Severson: Normal and Abnormal Respiratory System

Question 1

Where does the laryngotracheal groove and diverticulum develop?

Answer 1

The Laryngotracheal groove develops from the VENTRAL WALL of the PRIMITIVE PHARYNX (caudal to the 4th pair of pharyngeal pouches).

It DEEPENS to form the RESPIRATORY DIVERTICULUM.

Question 2

What germ layer contributes to the epithelial lining and glands of the larynx?

Answer 2

ENDODERM

Question 3

What germ layer contributes to the supporting wall (CT, cartilage and smooth muscle)?

Answer 3

Splanchnic mesenchyme of the forgegut

Question 4

What is the purpose of the tracheoesophageal folds and septum?

Answer 4

They divide the cranial part of the foregut into a LARYNGOTRACHEAL TUBE.(primordium of the larynx, trachea, bronchi and lungs) and a DORSAL PORTION (primordium of the oropharynx and esophagus).

Question 5

What branchial arch cartilages contribute to the laryngeal cartilages?

Answer 5

4th and 6th pharyngeal arches

Question 6

What cells form the cartilagenous tissue?

Answer 6

MESENCHYME from neural crest cells

Question 7

What branchial arches give rise to the laryngeal muscles?

Answer 7

MYOBLASTS from the 4th and 6th pharyngeal arches

Question 8

What nerves innervate the laryngeal muscles?

Answer 8

vagus nerve

superior laryngeal and the recurrent laryngeal

Question 9

What germ layers contribute to the laryngotracheal tube?

Answer 9

Endoderm

Question 10

What germ layer gives rise to the trachebronchial glands?

Answer 10

ingrowth of surface epithelium of ENDODERMAL ORIGIN

Question 11

What germ layer gives rise to the supporting walls?

Answer 11

Cartilage, CT and muscles are derived from SPLANCHNIC MESODERM

Question 12

What tissue forms the visceral and parietal pleura?

Answer 12

visceral- spanchnic mesoderm

parietal- somatic mesoderm

Question 13

What developmental defect has occurred when a tracheoesophageal fistula is present?

Answer 13

An abnormal communication between the TRACHEA and the ESOPHAGUS

*most common anomaly of the lower RT

Question 14

What is esophageal atresia?

What is it associated with?

Answer 14

An abnormal partitioning of hte TRACHEOESOPHAGEAL SEPTUM producing an abnormal communication between the trachea and the esophagus.

fistula

Question 15

When would gastric secretions possible cause pneumonitis?

Answer 15

When food or gastric contents enter lungs>

pneumonitis

Question 16

When would lipid pneumonia occur?

Answer 16

?

Question 17

When and why does polyhyraminos occur?

Answer 17

Amniotic fluid accumulates (polyhydramnios) because amniotic fluid cannot pass to the stomach and intestines for absorption and subsequent transfer via the placenta to the mother’s blood.

Question 18

How do the bronchi and lungs develop?

Answer 18

Laryngotracheal groove —> respiratory diverticulum —> tracheal bud —>
primary bronchial buds —> secondary bronchial buds —> segmental branches

Question 19

What is the usual cause of lung hypoplasia?

Answer 19

Usually associated with congenital diaphragmatic hernia.

Question 20

How many oligohydraminos cause lung hypoplasia?

Answer 20

Oligohydramnios= an insufficient amount of amniotic fluid

Causes pulmonary hypoplasia by allowing the uterine wall to compress the fetal thorax.

Question 21

Why does renal agenesis contribute to oligohydraminos?

Answer 21

Bilateral renal agenesis causes oligohydramnios because lack of urine production reduces the amount of amniotic fluid.

Question 22

What is potter’s syndrome?

Answer 22

Pulmonary hypoplasia and bilateral renal agenesis.

Question 23

At what week of development are type I and II alveolar cells evident in the developing lung?

Answer 23

26 weeks

Question 24

What is the earliest developmental period that respiration is possible?

Answer 24

16-26 weeks

Respiration is possible because of developing alveoli

Question 25

What are type I alveolar cells?

Answer 25

Squamous epithelium of endodermal origin

Pneumocytes

Question 26

What cells produce surfactant?

Answer 26

Type II alveolar cells

At about 20 weeks but doesn’t become sufficient until 26-28 weeks and continues to increase towards the end of preganancy.

Question 27

What is surfactant?

Answer 27

Surfactant serves to lower surface tension at the air-alveolar interface.

Maternal glucocorticoid (β-methasone) treatment during pregnancy accelerates fetal lung development and surfactant production.

Question 28

How is the amniotic fluid removed from the lung at birth?

Answer 28

Removal of fluid occurs :

(1) through the mouth and nose by pressure on the thorax during delivery
(2) into the pulmonary capillaries, and
(3) into the lymphatics.

Aeration at birth is the rapid replacement of intra-alveolar fluid by air. The lung fluid is derived from amniotic fluid, the lung tissue itself, and from secretions by the tracheal and bronchial glands.

Question 29

What is responsible for the occurrence of respiratory distress syndrome (hyaline membrane disease)?

Answer 29

Caused by a deficiency of surfactant

Question 30

Why is there a protein rich fibrin rich exudate in the alveolar space?

Answer 30

Injury to the alveolar wall results in a protein-rich, fibrin-rich exudation derived from the injured pulmonary epithelium and circulating blood substance.

Question 31

Who is likely to develop respiratory distress syndrome?

Answer 31

Respiratory distress syndrome accounts for 20% of all infant deaths in the newborn period.

Question 32

What morphological features of the lung accounts for death in newborns w/ respiratory distress syndrome?

Answer 32

Protein rich, fibrin rich esxudate is located in the alveolar spaces and forms a hyaline membrane (result is respiratory distress syndrome).

Question 33

How do the lungs of a stillborn and live infant differ?

Answer 33

Newborn lungs: contain air and float in water.

Stillborn infant’s lungs: firm and sink when placed in water because they contain fluid, not air.

Question 34

Why do the lungs of stillborn infants sink in water?

Answer 34

They contain fluid NOT air.

Question 35

Where do congenital diaphragmatic hernias usually occur?

Answer 35

diaphgram

Question 36

What developmental anomaly is responsible for congenital diaphgragmatic hernias?

Answer 36

Failure of the diaphragm to close completely during development