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Flashcards in Respiratory System - HY Deck (45):

The distal end of the respiratory diverticulum enlarges to form the ...?

Lung bud.


The lung bud divides into ...?

2 Bronchial buds that branch into the main (primary), lobar (secondary), segmental (tertiary), and subsegmental bronchi.


The respiratory diverticulum initially is in open communication with the ...?

Foregut --> Eventually becomes separated by indentations of mesoderm called TRACHEOESOPHAGEAL FOLDS.


When the tracheoesophageal folds fuse in the midline to form the ..., the foregut is divided into the trachea ventrally, and the esophagus, dorsally.

Tracheoesophageal septum.


Tracheoesophageal fistula is ...?

An abnormal communication between the trachea and esophagus that results from improper division of the foregut by the tracheoesophageal SEPTUM.


Tracheoesophageal septum is generally associated with ...?

Esophageal atresia.


Esophageal atresia results in ...?



Tracheoesophageal fistula - Clinical features:

1. Excessive accumulation of saliva or mucus in the nose and mouth.
2. Episodes of gagging and cyanosis after shallowing milk.
3. Abdominal distention after crying.
4. Reflux of gastric contents into the lungs --> Pneumonitis.


Tracheoesophageal fistula - Diagnostic features:

1. Inability to pass a catheter into the stomach.
2. Radiographs demonstrating air in the infant's stomach.


In week ... of development, bronchial buds enlarge to form main (primary) bronchi.



How many segmental bronchi on the right and on the left?

Right --> 10.
Left --> 9.


Bronchopulmonary segment is ...?

A segment of lung tissue supplied by a segmental (tertiary) bronchus.
--> Surgeons can resect diseased lung tissue along bronchopulmonary segments rather than remove the entire lobe.


Congenital lobar emphysema is characterized by ...?

Progressive overdistention of one of the upper lobes or the right middle lobe with air.


Congenital lobar emphysema is a misnomer?

Yes - There is no destruction of the alveolar walls (no emphysema).


Congenital lobar emphysema - Etiology:

Although the exact etiology is unknown --> Many cases involve COLLAPSED bronchi due to FAILURE of bronchial cartilage formation.


Congenital lobar emphysema - During the first days of life ...?

FLUID may be trapped in the involved lobe --> Opaque, enlarged hemithorax.


Congenital bronchogenic cysts ...?

Represent an abnormality in bronchial branching and may be found within the mediastinum (most commonly) or intrapulmonary.


Intrapulmonary cysts in congenital bronchogenic cysts are ...?

Round, solitary, sharply marginated, and FLUID-FILLED and do NOT initially communicate with the tracheobronchial tree.


The lung matures in a ... direction, beginning with the largest bronchi and proceeding outward.

Proximal-Distal direction.


The 4 periods of lung development:

Weeks 7-16 --> Pseudoglandular period.
Weeks 16-24 --> Canalicular period.
Weeks 24-birth --> Terminal sac period.
Week 32-8years --> Alveolar period.


Features of the pseudoglandular period (7-16):

1. Resembles EXOCRINE gland --> Numerous endodermal tubules are lined by a simple columnar epithelium + surrounded by mesoderm containing a modest capillary network.
2. Each endodermal tubule branches into 15-25 terminal bronchioles.
3. Respiration is NOT possible, and premature infants cannot survive.


Canalicular period (16-24) - Features:

1. Terminal bronchioles branch into three or more respiratory bronchioles.
2. Respiratory bronchioles subsequently branch into three to six alveolar ducts.
3. Terminal bronchioles + respiratory bronchioles + alveolar ducts --> Lined by simple cuboidal epithelium --> Surrounded by mesoderm containing a prominent capillary network.
4. Premature infants born before week 20 rarely survive.


Terminal sac period (weeks 24-birth) - Features:

1. The alveolar ducts bud off TERMINAL SACS, which dilate and expand into the surrounding mesoderm.
2. Terminal sacs are separated from each other by PRIMARY septae.
3. Simple cuboidal epithelium within the terminal sacs differentiates into type I pneumocytes (thin, flat cells that make up part of the blood-air barrier) + type II pneumocytes (secrete surfactant).
4. Terminal sacs are surrounded by mesoderm that contains a rapidly proliferating capillary network.


Premature infants born between week 25-28 can survive with ...?

Intensive care --> Adequate vascularization + Surfactant levels = Most important factors for the survival of premature infants.


Alveolar period (Birth-8 yrs) - Features:

1. Terminal sacs are partitioned by SECONDARY SEPTAE to form ADULT ALVEOLI.
2. About 20-70million alveoli are present at birth.
3. About 300-400million alveoli are present by 8 years of age.
4. After birth, the increase in the size of the lung is due to an increase in the number of respiratory bronchioles.
5. On CXR --> Lungs of a newborn infant are DENSER than an adult lung because of the fewer mature alveoli.


Aeration at birth is ...?

The replacement of lung liquid with air in the newborn's lung.


In the fetal state, the FRC of the lung is filled with ...?

Liquid secreted by fetal lung epithelium via Cl transport using CFTR.


At birth, lung liquid is eliminated by ...?

A reduction in lung liquid secretion via Na transport by type II pneumocytes and resorption into pulmonary capillaries (major route) and lymphatics (minor route).


Lungs of a stillborn baby will ... when placed in water because they contain fluid rather than air.



Pulmonary agenesis is ...?

The complete absence of a lung or a lobe and its bronchi --> Rare condition caused by failure of bronchial buds to develop.


Unilateral pulmonary agenesis is ...?

Compatible with LIFE.


Pulmonary aplasia is ...?

The absence of lung tissue BUT the presence of a rudimentary bronchus.


Pulmonary hypoplasia is ...?

A poorly developed bronchial tree with abnormal histology.


Pulmonary hypoplasia classically involves ...?

The RIGHT lung + Right sided obstructive congenital heart defects.


Pulmonary hypoplasia can also be found in association with ...?

A congenital diaphragmatic hernia which compresses the developing lung.


Pulm. hypoplasia can also be found in association with ...?

Bilateral renal agenesis.


Composition of surfactant:

CH --> 50%.
DPPC --> 40%.
Surfactant proteins A,B,C --> 10%.


Hyaline membrane disease accounts for ...-...% of deaths in premature infants.



Hyaline membrane disease is also prevalent in other risk groups:

1. Infants of DIABETIC mothers.
2. Infants who experience FETAL ASPHYXIA.
3. Maternofetal hemorrhage --> Damages type II pneumocytes.
4. Multiple-birth infants.


The hyaline membrane disease in premature infants cannot be discussed without mentioning the ... .

Germinal Matrix Hemorrhage (GMH).


What is the germinal matrix?

Is the site of proliferation of neuronal + glial precursors in the developing brain, which is located above the caudate nucleus, in the floor of the lateral ventricles, and in the caudo-thalamic groove.


The germinal matrix also contains a rich network of ...?

Fragile, thin-walled blood vessels.


The brain of the premature infant lacks the ability to ...?

Autoregulate the cerebral blood pressure.


Incr. arterial pressure in the blood vessels of the germinal matrix leads to ...?

1. Cerebral palsy.
2. Mental retardation.
3. Seizures.


1st sign of lung development:

Formation of the respiratory (or laryngotracheal) diverticulum in the ventral wall of the primitive foregut during week 4.