Normal & Abnormal Development of the Respiratory System - Severson

Question 1

Where does the laryngotracheal groove and diverticulum develop?

Answer 1

• Groove:
  
  • Ventral wall of the primitive pharynx
    
    • caudal to the 4th and 6th pharyngeal pouches
• Diverticulum:
  
  • groove deepens to form respiratory diverticulum

Question 2

What germ layer contributes to the epithelial lining?

Answer 2

Endoderm

Question 3

What germ layer contributes to the supporting wall of the developing trachea?

Answer 3

• Connective tissue, cartilage, and smooth muscle develop from → splanchnic mesenchyme of the foregut
  
  • (except laryngeal cartilage develops from neural crest mesenchyme)

Question 4

What is the purpose of the tracheoesophageal folds and septum?

Answer 4

They play a significant role in the separation of the esophagus and developing respiratory system (trachea).

Question 5

What branchial arch cartilages contribute to the laryngeal cartilages?

Answer 5

4th & 6th pharyngial arches

Question 6

What cells form the cartilaginous tissue?

Answer 6

Neural crest cells

Question 7

What branchial arches give rise to the laryngeal muscles?

Answer 7

4th & 6th pairs of pharyngeal arches

Question 8

What nerves innervate the laryngeal muscles?

Answer 8

• Vagus nerve
  
  • Superior laryngeal (sensory fibers)
  • Recurrent laryngeal (motor fibers)

Question 9

What germ layers contribute to the laryngotracheal tube?

Answer 9

• Surface epithelium → endoderm
• Tracheal glands → endoderm
  
  • (develop from an ingrowth of surface epithelium)
• Cartilage, connective tissue, & muscle → splanchnic mesoderm

Question 10

What germ layer gives rise to the tracheobronchial glands?

Answer 10

Endoderm

Question 11

What germ layer gives rise to the supporting walls of the laryngotracheal tube?

Answer 11

Splanchnic mesoderm

Question 12

What tissue forms the visceral and parietal pleura?

Answer 12

• Visceral → splanchnic mesoderm
• Parietal → somatic mesoderm

Question 13

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

Answer 13

Esophageal atresia

(blind ending esophagus)

Question 14

When would gastric secretions possibly cause penumonitis?

Answer 14

when food or gastric contents enter the lungs

(happens if esophageal atresia occurs)

Question 15

When would lipid pneumonia occur?

Answer 15

***

Question 16

When and why does polyhydramnios occur?

Answer 16

• When?
  
  • tracheoesophageal fistula (esophageal atresia)
• Why?
  
  • 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 17

How do the bronchi and lungs develop?

(Hint: 6 steps)

Answer 17

1. Laryngotracheal groove →
2. Respiratory diverticulum →
3. Tracheal bud →
4. Primary bronchial buds →
5. Secondary bronchial buds →
6. Segmental branches (bronchopulmonary segments)

Question 18

What is the usual cause of lung hypoplasia?

Answer 18

Congenital diaphragmatic hernia

(uterus creats increased pressure on chest wall)

Question 19

How may oligohydramnios cause lung hypoplasia?

Answer 19

• there is an insufficient amount of amniotic fluid
  
  • causes pulmonary hypoplasia by allowing the uterine wall to compress the fetal thorax

Question 20

Why does renal agenesis contribute to oligohydramnios?

Answer 20

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

Question 21

What is Potter’s syndrome?

Answer 21

pulmonary hypoplasia and bilateral renal agenesis

Question 22

What are type I and type II alveolar cells?

Answer 22

• Type I
  
  • squamous epithelium pneumocytes of endodermal origin
    
    • small, thin
• Type II
  
  • pneumocytes lining the alveoli that begin to secrete pulmonary surfactant
    
    • large, protrude

Question 23

What cells produce surfactant?

Answer 23

Type II Alveolar Cells

Question 24

What is surfactant?

Answer 24

• phospholipids and two proteins
  
  • lowers surface tension at the air-alveolar interface

Question 25

What is the earliest developmental period that respiration may be possible?

Answer 25

24-26 weeks

terminal saccular period

Question 26

About when does an individual have the maximum number of alveoli?

Answer 26

8 yoa

Question 27

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

Answer 27

Removal of amniotic fluid occurs:

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

Question 28

What is responsible for the development of congenital lung cysts?

Answer 28

Formed by dilation of terminal bronchioles due to a disturbance in bronchial development during late fetal life. Lungs have a honeycomb appearance.

Question 29

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

Answer 29

caused by a deficiency of surfactant and injury to the alveolar wall resulting in a protein-rich, fibrin-rich exudation into the alveolar spaces and formation of hyaline membranes

Question 30

How do the lungs of a stillborn and live infant differ? Why do the lungs of stillborn infants sink in water?

Answer 30

• Newborn lungs
  
  • contain air and float in water
• Stillborn lungs:
  
  • are firm and sink when placed in water because they contain fluid, not air