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IMED3001 > Development of Respiratory System > Flashcards

Development of Respiratory System Flashcards

1
Q

What are the stages of development?

A

Embryonic Period (Fertilization until week 10 of gestation (week 8 of development)) Fetal Period (Week 8 of development (week 10 of gestation until 38th week of development (40th week of gestation))

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2
Q

What happens in the embryonic period?

A

Formation of 3 germ layers and major organs begin development.

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3
Q

What happens during the fetal period?

A

Organs continue to develop and their structure and function is refined

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4
Q

When is the respiratory diverticulum first formed?

A

4th week of development

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5
Q

How is the respiratory tract formed?

A

First a ventral outgrowth called the respiratory/laryngotracheal diverticulum appears on floor of caudal end of primordial pharynx maintaining connection to foregut. Foregut and respiratory diverticulum are separated by tracheoesophageal septum. Bronchial buds differentiate to form the primordia of the primary bronchi by the 5th week. The primary bronchi divide into secondary bronchi and then segmental bronchi by the 7th week. 17 orders of branches are made by the 24th week (7 additional branches after birth)

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6
Q

What does the tracheoesophageal septum do?

A

It divides the foregut and respiratory diverticulum into dorsal and ventral portions.

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7
Q

What does the dorsal portion of the respiratory diverticulum become?

A

The pharynx and the oesophagus

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8
Q

What does the ventral portion of the respiratory diverticulum become?

A

The larynx, trachea, bronchi, and lungs

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9
Q

When are the primary bronchi formed?

A

Bronchial buds differentiate to form the primordia of the primary bronchi by the 5th week.

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10
Q

When are the secondary bronchi formed and what do they give rise to?

A

The primary bronchi divide into secondary bronchi and then segmental bronchi by the 7th week.

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11
Q

How many orders of branches are there by the 24th week of development?

A

17 orders

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12
Q

How many orders of branches are there in respiratory bronchioles after birth?

A

7 additional orders of branches are made before lung takes final shape;

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13
Q

What gives rise to the epithelium and glands of the respiratory tract?

A

The endoderm

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14
Q

What gives the cartilage, smooth muscle and connective tissue of the respiratory tract?

A

The splanchnic mesoderm

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15
Q

What parts of the lung are formed by the splanchnic mesorderm?

A

Visceral pleura Bronchial buds

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16
Q

What parts of the lungs are formed by the somatic mesoderm?

A

Parietal pleura, parietal peritoneum and parietal layer of pericardium.

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17
Q

What are the stages of lung maturation?

A

4 periods: Pseudoglandular (6 - 16 weeks) Canalicular (16 - 26 weeks) Terminal sac ( 26 weeks - Birth) Alveolar (32 weeks - 8 years)

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18
Q

What part of development does the pseudoglandular stage occur? What happens during the pseudoglandular stage of embryonic lung development?

A

Starts in fetal period of development and continues until the 16th week. In this period developing lungs somewhat resemble an exocrine gland (it contains acini and a secretory duct) and by the end of this period (at 16 weeks) all the major elements of the lung are formed except the parts involved with gas exchange. During this stage respiration is impossible and fetuses born in this stage are unable to survive.

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19
Q

Why is there an overlap between the stages of lung development?

A

The Cranial/apical segmental bronchi develop faster than the basal segmental bronchi

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20
Q

What happens during the canalicular period?

A

The tissue will become more vascular and the respiratory part of the lungs are formed which include the respiratory bronchioles and the primordial alveolar ducts are formed. Surfactant production begins in the 20th - 22nd week. Limited respiration is possible by the end of this stage

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21
Q

On what weeks of development does the canalicular period occur?

A

16 - 26

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22
Q

When does surfactant production happen?

A

Begins in the 20th to 22nd week

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23
Q

Is respiration possible during the pseudoglandular stage?

A

No, respiratory part of lungs have not formed yet

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24
Q

Is respiration possible during the canalicula period?

A

Yes, but a limited amount of respiration is possible due to presence of thin-wallled terminal sacs (primordial alveoli)

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25
Q

What happens during the terminal sac period?

A

Many more terminal sacs appear (primordial alveoli). Terminal sacs at this stage are lined by squamous type I pneumocytes and rounded type II pneumocytes. The epithelial lining of terminal sacs become thin and capillaries begin to bulge into developing alveolar wall creating blood-air barrier. Surfactant production is sufficient and adequate for gas exchange to occur which allows premature fetus to survive.

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26
Q

At what stage is the terminal sac period?

A

26 weeks until birth

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27
Q

What happens during the alveolar period?

A

The epithelial lining of the terminal sacs containing type I pneumocytes becomes extremely thin squamous cells which are capable of gas exchange. The definitive/true alveoli are formed. However, 95% of mature alveoli do not form until after birth. By late fetal period the lungs are capable of respiration because the blood-air barrier is thin enough top allow gas exchange.

28
Q

At what stage is the blood air barrier first established?

A

In the Terminal sac period

29
Q

What time period is the alveolar period?

