Development of the Respiratory System Flashcards

1
Q

Describe the development of the neural crest

A

Part of the ectoderm will develop into the neural groove and the tips of the walls of this groove are called neural crest cells.

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2
Q

What do the parietal (somatic) and visceral (splanchnic) mesoderm form?

A
Parietal = body walls,
Visceral = Surround the organs
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3
Q

Describe what occurs in lateral plate mesoderm folding

A

The parietal layer of the lateral plate mesoderm merges with the ectoderm. The primitive yolk sac will become pinched and will form the digestive tract or gut tube and the visceral layer will envelope the future gut tract. Finally the parietal layer and ectoderm merge and fuse in the ventral midline.

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4
Q

What does the connection between the gut tube and secondary yolk sac form?

A

Vitelline duct

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5
Q

At the end of lateral folding, what is present?

A
  • A cavity which will become the thoracic, abdominal and pelvic cavity.
  • A body wall made out of the surface ectoderm and parietal lateral plate mesoderm below it.
  • Gut tube, suspended by visceral layer of lateral plate mesoderm
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6
Q

What occurs while the lateral folding takes place?

A

Cranio-caudal folding which it where head and tail meet with the two lateral folds at the umbilicus.

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7
Q

Describe the start of the development of the lung buds at week 4

A

In the cervical region of the gut tube, the respiratory diverticulum starts to appear. It begins to expand ventrally towards the chest. Meanwhile tracheo-oesophageal ridges (folds) grow towards each other and split the respiratory diverticulum from the gut tube. The diverticulum bifurcates into two branches. Later these expand. Terminal ends of these are called lung buds.

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8
Q

What are pharyngeal arches?

A

Growth of mesenchyme tissue in the cranial region resulting in formation of arches which are separated by pharyngeal clefts

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9
Q

How many pharyngeal arches are there?

A

5, numbered; 1,2,3,4,6.

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10
Q

When do the pharyngeal arches begin to develop?

A

4-5th week of development

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11
Q

Where does the laryngeal orifice arise?

A

In-between the laryngeal and epiglottic swellings

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12
Q

What is maintained despite the tracheo-esophageal septum separates gut tube and resp tract.

A

The laryngeal opening. This is because both nose and mouth share a common pathway

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13
Q

What does the upper, middle and lower end of the respiratory diverticulum become?

A

Upper - Larynx,
Middle - Trachea,
Lower - Tertiary bronchi, bronchioles and alveoli.

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14
Q

What is the respiratory diverticulum developed from?

A

Endoderm and is then surrounded by the visceral layer of lateral plate mesoderm

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15
Q

Describe what occurs when the bronchial tree begins to develop?

A

It pushes the viseral layer of lateral plate mesoderm which becomes the visceral pleura

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16
Q

Epithelium of the respiratory system is derived from what?

A

Endoderm

17
Q

Besides respiratory epithelium, what is the rest of the respiratory system developed from?

A

Mesoderm

18
Q

Describe the four overlapping stages in lung development

A

1) Pseudoglandular
2) Canicular
3) Terminal Saccular
4) Alveolar

19
Q

What stages of lung are not compatible with life

A

The first two stages and at this point the sections involved in gas exchange are not developed yet.

20
Q

What occurs from 20 weeks that allows a foetus to be able to survive in a NICU

A

Type 2 pneumocytes being to secrete surfactant

21
Q

From what gestation age can a foetus can survive on its own?

A

28 weeks onwards

22
Q

What are the four sources of origin from the diaphragm?

A

1) Pleura-peritoneal fold
2) The pleura-peritoneal fuse with the septum transversum (2)
3) Mesentery of the oesophagus (from which the crura develop.
4) Muscular in-growth from the body wall.

23
Q

What forms the central tendon of diaphragm?

A

The septum transversum which contains myoblasts from somites in C3,4,5.

24
Q

What happens if something goes wrong and the tracheo-esophageal folds do not fuse properly

A

in 90% of cases there will be communication between the trachea and oesophagus called a tracheo-oesophageal fistula, which is usually accompanied by oesophageal atresia.

25
Q

What occurs in other form of tracheo-esophageal folding abnormalities

A

When the baby attempts to feed, milk enters the trachea causing chocking and possible development of pneumonitis and pneumonia. Also possibility of retrograde passage of gastric acid from GI tract into respiratory

26
Q

What occurs in oesophageal atresia?

A

During normal pregnancy, the foetus swallows amniotic fluid which is reabsorbed from the gut and returned to maternal circulation. If oesophageal atresia develops then this circulation of fluid is prevented and polyhydramnios develops.

27
Q

How does failure in fusion of diaphragmatic origins cause?

A

Diaphragmatic hernia

28
Q

What is respiratory distress syndrome?

A

Insufficient surfactant results in the collapse of the alveolar wall during expiration.

Deficiency of surfactant secretion results in respiratory distress syndrome. Treatment can be artificial surfactant and treatment with glucocorticoids to stimulate surfactant secretion