pulmonary 1 Flashcards
How many periods does it take to develop the lung?
5
What are the periods of lung development?
1) Embryonic (weeks 4-7)
2) Pseudoglandular (weeks 5-16)
3) Canalicular (weeks 16-26)
4) Saccular (weeks 26-birth)
5) Alveolar (weeks birth-8 years)
Describe the embryonic stage of lung development.
Lung bud-> trachea-> mainstem bronchi-> secondary (lobar) bronchi-> tertiary (segmental) bronchi
Errors at this stage can lead to TE fistula.
Describe the Pseudoglandular stage of lung development.
Endodermal tubules-> terminal bronchioles. Surrounded by modest capillary network.
Respiration impossible, incompatible with life.
Describe the Canalicular stage of lung development.
Terminal bronchioles-> respiratory bronchioles-> alveolar ducts. Surrounded by prominent capillary network.
Describe the Saccular stage of lung development.
Alveolar ducts-> terminal sacs. Terminal sacs separated by primary septae. Pneumocytes develop.
Describe the Alveolar stage of lung development.
Terminal sacs-> adult alveoli (d/t secondary septation). In utero, “breathing” occurs via aspiration and expulsion of amniotic fluid-> increase in vascular resistance through gestation. At birth, fluid gets replaced w/ air-> decrease in pulmonary vascular resistance.
At birth: 20-70 million alveoli
By 8 years: 300-400 million alveoli.
What are the 2 congenital lung malformations?
1) Pulmonary hypoplasia= poorly developed bronchial tree w/ abnormal histology usually involving the right lung. Associated w/ congenital diaphragmatic hernia, bilateral renal agenesis (Potter Syndrome).
2) Bronchogenic cysts= Caused by abnormal budding of foregut & dilation of terminal or large bronchi. Discrete, round, sharply defined & air-filled densities on CXR. Drain poorly & cause chronic infections.
What are Type I pneumocytes?
Thin squamous cells present in the alveoli, functioning in optimal gas diffusion.
Where are Type I pneumocytes found?
97% of alveolar surfaces. (line the alveoli)
What is the role & epithelium of Type I pneumocytes?
Squamous. Thin for optimal gas diffusion.
How is collapsing pressure calculated?
P = (2 x surface tension) / radius.
What is the function of Type II pneumocytes?
Secrete pulmonary surfactant –> decrease alveolar surface tension; prevent alveolar collapse, decrease lung recoil & increase compliance.
What type of cells, histologically, are Type II pneumocytes?
Cuboidal.
Do Type II cells originate from Type I cells, or are Type II cells progenitors for Type I cells?
Type II cells are progenitors for Type I cells. Type II cells can also give rise to other Type II cells.
When do Type II cells proliferate?
In lung damage.
What is the Law of Laplace?
As the radius decreases upon expiration, alveoli have an increased tendency to collapse.
What does ‘atelectasis’ mean, and how is it caused?
DEFINITION collapse of alveoli.
CAUSES obstruction, compression, or contraction –> damage to Type II pneumocytes –> loss of surfactant.
Even reinflation may not return full function due to the loss of surfactant.
What is surfactant, chemically?
A complex mix of lecithins, most importantly dipalmitoylphosphatidylcholine.
What are Clara (Club) cells?
Nonciliated, columnar cells with secretory granules.
What do Clara cells secrete?
A “watery” component of surfactant.
What are the functions of Clara cells?
To secrete a component of surfactant, to degrade toxins, and to act as reserve cells.
When does surfactant synthesis begin?
Around week 26 of gestation.
When are mature levels of surfactant reached?
Around week 35 of gestation.
If a child is born premature, is it likely that they will produce sufficient levels of surfactant?
No.
At risk of developing atelectasis.
What measurement indicates if a fetus has mature lung function?
Lecithin : sphingomyelin above 2. This can be measured in the amniotic fluid.
What is the cause of neonatal respiratory distress syndrome?
Inadequate surfactant –> increased surface tension –> alveolar sac collapse after expiration –> formation of hyaline membranes.
What lecithin:sphingomyelin ratio in amniotic fluid is predictive of neonatal RDS?
Ratio <1.5.
With what is neonatal RDS associated?
Prematurity: adequate surfactant levels are not reached until week 35.
