Chapter 15: Normal fetal lung development Flashcards
What is required for normal fetal lung development?
1. Enough space in the thoracic cavity for the lungs to grow
2. Ability to inhale
- -Chest wall has to be able to move
- -Must have enough amniotic fluid
Except for the vocal cords, the entire respiratory tree is lined by what type of epithelium?
Pseudostratified columnar ciliated epithelium
Bronchia mucosa contains population of neuroendocrine cells with neurosecretory granules containing which factors?
- 1. Calcitonin
- 2. 5HT
- 3. Bombesin (gastrin releasting peptide)
Numerous mucus-secreting goblet cells and submucosal glands are dispersed throughout the walls of which parts of the respiratory tree?
Trachea and bronchi
BUT NOT BRONCHIOLES
How do normal lungs grow?
Normally from bronchus => alveoli (branching)
What 3 things do we want as our lungs grow?
- Airways to branch: larger airways will conduct the air to acinar units where gas can exchange.
- Rigid, open aiways
- Thin wall with high vascularity for gas exhchange
Diffusion distance between capilliary and basal lamina of the aveoli must be small.
Why?
Because RBC have less than one second to dump CO2 and pick up O2
What makes the wall of a aveoli?
- Capillaries with associated endothelium
- BM and interstitium.
- Type 1 pneumocytes line the aveolus
- Type 2 pneumocytes make surfactant to decrease ST and replace type 1
- Aveolar pores of Kohn
What are alveolar pores of Kohn
Pres that allow aveoli to share air with one another.
Only problem is that they also allow bacteria, cells, junk to pass between aveoli
What are the 4 congenital anomalies we will talk about?
1. Pulmonary hypoplasia
2. Foregut cysts
3. CPAM/CCAM (congeintal pulmonary adenomatoid malformation)
4. Pulmonary sequestration
Pulmonary hypoplasia occurs in utero and what are 2 major causes?
- Not enough space for lung to grow
* d/t conginital diagphragmatic hernia that pushes abdominal organs into thorax - Inability to inhale
- oligohydramnois (not enough amnoitic fluid)
- probs moving chest wall
- malformation in the airway (tracheal stenosis)
Do babies born with pulmonary hypoplasia have a good change of living?
No (95% die). If the weight of the lung is less than 40% of NL => immediately die.
Foregut cysts are?
and where do they occur most often?
Cysts from of the foregut
Hilum/middle mediastinum
Foregut cysts are most often located where in the lungs and which classification/type is most common?
Treatment?
Hilum or middle mediastinum
- Bronchogenic = most common; can also be respiratory, ESO, gastroenteric
- Excision = curative!
Histology of a foregut cysts will reveal what?
How are they discovered?
Normal respiratory epithelium, thus it is NOT a neoplasm.
By accident d/t complications: rupture, cause infection or compress airways
Congenital pulmonary adenomatoid malformations (CPAM/CCAM) are caused by what?
“Arrested development”of pulmonary tissue that forms intrapulmonary cystic peice of abnormal lung tissue THAT connect to tracheobronchial airway and pulmonary vasculature.
Via which imaging modality can congenital pulmonary adenomatoid malformations be detected?
Fetal ultrasound
Congenital pulmonary adenomatoid malformation (CPAM) can be deadly due to what?
What is a complication?
- Hydrops
- Pulmonary hypoplasia
- Infection or if it is large, it can cause pulmonary hypoplasia.
Pulmonary sequestration is what?
How is it different from CPAM?
Intra or extra-pulmonary peice of nonfunctioning lung tissue that forms into a bud but does NOT connect to the tracheobronchial airway and has its OWN blood supply.
Where do pulmonary sequestrations usually grow?
Lower left lobe (can be intralobular or extralobular)
When do intralobular pulmonary sequestration (ILS) present and what is a complication?
Older children and adults
Because ILS do not get air (even though they have their own BS), they have an increased liklihood of infection and abbsess formation (so come to ATN later)
Extralobar pulmonary sequestrations present when and come to ATN how?
How are they different from intralobular pulmonary sequestration?
- Present after birth as mass lesions and come to ATN earlier bc they bb usually has other congenital foregut anomies, especially CARDIAC and UPPER GI.
