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BMS12 > Respiratory System Histology > Flashcards

Respiratory System Histology Flashcards

1
Q

What are the structures of the upper respiratory tract?

A

Nasal cavity

Paranasal sinuses

Oral cavity

Pharynx

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2
Q

What are the functions of the upper respiratory tract?

A

Filtration via nasal hairs

Humidify and warm inhaled air to prevent damage to epithelium

Smell

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3
Q

Where does the lower respiratory tract start?

A

Larynx

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4
Q

What is the function of the larynx?

A

Phonation

Sphincter stops things entering respiratory tract

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5
Q

List the arrangement of the lower respiratory tract from the trachea to the alveolar sacs.

A

Trachea

Primary bronchi

Secondary bronchi

Tertiary bronchi

Terminal bronchioles

Respiratory bronchioles

Alveolar ducts

Alveolar sacs

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6
Q

What is the alternative name for secondary bronchi and why?

A

Lobar bronchi

One per lung lobe

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7
Q

What is the alternative name for tertiary bronchi and why?

A

Segmental bronchi

Reflects bronchopulmonary segmentation

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8
Q

Describe typical respiratory epithelium.

A

Pseudostratified, columnar, ciliated epithelium with goblet cells

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9
Q

What is the length of cilia often the same as?

A

Diameter of nucleus

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10
Q

What cells are found in the trachea/bronchi?

A

Tall columnar ciliated cells

Goblet cells

Neuroendocrine/Kulchitsky cells

Basal cells

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11
Q

What do Kulchitsky cells do?

A

Secrete serotonin, bombesin and calcitonin which affect the smooth muscle beneath the epithelium

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12
Q

What is the function of the goblet cells and submucosal glands of respiratory epithelium?

A

Produce mucus to trap dust, bacteria and viruses

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13
Q

What is the ‘muco-ciliary escalator’?

A

Coordinated beating of cilia propels mucus from as low as bronchioles to the pharynx

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14
Q

What is the function of the serous secretions of the submucosal glands for the respiratory epithelium?

A

Humidifies inspired air to prevent dehydration and damage

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15
Q

How long are cilia?

A

7-10um

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16
Q

Describe the structure of a cilium.

A

20 microtubules arranged as 9 doublets around a central pair (9+2)

Microtubules growing out from a basal body (similar to centrioles)

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17
Q

What is the function of the C-shaped cartilage rings of the trachea?

A

Prevent collapse during inspiration and expiration

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18
Q

What joins the free ends of the cartilage of the trachea?

A

Trachealis muscle

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19
Q

What is the function of trachealis muscle?

A

Contraction reduces diameter of trachea to raise intrathoracic pressure

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20
Q

What type of muscle is trachealis muscle?

A

Smooth muscle

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21
Q

Describe the layers of the trachea.

A

Tall respiratory epithelium

Highly cellular and vascular lamina propria rich in elastin

Submucosa contains mucoserous glands (with ducts) located mainly between ends of cartilaginous rings

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22
Q

How do the layers of the primary bronchi compare to the trachea?

A

Shorter respiratory epithelium

Fewer goblet cells proportionally

Discontinuous smooth muscle layer separates lamina propria and submucosa

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23
Q

How is the cartilage different in the bronchi compared to the trachea?

A

Plates rather than C-shaped rings

24
Q

Describe the layers of tertiary bronchi.

A

Tall columnar respiratory epithelium with little pseudostratification (mainly simple)

Even fewer goblet cells

Complete layer of smooth muscle below lamina propria

Few mucoserous glands

25
Q

How do you differentiate between a bronchus and bronchiole?

A

Bronchi have cartilage whereas bronchioles do not

26
Q

How wide are the airways of bronchioles?

A

<1mm

27
Q

Describe the layers of bronchioles. (4)

A

Columnar respiratory epithelium gradually changes to cuboidal

Discrete bundles of smooth muscle

No submucosal glands

Goblet cells only present in larger bronchioles

28
Q

What is the smallest, purely conducting airway?

A

Terminal bronchioles

29
Q

Describe terminal bronchioles.