C-section: d/t lack of release of stress-induced steroids (fetal glucocorticoids) –> no increased synthesis of surfactant.
Maternal diabetes: increased fetal glucose-> increased fetal insulin-> decreased surfactant levels.
What are the clinical features of neonatal RDS?
Increasing respiratory effort after birth, tachypnea with use of accessory muscles, grunting, hypoxemia with cyanosis, CXR showing “ground-glass” appearance of lung.
What are the complications of neonatal RDS?
(1) Persistently low O2 tension –> hypoxemia –> increased risk of PDA, necrotizing enterocolitis.
(2) Therapeutic supplemental oxygen–> increased risk of free radical injury (O2 can be toxic!) –> “RIB”.
R= Retinopathy of prematurity
I= Intraventricular hemorrhage
B= Bronchopulmonary dysplasia.
What is the treatment for neonatal RDS?
Maternal steroids before birth; artificial surfactant for infant.
What is the order of structures in the Respiratory tree?
Trachea-> bronchi-> bronchioles-> terminal bronchioles-> respiratory bronchioles-> alveolar sacs.
What does smoking do to the epithelial lining of the trachea?
Pseudo stratified ciliated columnar-> squamous (via metaplasia & now sputum cannot be cleared).
Where is the highest & lowest resistance in the Respiratory Tree?
Highest= medium-size bronchi (turbulent airflow).
Lowest= terminal bronchioles (high CSA).
What is the conducting zone?
The larger airways that warm, humidify, and filter air without participating in gas exchange (i.e. anatomic dead space).
What are the large airways of the conducting zone?
Nose, pharynx, trachea, bronchi.
What are the small airways of the conducting zone?
Bronchioles and terminal bronchioles (large #’s in parallel-> least airway resistance).
To what level of the conducting zone will cartilage and goblet cells extend?
Bronchi.
To what level of the conducting zone will pseudostratified ciliated columnar cells extend?
Terminal bronchioles.
Clear mucus & debris from lungs (mucociliary escalator).
To what level of the conducting zone will smooth muscle cells extend?
Terminal bronchioles.
What is the respiratory zone?
The airways participating in gas exchange.
What are the airways of the respiratory zone?
Lung parenchyma; respiratory bronchioles, alveolar ducts, alveoli.
What is the histology of the respiratory bronchioles?
Cuboidal cells.
What is the histology of the alveoli?
Simple squamous cells.
You see simple squamous cells on a histology slide. From what level of the respiratory system is the slide?
Alveoli or alveolar ducts.
You see pseudostratified ciliated columnar cells on a histology slide. From what level of the respiratory system is the slide?
Terminal bronchioles or above.
You see cartilage on a histology slide. From what level of the respiratory system is the slide?
Bronchi or above.
You see goblet cells on a histology slide. From what level of the respiratory system is the slide?
Bronchi or above.
You see cuboidal cells on a histology slide. From what level of the respiratory system is the slide?
Respiratory bronchioles.
Are cilia present in the respiratory zone?
No.
Where in the respiratory system may macrophages be found?
Alveoli-> clear debris & participate in the immune response.
Which lung has three lobes?
Right lung.
Which lung has two lobes?
Left lung; in place of the middle lobe, the lung accommodates the space necessary for the heart.
Left Lung has Less Lobes.
Which lung has a lingula?
Left lung.
Lingula is a tongue shaped portion of the left lung.
Which lung is the more common site for inhaled foreign bodies and why?
Right lung; right main stem bronchus is wider and more vertical.
“Swallow a bite, goes down the right.”
The relation of the pulmonary artery to the bronchus at each lung hilum is described by?
RALS: Right Anterior; Left Superior.
If a patient aspirates a peanut while upright, where in the lungs will it be found?
Inferior (AKA basilar) portion of the right inferior lobe.
If a patient aspirates a peanut while supine, where in the lungs will it be found?
Superior portion of the right inferior lobe OR posterior portion of the right upper lobe.
What structures perforate the diaphragm at T8, T10, and T12, respectively?
T8= IVC
T10= esophagus, vagus nerve (CN 10)
T12= aortic (red), thoracic duct (white), azygous vein (blue).
“I 8 10 Eggs At 12.”
What is the innervation of the diaphragm?
C3, C4, C5 (phrenic nerve).
–C3, 4, and 5 keep the diaphragm alive–