Development of lungs Flashcards

1
Q

Start of respiratory development

A

Respiratory primordium develops as a ventral groove in the floor of the foregut (originally from the gut tube)

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2
Q

Foregut

A

Region from mouth to pancreas

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3
Q

Respiratory primordium

A

Gives rise to the trachea, larynx, lungs

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4
Q

General development steps of respiratory system

A
  1. Respiratory primordium develops as a ventral groove in floor of foregut
  2. Groove deepens and forms elongated outgrowth called laryngo-tracheal groove
  3. The laryngo-tracheal groove becomes separated from the foregut by two trachea-oesophageal grooves (one on each side). These two grooves move towards each other and fuse to form the trachea-oesophageal septum and form the laryngo-tracheal tube. The portion of the foregut that was cut off from this will become the pharynx
  4. Laryngo-tracheal tube becomes the primitive trachea and eventually splits into two bronchial buds
    - Primitive trachea- mesenchyme (neural crest derived) gives rise to cartilaginous tracheal rings and smooth muscle of the trachea. Endodermal lining becomes ciliated, pseudostratified respiratory epithelium with goblet cells.
  5. Lung buds grow caudo-laterally becoming principle bronchi (left bud will be more lateral; right more caudal).
  6. Principle bronchi bud into lobar bronchi.
  7. Lobar bronchi will push into developing pleural cavity, become surrounded by mesenchyme and form the pleura
  8. Lobar bronchi will bud into segmental bronchi
  9. Segmental bronchi divide up to 20 times (species dependent) into terminal bronchioles (which are lined with endodermal derived epithelium)
  10. Terminal bronchioles divide further into respiratory bronchioles
  11. More divisions create secondary tubules called canalicules or alveolar ducts
  12. Canaliculi form terminal saccules. These divide further into blind saccules that will differentiate into alveoli (saccular phase) OR the alveoli differentiation will occur first on the terminal saccules (alveolar phase).
  13. Primitive alveoli that allow newborn to breath initially are developed into mature alveoli
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5
Q

Primitive trachea

A
  • Endodermally lined. Becomes ciliated, pseudostratified respiratory epithelium with goblet cells
  • Mesenchyme around it is neural crest derived and gives rise to cartilaginous tracheal rings and smooth muscle of trachea.
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6
Q

Periods of bronchi and lungs development

A
  • Embryonic- primordium of lungs and bronchi formed
  • Fetal- ramified bronchi are formed and preliminary structures produced for gas exchange
  • Postnatal- definitive structures for gas exchange called alveoli develop and lungs take on their adult form. Marked by extensive growth of respiratory bronchioles, accules and alveolar development.
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7
Q

Fetal period development subdivisions

A

Pseudo-glandular
- Segmental bronchi divide lots into terminal bronchioles

Canalicular
- Terminal bronchioles divide into respiratory bronchioles. Further divisions create secondary tubules called canalicules or alveolar ducts

Saccular
- Terminal saccules divide further into blind saccules that will differentiate into alveoli

Alveolar
- alveoli differentiation will occur first on the terminal saccules

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8
Q

Tracheal bronchus

A

develops from the trachea to supply right cranial lobe in cattle, sheep, and pigs

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9
Q

Pleural cavity development

A
  • heart and lungs will originally be surrounded by left and right segments of pleuro-pericardial cavity
  • Pleuro-pericardial folds (folds of mesoderm) will grow medially into the left and right parts of the pleuro-pericardial cavity and will eventually fuse to separate the two cavities
  • heart will be suspended in one pericardial cavity. Lungs will be in the pleural cavity
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10
Q

What lines terminal bronchioles?

A

Lined with endodermal derived epithelium

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11
Q

Lungs during gestation

A

Lungs were filled with fluid secreted from developing alveolar cells and glands in system, and from amniotic fluid that was aspirated by fetus.

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12
Q

Lungs in postnatal period

A
  • Fluid is expelled
  • Anything left over is absorbed by epithelial cells
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13
Q

Subdivisions of canine lungs

A

Linked by lobar branches
Left
- Cranial lobe (has a cranial Lobe and a caudal lobe)
- Caudal lobe

Right
- Cranial lobe
- Middle lobe
- Accessory lobe
- Caudal lobe

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14
Q

Subdivisions of porcine lungs

A

Linked by lobar bronchi except the right cranial lobe

Left
o Cranial lobe (has a cranial Lobe and a caudal lobe)
o Caudal lobe

Right
o Cranial lobe- Linked by tracheal bronchus
o Middle lobe
o Accessory lobe
o Caudal lobe

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15
Q

Subdivisions of ovine lungs

A

Left
- Cranial lobe (has a cranial part and a caudal part)
- Caudal lobe

Right
- Cranial lobe (has a cranial and caudal part)- Linked by tracheal bronchus
- Middle lobe
- Accessory lobe
- Caudal lobe

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16
Q

Subdivisions of equine lungs

A

Linked by lobar branches

Left
- Cranial lobe
- Caudal lobe

Right
- Cranial lobe
- Accessory lobe
- Caudal lobe
- No middle lobe as missing bronchus

17
Q

Subdivisions of bovine lungs

A

Left
- Cranial lobe (cranial and caudal parts)
- Caudal lobe

Right
- Cranial (has cranial and caudal parts)- Linked by tracheal bronchus
- Middle lobe
- Accessory lobe
- Caudal lobe

18
Q

Emphysema

A
  • Damage to walls of alveoli
  • Loss of lobes. Alveoli compress together and there is a loss of surface area. Decrease in gas exchange and therefore breathing issues