The Lung Part 1

Question 1

Development of the respiratatory system

Answer 1

• Respirtatory system is an outgrowth from the ventral wall of the foregut
• Midline trachea develops two lateral outpocketings–the lung buds which divide into lobar bronchi (3 on right, two on left)

Question 2

Bronchi composition

Answer 2

• firm cartilaginous walls for mechanical support
• Lined with columnar ciliated epithelium with abundant subepithelial glands that produce mucus that prevents entry of microbes

Question 3

Aspirated foreign material tends to enter which side of the lung more often (left or right)?

Answer 3

-Right

Question 4

Arterial supply to the lungs

Answer 4

-Pulmonary and bronchial arteries

Question 5

Difference between brochi and bronchioles

Answer 5

• Bronchi has cartilage

- Bronchioles are branches of bronchi and LACK cartilage and submucosal glands in their walls

Question 6

Order of branching of lungs

Answer 6

-Bronchi–>bronchioles–>terminal bronchioles–>acinus (made of respiratory bronchioles, alveolar ducts and alveolar sacs)

Question 7

Sites of gas exchange

Answer 7

Alveoli

Question 8

What is a pulmonary lobule?

Answer 8

-A cluster of 3-5 terminal bronchioles, each with its appended acinus

Question 9

Vocal cords vs. respiratory tree epithelium

Answer 9

• vocal cords covered by stratified squamous
• the rest of resp tree (larynx, trachea, and bronchioles) lined by PSEUDOSTRATIFIED, tall, COLUMNAR, CILIATED epithelial cells

Question 10

Bronchial mucosa contains what kind of cells? What do these cells do?

Answer 10

• neuroendocrine cells

- Have neurosecretory type granules and release serotonin, calcitonin and gastrin releasing peptide (bombesin)

Question 11

Where are mucus secreting goblet cells and submucosal glands located?

Answer 11

-dispersed throughout the walls of trachea and bronchi (but NOT THE BRONCHIOLES!!!)

Question 12

Microscopic structure of alveolar walls/alveolar septa consist of

Answer 12

• network of anastomosing capillaries lined with endothelial cells
• Basement membrane and surrounding interstitial tissue
• Alveolar epithelium
• Alveolar macrophages–loosely attached to alvoelar epithelium or free within alveolar spaces

Question 13

Basement membrane and surrounding interstitial tissue of alveolar walls

Answer 13

• separate endothelial cells from alveolar lining epithelial cells
• thin portion of septum–BM of epithelium and endothelium are fused
• Thick portion of septum–separated by interstitial space (pulmonary interstitium) containing elastic fibers, collagen, smooth muscle cells, mast cells and rare lymphocytes and monocytes

Question 14

Alveolar epithelium composition

Answer 14

• Continuous layer of two cell types:
• flattened platelike type 1 pneumocytes covering 95% of alveolar surface
• Rounded type II pneumocytes

Question 15

surfactant

Answer 15

• forms a very thin layer over the alveolar cell membranes
• involved in repair of alvolar epithelium through their ability to give rise to type I cells
• Produced by type II pneumocytes!!

Question 16

Pores of Kohn

Answer 16

• The alveolar walls are perforated by pores of Kohn

- permit the passage of bacteria and edudate between adjacent alveoli

Question 17

Are developmental anomalies of the lung common or rare? Which are the ones most commonly seen?

Answer 17

• RARE!
• The more common of these include:
• Pulmonary hypoplasia
• Foregut cysts
• Pulmonary sequestration

Question 18

Less common congenital abnormalities include

Answer 18

• tracheal and bronchial anomalies (atresia, stenosis, tracheesophageal fistula)
• vascular anomalies
• congenital pulmonary airway malformation
• congenital lobar overinflation (emphysema)

Question 19

Pulmonary hypoplasia

Answer 19

• defective development of both lungs (one may be more affected than the other)
• decreased weight, volume and acini for body weight and genstational age
• caused by abnormalities that compress the lung or impede normal lung expansion in utero
• severe hypoplasia is fatal in early neonatal period

Question 20

Abnormalities that compress the lung or impede normal lung expansion in utero leading to pulmonary hypoplasia

Answer 20

• congenital diaphragmatic hernia

- Oligohydramnios

Question 21

Foregut cysts arise from

Answer 21

• abnormal detachments of primitive foregut
• most often located in hilum or middle mediastinum
• can be bronchogenic, esophageal or enteric

Question 22

Bronchogenic cysts

Answer 22

-rarely connected to tracheobronchial tree
lined by ciliated pseudostratified columnar epithelium
-wall contains bronchial glands, cartilage and smooth muscle
-present due to compression of nearby structures or are found incidentally