- Have their own BS, pleura and AIRWAY
What is atelectasis?
atelectasis is decreased expansion or loss of volume affecting the lungs
Atelectasis is a reversible disorder, except in cases caused by what?
Contraction atelectasis
What are the 3 main types of acquired atelectasis and what is each caused by?
- Resorption due to complete obstruction of airway (ex d.t a mucus plugs) => decreases air to lungs and reduce lung expansion.
- Compression due to an accumulation of material or air in the pleural cavity (i.e., transudate/exudate/blood or pneumothorax)
- Contraction due to local or fibrotic changes in the lung/ pleura prevents expansion (problem directly related to lung)
Which type of acquired atelectasis causes the mediastinum/trachea to shift toward the affected lung; which type causes a shift away?
- Resorption —> mediastinum shifts toward affected lung
- Compression –> mediastinum shifts away from affected lung
Which type of acquired atelectasia occurs in the setting of asbestosis?
Contraction atelectasis
Hemodynamic pulmonary edema is d/t due to an increase in what; most commonly occuring in what setting?
1. Increased hydrostatic pressure =>
Left-sided CHF
2. Or decreased in oncotic pressure
3. Or increase capillary permability (dmg to alveolar/endothelial wall)
What can you see in this picture?
Pulmonary edema: pink proteinaceious material in aveolar spaces
What is the histological appearance of of the alveolar capillaries in hemodynamic pulmonary edema?
Engorged, and an intra-alveolar transudate appears as finely granular pale PINK material
Where does fluid accumulate 1st in pulmonary edema due to hydrostatic pressure being greatest in these sites (dependent edema)?
Basal regions of the lower lobes
Pulmonary edema can also be due to decreased oncotic pressure, which cause “leaking out”. What 4 things can cause this?
- Hypoalbuminemia
- Nephrotic syndrome
- Liver disease
- Protein-losing enteropathies
What other mechanisms can cause the pushing out of fluid, resulting in pulmonary edema?
- Too much volume
- Obstruction of pulmonary vein
What can injure the alveolar wall => cause pulmonary edema?
- Infections: bacterial pneumonia
- Inhaled gases: high [O2] and smoke
- Liquid aspiration: gastric contents; near drowing
- Radiation
What are 2 causes of pulmonary edema that we arent sure how it results in it?
1. Brain injury
2. High altitude
How does pulmonary edema affect airflow to lungs?
Decrease air to lungs.
In long-standing pulmonary congestion (i.e., mitral stenosis), hemosiderin-laded macrophages are abundant, and what is the gross morphology of the lungs?
Soggy lungs become firm and brown (brown induration)
Differentiate acute lung injury (ALI) and acute respiratory distress syndrome (ARDS).
How are they alike?
ALI: abrupt hyoxemia (<300) and BILATERAL pulmonary infiltrate without cardiac failure.
ARDS is a more severe ALI that occurs as hypoxia (<200) worsens and is more severe on the ARDS spectrum.
How do we diagnose with Diffuse Alveolar Damage (DAD)?
Pathologists diagnose this as the histological manifestations of ARDS/ALI, caused by inflammation d/t increased vascular permability that occurs in both.
When the edema associated with pneumonia fails to stay localized and instead becomes diffuse alveolar edema what fatal condition may this lead to?
ARDS
A patient comes in who we think has ALI, what must his arterial blood gas be?
Less than or equal to 300 (PaO2/FiO2)
Describe the pathogenesis of ALI/ARDS
- Injury to the pneumocytes and pulmonary endothelium => activating endothelium
-
Neutrophil adhere and leak into interstitium and alveoli => degranulate and release inflammatory mediatorys (proteases, ROS and cytokines)
* Macrophage migration inhibitory factor (MIF) promotes the cycle of pro- inflammation and damage => more injury and endothelial damage
-
Neutrophil adhere and leak into interstitium and alveoli => degranulate and release inflammatory mediatorys (proteases, ROS and cytokines)
- Damage causes pulmonary capillaries to become leaky => accumulation of intraalveolar/interstitial edema
* Type 2 pneumo are damaged => fucks up surfactant => fucking up gas xchange
* Thick, protein rich edema, fibrin and debris from dead cells (necrosis) => form hyaline membranes
- Damage causes pulmonary capillaries to become leaky => accumulation of intraalveolar/interstitial edema
- 4. Resolution of injury: damage prevents cells from preventing edema. If inflammation decreases, MO release TGF-B and PDGF to help grow fibroblast and deposit collagen => fibrosis of alveoli.