A

32 weeks until 8 years

30
Q

How many alveoli do full-term newborns have? How much does this change after birth?

A

50 million increasing to 300 million alveoli by age 8. (Per lung)

31
Q

What forms the blood-air barrier?

A

Thin layer of surfactant Type I pneumocyte and its basal lamina Intervening connective tissue Capillary endothelial cells and its basal lamina

32
Q

What separates alveoli from each other?

A

A septum containing pneumocytes (type I), reticular CT and elastic Connective Tissue

33
Q

What are the 2 layers of basal membrane?

A

Basal lamina and reticular lamina (amount of reticular lamina decides the thickness of the blood-air barrier)

34
Q

How thick is the respiratory membrane?

A

Varies from 0.1 - 1.5 micrometers

35
Q

What is the function of the alveolar fluid?

A

It acts as a medium for gas exchange. It keeps alveoli moist to prevent dryness and to maintain tension in the surface.. Maintains surface tension of alveoli to prevent collapsing when breathing out and the surfactant reduces surface tension caused by alveolar fluid by making the alveoli easier to inflate after they come together (preventing adhesion of membranes).

36
Q

What is the reticular lamina of the epithelium?

A

Reticular and collagenous fibers.

37
Q

What is the basal lamina of the epithelium?

A

Extracellular matrix produced by alveolar epithelium

38
Q

What are the most common types of cells in the alveoli?

A

Type I pneumocytes

39
Q

What fills the gaps between cells of the alveoli?

A

Tight junctions which prevent leakage of blood/fluid from alveolar septum to alveolar space.

40
Q

What type of arrangement and shape are type 2 pneumocytes?

A

More rounded or cuboidal and smaller in number (5% of alveolar surface)

41
Q

Which cells produce surfactant?

A

Type II pneumocytes Clara cells

42
Q

What role (besides preventing alveoli from collapsing) does surfactant have?

A

It modulates immune function by attaching to surface of pathogens.

43
Q

What do type II pneumocytes do?

A

Produce surfactant Act as stem cell progenitors for type I pneumocytes

44
Q

What is respiratory distress syndrome?

A

Prematurely born babies don’t produce enough surfactant resulting in an inability to breathe at birth. (This most commonly occurs at 28th - 32nd weeks of labour)

45
Q

What is the treatment for babies born with respiratory distress syndrome?

A

Betamethasone injections to stimulate further production of surfactant

46
Q

What cells are present in alveoli?

A

Type I and II pneumocytes Clara cells Alveolar macrophages (Dust cells)

47
Q

What is the colour of alveolar macrophages on histology slides and why?

A

They are slightly darker than type II pneumocytes due to their carbon and dust content.

48
Q

What are the types of macrophages in the alveoli?

A

Alveolar macrophages Septal macrophages (monocytes circulating in capillaries)

49
Q

What is the function of septal macrophages?

A

They engulf escaping red blood cells that enter into septum.

50
Q

What are the 2 tissues of lung parenchyma?

A

Reticular tissue (Forms the framework of the lung parenchyma) Elastic fiber (Allows the lung to expand during inspiration and to deflate during expiration)

51
Q

What tissue are the visceral and parietal pleurae made up of?

A

Both layers are composed of simple squamous epithelium.

52
Q

What is mesothelioma?

A

Malignant tumour of the pleura, peritoneum, or pericardium. It is common in workers that are exposed to asbestos for a long period of time.

53
Q

What happens to the height of the respiratory epithelium as we move further and further down the respiratory tract?

A

The height decreases gradually.

54
Q

At what point going down the respiratory tract does the pseudostratified epithelium become simple epithelium?

A

The pattern becomes less pseudostratified gradually until it is simple at the respiratory bronchioles.

55
Q

Where are clara cells located?

A

Only in the bronchioles

56
Q

Where are glands and hyaline cartilage located in the respiratory tract?

A

Only within the conducting part of the respiratory tract except for terminal bronchioles.

57
Q

Diagram that summarizes histology of lower respiratory tract:

A
58
Q

How many costochondral joints are there?

A

10 costochondral joints on each side.

59
Q

What is the difference between a symphysis and a synchondrosis?

A

Symphysis contains a layer of fibrocartilage. Synchondrosis joints are joined together by a layer of hyaline cartilage.

60
Q

What kind of joint joins the lower ribs together?

A

Synchondrosis

61
Q

At what level do the ribs start joining each other before reaching the sternum?

A

At the level of the 6th rib onwards.

62
Q

What is a synovial plane joint?

A

The end of the bones joining each other is flat

63
Q

What kind of joint is the manubriosternal joint?

A

Symphysis

64
Q

What happens at the costotransverse joint during ventilation?

A

Costal tubercle articulates with transverse process of the spine.

Upper 6 costotransverse joints are ovioid joints (convex joints that fit into concave transverse processes). Lower 4 costotransverse joints are plane synovial joints.

When external intercostal muscles pull on the rib that causes ribs to move upward and forward like a pump handle.

Lower 4 are raise forward and flat like a bucket handle.

65
Q
A

IMED3001 (46 decks)

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