A

Simple cuboidal ciliated epithelium

Clara cells

Terminate in respiratory bronchioles

30
Q

What is the function of Clara cells?

A

Secrete components of surfactant

May also be stem cells

31
Q

What is surfactant?

A

Protein and lipid mixture which lowers surface tension of aqueous surfaces

32
Q

How does cystic fibrosis affect the lungs?

A

Defective chloride transporter in surfactant secreting cells

Impaired effect of surfactant so hard to breathe

33
Q

Describe respiratory bronchioles.

A

Similar to terminal bronchioles but have single alveoli in their walls

Terminate in alveolar ducts

34
Q

Describe alveolar ducts.

A

Passageway made up entirely of alveoli

Supported by a spring-like spiral thread of smooth muscle cells, collagen and elastin which recoils during exhalation

Terminate in alveolar sacs/alveoli

35
Q

What is the function of alveoli?

A

Site of gas exchange

36
Q

Describe type 1 pneumocytes.

A

Squamous cells lining alveoli

Flat and thin for efficient exchange

37
Q

Describe type 2 pneumocytes.

A

More rounded and found especially at angles between adjacent septa

Secrete surfactant

Stem cells

38
Q

How do type 2 pneumocytes produce surfactant?

A

Contain lamellar bodies rich in phospholipids and cholesterol

Phospholipids released by exocytosis and combine with secreted surfactant proteins

Tubular lipoprotein lattice coats cell surfaces

39
Q

Which phospholipid is especially rich in lamellar bodies of type 2 pneumocytes?

A

Dipalmitoyl phosphatidylcholine

40
Q

How is the alveolar wall adapted for gas exchange?

A

Extensive capillary plexus

Endothelial cells share a common basal lamina with type 1 pneumocytes to create a thin diffusion barrier (as little as 0.2um)

41
Q

What is the function of alveolar macrophages?

A

Remove inhaled particulate matter from alveoli

42
Q

What happens to dust-laden alveolar macrophages?

A

Crawl back to ciliated part of tract to join muco-ciliary escalator

OR

Travel to lymph nodes via lymphatics present at bronchiole level

43
Q

What are alveolar pores?

A

Small openings in alveolar wall, 8-10um dia.

44
Q

What are the functions of alveolar pores?

A

Allow equilibration of pressure between adjacent alveoli

Provide an alternative route for air circulation in case of blockages

45
Q

What is the function of alveolar elastin?

A

Support alveolar walls (especially condensed around openings of alveoli)

With collagen and smooth muscle form a 3D spiral network to support the lung parenchyma as a whole - important for passive recoil

46
Q

What happens to alveolar elastin in emphysema and what does this cause?

A

Destruction of elastin contributes to breakdown of alveolar walls

Inefficient recoil leading to shortness of breath

47
Q

What is the anatomical dead space and its average value?

A

Volume of purely conducting airways, ~150ml (third of an average breath)

48
Q

What is the physiological dead space?

A

Volume of alveoli contributing little to gas exchange due to damage or poor blood supply

49
Q

Describe the pulmonary arteries. (4)

A

Supply deoxygenated blood

Bifurcate along with adjacent bronchi

Elastic in character up to bronchioles then changes to muscular

Relatively thin-walled (lower pressures)

50
Q

How does pulmonary systolic pressure compare to systemic systolic pressure?

A

5 times lower

51
Q

Describe bronchial arteries.

A

Muscular arteries

Supply oxygenated blood to bronchi, bronchioles and pleura

52
Q

When do the pulmonary and bronchial arteries anastomose?

A

At levels of respiratory bronchioles

53
Q

Are there valves in the pulmonary veins?

A

No

54
Q

How does blood from the bronchial arteries return to the heart?

A

Via alveolar capillaries (after anastomosing) draining into pulmonary veins to left heart

Small proportion via azygos and hemiazygos veins into right heart

55
Q

Describe the lymphatic system of the lungs.

A

Absent from alveoli - fluid diffuses from interstitium to small lymphatics around respiratory bronchioles

Drain into larger lymphatics which follow airways back to hilum, passing through the hilar lymph nodes

BMS12 (7 decks)

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