps most foreign particles and bacteria that reach the lower airways.
The conducting airways, nerves, lymph nodes, large pulmonary vessels, and membranes (pleurae) that surround the lungs.
Keeping the lung free of fluid and providing immune defense.
The amount of effective ventilation is calculated by multiplying the ventilatory rate (breaths per minute) by the volume of air per breath (liters per breath, tidal volume).
The control of the pulmonary circulation plays a role in the appropriate distribution of blood flow.
Mucus.
In newborns.
From the upper thoracic and cervical ganglia of the spinal cord.
A lipoprotein that coats the inner surface of the alveolus, facilitates its expansion during inspiration, lowers alveolar surface tension at end-expiration, and prevents lung collapse.
Alterations in the major and accessory muscles of inspiration and expiration, elastic properties of the lungs and chest wall, and resistance to airflow through the conducting airways.
Breathing is usually involuntary because homeostatic changes in the ventilatory rate and volume are adjusted automatically by the nervous system to maintain normal gas exchange.
The pattern of breathing can be influenced by emotion and by disease.
Elastic fibers provide flexibility and strength to the respiratory structures.
At about a 45° angle.
The cross-sectional area of the airways increases to 20 times that of the trachea.
The pulmonary system consists of upper and lower airways, the chest wall, and pulmonary circulation.
The area between the two pleurae.
The mediastinum is the space between the lungs that contains the heart, great vessels, and esophagus.
The conducting airways consist of upper and lower airways.
Cilia propel the mucous blanket and entrapped particles toward the oropharynx, where they can be swallowed or expectorated.
The alveolar epithelium, the alveolar basement membrane, an interstitial space, the capillary basement membrane, and the capillary endothelium.
Not all of its capillaries drain into its own venous system; some empty into the pulmonary vein.
The caliber decreases, increasing pulmonary artery pressure.
The product of ventilatory rate and tidal volume is called the minute volume (or minute ventilation) and is expressed in liters per minute.
Hypoxic pulmonary vasoconstriction is a physiologic response to changes in the environment and pulmonary pathologic conditions that affect alveolar oxygen content (PAO2).
Cartilage.
Columnar cuboidal epithelium.
A reflex that decreases ventilatory rate and volume when stretch receptors are stimulated.
The autonomic nervous system (ANS).
Type I alveolar cells and type II alveolar cells.
The pH or concentration of hydrogen ions.
The DRG receives afferent impulses from peripheral chemoreceptors in the carotid and aortic bodies, which detect the PaCO2 and the amount of oxygen in the arterial blood (PaO2).
Cilia help to move mucus and trapped particles out of the respiratory tract.
They prevent collapse of the larynx during inspiration and swallowing.
It connects the larynx to the bronchi, the conducting airways of the lungs.
Into lobar bronchi, then to segmental and subsegmental bronchi, and finally end at the terminal bronchioles.
No, it does not.
The membrane covering the lungs.
The conducting airways are the portion of the pulmonary system that provides a passage for the movement of air into and out of the gas-exchange portions of the lung.
The shared alveolar and capillary walls.
The systemic circulation.
At the hilus through a series of mediastinal lymph nodes.
'Respiratory rate' actually refers to the ventilatory rate, or the number of times gas is inspired and expired per minute.
Gas transport between the alveoli and pulmonary capillary blood depends on a variety of physical and chemical activities.
Lung hypoxia activates many hypoxia-dependent genes in pulmonary vascular endothelial cells to produce a variety of chemicals and growth factors.
Bronchoconstriction and increased ventilatory rate.
They thin.
In alveolar ducts.
Equilibrium, or equal stimulation of contraction and relaxation.
The pulmonary circulation has a lower pressure and resistance.
No, it does not.
An artery or arteriole.
The respiratory center is composed of several groups of neurons located bilaterally in the brainstem: the dorsal respiratory group (DRG), the ventral respiratory group (VRG), the pneumotaxic center, and the apneustic center.
False cord
Tracheal cartilage provides structural support to the trachea.
U-shaped cartilage.
At the hila, or 'roots' of the lungs.
Permanent pulmonary artery hypertension, which eventually leads to cor pulmonale and heart failure.
It is contained by the chest wall and encases the lungs.
The pulmonary system normally functions efficiently under a variety of conditions and with little energy expenditure.
Carbon dioxide (CO2) and oxygen (O2).
The glottis is the slit-shaped space between the true vocal cords.
Surfactant enhances phagocytosis of pathogens and allergens in alveoli and down-regulates inflammatory responses.
Large quantities of blood.
A low alveolar partial pressure of oxygen (PaO2).
CO2 elimination is necessary to maintain a normal partial pressure of arterial CO2 (PaCO2) of 40 mmHg and normal acid-base balance.
Remodeling is a process by which the vascular wall becomes scarred and thickened, resulting in permanent decreases in luminal diameter, increased resistance to blood flow, and permanent pulmonary artery hypertension.
They are attacked by cellular components of the inflammatory response and antibodies of the secretory immune system.
Respiratory bronchioles, alveolar ducts, and alveoli.
They permit some air to pass through the septa from alveolus to alveolus, promoting collateral ventilation and even distribution of air among the alveoli.
pH, PaCO2, and PaO2.
PaCO2 decreases below that of the CSF, and CO2 diffuses back out of the CSF, returning its pH to normal.
They are an integral part of the alveolar septa.
They provide structure.
Mean pulmonary artery pressure is 18 mmHg; mean aortic pressure is 90 mmHg.
PaCO2 increases.
They regulate blood flow through their respective capillary beds.
Major and accessory muscles of inspiration and expiration, elastic properties of the lungs and chest wall, and resistance to airflow through the conducting airways.
It contributes to control of lung inflammation and innate and adaptive immunity.
CO2 diffuses across the blood-brain barrier into the CSF until the partial pressure of CO2 is equal on both sides.
They are sensitive to very small changes, equivalent to a 1 to 2 mmHg change in PaCO2.
At the hilus.
In aortic bodies, the aortic arch, and carotid bodies at the bifurcation of the carotids.
At the terminal bronchiole.
They send signals to the respiratory center to increase ventilation.
They become insensitive to small changes in PaCO2 and regulate ventilation poorly.
Ventilation increases much more than it would in response to either abnormality alone.
Oxygen levels in arterial blood (PaO2).
They are not as sensitive.
When PaO2 drops to approximately 60 mmHg.
When central chemoreceptors are 'reset' by chronic hypoventilation.
The mechanics of breathing.
