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Resp Anatomy > Embryology > Flashcards

Embryology Flashcards

1
Q

What is the resp system an outgrowth of

A

Foregut endoderm

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2
Q

What is the EPITHELIUM derived from

A

Foregut endoderm

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3
Q

What does the SPLANCHNIC MESODERM give rise to

A

Connective tissue

Smooth muscle

Cartilages

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4
Q

What will the outermost splanchnic mesoderm become

A

The visceral pleura that surrounds the lungs

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5
Q

What gives rise to the parietal pleura

A

Somatic mesoderm

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6
Q

Week of the EMBRYONIC phase

What does it develop

A

During the 4th week

Development of trachea and mainstem bronchi

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7
Q

What are the last 4 phases of resp development associated with

A

The development of the distal airways and lungs

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8
Q

After what week can a baby survive

A

22 weeks

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9
Q

What does the embryonic phase begin with

A

An endodermal outgrowth of the foregut called the RESPIRATORY DIVERTICULUM

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10
Q

What does the respiratory diverticulum become

A

The LARYNGOTRACHEAL TUBE with a swollen end called the TRACHEAL BUD

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11
Q

What does the tracheal bud become

A

Trachea

Bronchi

Bronchioles

Lungs

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12
Q

How do the trachea and oesophagus form

A

2 folds appear in the lateral wall of the laryngotracheal tube near its origin

=> TRACHEOESOPHAGEAL SEPTUM, separating the laryngotracheal tube in front from the developing oesophagus behind

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13
Q

What happens as the tracheal bud elongates

A

The surrounding splanchnic mesoderm will differentiate to form the connective tissue, SM and cartilage found in the mature trachea

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14
Q

What happens at the end of the 4th week

A

The tracheal bud branches to form the primary bronchial buds

As these buds grow laterally they grow into the pericardioperitoneal canal on each side, carrying a covering of splanchnic mesoderm with them

Pericardioperitoneal canals now become the PRIMITIVE PLEURAL CAVITIES

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15
Q

Pathway of branching from the PRIMARY BRONCHIAL BUDS

A
  1. Secondary (lobar) bronchii - 3 on the right and 2 on the left
  2. Tertiary (segmental) bronchii - 10 on the right and 8 on the left - 7th WEEK

Then intersegmental bronchii, bronchioles, terminal bronchioles and respiratory bronchioles

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16
Q

When do respiratory bronchioles first appear

A

24th week

By this time, there are about 17 generations of branches

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17
Q

What happens as each generation branches

A

Surrounding mesenchyme differentiates to form the associated CT, SM and cartilage

18
Q

Weeks of the pseudoglandular phase

A

6-17 weeks

Resp portion of the resp system does not develop before this => foetus born before 16 weeks will not survive

19
Q

What part of the resp system is developing in the pseudoglandular phase

A

Conducting portion of the airway is developing

20
Q

Changes in structure during the pseudoglandular phase

A

Endodermal component differentiates into resp epithelium

Trachea and bronchii invaginates to form the tracheal and bronchial glands

21
Q

What forms around the developing epithelium

A

CT and SM and possibly cartilage

22
Q

Weeks of the canalicular phase

A

17-26 weeks

Respiratory portion of resp system develops

23
Q

Structural changes during canalicular phase

A
  • 3 generations of branching of the terminal bronchioles occurs giving rise to the respiratory bronchioles opening into ALVEOLAR DUCTS
  • The mesenchyme surrounding the respiratory bronchioles thins during further branching allowing the airspaces to widen
24
Q

As the alveolar ducts widen, what happens to the epithelium

A

Initially cuboidal, it thins so that many of its cells become squamous

these are TYPE I PNEUMOCYTES

25
Q

Name the remaining cuboidal cells of canalicular phase

A

Type II pneumocytes - accumulate lamellar granules storing surfactant

26
Q

What coincides with the formation of these squamous cells

A

A massive increase in the degree of vascularisation of the developing lung tissue, with many capillaries found in close association to the alveolar ducts

27
Q

What change occurs towards the end of the canalicular phase

A

terminal saccules appear at the ends of the alveolar ducts

-> definitive alveoli will develop from these

technically gas exchange can occur so a foetus born after the 22nd week can survive

28
Q

Weeks of the terminal saccular phase

A

26 weeks-birth

Period during which the definitive respiratory portion of the resp system develops

29
Q

What are the HIGHLY ATTENUATED walls of the alveoli in close contact with

A

The surrounding capillaries forming the blood-air interface

30
Q

What is CRUCIAL to the compliance of the alveoli

A

Elastic fibres deposited beneath the epithelium of the alveoli

31
Q

Where is surfactant secreted

When does surfactant secretion markedly increase

A

Secreted onto the air surface of the alveoli

The amount of surfactant increases markedly in the 2 weeks prior to birth

32
Q

When does surfactant production begin

What happens at 28 weeks

A

Begins at 20 weeks

It is not until 28 weeks or so that sufficient terminal saccules, alveoli and surfactant are present to permit survival of the premature foetus

33
Q

When does the alveolar phase begin

A

In the 32nd week when the first definitive alveoli appear and continues after birth to about 8

34
Q

What is the alveolar phase marked by

A

An increase in the number of alveoli

An increase in the size of newly developed alveoli

(Lung growth after birth is primarily due to increases in alveolar number)

35
Q

What are the developing lungs filled with

A

amniotic fluid

36
Q

Importance of amniotic fluid

A
  • its presence is important for lung development
  • OLIGOHYDRAMNIOS - lung development does not occur fully due to insufficient amniotic fluid
  • Probably serves to drive expansion of the air spaces
37
Q

What does lack of surfactant cause

A

Respiratory Distress Syndrome = Hyaline Membrane Disease

  • alveoli contains fluid with a high protein content - resembles glassy or hyaline membrane on alveolar surface
38
Q

How can surfactant production be increased

A

By treatment with steroids, either before or after birth

Surfactant can be administered exogenously after birth, greatly relieving RDS

39
Q

When do foetal breathing movements begin

A

Prior to birth, and these movements draw and expell amniotic fluid into and out of the lungs

Allows resp muscles to function at birth

40
Q

What does the outermost layer of splanchnic mesoderm differentiate into

A

A layer of simple squamous mesothelium - visceral pleura, which is continuous at the lung root with the parietal pleura

41
Q

What is the parietal pleura

A

A layer of simple squamous mesothelium which differentiates from the somatic mesoderm and lines the walls of the pleural cavities

Resp Anatomy (10 decks)

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