Following the fibroproliferative phase in ARDS, what 2 pathways may ensue and the result of each?
- Resolution: restoration of normal cell structure and fx: we can breath n shit
- Fibrosis: fucks up normal cell struture and is irreversible
What are the 3 stages of ARDS?
- Exudative: edema, hyaline and neutrophils
- Proliferative: fibroblast proliferate and organize and early fibrosis
- Fibrotic: extensive fibrosis and loss of structure of alveoli OR
Resolution of normal cell structure and function
What causes the formation of hyaline membrane?
Edema
Fibrin
Dead cells
What is this and what does it result in?
Hyaline membrane increases the distance between capillary and alveoli => decrease aeration => mismatch in how much air your breathing in vs how much is getting in lungs (ventillation:perfusion mismatch) => decrease in PaO2/FiO2
ALI/ARDS is more common and associated with a worse prognosis in whom?
Chronic smokers and alcoholics
During the acute stage of ALI/ARDS what is seen morphologically in the lungs?
1. Lungs are heavy, firm, red and boddy
2. Congestion, edema fibrin and DAD
3. Haline membrane
What is a pathological dx of ARDS (DADS)?
HIE
1. Hyaline memrbane
2. Intersitial edema
3. Epithelial necrosis
What is seen on radiographic imaging of patient with ALI?
Diffuse bilateral infiltrates
Pt’s with ALI will have what sx’s?
- Profound dyspnea and tachypnea
- Followed by ↑ cyanosisand hypoxemia
What is the cause of the ventilation perfusion mismatch and hypoxemia in ALI/ARDS?
- Poorly aerated regions continue to be perfused
- Perfusion = normal; but ventilation = decreased
ARDS is a diagnosis of exclusion using the criteria which can be remembered with mnemonic A.R.D.S.
- Abnormal CXR (bilateral lung infiltrates)
- Resp failure w/t 1 week of damage to aveoli (abrupt)
- Decreased PaO2/FiO2 (<200)
- Sx not d/t HF/too much fluid
The causes of ARDS may be remembered with “SPARTAS.”
- Sepsis
- Pancreatitis/Pneumonia
- Aspiration
- uRemia
- Trauma
- Amniotic fluid embolism
- Shock
How is the diagnosis of Acute Interstial Pneumonia (AIP) different from classic ARDS.
Everything is the same (clinical presentation/histo) except WE DO NOT KNOW WHY IT OCCUTS
When do most deaths associated with Acute Interstitial Pneumonia occur?
Within 1-2 months
Which 2 obstructive lung diseases are grouped together and referred to as COPD?
- Chronic bronchitis
- Emphysema
What is the difference between obstructive lung disease and restrictive lung disease?
- OLD occurs d/t decreased airflow d/t partial/complete obstruction that causes hyper-expanded lungs.
- Restrictive lung disease is reduced expansion of lungs and decreased total lung capacity.
How does the FEV1/FVC ratio differ for restrictive lung disease and obstructive lung disease?
RLD: normal FEV1/FVC. Both values decrease, keeping the ratio the same
OLD: Decreased FEV1 (amount of air you force out in 1 second), but normal FVC (amount of air that you can force out after taking a deep breath in) => decreases FEV1/FVC ratio
What are the causes of obstructive lung disease?
What are they most often caused by?
- 1. COPD
- 2. Asthma
- 3. Bronchiectasis
- 4. Emphysema
- Smoking
What are the causes of restrictive lung disease?
- 1. Pulmonary fibrosis
- 2. Rheumatoid Arthritis
What is the dominant pathogenic mechanism of chronic bronchitis?
Irritation of the airways d/t inhalation of
- Tobacco smoke
- Dust from grain, cotton, and silica
Irritants will damage the epithelium and interfere with cilia, preventing mucus clearance.
Chronic bronchitis is associated with what 2 symptoms?
A small-airway disease where the patient has inflammation of the airway and a productive cough.