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Flashcards in Week 2 Resp Deck (24):
0

What embryonic tissue is the respiratory system mainly derived from?

Endoderm

1

What embryological structure does the respiratory system start forming from?

Primitive foregut.
The pharynx buds off anteriorly on the foregut, which is composed of endodermal tissue

2

What is this early pharyngeal 'bud' known as?

Respiratory diverticulum

3

When does a septum form between the early oesophagus and trachea?

Week 4 of gestation

4

At what week do lung buds form from the respiratory diverticulum?

Week 5

5

What weeks of gestation make up the embryonic period of respiratory development?

Weeks 0-7

6

What are the olfactory placodes?

An invagination of ectoderm which goes on to form the nasal cavity. Present on the anterior aspect of the head of the embryo at week 4.

7

What structures do the lungs buds form?

All of the respiratory structures inferior to the larynx, including the trachea, bronchi and the alveoli

8

What is the fate of the mesoderm that surrounds the lung buds in early development

It goes on to form the blood vessels, cartilage and other structures of the lungs

9

How does the conducting system of the lungs develop?

The distal parts of the trachea bifurcate to form the two primary bronchial buds, which then proceeds to grow and branch outward forming secondary, tertiary etc buds which form the bronchiole branches

10

What weeks of development make up the pseudo glandular stage?

Weeks 7 to 16

11

Characteristics of the pseudo glandular stage?

Thick stroma of the lungs separates the epithelia of the alveoli from the capillaries.
Epithelia not yet differentiated into simple squamous type 1 cells yet
No ability for gas exchange to take place

12

What weeks of development make up the canalicular stage?

16-26

13

What are the characteristics of the canalicular stage?

Big proliferation of capillaries, starting to form around the alveoli but still capillaries not in contact with the alveolar cells for gas exchange. Stroma starting to thin out

14

What weeks of development make up the saccular stage?

Weeks 25-35

15

What are the characteristics of the saccular stage?

Gas exchange can now occur. Type 1 cells fused with I the capillary endothelium. Stroma has thinned further. Viable amounts of surfactant produced.

16

What weeks of development make up the alveolar stage?

35 weeks to 18 months post natally

17

What are the characteristics of the alveolar stage?

Formation of several million alveoli, saccules invaginating to form the cup like alveoli
Further thinning of septal walls leaves greater volume in the alveoli
Type two cells differentiate into type 1 cells
All about optimising volume for gas exchange!

18

How do the bronchioles stay open when there is no cartilage scaffolding?

Smooth muscle keep tone in the airways to prevent their collapse

19

Why would you be more likely to have a foreign body in the left bronchi than the right?

The right is shorter, wider and less horizontal than the left

20

What is the histological transition from the terminal bronchioles (where gas exchange does not occur) to the alveoli?

Transitions from pseudo stratified ciliated columnar to cuboidal in the respiratory bronchioles.
By the time the airways become the alveolar ducts the epithelia has transitioned into simple squamous

21

What is the role of elastic fibres in the respiratory zones of the lungs?

Providing elasticity and ability to spring back after filling with air

22

What is the role of the fluid secreted from the alveolar epithelial cells in foetal development?

Flush out debris from lung and prevent lung tissue from collapsing. It maintains a positive pressure relative to the amniotic fluid. This stimulates the lungs to grow.

23

What is a polyhydroamnios?

An abnormally large amount of amniotic fluid surrounding the baby. Can be due to a tracheosophageal fistula