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Pulmonary system > Microscopic Anatomy of the Airways > Flashcards

Microscopic Anatomy of the Airways Flashcards

1
Q

Respiratory system components

A

1) Pair of lungs

2) Airways that lead to and from the lungs

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2
Q

Functions of respiratory system

A

1) Inspiration and exhalation of air
2) Gas exchange
3) Olfaction (smell)
4) Phonation (speech)

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3
Q

Two divisions of structures of the respiratory system

A

1) Conducting structures

2) Respiratory structures

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4
Q

Conducting airways

A

1) Nasal cavities
2) Nasopharynx, oropharynx, larynx
3) Trachea
4) Bronchi
5) Bronchioles

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5
Q

Function of conducting airways

A
  • warm and humidify air

- remove foreign particles so don’t damage the delicate structures where gas exchange occurs

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6
Q

Respiratory structure - composition

A
  • respiratory bronchioles

- pulmonary alveoli (alveolar ducts, alveolar sacs, alveolus)

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7
Q

Function of respiratory structures

A

-gas exchange

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8
Q

Histological plan for conducting airways - components

A
  • mucosa (inner most layer)
  • submucosa
  • adventitia
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9
Q

Composition of mucosa

A

-respiratory epithelium on top of a basement membrane and a lamina propria

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10
Q

Composition of submucosa

A

-loose connective tissue containing seromucous glands

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11
Q

Adventicia

A
  • outer, connective tissue layer

- binds airways to adjacent tissues

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12
Q

Respiratory epithelium other name

A

Pseudostratified ciliated columnar epithelium with goblet cells

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13
Q

Requirements of air before enters respiratory epithelium

A

-must be conditioned (needs to be humidified and cleaned of particles/pathogens)

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14
Q

What carries out the process of conditioning

A
  • cells in respiratory epithelium

- airway lining fluid

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15
Q

Cells of respiratory epithelium

A
  • ciliated columnar epithelial cells
  • goblet cells
  • basal cells
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16
Q

Role of goblet cells in respiratory epithelium

A

-produce mucous that line all but the smallest airways

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17
Q

Role of basal cells

A
  • sit along basement membrane

- act as stem cells – renewal population for both columnar epithelial and goblet cells

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18
Q

Role of ciliated columnar epithelial cell

A

-cilia propels mucous and debris out of airways

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19
Q

Origin of mucous that lines the airways

A
  • goblet cells

- seromucous glands

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20
Q

Why lungs are susceptible to damage by inhaled pathogens/particles/toxic chemicals

A

Gas exchange dependent on very thin and delicate blood air barrier

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21
Q

How gas exchange regions in the lungs are protected from inhaled pathogens/particles/toxic chemicals

A

Airway lining fluid

  • comprised of:
    a) peri-cilliary layer (low viscosity - secreted by epithelial cells)
    b) mucous blanket -thick on top of pericilliary layer
  • pathogens get caugh in this plane
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22
Q

Mucociliary escaltor -explain what is happening

A

Peri-cilliary layer = layer that cilia will do majority of beating in
-only the tops of the cilia grab onto mucous blanket to propel it up the airways moving to the larynx for clearance

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23
Q

Respiratory diseases associated with impaired ciliary function-what’s going on?

A

A problem with the peri-ciliary layer

a) too viscous and cilia can’t beat
b) disipeared completely and cilia can’t function

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24
Q

Metaplasia -definition

A

Replacement of one type of epithelium with another

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25
Q

Where does metaplasia of the respiratory tract typically occur

A

-Where pattern of airflow is altered i.e. when forceful airflow occurs

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26
Q

Smoking –> how leads to metaplasia

A
  • respiratory epithelium will compensate for constantly being under attack by increasing the number of goblet cells by producing more mucous to try and trap particulates of smoke
  • results in increase mucous that is difficult to clear and leads to chronic coughing
  • chronic coughing = forceful airflow/change in pattern airflow
  • this results in the replacement of ciliated columnar cells to squamous cells
  • squamous = more sturdy = stronger where there is a change in airflow but at same time -reduced number of ciliated cells to clear mucous
  • change is reversible if irritant is eliminated or can lead to metaplastic transformation
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27
Q

Function of the trachea

A
  • conduit for air

- condition inspired air (lined with respiratory epithelium)

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28
Q

Four definable layers of the trachea

A

1) Mucosa
2) Submucosa
3) Cartilaginous layer
4) Adventitia layer

29
Q

Mucosa of trachea composition

A

Respiratory epithelium

30
Q

Submucosa of trachea composition

A

-Seromucous glands

31
Q

Cartilagenous layer composition

A

-16-20 cartilagenous rings (C-shaped rings

32
Q

Function of cartilagenous layer

A

-flexible, maintains patency of trachea

33
Q

Adventitia composition and function

A
  • loose connective tissue

- binds trachea to other structures

34
Q

Tracheobronchial tree function

A

-air moves from trachea into lungs via this path

35
Q

Number of generations of airways within tracheobronchial tree

A

-airway divides approximately 23 times

36
Q

Average number of terminating pulmonar acini + alveoli

A
  • 30, 000 pulmonary acini

- each containing more than 10,000 alveoli

37
Q

Regular dichotomy model

A

Model that predicts that each airway will branch into 2 equally sized daughter airways
-in reality daughter bronchi are never actually the same size and sometimes there is trifurcations

