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Second Year - Biomedical Sciences BS22001 > Lecture 22 - Lung Development, Structure And Gas Movement > Flashcards

Lecture 22 - Lung Development, Structure And Gas Movement Flashcards

(81 cards)

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1
Q

What are the five phases of lung development

A 
Phase 1 - Embryonic
Phase 2 - Pseudoglandular
Phase 3 - Canalicular
Phase 4 - Saccular
Phase 5 - Alveolar
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2
Q

What doe the five phases of lung development lead to

A

The formation of the alveolar blood-gas barrier

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3
Q

What is established during phase 1

A

The basic lung structure as a template for further growth

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4
Q

When does the formation of the right and left lobes occur

A

Between 26 days and 6 weeks

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5
Q

What does the primordial lung develop as

A

Buds which extend outwards from the foetal foregut

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6
Q

What is established in phase 2

A

The branched network of gas conducting airways

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7
Q

When does phase 2 occur

A

Between weeks 6-16 of gestation

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8
Q

What creates a distending pressure

A

Fluid secretion into the airway

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9
Q

What does the distending pressure give

A

Mechanical support for the growth of the airway in three dimensions

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10
Q

At the end of phase 2 what has happened to the airways and vasculature

A

They have developed to completely fill the space available in the chest cavity

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11
Q

What is the developmental outcome of phase 2

A

The formation of the conducting airways of the lungs and accompanying blood vessel

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12
Q

What is the airways and accompanying blood vessels of the lung known as collectively

A

The respiratory tree

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13
Q

What type of branching does the airway of the lung follow

A

Irregular dichotomous branching

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14
Q

What are the advantages of irregular dichotomous branching

A

It achieves even dispersion of gas among terminal airways branches and the mechanical strain is dispersed evenly among units

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15
Q

What does the regulated increase of the number of airways at each branch allow

A

The dispersion of airflow resistance

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16
Q

What drives fluid movement into the airway lumen

A

A chloride gradient

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17
Q

What happens in phase 3

A

The airways and blood vessels meet to form an interface known as the blood-gas barrier

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18
Q

When does phase 3 occur

A

Between weeks 16-24 of gestation

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19
Q

What is the onset of phase 3 marked by

A

The extensive angiogenesis within the mesenchyme that surround the more distal reaches of the embryonic respiratory system which forms dense capillary network

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20
Q

The increase of the diameter of the air is accompanied by

A

A decrease in epithelial thickness to a more cuboidal structure

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21
Q

When does epithelial cell differentiation occur

A

Canalicular phase (phase 3)

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22
Q

What does differentiation of the mesenchyme progressing down the developing respiratory tree give rise to

A

Chondrocytes, fibroblasts and myocytes

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23
Q

What is the earliest stage of lung development that a premature baby could survive at

A

Canalicular (phase 3)

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24
Q

During phase 4 the first what occurs

A

The first septal fold of the early alveolus occurs

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25
What does phase 4 define
The gas exchange zone of the lungs
26
What is the gas exchange zone of the lungs known as
The respiratory acinus
27
When does phase 4 occur
Between weeks 24-36 of gestation
28
What happens during phase 4
The branching and growth of the terminal sacs or primitive alveolar ducts and continued thinning of the storm bringing the capillaries into apposition with the prospective alveoli
29
The completion of what differentiation occurs during phase 4
The pneumocyte differentation
30
What do type I pneumocytes differentiate from
Cells with type-II like phenotypes
31
What happens to type I pneumocytes
They flatten, increasing the epithelial surface area by dilation of the saccules
32
The production of what is fully functional in phase 4
Surfactant
33
What has formed by 26 weeks
A rudimentary though functional blood-gas barrier
34
Through what process does further maturation the alveoli occur
Further enlargement of the terminal sacs, deposition of elastic foci and development of vascularised septae around the foci
35
What continues to thin to allow the capillaries to protrude into the alveoli
The stroma
36
When the septa forms what happens
Bifurcation of the airway terminus
37
What does the septum contain
Two closely apposed capillary networks
38
What is the patency of the thin-wall airway maintained by
Cl- driven secretion into the luminal space
39
What happens during phase 5
The gas exchange surface area is increased
40
When does phase 5 occur
36 weeks to 6 years
41
What clears the lungs of fluid
Na+ driven fluid adsorption in the lung lumen
42
When does pulmonary circulation become fully established
When the umbilical cord is cut off
43
How does enlargement of the gas exchange surface occur
By pocketing on the wall of the saccular lung
44
What are the basic anatomical features of the lungs
The trachea, pleura, bronchi and alveoli
45
Where does the trachea run from/to
It runs from below the larynx (C6/7) to the carina
46
What is the trachea composed of
C-shaped cartilage and small muscles that connect the cartilage
47
Which direction do the C-shaped cartilage face
Anteriorly
48
When the trachea bifurcates what does it give
The left and right main bronchi
49
What is the main function of the lungs
To oxygenate the blood
50
What does the parietal pleura line
The pulmonary cavity
51
What are the different parts of the parietal pleura
Cervical, costal, diaphragmatic and mediastinal
52
What is the pleura that covers the lungs
Visceral pleura
53
What is the name for the sleeve of pleura that hangs from the lung root
The pulmonary ligamnet
54
What do the main bronchi go onto form
Lober bronchi
55
What do lober bronchi go onto form
Segmental bronchi
56
How many lober bronchi are in the left lung
Two
57
How many lober bronchi are in the right lung
Three
58
What are attached to the bronchi
Alveoli
59
What are the respiratory surfaces within the lung
The alveoli
60
What are alveoli
Air-filled spaces that are closely associated with capillaries within the lungs
61
What type of gradient does gas follow
A partial pressure gradient
62
What does partial pressure tell you
The direction of movement of gas
63
What is the ENaC
A Na+ selective ion channel
64
Where is ENaC found
In all secretory epithelia
65
What increases during the third trimester of pregnancy
The maternal cortisol levels
66
What happens when cortisol enters the foetal circulation
It induces the ENaC subunit gene expression and membrane insertion in epithelial cells lining the foetal airways
67
During labor what activates the ENaC
The rise in the level of adrenaline within the mum which passes into foetal circulation
68
What does the ENaC channel allow for
Fluid to be rapidly cleared from the foetal lung in preparation for the first breath
69
What are the two advantages of airway branching
It causes an increase in the surface area for gas exchange and dissipates resistance to air flow as airway diameter narrows towards the respiratory zone
70
What drives the bulk of gas into the conductive zone
Net pressure caused by expansion and relaxation of the chest cavity
71
When will gas move into the alveoli
When the alveolar pressure is less than the atmospheric pressure and the airway is open
72
How does gas movement in the airways arise
By convection
73
When will gas move out of the alvoli
When the alveolar pressure is greater than the atmospheric pressure and the airway is open
74
What is alveolar pressure the sum of
Elastic recoil pressure and pleural pressure
75
What muscles are involved in inspiration
The diaphragm, external intercostal and the accessory muscles
76
What nerves control the diaphragm
The phrenic nerves
77
What happens to the diaphragm during inspiration
It flattens on contraction
78
What are external intercostal muscles innervated by
The intercostal nerves
79
What are the accessory muscles
The sternomastoid, scalenes anterior, medius and posterior, and the pectoralis major and minor
80
What happens to the intrapleural pressure as the chest expands
It falls
81
What muscle are involved during forced expiration
The internal intercostal muscles

Second Year - Biomedical Sciences BS22001 (28 decks)

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