Question 23

Pulmonary sequestration

Answer 23

• discrete area of lung tissue that:
• lacks any connection to airway system and
• has abnormal blood sypply arising from aorta and branches

Question 24

Extralobar vs. intralobar sequestrations

Answer 24

• Extralobar: external to lung; seen in INFANTS as MASS LESIONS
• Intralobar: occur within lung; present in OLDER children, due to recurrent localized infection or bronchiectasis

Question 25

Atelectesis

Answer 25

- incomplete expansion of lungs (neonatal) or collapse of previously inflated lung creating areas of airless pulmonary parenchyma - 3 types: Resorption, compression or contraction atelectasis

Question 26

Resorption atelectasis

Answer 26

- Complete obstruction of airway - over time, air resorbed from dependent alveoli, which collapse - lung volume decreased so mediastinum shifts TOWARDS the atelectatic lung

Question 27

What causes airway obstruction (resorption atelectasis)?

Answer 27

- excessive secretions (mucus plugs) - exudates within smaller bronchi (bronchial astma, chronic bronchitis, bronchiectasis and postoperative states) - Aspiration of foreign bodies and fragments of bronchial tumors may also lead to airway obstruction and atelectasis

Question 28

Compression atelectasis

Answer 28

- results from accumulation of lots of volume of fluid (transudate, exudate, blood), or tumor or air (pnemothorax) in the pleural cavity - mediastinum shifts AWAY from the affected lung

Question 29

Contraction atelectasis

Answer 29

-focal or generalized pulmonary or pleural fibrosis prevents full lung expansion

Question 30

Consequences of atelectasis

Answer 30

-reduces oxygenation and predisposes to infection

Question 31

Atelectasis is reversible or irreversible?

Answer 31

-reversible except for cases caused by CONTRACTION

Question 32

Pulmonary edema

Answer 32

- Leakage of excessive interstitial fluid which accumulates in alveolar spaces - caused by hemodynamic disturbances (hemodynamc or cardiogenic pulmonary edema) or from increases in capillary permeability from microvascular injury - produces heavy wet lungs

Question 33

Hemodynamic pulmonary edema is due to

Answer 33

- Increased hydrostatic pressure (left sided CHF) - Fluid accumulates at basal regions of lower lobes bc hydrostatic pressure greatest here (dependent edema) - Alveolar capillaries engorged and intra-alvolar transudate appears as finely granular pale pink material - see alveolar microhemorrhages and hemosiderin-laden macrophages (heart failure cells) - in longstanding pulmonary HTN (mitral stenosis), hemosiderin laden macrophages abundant and fibrosis and thickening of alveolar walls cause lungs to be firm and brown (brown induration) - impairs respiratory function and predisposes to infection

Question 34

Causes of hemodynamic edema

Answer 34

- Increased hydrostatic pressure--most common cause! - Decreased oncotic pressure - Lymphatic obstruction

Question 35

Causes of Increased hydrostatic pressure leading to hemodynamic edema

Answer 35

- left sided heart failure - volume overload - pulmonary vein obstruction

Question 36

Causes of decreased oncotic pressure leading to hemodynamic edema

Answer 36

- Hypoalbuminemia - Nephrotic syndrome - Liver disease - Protein-losing enteropathies

Question 37

Causes of edema due to alveolar wall injury (microvascular or eptihelial injury)

Answer 37

-Direct injury | Indirect injury

Question 38

Causes of direct injury leading to edema due to alveolar wall injury

Answer 38

- Infections: bacterial pneumonia - Inhaled gases: high concentration of oxygen, smoke - Liquid aspiration: gastric contents, near-drowning - Radiation

Question 39

Causes of indirect injury leading to edema due to alveolar wall injury

Answer 39

- Septicemia - Blood transfusion related - Burns - Drugs and chemicals: chemotherapeutic agens (bleomycin), other medications (methadone, amphotericin B), heroin, cocaine, kerosene, paraquat - Shock, trauma

Question 40

Causes of edema of undetermined origin

Answer 40

- High altitude | - Neurogenic (central nervous system trauma)

Question 41

Edema caused by microvascular (alveolar injury)

Answer 41

- Noncardiogenic pulmonary edema - injury to alveolar septa - Primary injury to vascular endothelium or damage to alveolar epthelial cells (with secondary microvascular injury) produces inflammatory exudate that leaks into interstitial space and alveoli - In most cases of pneumonia, edema is localized but when diffuse, alveolar edema contributes to fatal condition--acute respiratory distress syndrome (ARDS)