38
Q

Histology of bronchi

A

-initially similar histologically to trachea
-when enter the lung at hilum will several important histological differences
1) Rings of cartilage are replaced by irregular cartilage plates
2) Circular layer of smooth muscle
Five layers:
-mucosa
-muscularis
-submucosa
-cartilage layer
-adventitia

39
Q

Branches of main bronchi

A

Intrapulmonary bronchi (characterized by successive, dichotomous branching)

40
Q

Histological changes as bronchi become smaller

A

1) the amount of cartilage decreases (but still bronchi not directly embedded in lung tissue - do not rely directly on elastic component of lung to keep airways open)
2) respiratory epithelium becomes reduced in height
3) still have layer of smooth muscle

41
Q

Somewhere around generation 11 what happens

A
  • conducting air passage is < 1mm in diameter
  • no cartilage -embedded directly in lung tissue and rely on its elastic properties to keep the airway open
  • do not have submucosal glands - in rely small airways don’t want mucus
  • still have smooth muscle (responsible for star-shaped lumen of bronchioles)
  • epithelial lining changes
    a) simple columnar epithelium (where airways are larger)
    b) simple cuboidal epithelium (where airways are smaller)
  • goblet cells replaced by clara cells
42
Q

Structure of clara cells

A
  • non-ciliated

- dome shaped

43
Q

Abundancy of clara cells

A

Represent 75-85% of cells lining the bronchioles

44
Q

Function of clara cells

A

1) Secrete surfactant to reduce surface tension
2) Clara cells secretory protein (CCSP)**function?
3) Ingestion and breakdown of toxins
4) Produce enzymes to breakdown mucus
5) Lysozymes (antimicrobial)

45
Q

Asthma

A
  • intermittent reversible airway obstruction
  • episodes of chest tightening, wheezing, coughing, shortness of breath (all the result of narrowing of airway)
  • generally in response to inflammatory mediator that will induce contraction of smooth muscle in airway wall)
46
Q

Bronchoconstriction

A

Contraction of airway smooth muscle

47
Q

Allergen induced asthma

A
  • one of the many types of asthma

- where allergens are the trigger for bronchoconstriction (inflammatory stimuli)

48
Q

Inflammatory cells in airway walls

A

1) Eosinophils
2) Mast cells
3) Neutrophils
4) Lymphocytes

49
Q

Role of mast cells

A
  • have IgE receptors
  • in response to allergen - IgE receptors activate the mast cells
  • mast cells release spasmogens that induce contraction of airway smooth muscle
50
Q

Role of eosinophils

A

-also release mediators that are spasmogens

51
Q

Neutrophil role

A

-release proteases that damage epithelium

52
Q

Airway changes in asthmatic

A

1) Goblet cells hyperplasia *(chronic)
2) Airway inflammation
3) Bronchoconstriction

53
Q

Goblet cell hyperplasia - result

A

Mucous hypersecretion

54
Q

Airway remodelling

A

-body tries to fix localized areas of damage
1) increase in connective tissue surrounding epithelium
2) increase in numbers of layers smooth muscle surrounding the airway (strengthens the contraction)
= subepithelial fibrosis?

55
Q

Respiratory structures

A

1) Respiratory bronchioles

2) Alveoli

56
Q

Respiratory bronchioles-function

A
  • transition
  • close to where branche with bronchioles still mainly function for air conduction
  • further down greater role in gas exchange
57
Q

Histology of respiratory bronchioles

A
  • close to bronchioles:
  • simple cuboidal epithelium (ciliated) and clara cells (non-ciliated)
  • distal segments (closer to alveoli):
  • clara cells predominate
  • alveoli extend from lumen of respiratory bronchioles
58
Q

Alveoli

A
  • terminal air spaces in the lung

- where gas exchange occurs

59
Q

Components alveolus

A
  • alveolar septa
  • alveolar epithelial cells (continuous lining)
  • network of capillaries
  • alveolar macrophages
60
Q

Function of alveolar septa

A
  • framework (for structure of alveoli to sit in)

- structure that blood vessels articulate with

61
Q

Compositionn of alveolar septa

A
  • type IV collagen fibers

- elastic fibers

62
Q

Cell composition of alveolar epithelium

A
  • type I pneumocytes

- type II pneumocytes

63
Q

Type I pneumocytes

A
  • thin squamous cell
  • large surface area to faciliate gas exchange
  • linked by tight junctions (restrict movement in and out of airspaces)
  • cover 95% of alveola surface
64
Q

Type II pneumocytes

A
  • cuboidal cells
  • more numerous but because of shape only cover 5% of alveolar surface
  • do not function in gas exchange directly - secrete surfactant to prevent alveolar collapse
  • usually located in septal junctions
65
Q

Blood air barrier

A
  • structure where gas exchange occurs
  • represent areas of minimal thickness (have only thin type I pneumocytes + thin capillary endothelium - share basal lamina (fused) - creased barrier of minimal thickness = 0.3- 0.5 um which allows for rapid gas exchange)
66
Q

Dust cells/alveolar macrophages location

A

Blood air barrier

67
Q

Dust cell/alveolar mac function

A

-Scavenging foreign bodies (dust particles, pathogens, etc) and remove

68
Q

How dust cells can be identified at

a) LM level
b) EM level

A

a) LM level:
- can see ingested particles (brown dots)
b) EM level:
- share features common to all macrophages
- primary and secondary lysosomes in cytoplasm

Pulmonary system (19 decks)

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